How accurate is Finding Nemo? 

How accurate is Finding Nemo: Explained by Ocean Generation.

Finding Nemo introduced millions to the technicolour world of coral reefs.  

But beneath its heartwarming tale of family reunion lies a treasure trove of marine biology – some spot-on, some wildly imaginative. Let’s dive in and separate the science from the storytelling. How accurate is Finding Nemo?  

Let’s start by identifying some of the main characters.  

Who are the fish in Finding Nemo?  

The clownfish 

Nemo and Marlin are orange clownfish or clown anemonefish (Amphiprion percula), and their home-bound lifestyle is spot-on. Unlike their cartoon counterparts gallivanting across the Ocean, real clownfish are the ultimate homebodies. Adult clownfish rarely venture more than a few metres from their host anemone, making Marlin’s anxiety about Ocean exploration biologically justified rather than neurotic. 

Finding Nemo: Nemo and Marlin are orange clownfish. Posted by Ocean Generation.

What type of fish is Dory? 

Dory goes by a lot of names: regal tang, palette surgeonfish, blue tang, royal blue tang, flagtail surgeonfish, regal blue tang to name a few (Paracanthurus hepatus).  

Regal tangs like Dory are common throughout the Indo-Pacific, so her presence on the Great Barrier Reef checks out perfectly. However, her famous memory problems contradict everything we know about fish cognition. Studies show that P. hepatus can remember spatial layouts for months and demonstrate complex social learning. More on fish brains later.  

Dory in Finding Nemo is a regal tang. Posted by Ocean Generation.

How accurate are the fish in Finding Nemo? 

Mr Ray the spotted eagle ray (Aetobatus narinari) makes a charismatic teacher, though real eagle rays are typically solitary creatures who’d probably skip group activities in favour of a solo swim.  

Gill the Moorish idol (Zanclus cornutus) represents one of the aquarium trade’s biggest challenges. These stunning fish are notoriously difficult to keep alive in captivity due to their specialised diet of sponges and tunicates (a group of marine invertebrates that include sea squirts which look, to non-divers like coloured blobs on the reef). This explains Gill’s dissatisfaction with captivity and desperate escape plans.  

The film shows a fish dropping their kids off to Mr Ray’s class using their mouth, representing one of nature’s most devoted parenting strategies.  

Cardinalfish (Apogon species) are the most common marine mouthbrooders, with males incubating eggs in their mouths for 8-10 days. This explains why they seem unable to speak clearly – try having a conversation whilst holding 200 delicate eggs in your mouth without swallowing. The cartoon, however, doesn’t look much like a true cardinalfish. 

Supporting cast of Finding Nemo.

Crush and Squirt are green turtles (Chelonia mydas), shown as current riding nomads, which is entirely accurate. Green turtles have been tracked making migrations of almost 3000km (1,864mi)!  

Our current estimates are that green turtles live to approximately 80 years old, so the claim that Crush from Finding Nemo is 150 is a bit steep. Turtles aren’t known to travel in family groups, but Squirt does show the independence of a baby turtle. Right from the egg, turtles are fending for themselves, which Squirt shows they are more than capable of.

Do sea turtles really cruise the East Australian Current

The East Australian Current (EAC) serves as nature’s highway in Finding Nemo, and this isn’t just Pixar imagination. The EAC is a genuine part of the Oceanic conveyor belt (global network of currents circulating water), flowing southward along Australia’s eastern coast at speeds up to 1.5 metres per second

Crush’s “express lane” concept isn’t pure fantasy either. Ocean currents do have acceleration zones, particularly near topographical features like seamounts and continental shelf breaks. These current jets can provide genuine fast-track transport for marine life, making the turtle highway a plausible, if simplified, representation of oceanic dynamics. 

Green turtles (Chelonia mydas) really do use these currents for epic migrations, though their navigation system is far more sophisticated than simple current-following. The sea turtles use magnetic field detection to create internal GPS systems, imprinting on magnetic signatures as hatchlings and using these for navigation throughout their lives

Green turtles use Ocean currents. Posted by Ocean Generation, leaders in Ocean education.

Are the vegetarian sharks possible? 

Bruce and his gang’s “fish are friends, not food” philosophy in Finding Nemo might seem biologically ridiculous, but nature occasionally surprises us.  

Bonnethead sharks (Sphyrna tiburo) can derive up to 62% of their nutrition from seagrass, making them the Ocean’s most successful vegetarian predators. These remarkable sharks have evolved specialised digestive adaptations to break down plant cellulose – essentially becoming underwater cows with teeth.

Whilst no shark is completely vegetarian (they still eat crabs, especially when they are older), the bonnethead’s plant-munching abilities suggest that Pixar’s gentle giants aren’t entirely impossible – just highly evolved.  

Bonnethead sharks are vegetarian. Posted by Ocean Generation.
Bonnethead sharks photo by Robin Riggs

Other creature features in Finding Nemo 

Pixar’s attention to detail shines with creatures like the Spanish dancer (Hexabranchus sanguineus) – a spectacular sea slug that really does inhabit the Great Barrier Reef and can reach 40cm in length. These crimson beauties are nature’s underwater flamenco performers, funky reef rugs on a magic carpet ride over the corals.  

However, some characters are biogeographical impossibilities. They wouldn’t be in the same scenes.  

The anglerfish is most likely a black sea devil (Melanocetus johnsonii), the same species filmed swimming to the surface in early 2025. Whilst visually terrifying, the encounter represents a fundamental ecological error. These deep-sea specialists live 200-2,000 metres (656 – 6561ft) down, where they’d never encounter shallow reef fish. Our clownfish friends don’t usually stray below 15m (49,2 ft). The poor blobfish is a good example of what happens when you take an animal out of the pressure range it’s adapted to.  

Similarly, Nemo’s classmate Pearl is a flapjack octopus (Opisthoteuthis californiana). These are usually hanging out at depths of 200-1,500 metres (656 – 4,921 ft). These adorable cephalopods (who had a new species found in 2025) are built for life under crushing pressure and would be about as comfortable in shallow reef waters as a penguin in the Sahara.  

Let’s really get stuck in. Pearl talks about one of their arms (they say tentacles, but we know octopus have arms) being shorter than the rest. This means two things – that Pearl is a male octopus, and that arm is their hectocotylus, or an arm shorter than the rest that’s specialised to store and transfer sperm during mating.  

Spanish dancer, anglerfish and flapjack octopus in Finding Nemo. Posted by Ocean Generation.
Anglerfish: @jara.natura & @laiavlr / Condrik, Flapjack octopus: Monterey Bay Aquarium

Finding Nemo got it wrong? Let’s talk clownfish reproduction and genders

Since we are ruining childhoods, let’s address the elephant seal in the room. Brace yourself for the biological bombshell that completely rewrites Nemo’s story. 

Clownfish live together in anemones, with the largest individual as the matriarchal female. The largest male mates with her, with other smaller males helping with the chores and waiting their turn.  

When Coral, Nemo’s mum, died in that barracuda attack, the real biological story would be different. Within 10-18 days, Marlin would undergo a complete sex change, transforming into Marlina – the new dominant female clownfish of the anemone. This isn’t just changing wardrobes; it’s a full hormonal makeover involving suppressed testosterone and elevated oestrogen. 

But would Marlina then mate with Nemo, as some marine biologists suggest? (Because Nemo was the only clownfish in the anemone.) Probably not. Studies show that clownfish larvae typically disperse 7-12 kilometres from their birth sites, and genetics prove most anemone families aren’t actually related. Marlina would more likely wait for a wandering young male to join the family and restart the dynasty properly. Thank goodness.  

Does Mr Ray actually teach anything? 

We love that Mr Ray’s impromptu biology lessons contain genuine scientific gems, though we do have notes. His Ocean zone definitions are accurate – the mesopelagic (200-1,000m or 656 – 3,280ft), bathypelagic (1,000-4,000m or 3,280 – 13,123ft), and abyssopelagic (4000m+ or 13,123ft+) zones represent real oceanographic divisions with distinct communities. 

His species song (it’s called ‘Let’s name the species’, if you want to look it up) is catchy and gives a fun overview of the species you can find on a coral reef.  

Ocean animals in Finding Nemo. Posted by Ocean Generation, leaders in Ocean education.

“Cnidaria” would be more accurate than “coelentera”. Coelentera is an old term grouping a lot of the animals he goes on to name: hydrozoa (hydriods like the Portuguese man-o’-war), scyphozoa (true jellyfish), anthozoa (coral and anemones) and ctenophora (comb jellies). Add in the porifera (sponges), byrozoa (colonies of moss animals), echinoderma (urchins and sea stars) and “some fish like you and me” and you have a pretty comprehensive overview of life of the reef.  

Mr Ray’s excitement about “stromalitic cyanobacteria” is understandable and surprisingly sophisticated for a children’s film. These layered rock formations, created by ancient cyanobacteria, represent some of Earth’s earliest life. They were crucial in the Great Oxygenation Event 2.4 billion years ago. We can thank them for introducing oxygen to the atmosphere! Even now, the Ocean provides around half the oxygen we breathe.  

Fish cognition: Smarter than we thought 

Dory’s memory issues might be Hollywood fiction, but fish intelligence is no joke. Recent research has revolutionised our understanding of piscine cognition. Fish can recognise individual faces, remember complex spatial maps, use tools, and even show signs of self-awareness

Cleaner wrasses (Labroides dimidiatus) pass the mirror test – a cognitive benchmark previously thought exclusive to mammals and birds. Meanwhile, archerfish demonstrate remarkable learning abilities, accurately spitting water at insects with ballistic precision that would make a sniper jealous. 

The idea that fish have three-second memories is complete codswallop. Goldfish can remember things for months, whilst cichlids can recognise their offspring years after separation. If Dory existed, she’d likely be suffering from a very specific neurological condition rather than general fish amnesia. 

(additional note – read What A Fish Knows By Jonathan Balcombe for more) 

Finding Nemo got it wrong? Posted by Ocean Generation.

Scientific pet peeves in Finding Nemo 

The blue whale 

The film shows Marlin and Dory falling to the back of the throat, to be blown out of the blowhole into Sydney harbour. But blue whales can’t blow something out of its blowhole from its mouth.  

A whale’s blowhole is linked to the lungs, nothing else. It isn’t spurting water out, it’s a mix of mucus and water on its skin (think blowing your nose when you’re wet). Scientists can actually find out a lot from a whale from its snot, and they use ‘SnotBots’ – drones to collect whale blowhole bits.  

The jellyfish 

The jellyfish in Finding Nemo aren’t really any specific jellyfish, just mash of a few features to create a generic jelly. The closest real-life versions are the maeve stinger (Pelagia noctiluca) or the Amakusa Jelly (Sanderia malayensis), but neither are a perfect fit.  

Despite the sound effects, they don’t electrocute their prey – they have small cells firing tiny needles loaded with venom into anything that touches them.  

Marlin claims “I am used to it”. There isn’t much science to say that would help. Remember Nemo brushing in the anemone before school? That is science! Clownfish avoid being stung as they have a protective mucus layer similar to the anemone (it has to avoid stinging itself). They brush up against the anemone to coat themselves in the mucus, keeping them safe from stings. But this is specific to their home anemone and wouldn’t help much against a smack of generic jellyfish. Marlin isn’t any more jellyfish-proof than any other reef resident. 

A blue whale can't blow something out of its blowhole from its mouth.

So, is Finding Nemo accurate

Finding Nemo succeeds brilliantly in capturing the wonder of marine life whilst taking considerable liberties with biological reality. Its greatest accuracy lies in depicting clownfish territorial behaviour and anemone relationships, whilst its most glaring errors involve biogeographical impossibilities that would make any marine biologist wince.

We can’t not mention how clownfish would actually react in Marlin’s situation – a biological reality that completely transforms the story’s foundation. It’s a perfect example of how nature’s truth can be stranger and more complex than fiction. 

Perhaps the real magic lies not in perfect scientific accuracy, but in inspiring curiosity about the Ocean’s genuine wonders. After all, reality is often far more extraordinary than anything Pixar could animate. 

FIN. 

Why is the sound of coral reefs important? Explained. 

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11 of the best Ocean books

Man reading a book on a rocky coast with waves crashing nearby.

The best Ocean books: recommended by the Ocean Generation team

The Ocean is simply magnificent. In celebration of its importance and the wonder the sea invokes, we’re sharing 10 of our favourite Ocean books. 

Our Ocean has been inspiring authors for centuries. Whether you’re an avid bookworm, just want to learn more about the Ocean or dipping your toes into Ocean literacy, these reads are sure to educate, empower and connect you more deeply to the Ocean.

1) How to Read Water by Tristan Gooley

Suggested by: Lucy, Fundraising and Partnerships team 

About the book

An accessible guide that teaches you to decode the signs of rivers, lakes, puddles, and the Ocean (from ripple patterns to the colour of water).  

In Lucy’s words: “I enjoy this book because anyone can read it. Tristan Gooley encourages his readers to get to know your local landscapes better by reading its signs and patterns. He’s an advocate for connecting with nature from a deeper perspective – in ways our ancestors did.” 

Cover of "How to Read Water" by Tristan Gooley – a guide to reading water signs in nature.

Why Lucy chose it: 

“It gives you the power to be more present when in nature.”

2) Blue Mind by Wallace J. Nichols

Suggested by: Nadia (Fundraising and Partnerships) and Gemma (Youth Engagement) and…pretty much everyone else. We love this book! 

About the book

Blue Mind explores the science behind how being near, in, on, or under water can improve our mood, performance, and overall wellbeing. This Ocean book is a powerful blend of neuroscience, psychology, and personal stories.

Cover of "Blue Mind" by Wallace J. Nichols – a book about the mental health benefits of being near water.

Why Nadia chose it: 

“I read it when I first joined Ocean Generation. It’s a compelling exploration of our mental health and how it is impacted by our connection to the water and nature.” 

Why Gemma chose it: 

“It really shows just how important water and the Ocean are to all of us, particularly to our mental health.”

3) What A Fish Knows by Jonathan Balcombe

Suggested by: Will, Science team 

About the book

This Ocean book challenges what we think we know about fish. Balcombe uses scientific research to prove that fish are not just swimming creatures – they feel pain, communicate, play, and have personalities. This is a must-read for anyone who wants to dive deeper into marine life. 

Cover of "What A Fish Knows" – a science book revealing surprising facts about fish behaviour. Shared by Ocean Generation in an article of Ocean books.

Why Will chose it: 

“Consistently one of my favourite fishy books!”

4) The Sea Around Us by Rachel Carson

Suggested by: Jo Ruxton, founder 

About the book

Written in the 1950s, this award-winning book is lyrical and scientific. It paints a picture of the Ocean before plastic pollution and climate breakdown. It offers a historical baseline to help us understand how much has changed — and how much we still have to protect.  

Cover of "The Sea Around Us" – Rachel Carson’s classic Ocean science book.

Why Jo chose it: 

“This book is a snapshot of how the Ocean used to be, all in balance, before human destruction.”

5) The Brilliant Abyss by Helen Scales

Suggested by: Storm, Comms team 

About the book

In this book, Helen Scales dives into the darkest parts of the Ocean to show how life thrives in extremes. And how these little-known deep-sea regions are vital to the health of our entire planet.

Cover of "The Brilliant Abyss" by Helen Scales – a book about the deep Ocean's mysteries.

Why Storm chose it: 

“I love this book because it lifts the veil on the deep sea, a place most of us will never visit. The deep Ocean holds some of the greatest mysteries of our planet and I find it fascinating! This book balances scientific discovery with Ocean wonder really well, too.”  

6) The Salt Path by Raynor Winn

Suggested by: Kavina, Youth Engagement team 

About the book

A memoir of loss, resilience, and wild places. The Salt Path follows a couple who trek 1013km/ 630 miles along the Ocean-swept South West Coast Path of England. It’s about their journey and the healing power of nature (particularly the Ocean).  

Cover of "The Salt Path" – a coastal memoir about healing and walking the South West Coast.

Why Kavina chose it: 

“It weaves together the incredibly challenging and healing relationship we have with water as a couple take on the South West Coast Path whilst coming to terms with loss.”

7) White Caps by Jacques Cousteau

Suggested by: Victoria, CEO of Ocean Generation 

About the book

White Caps is a classic! It was written by legendary explorer, Jacques Cousteau. Readers get a first-hand view of the Ocean’s mystery and magnificence, from his perspective. It’s part adventure, part love letter to our Ocean, and full of curiosity. 

Cover of "White Caps" by Jacques Cousteau – a legendary Ocean explorer’s memoir.

Why Victoria chose it: 

“It was the first book I was given about the Ocean. I wanted to be him when I grew up. It’s taken me 50 years since then to finally reach the Ocean in my career, so I guess the moral of that story is ‘Never Give Up!’”

8) What The Wild Sea Can Be by Helen Scales

Suggested by: Will, Science team 

About the book

Marine biologist, Helen Scales, takes us on a journey across marine ecosystems: seagrass meadows, deep-sea trenches, and coral reefs. The book shares stories of resilience, adaptation, and hope. It’s a beautifully written call to action, urging us to protect the wild heart of our blue planet.   

Cover of "What The Wild Sea Can Be" – Helen Scales’ book about Ocean resilience.

Why Will chose it: 

“It is an honest representation of the state of our Ocean, with an Ocean Generation flavour of optimism looking forward.”

9) The Blue Machine: How the Ocean Works by Helen Czerski

Suggested by: Storm, Comms team 

About the book

Oceanpgrapher and physicist, Helen Czerski, connects the Ocean’s complex systems to climate and biodiversity impacts. This book makes Oceanography accessible and highlights the Ocean’s role in Earth’s climate and ecosystems. 

Cover of "The Blue Machine" by Helen Czerski – explaining how the Ocean system works.

Why Storm chose it: 

“The Ocean is more than a body of water. This book shows us just that: how the Ocean is a powerful, living system that shapes our whole planet. It’s a beautiful example of science meets rich, textured storytelling.” 

10) Whale Fall by Elizabeth O’Connor

Suggested by: Agnes, Comms team 

About the book

Set in a remote coastal village, in the UK, this novel follows a woman grappling with her past while surrounded by the wild, untamed Ocean. It’s atmospheric, almost poetic, and perfect for readers who love storytelling where the natural world is deeply felt.

Cover of "Whale Fall" by Elizabeth O’Connor – a literary novel set in a coastal Ocean village.

Why Agnes chose it: 

“I enjoyed the book because it shows the connection between the Ocean and the inhabitants of a remote island, but without romanticising it. This sort of lifestyle rarely exists today so it was really interesting to learn about it through the story of a young Welsh woman, a whale, and some English researchers.”

11) Life of Pi by Yann Martel

About the book

While this isn’t a science book, we’ve added it to the list for our fiction lovers. Life of Pi is an award-winning novel about survival at sea. It explores faith and the majesty (and brutality) of the Ocean.  

Pi’s deep respect for the Ocean and its creatures makes this quite a philosophical read for Ocean lovers. 

Cover of "Life of Pi" – a fiction novel about survival at sea and Ocean reverence.

What are your favourite Ocean books?

When we understand the Ocean, we care for it. And when we care, we take action. 

In their own ways, each of these books reminds us why take action to protect the Ocean.  

If we’ve missed one of your favourites, share it with us on social media. We’re @OceanGeneration everywhere.  

Why is the sound of coral reefs important? Explained. 

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Can we rebuild coral reefs? The promising (and weird) world of coral reef restoration 

Can we rebuild coral reefs? Posted by Ocean Generation.

Here’s what you need to know about coral reef restoration: 

Corals are cool. But the reefs face danger. A warming Ocean causes corals to bleach more regularly. Some estimates say we have already lost 50% of the world’s coral reefs.  

While we work to reduce the emissions of greenhouse gases, to keep our world from warming, we can also look to support the recovery and rebuilding of impacted coral reef systems. So today we ask: how can we restore our coral reefs (and how is a coral reef like a struggling orchestra)? 

Why should we care about coral reefs? 

Anyone that has had the privilege of diving on a coral reef will tell you how special these places are.  

Reefs cover less than 0.1% of our Ocean floor but support 20-30% of marine species. We have tried to estimate the economic value coral reefs bring, but it’s a difficult area, and economists can’t agree on the price tag.  

The range of $30 billion to over $300 billion puts coral reef value somewhere between “tremendously valuable” to “astronomically precious”. Include the goods and services provided by coral reefs and the estimated figure is $2.7 trillion. Trillion with a T.  

Coral reefs are excellent shields – healthy reefs can absorb 97% of wave energy. This protects our coasts, on which many of us live. Think of the most famous reef in the world – the Great (what?) Reef for example. 

So, we have to keep our corals around. The question is: how are we going to?  Let’s take a look at the three most common coral reef restoration methods. 

How can we help corals survive? Posted by Ocean Generation.
Image credits: Coral gardening photo by the BBC, Microfragmentation photo by Blue Corner Dive

What is coral gardening? 

The most used method of reef restoration is coral gardening.  

Fragments of healthy coral are taken from an existing coral reef and placed in a nursery. This nursery is set up for the baby coral to thrive. When the corals reach a big enough size, they are ‘planted’ back onto the reef.  

This is a very accessible, increasingly cheap way of tackling coral decline. Costs are estimated to drop from $150-$400 per coral to <$10 per coral with improving techniques. It doesn’t require expensive equipment, and is a very visible, practical way to engage communities.  

Does coral gardening work long-term?  

Not sure. Short-term results? Pretty promising. Two large projects (Coral Reef Foundation in Florida and CARMABI in Curaçao) claim over 80% survival after one and three years respectively.  

However, it isn’t all sunshine and coral roses. These figures aren’t peer-reviewed (cross-examined by other scientists) and likely reflect best-case scenarios for certain coral species.  

A more accurate long-term figure is likely 30-50%, and although it does increase coral cover, does not comprehensively improve reef health.  

A healthy coral reef is diverse.  

Gardening projects, however, tend to focus on fast-growing genus like Acropora, ignoring slower growing (but just as important) species.  This results in ‘restored’ reefs that are low in biodiversity.

Coral gardening projects tend to focus on fast-growing species. Explained by Ocean Generation.

It’s like trying to have an orchestra with only violins. It is technically music, and possible to even be good, but lacks the depth and the magic of the interplay between instruments that brings it to life.

(One of our marine scientists favourite orchestral pieces is the Planet Earth II Suite: the layering of the song as different instruments come in make your soul soar. What other piece can boast having sleigh bells?? Listen here.) 

This coral restoration method is also limited in scalability – can it be used to make a big difference?

Coral gardening is like trying to replant the Amazon by using window boxes. It’s cost effective, and great for fast-growing corals. BUT it produces reefs with low genetic diversity (making them vulnerable to disease) and low species diversity.  

Gardening alone isn’t going to save our coral reefs.  

Can cutting corals into tiny bits help? 

Microfragmentation is chopping up coral colonies into little pieces. The fragments are placed next to each other, and will grow out, to form larger colonies.

The key advantage here is in the species this method targets, such as star or brain coral. 

Where, with coral gardening, we are predominantly working with fast-growing corals, this is for the slow-growing corals that are key to reef building, and for whom other methods won’t be effective. These are the bass section in our orchestra: there are less of them, and they are slower, but still crucial to the symphony.  

Studies have suggested that this method of coral restoration can accelerate the growth of massive colonies by 10-15%.  

However, this is limited to massive species and carries the same dangers of limited genetic diversity as gardening, if few donor colonies are used.

As coral reproduction is strongly linked to size, smashing colonies into little bits certainly impacts their reproductive capacity in the short term. Currently, we don’t know how much or how long that effect lasts. 

While this method is an excellent boost for the big boys on the reef, it’s not a reef-wide solution. If it’s used with more conventional gardening, you can help specific species of corals grow more successfully. But how can we support the entire reef system, in all its complexity and diversity? 

Microfragmenttaion, a coral reef restoration method, can help slow growing corals. Posted by Ocean Generation.

How do corals reproduce? 

Coral reproduction is weird. A few nights of the year, all the corals on the reef will release their eggs and sperm to mix in the Ocean currents. These are called coral spawning events. 

The fertilised eggs will be Ocean floaters until they find a spot to settle. Most species settle within two weeks, but some can take as long as to 2 months.  

Can we increase the amount of coral larvae settling?  

There’s growing appreciation of the different ways coral larvae decides where to settle. We now know that the sounds produced by a healthy reef act as a draw for young corals (find out more about the sounds of a coral reef here). Similarly, we are now realising that young corals “smell” their way to their new home.  

What can we do with this information? We can advertise reefs in a way young corals can understand. Speakers playing the noises of healthy reefs, and a newly engineered gel releasing chemical cues replicating a healthy reef are some examples.  

These solutions increase coral settlement, helping the reef rebuild itself. This is like advertising for more players in the orchestra, looking to bring in new talent. But what if we take that further?  

Coral spawning is fascinating. Explained by Ocean Generation, leaders in Ocean education.

How do you help corals have more babies 

The Ocean is becoming a lot less of a love nest as it warms. The success rates of coral fertilisation drop with rising temperature and acidity.  

So, how can we help the corals? By collecting the eggs and sperm during spawning events and taking them back to the lab. There, they have the best chance at fertilisation, and the larvae can be reared until they are ready to settle. Then, they can be released back to the reef.  

We can protect the coral at their most vulnerable stage of life.  

In the wild, less than 1% of coral larvae will make it to settlement. Of those that do, up to 90% won’t survive the first few months. The proportion of larvae to survive to a juvenile coral is minute, somewhere between 0.001 – 0.1%.  

Through assisted reproduction, the success rates are still low, but much higher than the wild. Some studies have shown survival rates to a year to be 0.1-1%. That might seem small, but it’s at least ten times better than the chances for a wild coral larvae. Others show an increase in coral cover after nearly three years. Even more promising? Drop the young corals in, rather than manually fixing them to the reef (a seeding approach), survival rates after a year can reach a whopping 9.6% while the costs remain low.

Here’s the real magic: these methods keep the gene pool diverse and interesting.    

Coral reef restoration methods. Explained by Ocean Generation.

We’ve already discussed fragment-growing methods like coral gardening and micro-fragmentation. But unlike fragment growing (which is basically coral cloning), assisted reproduction gives us reefs with genetic variety – think coral cousins rather than identical twins. And that variety? It makes reefs more resilient long term.  

This would be the equivalent of sponsoring a musical training programme, nurturing the next generation to guarantee the success of our orchestra.  

Where’s the catch?  

All the data here comes from projects with scientists doting on every need of the corals. Basically: If we were to strip back the money and the monitoring, the survival rates of corals will probably take a hit.  

Assisted reproduction works with the natural reefs, which is its strength as it maintains diversity and avoids the risks of disrupting the ecosystem with new species. It’s also a weakness, as some reefs have lost too many sexually mature corals to rebuild themselves.  

While it may not be the most efficient way to resurrect a reef, assisted reproduction could make the difference on degraded reefs needing a boost.  

Are artificial reefs the answer? 

Like corals, people are great builders. Like us, corals need a good foundation to build on. Some of the most fun coral reef projects focus around providing those foundations, through concrete blocks and 3D printed units.  

These foundations can encourage our polyp pals (AKA: coral babies) to settle down and make their home. We can build a new concert hall for our orchestra.  

These structures provide habitat immediately for non-coral animals to use as well (little fishies can hide and sponges and algae can grow).  

We have also found that running electricity through a concrete foundation helps coral growth (now that’s current science).  

Artificial coral reefs are a good initial boost.  

Plus, it works quickly and can be scaled up easily. Like coral gardening, artificial reef building is accessible enough for local communities to get their hands wet. And there’s nothing like a concrete reef structure to make conservation visible *literally* and raise the profile of reef protection efforts. 

Artificial coral reefs are a reef restoration method. Posted by Ocean Generation.

But we don’t have a silver bullet here. There is concern that they could act as an ‘ecological trap’. They are fish magnets, not factories – they concentrate, not create.

Natural reefs and their residents settle and thrive not just because of a hard surface, but because there are good water conditions, plenty of food for their inhabitants and their populations are balanced.  

A reef in a poor location could end up negatively impacting the local fish. Imagine a new housing estate, but with no water and no shops. And acid rain. And bears. This is not a good housing estate.  

For artificial coral reefs to work they must be designed AND located with care and understanding. Don’t build a concert hall with terrible acoustics, no electricity and no public transport links. You need to know the area you are building in.  

Can we make super corals to survive climate change? 

None of the approaches so far tackle the root issue. The main threat to coral reefs is that the Ocean is changing faster than they can cope with.  

Could the answer then lie in us accelerating their adaption, selecting the more heat-resistant corals as evolution does, but faster?  

Our orchestra can experiment with new instruments and compositions to make a new sound.  

What is a super coral? 

Through selective breeding (choosing corals that can take the heat and breeding them) and microbial manipulation (like giving corals a probiotic yogurt, with beneficial bacteria and other tiny friends), we may be able to create ‘super corals’.  

When it works, it works brilliantly. Some lab studies showed that selectively bred corals could handle Ocean temperatures 1.5 degrees warmer than their non-selected colleagues.  

It’s an approach that directly addresses the main threat to corals, temperature rise, and could produce corals able to thrive in the predicted conditions of the Ocean in 2100

But temperature isn’t the only thing at work. These super corals have shown decreased resistance to Ocean acidification, the co-conspirator to Ocean warming. Think of a triathlete that can swim *like a fish* but also cycles like one. One-trick ponies aren’t what we’re going for when it comes to building healthy coral reefs.  

Our high performer corals also put a lot of energy into being super, so have less to put into growth and reproduction.  

What are super corals? Explained by Ocean Generation.

Another simple hesitation is the amount we don’t know. How could the super corals fit in? Will they outcompete naturally evolving corals? Disrupt ecological balances we don’t yet understand? Will our new music find an audience? 

Despite these challenges, assisted evolution remains a promising way for reef conservation in a rapidly warming world.  

As one researcher memorably put it: “We’re not playing God with corals; we’re simply giving evolution a helping hand when we’ve rather inconsiderately moved the finish line.”  

But if we are making new music, maybe we need a different orchestra set up. 

Is coral reef restoration the way to go to save reefs?  

New approaches and ways of thinking suggest that we should embrace our changing world.

We may not be able to ‘restore’ our reefs to the way they were, as our world is not the same as it was. Instead of spending time, money, and effort trying to build the reefs that used to exist, we could help build a reef that can thrive in the future conditions of the Ocean.  

To play to the tune of the future, maybe we need more woodwind and brass. Think more jazz improvisation than classical recital.  

This could offer a more pragmatic approach, acknowledging that full restoration is not feasible in the long term. It focuses on ecosystem function rather than maintaining the old reefs and could integrate the use of ‘super corals’.  

But this comes with the issues of the unknown.  

Ecosystems are notorious for their chain reactions. Tweak one thing, and something you thought completely unrelated is affected.  Bring wolves back to Yellowstone? Suddenly the rivers change course. Remove tiger sharks from an area? Watch the dugongs reduce the seagrass to mud flats since they don’t have to watch their backs. 

How would the new ecosystem function and effect the life around it? What if the new saxophonist doesn’t get on well with the trombone players? What if the audience don’t like it? 

Coral reefs support 25-30% of marine species.

So how are we doing with coral reef restoration? 

One estimate calculates that less than 0.1% of degraded reef area is under active restoration. Most projects are small-scale (100m2 or less) and short-term, with monitoring lasting less than 18 months.  

Restoring just 10% of degraded reefs could cost billions.  

The reality is most restoration projects are in convenient places, not where the corals will thrive. This renders most restoration projects vulnerable. Some can be completely lost after promising growth

But reef restoration is a stark reminder – humanity can act.  

Coral bleaching is among the most visual representations of our changing climate. But the time, effort and care that is devoted to restoring coral reefs around the world shows the desire to protect our natural world.  

For us to have healthy coral reefs, to have our orchestra really sing, we need to combine approaches. We can’t focus only on strings or on bringing in the young talent. We need to support the whole orchestra so we can enjoy the music.  

As corals have been a poster child for the degradation of our world, so too could they be the success story. Every young coral nurtured today could be the foundation of a healthy future reef, different to yesterday’s maybe, but no less important for our blue planet.  

Why is the sound of coral reefs important? Explained. 

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Why is the sound of coral reefs important? Explained. 

Why is the sound of coral reefs important? Explained by Ocean Generation.

Take a deep breath. Immerse yourself. Imagine diving onto a coral reef. Multicoloured arms reach up from the seabed, fish fly by on their busy way, shrimps clean their clients, anemones wave in the water.

Energy and movement surround these bustling underwater cities. Let us explore the sounds of coral reefs (and let’s see how many synonyms for noise we can get in).  

Had we asked you to put yourself in the jungle, or on a busy city street, you would have probably filled your ears with the calls of unseen birds and insects, or the honking of a taxi and chatter of fellow bipeds. The sounds of bustling coral reefs are just as diverse and entrancing.  

What sounds can you hear on a coral reef? 

Whistles, pops and hums. This background noise often stays as exactly that: background, largely unnoticed. Yet through advancements in bioacoustic research, we have begun to dissect the noises coral reefs make and realise their importance. 

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Video by Will Steen

If you take deliberate notice you will begin to hear the background crackle produced by the sharp pops of pistol shrimp. Pistol shrimp produce sounds exceeding 200 decibels at the source – a conversation is around 60 dB, city traffic 85dB and a jet engine 30m (100ft) away is approximately 150dB. Using their specially modified claws, they rip the water apart, creating cavitation bubbles that briefly reach temperatures comparable to the sun’s surface (up to 4,700°C).  

Then you hear the grunts of clownfish families talking to each other in their anemones. Gradually the other croaks, growls and even fish blowing raspberries come to your attention, and where there was only white noise is now a rich tapestry of sound. Coral reefs are bursting with sound and life. In fact, reefs support over a quarter of all marine life. 

Pistol shrimp and clownfish an coral reef. Posted by Ocean Generation.
Pistol shrimp: Arthur Anker/Flickr

Why is sound so important for coral reefs?  

The coral reef soundscape is crucial not only for the individuals communicating with each other, but for the survival of the reef itself. 

Residents of coral reefs use sound in different ways. The ambon damselfish can be heard singing to attract a mate; saddleback clownfish grunt to other members of their colony, warning of potential predators. And predators use sound to co-ordinate their hunts.  

Each coral reef has its own acoustic signature, defined by the population it supports.  

We now understand that young animals will listen out from the open sea and select their future home by listening to it.  

This means that the health and resilience of coral reefs depends (at least in part) on their residents’ din. Recently, even coral larvae have been shown to move towards the sounds of a healthy reef, called home by the hubbub.  

Each whistle and whoop add to the cacophony of the reef: a healthy reef is a loud one.

Each coral reef has its own acoustic signature. Explained by Ocean Generation, leaders in Ocean education.

Why is listening to coral reefs important?  

Marine biologists are unpacking the cacophony for science. By listening in and identifying the various reef rumblings, we can identify who’s there.  

This is better than just looking at coral reefs, as we can find the species good at hiding and the nocturnal. We’re even putting AI to work to identify the sounds for us. 

How does human noise impact coral reefs? 

There are some new faces on the coral reef: us. Say what you will about people, but we are rarely subtle.

Our visitations to the marine world bring our own katzenjammer. Motorboats busy themselves buzzing around, whilst seismic surveyors searching for oil and gas fill the water with explosions, and construction work hammers the sea bed with steel piledrivers. 

Most of the noise on coral reefs comes from our boats – engines chugging and rattling, propellers producing bubbles through cavitation just as the pistol shrimp do – these bubbles bursting with a screech. We create an ‘acoustic fog’ – as described by bioacoustic researcher, Steve Simpson.

We are realising with more clarity the effect of our racket. When motorboat noise is present, fish are more vulnerable to predation, perhaps due to warning calls being drowned out, or confusion slowing reaction times.  

Fish show signs of stress and stop their usual activities, including parents fanning their eggs with oxygen-rich water. This can mean young fish don’t develop properly and less of them will survive.  

Human activities create acoustic fog.

As healthy reefs are noisy, the opposite is also true: damaged or dying reefs lose their song 

Coral reefs face many threats: from warming seas causing them to bleach and die, to increasing acidity making it harder for them to build their skeletons.  

In 2016, the most famous reef of them all, the Great Barrier Reef, boiled in hot seas and an estimated two-thirds of coral in the north of the reef died. With this we also lose its noise. In the north part of the reef, it’s 75% quieter than before.  

The reef lost its voice.  

As our fog of noise descends and reefs quieten under the stresses created by us, young crabs, coral and fish listening as they drift in the Ocean can’t hear their homes call to them. Less offspring to fill these underwater cities puts their future in further doubt. 

Why the sound of coral reefs matter? Explained by Ocean Generation.

What can we do to protect coral reef soundscapes? 

But hope isn’t lost! Whenever we give it a chance, nature exceeds our expectations to recover. 

The growing research in bioacoustics is pushing our understanding of the noisy world under the waves. As we learn more about our Ocean’s audio, the desire and ability to protect it grows too.  

“Sound is a pollutant we have the most control over, and we can really fix things” – Prof Steve Simpson 

Ongoing research is decreasing the noise of our engines, and protection of our marine areas is growing. We now know minimising our audio footprint will improve feeding and mating behaviours of the animals on the reef, allow parents to feed and nurture their young better, and give fish a better chance to avoid predators.  

We can now listen to a reef and learn how healthy it is. Phonic richness – the diversity of animal produced sounds – is greater on a healthy reef

Early experiments with acoustic enrichment show promise. When speakers play healthy reef sounds, they attract significantly more juvenile fish and some invertebrates than areas where no sound was played.   

While still experimental, this approach could potentially become one tool in the coral reef restoration toolkit. Read more about the other approaches to reef restoration here

Our Ocean is resilient and, as we deepen our understanding of it, we can more effectively protect it. 

Dunk your head again onto your imaginary coral reef, take a deep breath. Close your eyes. Just listen to the Ocean sing.  

(Final noise synonym count: 11) 

Why is the sound of coral reefs important? Explained. 

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What is coral bleaching?

What is coral bleaching?

What you need to know about coral bleaching:

White branches reaching out, stark against the blue. Where there was colour, now only ghostly white. This haunting transformation isn’t just a visual tragedy – it’s the silent SOS of some our Ocean’s most spectacular ecosystems. This is coral bleaching.

Coral reefs aren’t just beautiful — they’re nurseries for fish, protect coasts from storms, and feed millions of people. When coral reefs bleach, their whole ecosystem is at risk. But what is coral bleaching? What causes it, and why does it damage reefs? 

Are corals animals, plants or rocks?  

Corals are animals. Some may have stone skeletons and live with plants. But all corals are animals.

Corals are tiny animals called polyps. Each polyp has a soft body and a mouth surrounded by tentacles, like a little sea anemone or an upside-down jellyfish. All these animals are related – they are cnidarians (silent c), named after their cnidocytes – special cells that can sting.  

Where does coral’s colour come from? 

Corals are incredible animals. They build immense structures that provide homes for marine species, protect the coast and create oases in the ‘desert’ of tropical seas (there are very few nutrients in the waters of the tropical Ocean).  

To be able to do all this, they need some help. Corals have symbiotic algae called zooxanthellae living in their skin cells. Think of zooxanthellae as tiny solar-powered chefs living inside coral homes. 

Where does coral's colour come from? Explained by Ocean Generation.

They catch sunlight, cook up energy, and share over 80% of the meal with their coral landlords. The coral provides protection and prime real estate with an Ocean view. It’s a win-win (this is what symbiotic means) – until climate change cranks up the thermostat.  

It’s zooxanthellae that gives coral its colour. The magical, vivid world of coral reefs is painted by these little algae. Without them, corals are translucent, and the white of their calcium carbonate skeleton shines through.  

Why do corals bleach?  

The happy relationship between coral and zooxanthellae can be disrupted. When it is, this can lead to the expulsion of the algae from coral tissues, leaving the coral gleaming white (it is a spectrum, coral can partially bleach).  

The most common cause of coral bleaching is thermal stress AKA temperature. If conditions aren’t right, the systems that make photosynthesis (plants turning sunlight into food) can break.  

When these systems break, they can produce reactive oxygen species (ROS). ROS are produced in normal function, but too many ROS harm the coral. When the coral detects this build up, it acts in self-defence and throws the algae out

Usually, this is from it being too hot, but the system can be broken when it is too cold, or in too much sunlight, or exposed to harmful pollutants.

That’s a bit abstract. Let’s make an analogy.  

Imagine the coral as a battery, and the algae as a solar panel. Normally, the algae are providing energy to the battery from the sunlight. But if the solar panel gets too hot or is exposed to too much sunlight under a magnifying glass, it might start to malfunction. It starts to spark, so to protect itself the battery disconnects. Without its solar panels, our coral battery can only run on emergency power for so long before it’s completely drained. 

Why does coral bleaching happen? Explained by Ocean Generation.

History of coral bleaching – how long has bleaching been about? 

We’ve known about coral bleaching for nearly a century. In 1929, scientists first described it during extreme low tides. But it wasn’t until 1984 that a mass bleaching was documented, linked to unusually warm waters.  

Then came 1998 — the first global mass bleaching event, when around 16% of the world’s coral reefs were lost.  

Places like the Maldives, Seychelles, and reefs in the Indian Ocean lost nearly half their coral cover. 2023 saw the start of the fourth global coral bleaching event, that over the next two years saw an estimated 84% of the worlds coral reef areas bleached. 

Sounds bad, but this isn’t the end. 

Why do corals bleach?
Image credit: Great Barrier Reef Foundation

Does bleaching mean coral is dead? 

No. A bleached coral is still alive, it just doesn’t have its friend feeding it. This leaves the coral more vulnerable to disease, but also to starvation. Unless our battery reconnects to its solar panel, it will eventually run flat.  

Having repeated bleaching events reduces corals’ ability to recover. It’s like punching them while they are down.

When the coral eventually dies, it loses its white look and will begin to get covered with other algae and seaweed.

However, corals have shown us again and again they have an amazing ability to recover when given the chance.  

Different species of coral are more tolerant, and different species of zooxanthellae can take more heat too.  

Some species of coral bounce back faster than others; the marine equivalent of those friends who somehow recover from a night out while you’re still nursing a headache. The massive boulder corals? They’re the slow-but-steady marathon runners. The branching corals? More like sprinters – quick to bleach, but sometimes quicker to recover. 

After bleaching, it is possible that coral acquire more heat-tolerant photosynthesising friends, chefs that can take the heat in the kitchen. Corals aren’t going down without a fight.  

How can we help prevent coral bleaching? Explained by Ocean Generation, leaders of Ocean education.

How can we help the corals? 

There is a lot of work going into understanding corals, and reef restoration methods continue to be tested and implemented (read here for more.)

Corals are the poster child of Ocean health. They are impacted by all our Ocean threats, which means you can help wherever you are.

Every time you switch off an unnecessary light, choose a reef-safe sunscreen (free from oxybenzone, octocrylene or octinoxate), or select a sustainably caught fish dinner, you’re casting a vote for coral survival.

The future of coral reefs could be written in bleached white, or in vibrant technicolour. The pen, rather excitingly, is in your hands.  

Why is the sound of coral reefs important? Explained. 

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Why are blue-footed boobies blue? 

Why are blue footed boobies blue? Explained by Ocean Generation.

Or more accurately: Why do blue-footed boobies have blue feet?

The Galápagos Islands are full of the weird and the wonderful. One of their most iconic species is the blue-footed booby (Sula nebouxii), a marine bird that is found all along the Pacific coast. It is best known for its blue feet (which it was very creatively named after), making it really cool to look at but, why are they blue? To answer this question, let’s break it down into the how and the why.

The how: What are the mechanisms that cause blue-footed boobies’ blue feet?

Our first answer is potentially a killjoy one; they’re not actually blue, they just appear that way! 

Colours most often come from pigments, which absorb specific wavelengths of light, but the blue in blue-footed boobies doesn’t seem to come from a blue pigment. Blue pigments are actually very rare in nature – the funky blue mandarin fish is one of the few examples of an animal that makes any.

Instead, the blue in blue-footed booby feet is likely a structural colour which comes from light being reflected. The way different structures on animal surfaces are organised can affect the way that wavelengths of light reflect off their surface – like in the diagram:

The blue-footed booby has a layer of collagen under its foot skin, and the structure of this collagen likely makes them appear blue by reflecting only blue light wavelengths. This is the case for the majority of blue animals.

Pigments might still play a role though because blue-footed booby feet sometimes appear slightly greener which might be due to yellow pigments (blue + yellow = green!). These pigments are carotenoids which animals can’t actually make themselves. Instead, they get them from their diets and the food they eat can influence what colour they are.

For example, flamingos aren’t born pink – they’re born grey but become pink because of the carotenoids in their food. Similarly, if you eat too many carrots you could turn orange (but please don’t, that would be bad for you)

.In blue-footed boobies, these carotenoids from their diet can affect how bright their feet are. Biologists tested this by changing how much food blue-footed boobies were given – when they didn’t get food, their feet became duller but when they were fed again with fresh fish, their feet became brighter.. This is super cool and also super important to keep in mind for our next question…

The Why: Why have blue-footed boobies evolved blue feet?

The reason that anything in nature looks or works the way it does is because of evolution. Darwin’s theory of natural selection says that traits that increase survival will be passed on so the fact that blue-footed boobies have evolved blue feet suggests they might be helpful in some way. But what advantage do blue feet give them? To answer this we need to understand sexual selection.

What is sexual selection?

Great question! It can be thought of as a special type of natural selection where traits that increase reproduction (instead of survival) will be passed on. This can include animals choosing a mate based on preferences for certain traits, which increases the chances of animals with those traits reproducing and so, the trait is passed on. For example, peahens prefer peacocks that have larger, more colourful tails which means large colourful tails get passed on over time!

Sexual selection explained by Ocean Generation.

As it turns out, female blue-footed boobies prefer brighter feet

We know this because biologists carried out some fun experiments – they used make-up to make male feets look duller (who says biology isn’t a very serious science?). When males had duller feet, the females were less likely to mate with them. Brutal!

Biologists also did this to males that had already mated with females (because blue-footed boobies don’t lay all their eggs at once). When the feet of these males were made duller, females actually made their second eggs smaller so that they’d hatch smaller chicks. Even more brutal!

This suggests to us that females are deciding who to mate with based on foot colour and if the blue isn’t as bright as they like they want to reproduce with those males less. So, foot colour might be a sexually selected trait because it increases the chances of reproduction for the males!

Why do female blue-footed boobies like blue feet?

As lovely as the blue is, it’s not just that they really like the colour. The stakes are quite high for them; they are choosing males to father their offspring and want to make a good decision. So, if they are basing this off foot colour, foot colour likely contains information that is quite valuable. It is likely a signal.

What are signals?
Signals are behaviours or structures that have specifically evolved to change the behaviour or state of others by conveying information. The response of the receiver must also have evolved due to signals – it is important to understand what receivers have to gain from responding to signals.

As we already know, carotenoids from their diet can influence blue-footed booby foot colour. What’s even more interesting is that these carotenoid changes can influence the immune response and foot colour also correlates to immune response.

Why do female blue footed boobies prefer blue feet? Posted by Ocean Generation

Females might also be interested in how good of a parent males might be and foot colour might also signal this. When biologists swapped baby birds between nests, they found that the foot colour of the foster father was a pretty good indicator of condition (even though they weren’t genetically related).

So, to summarise: blue feet have potentially evolved because male foot colour might signal their condition, females want to reproduce with good condition males so they choose males based on foot colour.

What about female blue-footed boobies’ foot colour?

Male blue-footed boobies also seem to prefer brighter feet on females but the story is slightly less straightforward.

When female feet were made duller, the effects are mostly after they’ve already formed a pair, Blue-footed boobies form pairs then lay eggs but there is a courtship period before they lay an egg. In this period, females with duller feet received less courtship nest presentation (when birds add materials to nests) both from males they were paired with, and other males. 

In the period after egg-laying, making the female foot colour duller also had impacts on how much males incubated eggs. However, this was also affected by egg colour and size, which can indicate offspring quality. When females had duller feet, males incubated more in nests with a large egg but when they had colourful feet, males incubated both small and large eggs. Males also spent less time incubating small-dull eggs than small-colourful and large eggs.

So it seems that female foot colour is signalling something about their condition (and as an extension, the offspring’s) and the way males respond depends on the phase of reproduction they’re in. However, it also seems that foot colour isn’t the only useful indicator; egg size also is. 

One explanation might be that females have to decide between investing in their offspring (egg size) and signalling (foot colour) so foot colour might not give the whole picture. The mechanisms and reasons for this aren’t completely understood yet which just means there’s more left to learn about blue-footed boobies – exciting!

Understanding why animals look the way they do is important

It’s not just blue-footed boobies that use signals

Nature is full of quirks! Beyond blue-footed boobies, evolution has brought about an array of interesting signals throughout nature. Animal signals are incredibly cool and incredibly diverse; they come in all shapes and sizes (literally) and some of them are also less honest than others. For example, some mantis shrimp display a claw that looks threatening to scare off intruders even when they are actually weak.

The signals that animals display will evolve to reflect the context in which animals live, which might be the environment or how they interact with species.

For example, yellow warblers (a species of small bird) produce alarm calls to scare off parasites. However, the yellow warblers that live alongside blue-footed boobies on the Galapagos don’t produce these calls. Why? They don’t need to!

They have been geographically isolated from their parasites for thousands of years, while the warblers on the mainland have not. These alarm calls either evolved before the Galapagos warblers became isolated, and they then lost the behaviour, or the calls evolved only in the mainland warblers afterwards. Either way, they reflect the lack of parasites on the islands!

Mantis shrimp and yellow warbler also use signals. Posted by Ocean Generation

Understanding why animals look or behave the way they do could be very valuable to us. For example, in the blue-footed boobies, their feet could show when their condition is declining. Since we know feet colour has likely evolved to signal their condition, if the foot colour changes, this could be because their food quality and availability has changed. This could signal to us that they’re in trouble!

So, as well as being incredibly interesting, learning more about nature and how species have evolved could also be important to protecting them.

Why is the sound of coral reefs important? Explained. 

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Why can some animals live in fresh and saltwater? 

Why can some animals live in fresh and saltwater?

Fish that break all the rules by living in the Ocean and streams: 

Look into a river and you will find very different animals to the Ocean, even if they are just a few miles apart. Why are these wet worlds so different? In short – it is all about osmoregulation (explained below). 

Whether you live in the Ocean, in a river, on a mountain or in Thneedville (yes, that’s a Lorax movie reference) – everywhere has its challenges. One of the main challenges of living in saltwater (read more about why the Ocean is salty here) is maintaining the balance of water in an animal’s cells.

What is osmosis?
Water will travel from areas of high concentration to low concentration in an attempt to balance them (this is called osmosis). Salty water has lower water concentration than freshwater. 

Join us to explore the difficulties of swimming between the two worlds, some of the incredible journeys of the fish, like salmon, eels and bull sharks, that overcome them and crown the winner of the wet.  

What is osmoregulation? 

All living things need water, and they need salts. Maintaining the balance of both is tricky – too much or too little of either is fatal.  

Imagine a balloon full of water, but this balloon can let water in and out of it. This is our cell. The water in the balloon (our cell) has a little bit of salt in.  

If you put the balloon in a bucket of freshwater, water enters the balloon (by osmosis) to balance the concentration. This could end up bursting the balloon. Alternatively, putting the balloon in salty water will lead to the water leaving the balloon, shrivelling it.   

Osmoregulation explained by Ocean Generation.

Animals living in these environments have to adapt to avoid bursting or shrivelling – neither sound particularly fun.

Fish living in freshwater have to hold on to their salts and avoid water intake. Saltwater fish take in as much water as they can and excrete the extra salts.  

How do freshwater and saltwater fish stay hydrated AKA: do fish drink the water they live in? 

To maintain a good balance of water and salt, fish in different environments alter their drinking, gill function, kidneys and excretion (waste removal).  

Marine fish will constantly drink sea water, getting as much water in as possible. They actively remove salt from the water through cells in their gills. The pee of marine fish is highly concentrated urine (if you get dehydrated, your body does the same – your pee will be very yellow, with little water diluting it), minimising water loss.  

Freshwater fish, on the other hand, don’t drink water. They don’t need to. Think of the balloon example – they are saltier on the inside, so water wants to move in. Freshwater fish easily absorb water through their gills. They use energy to pump salts in, against the concentration gradient – they actively ingest salts. Their pee is very diluted, ensuring they don’t become swamped by discarding lots of water.  

How do fish stay hydrated? Explained by Ocean Generation.

Why can’t freshwater fish live in the Ocean?  

Knowing all that, let’s see what would happen now if we put a marine fish in freshwater. A marine fish wants to lose salt from its body and keep water. Think of the balloon – a marine fish invites water in, pushing salt out. This means the balloon will lose all its salts and get over filled with water. That is one unhappy fish.  

For a freshwater fish in the Ocean, the opposite happens. Used to a world with plenty of water and little salts, the balloon will shrivel as it is filled with more salts and loses water. The bottom line is the same – an unhappy fish.  

Are there fish that can live in both freshwater and salt environments? 

Amazingly, yes. There are examples of fish that can live in both marine and freshwater all over the world. There are two main types.  

  1. Anadromous fish are born in freshwater, spend most of their lives in the Ocean and then return to freshwater to spawn.  
  2. Catadromous fish live in freshwater most of their lives, returning to the Ocean to spawn. 

We will explore these groups through a couple of their most famous members, as well as a shark that makes it all look easy.  

Some fish live both in fresh and saltwater environments. Posted by Ocean Generation, leaders in Ocean education.
European eel photo by GerardM

How do salmon survive in both fresh and salt water 

Salmon are incredible fish.  

Not all salmon are anadromous: there are Atlantic salmon in North America called sebago, named after one of the lakes they are found in. More Atlantic salmon live in Norwegian, Swedish and Russian lakes; and yamame are a landlocked Japanese masu salmon.  

But some salmon travel thousands of miles between fresh and salt water over the course of their lives.

Chum salmon have been estimated to complete total migrations of over 10,000km (6,200 miles) across the North Pacific from feeding grounds to the Yukon river or streams in Japan.  

Anadromy appears to have evolved at a similar time that the Ocean cooled and became richer in food. This, coupled with the existence of landlocked variations, suggest that salmon were a freshwater fish that took to the sea, although this is not confirmed. What is certain is the incredible journeys and transformations many salmon go through to mate. 

For salmon, the movement from river to Ocean and back to river is integral to their life cycle.

The first few years of a salmon’s life are spent growing in the river, before they go to the food-rich Ocean. Here they gorge themselves, growing very quickly. After travelling many thousands of Ocean miles, they will return to the rivers they were hatched in, to spawn themselves.  

But how do they manage to conquer both environments?  

Through hormonal changes, salmon make behavioural and physiological changes to the ways they manage their osmotic balance. In freshwater, they won’t drink water – when in salt water they will drink a lot. Hormones change the fish’s physiology, increasing the number of ion transporters in the gills and kidneys to process the salt balance.  

The change is a costly one though, as salmon won’t feed during their return to freshwater, relying on fat reserves built up through years in the Ocean. They battle up their rivers, overcoming waterfalls, predators waiting on the banks and their own failing bodies to reach the same spot they hatched in. Here, they will spawn.  

For most of these fish, it is the last thing they do.  

Salmon move from river to Ocean and back.

What can salmon teach us? 

Just as rivers are the connection between us and the Ocean, salmon are among the clearest species to bridge that gap. And they feel the impact of people more keenly. Rivers are the frontlines, and salmon are in the trenches.  

Salmon rivers are best in old forests, as the tree roots hold the banks together and keep the rivers form – holding it narrow and fast flowing. Where forests are lost, the river can widen and the salmon population diminishes. And as we build dams to harness the power of the rivers, we block the salmon from getting home.  

The populations of salmon in different rivers show far more genetic variation than between people. Each salmon is genetically coded for its river home. Climate change, pollution, human development and fishing – salmon deal with a lot.  

But their adaptability is shown time and again. The genetic diversity they show allows them to overcome the challenges they face. Just as they are able to thrive in these two different worlds, they can take on the new world we are shaping.  

What do you call returning to the Ocean to reproduce? 

Catadromy is the mirror of salmon – starting life in the Ocean, living in freshwater and returning to the salt to spawn.  

European eels begin life as eggs riding Ocean currents, drifting through the Sargasso Sea near the Bahamas. They hatch into small, transparent, leaf-shaped larvae called leptocephali. Like so many (hungry, well-teethed) leaves in the wind, the Ocean carries the eels to the coasts of Europe, a journey taking 2-3 years.  

On reaching the coast, they metamorphose (change body shape) into glass eels – still small and see-through but eel-shaped. After up to a year, they change again into elvers (juvenile eels) and begin to travel up rivers. Here, they change again into yellow eels and can remain in freshwater for up to 20 years until they reach sexual maturity. 

This means an eel can be 23 years old before reproducing. When their time comes, they become silver eels, migrating down rivers towards the Ocean.  

European eels also switch between freshwater and the Ocean
Artwork by A. Cresci via nature.com

How do eels switch between living in fresh and saltwater? 

For the elvers and glass eels, they need to do the same as our salmon. They alter the salt uptake of their gills via specialised cells, increasing it in freshwater and decreasing in saltwater.

For many years, European eels were characterised by mystery. They were well known in the rivers of Europe, yet no one could find baby eels. Greek philosopher Aristotle suggested that they just appeared out of the mud, and this was the general belief for almost 2,000 years.  

It was Johannes Schmidt, a Danish biologist working in the early 20th century, who began to unveil the elusive eels. By finding progressively smaller eels across the Ocean, he followed the trail of breadcrumbs to the Sargasso Sea. He couldn’t find any spawning, but he drew the metaphorical arrow.  

It wasn’t until 2022 that we found the first direct evidence of adult European eels travelling to and reaching the Sargasso Sea. This study also shows us just how far the eels travel – up to 8,000km. If you’re ever lucky enough to see one of these eels, appreciate just how far it has come, and how far it still has to go.

The eels adapt twice, changing their whole bodies to swap salt for fresh and back. On the way back, the silver eels don’t feed. As with salmon, they rely on fat reserves for their journey, and their bodies slowly disintegrate, and once they have reached their spot, they reproduce and then die.  

But the switch doesn’t always have such dire consequences.  

European eel design on our sustainable apparel
European eel design on our sustainable apparel.
Available in our store. Every purchase supports our charity.

Are bull sharks the best sea-swappers? 

Yes. Bull sharks (Carcharhinus leucas) are the aquatic conquerors supreme. As we have seen, moving between fresh and salt water is tough. Most salmon only do it once, some can manage it a couple of times, their bodies failing them under the stress. Eels change their whole bodies when they make the switch. Yet bull sharks can move between fresh and saltwater with apparent ease.  

They have been found in unexpected places. In Africa, bull sharks are known as Zambezi sharks as they are found deep into the Zambezi river. They were initially described as a different species* – because no one expected a bull shark there. In Brisbane a bull shark was spotted swimming the streets after flooding in 2011, and they have been to Baghdad up the Tigris. They have even been found in Alton, Illinois, 2,800 km (1,740 miles) from the Gulf of Mexico.   

The ultimate tourist? A bull shark was reported in the upper reaches of the Amazon, in the Ucayali River, Peru. Nearly 5,080 km (3,157 miles) from the Ocean.  

How do bull sharks do it? 

Ready for some high-density science?  

They change how salty they are (in the balloon). In the Ocean, bull sharks’ blood is at least as salty as the water they are in due to the levels of urea and trimethylamine oxide (TMAO). But when in freshwater they excrete much more urea, lowering the salt concentration of their blood to minimise the gradient (the difference in saltiness).  

However, they are still more salty than freshwater, so they absorb water and lose salts through their gills. They change their salt and water processing to match their environment.  All sharks have rectal glands through which they excrete excess salt when in the Ocean. When in freshwater, bull sharks reduce the activity of their rectal gland to preserve these salts. The kidneys of bull sharks in freshwater go into overdrive, producing large amounts of dilute urine to avoid the balloon-popping scenario. Both the kidneys and the gills are triggered to actively uptake salts, while the liver changes urea production

On top of all this, bull sharks have to deal with the different densities of salt and freshwater. As anyone who has visited the Dead Sea will tell you, more salt = floaty (scientific term). So, bull sharks in freshwater reduce the densities of their livers to counter their reduced floaty-ness. Still, living in freshwater really does drag them down, which may be why they still mostly prefer the Ocean (can’t say we blame them).  

Bull sharks move between freshwater and saltwater. Explained by Ocean Generation, leaders in Ocean education.

Why do these species matter? 

These fish, as with our rivers, are great connectors. Their journeys are important to all those they encounter. By travelling between the separate biomes, they transport nutrients and link ecosystems, strengthening them.  

They are used as indicators of water quality and ecosystem health and provide food sources. Something harder to measure is their cultural importance, which resonates through many different social histories – they bring us closer together as well.

The challenges of moving between the Ocean and its fresh-water fingers are staggering. Yet these fish tackle it head on.  

Which do you find more impressive; the salmon battling bears and waterfalls to return to its river home; eel larvae drifting thousands of miles and swimming back, changing their whole body to tackle each step; or the bull shark that is just as at home in the heart of the Amazon as a reef in the Indian Ocean?

From the legend of the salmon, to the mystery of the eels, to the euryhaline hero the bull shark, these fish are truly conquerors of the coast.  

Book recommendations from our Marine Scientist 

When I am writing my articles, I use a variety of sources. One of the most engaging are the books. Here are a few I used for this article, do let us know if you have a read, and watch out for more recommendations.  

Blowfish’s Oceanopedia 

Salmon by Mark Kurlansky

Sharks of the World  

Additional sources:
*Peters, W. C. H (1852): Hr. Peter legte einige neue Säugethiere und Flussfische aus Mossambique vor. – Bericht über die zur Bekanntmachung geeigneten Verhandlungen der Königlich Preussischen Akademie der Wissenschaften zu Berlin. Aus dem Jahre 1852. Berlin, pp. 273–276. (not available online)

Why is the sound of coral reefs important? Explained. 

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Why are rivers important?

Why are rivers important? Posted by Ocean Generation.

From the creek whispering through a forest, to the confusion of huge currents twisting against each other in the channel. These flowing waters connect ecosystems, cultures, and continents — and ultimately, they connect us to the sea. Join us to explore why rivers are important.  

Read about the wider water cycle and how rivers fit into it here

Why are rivers amazing? What is an estuary? And what are the threats to these wet wonders? 

What are rivers 

Let’s start with a quick definition. Rivers are large, natural flowing streams of water. They have banks on either side, they have a source and a mouth. They meander through every continent, from a few kilometres to thousands long.  

Which is the biggest river?  

What does ‘biggest’ mean? Let us start with length, and to answer that, let us start with another question: where do rivers start? Finding where a river begins is notoriously difficult.  

It’s tricky to work out where that first drop comes from. Some rivers begin from a lake or a melting glacier. Others, like the Danube in Europe, start from a spring (water bubbling out of the ground). 

River origin leads to debates over which the longest river is – the Nile or the Amazon 

The Guinness Book of World Records gives the award to the Nile but does concede “which is longer is more a matter of definition than simple measurement”.  

The Nile, in Africa, has been estimated as great as 7,088 km (4,404 miles) in length, and the same paper puts the Amazon, in South America, at 6,575km (4,085 miles). 

However, a quick search will reveal some debate. 6,650 km (4,132 miles) is more commonly quoted for the Nile, and 6,400 km (3,976 miles) for the Amazon. 

Explorers are always trying to prove otherwise, measuring in a different way, from a different point, to a different point. 
We are #TeamNile.

Next, there is the deepest river in the world: the river Congo.  

It reaches depths of 220m. That is about as deep as the world record for SCUBA diving. By that depth there is little light, and the pressure from the water above is equivalent to having three adult orcas lying on top of you.  

The Amazon stands alone in the amount of water it gathers.  

Once rivers start their journey, they gather in momentum on their mission back to the Ocean. More precipitation and groundwater help fuel their flow, and other streams, known as tributaries, join it along the way.   

Approximately 209,000m^3/s of water enters the Atlantic from the Amazon. Imagine 75 hot air balloons filled with water, every second. This is equivalent to almost 20% of the total global river discharge, the total volume of water rivers release into the Ocean.  

The Amazon is more than the Nile, the Mississippi, in the USA, and the Chang Jiang (Yangtze), in Asia, combined. The brown waters can be seen as far as 100km (62 miles) out to sea, which provided an important navigation tool for sailors hundreds of years ago.  

The biggest rivers on Earth, posted by Ocean Generation.

Where are estuaries? 

Where the river reaches the Ocean, the interface is an estuary. They usually have a mix of fresh and salty water, known as brackish (there are some examples of freshwater estuaries in the Great Lakes of North America). 

Estuaries are highly productive, unique ecosystems. For many different animals they provide food, places to breed, nursery grounds and hosting migratory species.  

But why do rivers matter? 

Rivers are important, as fresh water is key to all life. Rivers have influenced our world historically, geologically and culturally. They support life where it would otherwise be unviable, on land and in the Ocean. They are the ultimate connector. 

Approximately 40 trillion cubic metres of water enters the Ocean from rivers every year. But it doesn’t come alone.  

As water moves over the land, it picks up hitchhikers (such as ions, making the sea salty – see more here). Material dissolves into the river, or the water pulls it along. These can lend colour to the river waters (and often their names). 

There is the Rio Negro in Brazil, named due to the humic acid from decomposing vegetation colouring the water black. The Red Rivers in Peru and North America, from the small pieces of rock containing iron oxides. The Drina in central Europe is green due to the limestone it flows over and the Hwang Ho (Yellow River) in China is named so because of the loess (a type of soil or sediment) it carries. 

They do more than just look good; these multicoloured masses are changing the world. 

Freshwater is key to all life on Earth. Posted by Ocean Generation.

How do rivers change the world? 

Flowing over rocks, mud and sand, each particle that the waters pick up change the course of the river and the shape of the land. Look around where you live, you can usually find the fingerprints of water at work.  

Rivers can cut away land and form new land, depositing the sediment it has picked up on the bank or in deltas where they meet the Ocean.  

The Colorado River, in North America, has produced the most remarkable example, carving away the landscape to produce the Grand Canyon, while the Nile Delta shows us how rivers build land too.  

The waters are full of nutrients, iron, nitrates and other essential building blocks for life. When these enter the Ocean, life flourishes.  

How are rivers and estuaries important for us? 

Rivers are incredibly important for one species in particular: us.  

The first great civilisations all rose up on rivers. The Nile, the Indus, the Tigris and Euphrates and the Huang all supported some of the earliest great cities in human history. Think of a big city – if it isn’t on the coast, we bet it is on a river. 

Rivers provide food: the last two very long uninterrupted rivers in Southeast Asia, the Irrawaddy and Salween, provide 1.2 million tonnes of catch annually and support agriculture of over 30 million people. In the US, approximately 68% of the commercial fish caught were caught in estuaries. 

The water rivers carry is crucial for drinking, domestic use and agriculture. More recently, we use it for power and industry, and transport.  

Rivers have held a central place in culture as well, connecting us and our world metaphysically.  

The Whanganui river in New Zealand has been regarded as an ancestor by the Māori people for centuries, and the Ganges is upheld as a place of healing and purity, personified by the goddess Ganga. In Japan, Shinto beliefs hold that each river has its own divine guardian, the Kawa-no-Kami.  

Across many different cultures, rivers have been celebrated and protected.  

Why do rivers matter? Posted by Ocean Generation, leaders in Ocean education.

What are the threats to the rivers? 

As much as rivers have impacted human civilisation, we have had our impact on them.  

Changes to our water cycle due to climate change have reduced the resilience of our rivers as they experience larger variations in flow. Add that to pollution, developing on their banks, extracting their flora and fauna and even stopping their flow – rivers have had it tough. 

In order to harness the power of our rivers, we have been interrupting their flow. Just 23% of rivers over 1000km long flow uninterrupted into the Ocean, broken up by an estimated 2.8 million dams. 

The water rivers carry is crucial

How does pollution affect rivers? 

It is important to realise there are lots of different types of pollution. The first and most obvious is big pollution – plastic, waste, shopping trolleys – that kind of thing. This rubbish can damage the life in the river itself, spoil the water for use and clog and disrupt the water flow.

The other kind of pollution is the small stuff – chemicals, microplastics and pharmaceuticals. These can disrupt aquatic wildlife, make the water unsafe to drink and accumulate through the food chain.  

The Ganges, in India, is now a stark example of river pollution. In Hinduism, the river is personified as the goddess Ganga, the goddess of purity.   

Just 37% of sewage is treated before entering the river. The banks are lined with tanneries, slaughterhouses, textile mills, chemical plants and hospitals. The waste that fills the river has an estimated 66% occurrence of waterborne disease and contains super-bacteria resistant to antibiotics.  

How are estuaries under threat? 

Estuaries face many of the same threats as rivers. An estimated 55% of global wetland areas has been lost since 1900, due to developing coastal areas. These wetlands provide unique habitats for their inhabitants, who often are not suited to either the freshwater or marine environments.  

We also benefit from the carbon dioxide absorption, offsetting our emissions, and the reduction in the risks of flooding and coastal erosion. 

But we are poisoning them too. Chemicals – pesticides and fertilisers – used in agriculture, are washed into rivers and accumulate in estuaries. This leads to nutrient overloading, or eutrophication, with harmful algal blooms appearing. When these die, the decomposition uses up the oxygen in the water – impacting the animals living there.

Estuaries absorb carbon dioxide. Posted by Ocean Generation

How can we look after our rivers? 

Everything is connected, which means you can make a difference from anywhere. Simply being aware of the connection you have with the Ocean is an important step. You can look after it, wherever you are.

Rivers connect us directly to the Ocean. A hot take? All life is essentially marine – everything is connected to and dependent on the Ocean. 

Along with estuaries, they provide important habitats, give us the water we need to survive and bring us closer together through transport and culture. But they are threatened in our new world. As ever, being aware is such a crucial first step to solving any issue.  

Educate others:  

  • Share information about river conservation and encourage others to take action. 
  • Engage in local initiatives that promote sustainable water management practices. 

Join community and advocacy events:

  • Participate in local river clean-up events to help maintain waterways and raise awareness 

Advocate for sustainable practices:

  • Support policies that protect rivers from pollution and over-abstraction 
  • Promote low-impact renewable energy to preserve free-flowing rivers 
  • Be aware of what you use. Harsh chemicals for cleaning and gardening will eventually enter our Ocean. Check your shampoo for harmful chemicals and microplastics. 

Next time you are by a river, take a moment. That is a direct line to the Ocean. See if you can understand the connection humans have felt with rivers throughout our history. Wonder at the power and beauty. Appreciate the importance of our rivers.  

You can make a difference from anywhere.

Why is the sound of coral reefs important? Explained. 

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What is the water cycle?

Why there is no water cycle without the Ocean.

Our planet is known as the blue planet, over 70% of it is covered in water, most of which is the Ocean.

This water shapes our landscapes, influences where life thrives, affects the health of our Ocean and the weather in our skies. 

The Ocean is always closer than you may think (not in a sinister, about-to-jump-out-at-you way. It’s more of a realising-it-is-Thursday-and-the-weekend-is-only-round-the-corner-kind-of-way). 

Take a moment, think: what is different from the water you drank this morning (if you haven’t had any, this is your reminder to drink some) and the water lapping up a warm tropical beach? Every drop of water, from what’s come out of your tap to the water five kilometres deep in the middle of the Pacific, is connected.   

It is all just at different points in the water cycle. 

How does the water cycle work? 

There are four processes that drive the water cycle: evaporation, transpiration, condensation and precipitation.  

How does the water cycle work? Explained by Ocean Generation.

Water is warmed and evaporates, becoming water vapour. Amongst the many good things plants do, they release water into the atmosphere through transpiration. These two processes are responsible for putting water vapour in our air, our atmosphere.  

Water vapour is invisible.  

The steam we see when we boil the kettle (or the clouds in the sky) is water becoming liquid again, on contact with the cooler air. That is condensation, the transition back from gas to liquid. When enough of this cloud cools and turns to water, it will clump together and fall as precipitation (snow, hail and rain).  

How is the Ocean connected to the water cycle? 

This water then starts its journey back to the centrepiece of the cycle: the Ocean. 

The Ocean holds 97% of the Earth’s water – approximately 1.34 billion cubic kilometres. 86% of evaporation is from the Ocean, and 78% of precipitation re-enters the Ocean, directly. You can’t have the water cycle without the Ocean. 

Ice holds 2% of global water and just 0.001% is in the atmosphere – that is all the clouds in the sky.  

But if we add all that up, there’s a little still on the table – or more accurately, on land. That is the groundwater, lakes, swamps and the rivers. Rivers make up only 0.0002% of the total water on Earth.

The Ocean holds 97 percent of water. Posted by Ocean Generation, leaders of Ocean education.

What does the water cycle do? Why is it important? 

There are five main points of importance for the water cycle: 

1. Regulating Climate:  
The water cycle helps distribute heat around the globe, influencing weather patterns and climate conditions. It absorbs and releases energy during evaporation and condensation, which affects temperature and weather. 

2. Sustaining Ecosystems:
The water cycle provides the water necessary for plant growth and supports all forms of life by delivering freshwater to ecosystems through precipitation.

3. Shaping Landscapes:  
The water cycle contributes to erosion and sedimentation, reshaping geological features over time. 

4. Circulating Minerals and Nutrients:
Water transports minerals across the globe, enriching sea and soil and supporting plant life. 

5. Maintaining Freshwater Supplies:
The cycle replenishes freshwater sources, such as rivers and lakes, which are essential for human consumption and agriculture. 

Imagine a world without a water cycle – what would it look like?  

Why is the water cycle important? Explained by Ocean Generation.

How is the water cycle changing 

Human activity is interfering with the hydraulic cycle at every stage.  

Deforestation means less trees to transpire and absorb rainfall. Urbanisation interrupts drainage and can increase surface runoff. When it rains, the water that would have been absorbed by the ground now hits tarmac and runs down the road. 

The single greatest threat to the water cycle, and therefore to all life on Earth, is climate change.  

How is climate change impacting the water cycle?  

Climate change is intensifying the hydraulic cycle. Higher temperatures lead to more evaporation, more water vapour in the atmosphere, which results in more intense storms and rainfall. At the same time, droughts are becoming harder to predict and more severe.

These changes directly threaten our lives. 

Water related events from 2024
2024 Summary Report – Global Water Monitor

Water is the life blood of our planet, and the water cycle is the pulse that keeps it alive. 

The hydraulic cycle regulates our climate, fertilises and maintains our ecosystems and shapes our world. We are changing it through our actions and activities.  

Understanding this cycle is the first step, but acting to protect it is the most important. The question is: what will we do to safeguard the blue heart of our planet? 

Why is the sound of coral reefs important? Explained. 

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Why is the Ocean salty?

Why is the Ocean salty? Explained by Ocean Generation

Everyone knows the Ocean is salty. But how did it get salty? Where did the salt come from? Is it getting more salty?  

These are all great questions to bring up as you ask for the salt over dinner. And after this explainer, you can answer them.  

Why is the Ocean salty: Explained 

Imagine a bowl. Now pour some slightly salty water into the bowl and put it into the sun on a hot day. Eventually, the water will evaporate, leaving that little bit of salt behind.  

Now, add some more slightly salty water to the bowl. The left-behind salt dissolves and mixes, making saltier water. Leave it in the sun again, the water will evaporate and leave salt behind. If you now attach a constant stream of slightly salty water into the bowl, you have a little model of our Ocean.  

Just like in the above example, rivers (the stream) bring tiny amounts of salt into the Ocean (the bowl) and the sun evaporates the water, leaving behind the salt. These amounts have built up over huge periods of time.  

Why is the Ocean salty: Explained by Ocean Generation

Where does the salt in the Ocean come from? 

Most of the salt in our Ocean comes from rocks on land. Carbon dioxide in the atmosphere dissolves into rainwater, making it slightly acidic. When it rains, this slightly acidic water can dissolve the rocks it falls on and over, in the form of ions (charged molecules).  

These ions, mostly sodium and chloride, are carried into rivers, which carry them into the Ocean.  

Some salt also comes from volcanic activity, where elements from the Earth’s core can be released into the Ocean through underwater volcanoes and hydrothermal vents.  

Why aren’t rivers salty? 

Rivers are, very slightly salty. Depending on what the water has run over on its journey (rocks, decomposing plants, your ex’s belongings etc.), the contents of each river, including salt levels, varies. 

For water to be considered freshwater, its salt content must be less than 0.05% salt (saltiness is also commonly shown as parts per thousand or ppt: 0.05% is 0.5ppt). This means freshwater can still have a little salt in. 

Between 0.05 and 3% salt content is brackish water, and saltwater is between 3 and 5% salt. Above 5% (or 50ppt) salt is brine.

Where does the salt in the Ocean come from: Explained by Ocean Generation.

What are the saltiest bodies of water in the world?  

One of the saltiest bodies of water is the Dead Sea. It was cut off from the river Jordan by damming in the 1950s, so there is no significant freshwater input. This means the water is gradually disappearing, as the water level drops close to 1.21 metres (4 feet) every year.  

Think back to our bowl of water example – the water evaporating leaves its salt behind, so the sea is getting more salty. Salinity is roughly 337ppt (33.7% salt) – ten times the average of the Ocean.  

But it isn’t the saltiest – that title goes to the Gaet’ale Pond in Ethiopia. It is a volcanic spring, with a salinity of 433ppt. You wouldn’t want to swim there – CO2 bubbling up presents the risk of suffocation and the hot, acidic water could leave painful burns.    

The saltiest bodies of water on Earth
Gaet’ale Pond photo by A.Savin

Does the Ocean vary in saltiness? 

Yes. Where there is more freshwater entering the Ocean, it’s less salty. This can be in places that rain a lot, have lots of rivers entering, or have ice melting. On average the Ocean has a salinity of 35 ppt. 

Have a look at the picture below. The red areas show high salinity, purple areas are low salinity. Try and work out why each area is the colour it is.

Snapshot of Ocean salinity
Snapshot of salinity on 2 March, 2025 as observed on SOTO.

The Baltic Sea is very enclosed, has lots of river input and rain, and little evaporation, so the Ocean surface can be around 10ppt. The Red Sea is much higher, 40ppt. This is due to very little rain or river input, and high evaporation.  

Is the Ocean getting saltier? 

The Ocean is now more in balance. If we go back to our bowl example, there is a bit we didn’t tell you about. Salt can mineralise at the bottom of the bowl – solidifying into rock, leaving the water. The amount of salt that mineralises is the same as the amount entering, so the Ocean stays the same level of salty.

So, with the next salty mouthful of Ocean water you get – thank the rocks and the rivers (and the rain and the sun).

Why is the sound of coral reefs important? Explained. 

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Galápagos Under Threat: Conservation, Climate Change and Hope

Galapagos under threat: Conservation, climate change and hope. Posted by Ocean Generation

Approximately 926 km (575 mi) off the coast of Ecuador lie the Islas Encantadas: the Enchanted Islands.

Better known as the Galápagos Islands, this collection of islands is named after the tortoises that once covered their shores.

Now, fewer in number (reduced to 15,000 from an original 250,000), these giant shelled residents reflect the degradation that the islands are experiencing. 

However, not all hope is lost. As our knowledge and appreciation of these incredible ecosystems has advanced, the Galápagos tortoise and the Galápagos Islands are becoming successful conservation stories. 

What is so special about the Galápagos Islands?

Below is a quote from the renown naturalist Charles Darwin. He is attributing the inspiration of his theory of evolution to the animals of the Galápagos Islands. Indeed, they are described as a ‘laboratory for evolution’, as they have a small number of species in distinct habitats, making them easy to study. 

Explore who Darwin was and how the Galápagos featured in his work here

“I have been now ever since my return engaged in a very presumptuous work and which I know no one individual who would not say a very foolish one. 

I was so struck with distribution of Galápagos organisms and with the character of the American fossil mammifers (AKA mammals) […] At last gleams of light have come, and I am almost convinced (quite contrary to opinion I started with) that species are not (it is like confessing a murder) immutable.”- C Darwin, 1844 to Hooker 

The Galapagos Islands are a laboratory for evolution. Posted by Ocean Generation.

Starting with Darwin’s visit in 1835, the islands have continued to be a focal point for scientific research and tourism.

Carrying his legacy are Peter and Rosemary Grant in 1973.  The two scientists lived the dream, moving to a remote island and watching birds. They studied the finches of the Galápagos and how populations responded to environmental conditions (for example, drought). Their observations were the first measurements of evolution in action.  

Made a UNESCO World Heritage Site in 1978, the Galápagos Islands are a place that showcases the wonders of the natural world.  

The unique species capture the imagination. They also act as a reminder of the stewardship humans have for our natural world.  

What threats do the Galápagos face? 

The Galápagos biosphere face human-made threats. Invasive species, direct human impacts such as building and pollution, climate change and overfishing all contribute to the decline of the species that make the islands unique.

Modern threats facing the Galapagos, posted by Ocean Generation.

How do invasive species threaten the Galápagos Islands? 

Humans have explored the world, linking remote places like never before, and  with us, we have brought some hitchhikers. According to the Charles Darwin Foundation, there have been 1,978 introduced species in the Galápagos, and of these, 1,898 have become established on the islands.  

Some were intentional: early pirates left goats and pigs on the islands as a food source they could come back to. Later, ornamental plants were brought for gardens, and cats and dogs for companionship.  

Others were stowaways. Rats and fire ants are two examples that managed to catch a ride into this haven, via ships or in delivered goods.  

This has made life harder for the residents. The Galápagos tortoises now have to compete with herds of goats for the vegetation they eat and hatchlings can be attacked by fire ants, cats and rats. Blackberry bushes out-compete native plants, killing off more food for the tortoise. Spanish cedars (a mid-sized tree) grow in thick stands making it challenging for the tortoises to gain access.  

Their world is changing faster than they can keep up with.  

What direct human impacts affect the Galápagos? 

More people live on and visit the Galápagos islands than ever before. The population has grown by 300% since 1990 and in the first half of 2024 alone the Galápagos accepted 142,473 visitors. 

As humans settle, we use land for agriculture and residence, reducing the land available for resident animals. This phenomenon is called land-use-change and is one of the biggest threats to global biodiversity today.  

The Galapagos thrives because of the Ocean

How is pollution impacting the Galápagos Islands?  

The islands waste collection grew 66% over the last decade to 28.6 tonnes per day, which needs shipping back to the mainland.  

But it is the waste that isn’t collected that causes more of an issue. According to Plastic Pollution Free Galápagos, over 8 tonnes of plastic is removed from the beaches each year, and 38 species have been entangled in or ingested plastic. Much of this plastic pollution this comes from the mainland, following the same route as the residents’ ancestors.  

How is climate change impacting the Galápagos Islands? 

The Galápagos thrives because of the Ocean surrounding it. Fed by nutrient-rich currents from the deep, the Ocean is full of life.  

However, climate change is slowing Ocean circulation, increasing the acidity and lowering oxygen levels of the water, reducing the amount of food supporting life on these islands. It also interferes with El Nino.  

What is the El Nino event?  

El Nino is a naturally occurring event, characterised by changes in Ocean upwelling and climate.  

Climate change is predicted to vary the strength and frequency of this event. Species on the Galápagos islands have adapted in incredible ways to deal with El Nino. For example, marine iguanas can shrink; reabsorbing bone mass, to deal with the scarcity of food.  

Climate change has major influence over the way our planet functions, coupled with the loss of population and resilience caused by other factors, populations will be stressed more than before.  

Marine iguanas at the Galapagos shrink to deal with food scarcity. Posted by Ocean Generation.

How does overfishing impact the Galápagos? 

The waters of the Galápagos are exceptionally rich and contain some of the highest densities of reef fish anywhere in the world.  

Largely, high densities of sharks (lots of sharks usually means a healthy Ocean). It is also a key spot for the largest fish in the Ocean, the whale shark – with 700 adult females passing through every year, most of them pregnant.  

We suspect this could be the location whale sharks come to give birth – hidden around the Galápagos could be the nursery for baby whale sharks!! 

Fishing has destroyed the majority of the coral reefs in this archipelago (an extensive group of islands), and sharks are targeted for their fins.  Hammerhead populations have seen a 50% decline since 2000. 13 of 28 species tracked over the last 20 years have declined sharply. 

In 2020, the tag of a whale shark called Hope suddenly logged fast movement above the surface of the water, indicating she had been caught by a fishing vessel. In 2017, a fishing boat containing the fins of 6,620 individual sharks was seized.  

The fish lover in us doesn’t like this. Losing sharks and habitats can disrupt the ecosystem, meaning less fish for feeding people. Most people like people, so most people also won’t like this.  

The Galapagos may be the nursery for baby whale sharks

What is being done to protect and restore the Galápagos Islands? 

But the Galápagos is proving we can make a difference.  

As a focal point for nature and evolution, it is only fitting that the Galápagos Islands are also a focal point of conservation efforts.  

Tourism is utilised to support the islands, with an entry fee of $200 per person. 40% of this goes directly to conservation efforts, ensuring the attraction of the islands is preserved by those attracted to it.  

Conservation efforts in the Galápagos: 

Conservation efforts use camera traps, satellite tags and intense gardening to give the natives a hand.  

The Galápagos Conservation Trust is spearheading an incredible citizen science project, Barcode Galápagos, aiming to describe the genetic profile of all species in the Galápagos. Employing local people, the venture will enable identification of new invasive species, tracking of the health of the Galápagos and tracking of illegal pet or shark fins. 

In light of the impacts of overfishing, Ecuador has protected 198,000 square km in the Galápagos Marine Reserve, including a 30,000km2 area where any fishing is prohibited. Research is being used to guide fishing practices. The aims are to reduce by-catch (the accidental trapping of unwanted marine creatures by commercial fishing nets) and waste. This ensures sustainable fishing practice, producing more fish with less effort. 

For our Galápagos tortoises, new conservation efforts aim to eradicate the invasive species threatening them, and even bring back species that were driven to extinction. 

Genetic analysis of surviving tortoises on the islands has found traces of Floreana tortoises, a species declared extinct in the 1850s. Through selective breeding programs, the Floreana Giant Tortoise could soon be roaming the islands again. 

Project Co-Galápagos targets a growing global issue – dependence on tourism and how to make it more environmentally friendly.  Co-Galápagos aims to be the global example of developing local communities in symbiosis (what a great word) with nature.

What does symbiosis mean? Symbiosis the interaction of different organisms living in close physical association, but in benefit to them both. 

The Galapagos thrives because of the Ocean

How does the Galápagos help us protect our world? 

Our abilities to understand the natural world have increased since Charles Darwin first sketched a marine iguana. We know and understand so much more about the Galápagos Islands, and the world, than we once did.  

This enables us to better protect it. The Galápagos are a unique environment due to their isolation, distinct habitats and rich biodiversity. They give us a microcosm of our planet. Charles Darwin realised this, and the islands gave him a chance to better understand the world by observing them.

Now, our world is changing, and again the Galapagos is the perfect place to understand the effects of those changes. 

The Galápagos Islands have provided inspiration in our understanding of the natural world, they are giving us the chance to understand how best to protect it.  

Why is the sound of coral reefs important? Explained. 

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Charles Darwin’s Galápagos Voyage and Theory of Evolution 

Charles Darwin’s Galapagos Voyage and Theory of Evolution. Posted by Ocean Generation.

A fresh breeze, the sounds of gulls calling, cold sea spray touching the cheeks, the slightest hint of rotten eggs in the air.

What was going through the mind of 26-year-old Charles Darwin on 15 September 1835, as he stood on the deck of HMS Beagle with the shapes of the Galápagos islands approaching? 

His letters home suggest two things. First, that he was homesick. Understandable after nearly four years away from England, which he had left at 22 years old – he truly was the pioneer of the gap year. He was also incredibly excited.

What Charles Darwin observed during his five week visit to the Galápagos would plant the seeds that would eventually grow into his Theory of Natural Selection 

In this article we will explore who Darwin was, how he came to be on the Galápagos, and the sparks of inspiration that he found there for his theory of evolution.  

Who was Charles Darwin? How did he end up on the Galápagos? 

Charles Darwin was nearly a little-known priest in Shropshire, in England. His father wanted Charles to get good employment, either following his footsteps to become a doctor or to become a man of the church. Aged 16, his father sent him to medical school in Edinburgh. His foray into the medical world was brief, however. After witnessing the brutality of surgery without anaesthetic (on a child), Charles knew he was not to be a doctor. He left the course after only two years.  

In those two years, Edinburgh did give him some important foundations; Darwin was taught geology, biological classification and taxidermy. He was also exposed to the radical ideas of the day. These denied the Divine design of humans and suggested that animals shared human mental abilities, like thinking, remembering or making decisions.  

Charles Darwin and the HMS Beagle, posted by Ocean Generation
HMS Beagle image from The Popular Science Monthly, Volume 57

On leaving Edinburgh he went to Christs College, Cambridge University, to complete a degree and take holy orders – ministry beckoned. He breezed through the degree and enjoyed his time at Cambridge. He would go out drinking, shooting and beetle collecting. College folklore claims the sounds of his shotgun would ring out as he fired blanks to extinguish candles in his rooms. 

It was at Christs that he met Professor John Stevens Henslow. Professor Henslow encouraged discussion around natural philosophy and introduced Darwin to some of the greatest minds of the era.  

It was Professor Henslow who got Charles Darwin on the voyage to the Galápagos. The Professor had been approached to be a naturalist and gentleman companion to accompany Captain Robert FitzRoy on a ship called HMS Beagle. His wife was… unwilling to let him go, so he instead recommended his protege, Charles Darwin.  

What was the mission of the HMS Beagle? 

The Beagle was sent on a two-year mission to map South America. It ended up being a five-year circumnavigation of the globe. Captain FitzRoy had completed a similar mission the year previous, and had thought a ‘naturalist’ would benefit the scientific productivity of the voyage. Few could argue with the scientific output of the Beagle.  

It was the Ocean that really started Darwin’s thinking about evolution.

While at Edinburgh Charles Darwin would collect sea slugs and sea pens, and was mentored by Robert Grant, an expert on sponges who encouraged him to study marine invertebrates. He began exploring classification and gave talks on his findings at the university.  

The Ocean got Darwin thinking, posted by Ocean Generation.
Sea pen image via Britannica

Onboard the Beagle, he made himself a plankton net with which he drew up trawls full of Ocean life. He wrote, “Many of these creatures, so low in the scale of nature, are exquisite in their forms and rich colours. It creates a feeling of wonder that so much beauty should be apparently created for such little purpose”.  

If the accepted worldview of the time was correct, and God made everything for humankinds’ benefit, why do these tiny organisms exist out at sea where no one sees them? The Ocean was creating Darwin’s first glimmers of insight.  

What are the Galápagos Islands? 

About 1,000km off the coast of Ecuador in the Pacific, are a group of islands called Islas Encantas, or Enchanted Isles. They are better known as the Galápagos.

The initial descriptions of the islands are at odds with the image of “enchanted islands”. The first man to discover the Galapagos, Fray Tomás de Berlanga, speaks of the inhospitality and lack of water on the islands.  

Captain Fitzroy, leader of the expedition Charles Darwin was part of, describes the first viewing of the Galapagos: “Black, dismal-looking heaps of broken lava, a shore fit for pandemonium”. Darwin himself compares them to the iron-foundries of Staffordshire, or the furnaces of Wolverhampton. Hardly flattering for either party.

So, not a tropical paradise. 

The Galpagos Islands is a volcanic archipelago off the coast of Ecuador. Posted by Ocean Generation.

The word galápagos comes from the Spanish word for saddle, the shape of some of the shells of the most famous residents of the islands – tortoises.  

Darwin reported that locals could determine the island tortoise by the shape of its shell. The implications of this did not occur to Darwin until later.

Unfortunately for science, and the tortoises, they were an excellent food source for long voyages. The Beagle collected 50, none of which made it back to England.  Tortoises became extinct on the island of Floreana in the 1840s, just ten years after Charles Darwin’s visit. However, careful genetic analysis and targeted breeding has created the possibility of de-extinction (click here for more). 

The names of the islands and the tortoises immediately hint at the special nature of the Galápagos.

Galapagos means saddle in Spanish.

From their discovery, the Galápagos were renowned for their rich biodiversity. 

Whalers came to benefit off the many sperm whales that gathered there, and tales of the lizards that lived there reached across the globe. 

It is important to clarify that Darwin was not struck with a bolt of genius immediately on seeing the islands.  

He was inquisitive, curious and observant about the natural world. He saw many things in the Galápagos, and documented and collected evidence he would later use to build and justify his arguments for evolution. 

But what was Charles Darwin’s theory of evolution? 

Darwin’s thinking was radical at the time. He was opposing the accepted position that species were ‘fixed’ – unchanging. This was tied into the strong Christian influence of the time – God had created all life, and it hadn’t changed since – with humankind superior to all. 

His work was an attack on the accepted views of his time: that man was supreme by divine making, and the order of the world was fixed. 

Observing the animals of the Galápagos and beyond, Darwin’s theory of natural selection proposed that the natural world was ever-changing, evolving.  

Within this, the idea that species change over time. Further, he suggested a world in which animals were not below humans, but simply different, surviving using different strategies.  

Darwin himself recognised that his theories opposed widely held beliefs. He likened publishing his work to confessing a murder. 

What did Charles Darwin find on the Galápagos? 

Darwin was in the archipelago (an area that contains a group of islands) for five weeks. During that time, he explored the islands, at one stage camping for nine days with only a few others, and collected specimens.  

Birds, reptiles, plants and plankton were all stashed in crates on board the Beagle. He was intrigued by what he found, writing in his journal, “the natural history of these islands is eminently curious, and well deserves attention.  

What’s the deal with Darwin and finches? 

If you have heard of Darwin, you have probably heard something about finches. He collected loads of finches from the Galápagos, and they became an iconic example of his theory of natural selection.  

The birds would even come to be named after the naturalist – Darwin’s finches. 

Darwin's finches are an iconic example of his theory of natural selection. Posted by Ocean Generation.
Drawing of the finches by John Gould, from “Voyage of the Beagle” , 1845

Far from being an example of his genius, the finches are an example of Darwin being human.  

He misidentified many of the finches he collected as blackbirds, wrens and “gross-bills”, and did not write down which bird came from which island. It was ornithologist John Gould of the Zoological Society of London who reported that this collection were all finches.  

After this realisation, Darwin looked again, and the differences in their beaks does lead him to commentone might really fancy… [that] one species had been taken and modified for different ends”. However, his poor documentation meant they could not be used as evidence in his work, and they do not appear in his book.  

Modern work has made the beaks of finches a poster child for natural selection. It was a clear visual example of the adaptions that can allow different animals to survive.  

On the Origin of Species: Darwin’s work, published 

Darwin held the Galápagos dear for the rest of his life. On The Origin of Species, his seminal work on natural selection, was not published until 1859, 23 years after returning to England.

The first sentence of the book affirms the importance of the voyage in developing his theory of evolution:  

When on board H.M.S. ‘Beagle,’ as naturalist, I was much struck with certain facts in the distribution of the inhabitants of South America, and in the geological relations of the present to the past inhabitants of that continent. These facts seemed to me to throw some light on the origin of species—that mystery of mysteries, as it has been called by one of our greatest philosophers.” 

In the interim, Darwin had been gathering evidence and forming arguments, bracing for the backlash and interrogation his theory would receive.  

On the Origin of Species, written by Charles Darwin is one of the most important scientific books.
Page from the 1859 Murray edition of the Origin of species by Charles Darwin.

How was Charles Darwin’s theory of evolution received?  

Darwin’s theories certainly made a splash.  

The book sold out the first edition before being released, and divided opinion.  

Predictably, the Church took a strong stance against it, along with some prominent scientists such as Darwin’s former Cambridge peer, Adam Sedgewick. International press put out cartoons and insults, often focused on the idea that humans descended from apes.  

But many scientists, especially geologists, supported Darwin’s work. Atheists were especially enthusiastic.  

Charles Darwin kept in close correspondence with supporters and opponents alike. Debate continued for decades after, until his theory was general accepted in the 1940s. 

The book went to six editions during Darwin’s lifetime and is now seen as one of the most important scientific books ever written.  

It fundamentally changed how people viewed the natural world and the place of humans within it; a lifetime’s work, from a man that explored and observed, inspired by the Ocean and the Galápagos.  

Quotes from Charles Darwin: Even the best scientists have bad days  

We can all relate to Darwin, on a very personal level, after reading some of his journal inserts and letters. Here are a few quotes that remind us even the brightest minds have down days:  

“But I am very poorly today & very stupid & hate everybody & everything.” – C. Darwin, letter to Charles Lyell 1861 

“I am rather low today about all my experiments, – everything has been going wrong” – Letter to W. D. Fox 1855 

“I beg a million pardons. Abuse me to any degree but forgive me- it is all an illusion (but almost excusable) about the Bees. I do so hope that you have not wasted any time for my stupid blunder. – I hate myself I hate clover & I hate Bees-” Letter to John Lubbock, 1862 

“I am very tired, very stomachy & hate nearly the whole world. so good night, & take care of your digestion which means Brain” – Letter to T. H. Huxley, 1860 


Thank you to Prof David Norman of Christ’s College for his time and writing. 

Why is the sound of coral reefs important? Explained. 

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