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Off the coast of Oregon, a fisher has helped rescue a young humpba…

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Between Tides is my personal column, normally for paid subscribers only. Think of it as an opinion column rather than one of my more rigorous science or policy pieces. It’s a chance for me to write down what I’m thinking or feeling, and hopefully, by the end of each one, there’ll be something useful for you, too.

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Something rather encouraging is happening beneath the water in Dorset. Bare patches of seabed, left behind by mooring chains scraping through seagrass, are gradually turning green again. The reason? It’s rather simple.

As some of my regular readers will know, I’m obsessed with krill at the moment, so after the incredibly disappointing end to this year’s …

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In rather disturbing news, a new UN report published yesterday estimates that human caused climate change has already reduced the ocean’s ability to absorb carbon by around 6%, compared with a world where we hadn’t changed the climate.

Around 30% of the carbon dioxide we pump out is currently being absorbed by the ocean, along with about 90% of the exces…

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How many protected areas has it created so far? None.

Only members that have formally joined can agree on one, and they haven’t held their first decision-making meeting yet. In January 2027, members will meet in New York for the first time.

What I don’t know is how long it will take to agree on the first area, or even where it will be.

This is a three-minute explainer on the High Seas Treaty.

What should I explain next?

Sources

• [The High Seas Treaty, UN page:] https://www.un.org/bbnjagreement/en

• [Full text of the treaty:] https://www.un.org/bbnjagreement/sites/default/files/2024-08/Text%20of%20the%20Agreement%20in%20English.pdf

• [Who has joined (UN Treaty Collection):] https://treaties.un.org/doc/Publication/MTDSG/Volume%20II/Chapter%20XXI/XXI-10.en.pdf

• [The first meeting of members, 11–22 January 2027:] https://www.un.org/bbnjagreement/en/COP/background

• [The first notice under the treaty’s sea-life sample rules (Ireland, July 2026):] https://www.un.org/bbnjagreement/en/notification-2026-002

• [High-seas protected areas set up so far:] OSPAR https://www.ospar.org/work-areas/bdc/marine-protected-areas/mpas-in-areas-beyond-national-jurisdiction and CCAMLR https://www.ccamlr.org/sites/default/files/91-03.pdf

• [How much of the ocean is protected:] https://iucn.org/press-release/202604/world-reaches-milestone-nature-10-ocean-now-officially-protected

• [Russia’s position, UN conference report (2023):] https://digitallibrary.un.org/record/4016005/files/A_CONF.232_2023_5-EN.pdf

The ocean is still full of secrets. Blue Planet 3 is coming out in a few days, and I genuinely cannot wait to hear the voice of my childhood once more, as Sir David shows us what’s going on beneath the surface.

Whilst we’re talking about secrets, did you know that there’s a whale that can grow to around ten metres long, and we only recognised it as a sep…

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Scientists in Japan have been running experiments where they’ve been putting pieces of plastic on the seabed and going back months later to see what happened to them. Some barely changed, while others had almost disappeared, and some of those samples were left more than five kilometres below the surface, far beyond the r…

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Finlay slept through the night last night, which hasn’t happened for a while. I woke up this morning feeling a bit more human than usual. It was still dark when I went downstairs to make myself a coffee. I had a bit of time before work, so I …

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An octopus can get into a fishing pot and help itself to the catch, and off southwest England, there are now so many of them that fishermen have been meeting scientists and government officials to work out how to make a living alongside them.

We’ve also got Atlantic currents recovering in a climate model, people doing more for sharks after swimming with …

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The Antarctic krill fishery has hit its 620,000 tonne trigger two years running. On Monday, CCAMLR’s 27 members begin two weeks of talks in Hobart, including on a replacement system that could allow a much larger fishery around the Antarctic Peninsula.

In January 2022, scientists aboard the National Geographic Endurance were off the South Orkney Islands when they came across hundreds of fin whales feeding on krill. They estimated at least 830, and possibly more than 1,100. Four commercial krill trawlers were fishing among them.

I spend a lot of my working life thinking about whales, so there’s something quite strange about that scene. Fin whales were nearly hunted to extinction during the twentieth century, yet here were hundreds of them back in Antarctic waters feeding together again, with fishing vessels working in the same water, competing for the thing the whales had travelled all that way to eat.

At first this sounds like quite a niche fishery story, but then you dive deeper and you’ve got krill near the base of one of the most interesting ecosystems on the planet.

Then you’ve got industry trying to catch it to produce supplements, pet food, salmon feed, that sort of stuff, and then you’ve got international politics, where they’re actually deciding how much to catch.

So there are really two things we need to consider: who’s catching the krill and who’s making the decisions.

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Between Tides is my personal column, normally for paid subscribers only. This one is open to everyone. Think of it as an opinion column rather than one of my more rigorous science or policy pieces. It’s a chance for me to write down what I’m thinking or feeling.

We went to stay with my parents at the weekend. A couple of years ago they retired to a little village in the New Forest. My dad took Finlay out for a walk with the dog, Meg. She’s a golden retriever, and a very curious one at that.

They were all walking through the forest, having a lovely time, and then Meg managed to come across and disturb a wasps’ nest.

Meg got stung. My dad got stung. A couple of wasps got inside Finlay’s dungarees.

I’d bought them from a charity shop for a pound because they were so wildly jazzy and colourful, outrageously seventies. I thought, oh, these would be fun. The first time I put them on him, it turned out they were the worst possible thing he could be wearing. The wasps got in from the top, made their way down to his legs and then got stuck in there.

He got stung fourteen times overall, on his legs, his face and his head.

We ended up in A&E because we were worried. I got lost and didn’t know where the entrance was, so I dropped Orkida and Finlay off at the ambulance bay doors. A paramedic walked in with her, and I proceeded to drive around and try to find a parking space. The signs were never obvious.

It wasn’t a gentle arrival, where we register him and let him play with the toys. It was rushing in through the back doors, where the critical patients go in. It turned out he was fine, but it was traumatic for all of us.

It’s really important to me that he doesn’t develop a fear of wasps, insects, bees and flies because of this.

The wasps were defending their nest. Then they got caught in his trousers, and their response was to sting and sting and sting. Understanding how it happened doesn’t change the fact that he was a two-year-old getting stung fourteen times.

He’s always loved bees. He has a fascination with them. My fear is that he’s now going to associate yellow and black with danger. Which, of course, is what those colours can signal. You see warning colours in bees, wasps and hornets, and in poisonous frogs. Their colours tell other animals there’s a danger there.

I want to explain how it all works, the reasons that they sting. That we need to take care and respect other animals, and that they have ways of defending themselves. How do you explain that to a two-year-old?

I like to snuggle up on the sofa with him and occassionally I’ll put on a wildlife documentary, but now I’m worrying that perhaps he’ll one day see a shark and then have a fear of sharks. Or a spider crab. They look a bit scary. Or an orca attacking a seal. How do I explain what’s happening while he’s watching it?

It makes me think about our fears and the way we act with nature. I wonder how much fear affects our response when we hear about sharks dying. They’re not smiley, happy and friendly like puppies and kittens and dolphins. How much of that starts before we’ve had a chance to understand them?

I’m in a privileged position, in that this is the world I work in. I’m very excited to teach him about it. He’s still only two, though, and I wonder how much I can explain now, and how much will have to wait.

I don’t want him to be scared of things before I’ve had a chance to explain them properly.

Between Tides usually goes to paid subscribers. If you’d like to read it regularly, you can upgrade below.

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Did Iceland just kill its last fin whale?

This is a three-minute explainer on Icelandic whaling. I’m going to be doing these more often. What should I explain next?

Between Tides is my personal column exclusively for paid subscribers. Think of it as an opinion column rather than one of my more rigorous science or policy pieces. It’s a chance for me to write down what I’m thinking or feeling, and hopefully, by the end of each one, there’ll be something useful for you, too.

Read more

The National Oceanic and Atmospheric Administration (NOAA) estimates that the main Hawaiian Islands population of false killer whales has been declining by about 3.5 per cent a year since 2013. On 16 September, it reported that two calves first photographed in February had both been seen again in August.

I spend most weeks looking at what is going wrong in the ocean. This week, enough of the evidence pointed the other way that I decided to give the whole Brief to good news.

Deep Dives

Two rare false killer whale calves were seen again in August

There are only about 140 false killer whales in the endangered population that lives around the main Hawaiian Islands. NOAA says just ten newborn calves have been documented in that population since 1999.

Staff from the Hawaiian Islands Humpback Whale National Marine Sanctuary photographed two newborn calves off Maui in February. One was swimming beside a female known as HIPc0363, which researchers at Cascadia Research Collective have followed since she was first seen as a juvenile in 2009. This is the first year they have recorded her with a calf, and they believe it is her first.

In August, staff from Captain Zodiac saw both calves again and contacted Cascadia. By then they were around eight months old and swimming strongly. NOAA says the first six months are an especially vulnerable period for young false killer whales.

Females generally reach reproductive age between eight and eleven years old, pregnancies last about 14 months, calves can nurse for up to two years and the available data suggest females usually give birth only once every seven to nine years. That can mean only four to seven calves across a female’s lifetime.

Read the NOAA Fisheries update

An oyster reef off South Tyneside survived its first North Sea winter

In October 2025, conservationists created a one-hectare native oyster restoration site off Whitburn, South Tyneside. Twenty specially designed reef cubes were placed on the seabed with 60,000 juvenile oysters and 100 tonnes of scallop shell, while 4,000 adult oysters were attached to the cubes. The structures give oysters hard surfaces to attach to and create shelter for other animals.

Nine months is too early to know whether a reef has been successfully restored, but it was enough time to see whether the oysters and the structures had made it through their first winter.

On 10 September, the Zoological Society of London (ZSL) reported the results of surveys by seven volunteer divers carried out in July, and all 20 cubes were still in place. ZSL said 99 per cent of the adult oysters attached to them were alive and healthy, juvenile oysters had survived the winter, and divers recorded fish, crabs, sea urchins, shrimps and squat lobsters using the reef.

Native oyster reefs disappeared from this part of the North East more than a century ago, and across the UK, ZSL says native oyster numbers have fallen by more than 95 per cent since the 1800s following habitat loss, over-harvesting, pollution and disease.

A study published in Ecosphere on 15 September gives us a much longer view. Researchers studied restored oyster reefs at Harris Creek in Chesapeake Bay six to ten years after restoration. The project covers about 1.4 square kilometres, and the researchers combined underwater video with high-resolution sonar to study both the reefs and the animals using them. The authors note that sonar can miss animals hidden within the reef or remaining still during a recording.

The habitat surveys found that restored reefs still had high oyster cover and more complicated three-dimensional structure years after restoration. In the smaller sonar comparison between restored and harvested reefs, the restored sites supported larger animals overall. Reefs restored using stone had the highest numbers of animals longer than 30 centimetres, while harvested reefs had more animals overall and more small schooling fish.

Read the South Tyneside update from ZSL

Pacific bluefin’s 2022 spawning stock was estimated at nearly twelve times its 2010 low

The stock assessment used in the International Scientific Committee’s latest Pacific bluefin status summary covers the period from 1983 to 2022. These are modelled estimates rather than counts of individual tuna.

The model put spawning stock biomass, the estimated weight of adult tuna capable of reproducing, at about 12,300 tonnes in 2010. By 2022, it was about 144,000 tonnes. That is nearly twelve times higher. Fishing pressure also fell substantially over the same period, particularly on younger tuna.

The international rebuilding plan had two stages. The second target was to get the spawning stock above 20 per cent of the level scientists estimate would exist without fishing. Pacific bluefin passed that target in 2021, and the 2022 estimate put it at around 23 per cent.

There’s also been a new management decision this month. At its annual meeting from 31 August to 4 September, the Inter-American Tropical Tuna Commission adopted new eastern Pacific catch measures for 2027 and 2028, along with an interim management procedure for deciding how future catches should change as the stock changes.

Read the latest Pacific bluefin status assessment

Quick Hits

Ships followed mandatory whale slowdowns 96 per cent of the time

Canada uses a mixture of mandatory and voluntary vessel measures for North Atlantic right whales in the Gulf of St Lawrence. The study here looked at the mandatory dynamic shipping zones. When a right whale is detected and a navigational warning is issued, vessels longer than 13 metres must stay at or below 10 knots in the affected zone.

A Marine Policy paper published online on 3 July 2026 analysed 11,509 journeys made by cargo ships, tankers and cruise ships across 49 slowdown periods between 2020 and 2023. Of the 3,944 transits through zones while a mandatory 10-knot restriction was active, 96 per cent were at or below the limit.

When vessels did go faster, the average speed was 10.54 knots, and none of the cruise ships in the study exceeded the limit during an active slowdown. The researchers also looked at speeds in neighbouring areas and found only small changes. The study measured ship behaviour rather than whale deaths, so it cannot tell us how many collisions the restrictions prevented.

Maryland gave common terns a floating place to nest

By 2020, fewer than 30 common tern nests remained in Maryland’s Coastal Bays. Conservation groups responded by putting a floating wooden nesting platform into the water to replace some of the sandy island habitat the birds had lost.

In its first breeding season, the raft held 23 nests and produced 22 chicks. During the 2026 season, biologists counted 376 nests there and another 84 on nearby Reedy Island, where natural habitat has also been restored.

Some birds that hatched on the raft are now nesting on Reedy Island.

New Zealand has extended limits on new Hector’s dolphin tourism permits

New Zealand’s Department of Conservation (DOC) announced on 11 September that it would place another ten-year moratorium on new marine mammal tourism permits around Banks Peninsula. Existing permits held by six operators in Akaroa and Lyttelton are unaffected, while the area covered by the moratorium has been expanded beyond Akaroa Harbour to waters around much more of the peninsula.

Banks Peninsula is an important stronghold for Hector’s dolphins, one of the world’s smallest dolphin species. DOC says around 15,000 remain and that research has found changes in behaviour and habitat use following repeated vessel interactions. The department says the wider area is intended to leave dolphins places where they can feed and socialise with fewer tourism and recreation vessels around them.

Scientists have described nine new sponge species in Alaska

On 10 September, NOAA Fisheries announced that scientists had described nine deep-sea sponge species from the Gulf of Alaska and Aleutian Islands that were previously unknown to science. The specimens came from annual bottom-trawl surveys dating back to 2012. There is an awkward bit to that: NOAA’s own research in Alaska has found that bottom trawling can remove and damage large sponges, with lower sponge densities still detectable years later.

The samples themselves have produced a lot of new information. One species was different enough for scientists to create a new genus, the category above species, for it. Another belongs to a group previously known only from tropical waters. The discoveries take the number of known sponge species in Alaska to 232, while researchers think many more remain unidentified in rocky deep water that normal bottom-trawl surveys cannot reach.

The genetic information from the new species has also been added to public databases used for environmental DNA, or eDNA, work, giving researchers more reference material when they analyse traces of DNA collected from seawater.

Read more from NOAA Fisheries

Hard Truth From The Sea

The bad news in the ocean can pile up so quickly that it starts to feel like the only direction of travel, and I think that’s why weeks like this matter.

Two rare whale calves are still swimming beside their mothers. Tuna numbers have climbed, ships are slowing down, terns are returning and oysters have survived a North Sea winter.

Each one shows us something that worked, now the challenge is to build on it.

If you fancy trying a paid subscription, it opens up the full archive, every investigation and back issue. If not, that’s honestly fine. I’m glad you turn up each week for this.

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See you next week.

Luke

A few months ago I put a date in my calendar where I wrote 'Iceland Ends Whaling'. It was my way of trying to manifest something (I've read a lot about the power of manifesting and thought I'd give it a crack).

I was in Reykjavik in June 2023 when Iceland suspended the hunt due to breaches of animal welfare law, and I shook fisheries minister Svandís Svavarsdóttir’s hand, thinking something had genuinely changed. But a month later the suspension was lifted, and the ships went back out and killed 25 whales (including an unborn calf) before the season ended.

On Sunday, ships Hvalur 8 and Hvalur 9 returned to Reykjavik harbour, ending Iceland’s 2026 fin whaling season, where 93 fin whales were killed in 94 days. The guns, harpoons and explosives have been taken off the ships, packed away for the winter, as they are each year, ready to be unpacked at the start of the next whaling season.

However, that season might not come, as the Icelandic government is preparing new whaling legislation, due to be introduced in February 2027, and the minister responsible has said it will contain a provision to ban whaling.

Hvalur still has a licence that would otherwise allow the hunt to continue through 2029, and Kristján Loftsson, comic book villain and owner of Hvalur, Iceland's only fin whaling company, has made it very clear that he does not intend to quietly accept a ban.

There is now a very real possibility, though, that among the 93 killed this summer was the last fin whale Iceland will ever kill commercially. For years I have watched people in Iceland fight this hunt. Scientists documenting what happens to whales after they are struck, Icelanders protesting, campaigners standing above the whaling station photographing bodies and brave activists climbing the masts.

I have also watched those same ships leave harbour time and time again, which is why I'm not quite ready to call this the end.

The date I chose in the calendar was Friday October the 23rd, so my manifestations aren't going to work this time, I don't think. But, I look forward to seeing what unfolds in the new year, and I hope that we finally get there.

No one was holding up a banner at the harbour this week saying WHALING IS OVER. After years of fighting for the end of whaling in Iceland, it might just be that a ship came quietly into the harbour, the engine was switched off, the harpoons were carried ashore, and that was that.

I really hope that is what's just happened.

It’s not the news you were hoping for, if you’re a fan of all things ocean. Cooling the planet would obviously still be an incredibly good thing, of course, and every tiny fraction of a degree we avoid truly does matter. It’s just that the ocean doesn’t respond in the way we would hope it might. Sea level can keep rising, reefs can be badly damaged along the way, and ocean conditions can keep changing long after global temperatures have started falling back down.

That’s what I’ve been coming to terms with this week, after reading through a new UN report.

I think we’ve sometimes talked about 1.5°C as like it’s a big old on/off switch. Stay below it and we’re okay, go above it and we’re buggered.

The reality is much messier than that, and that’s what this episode gets into.

I record Voice for the Blue because ocean stories deserve to be heard. I write Ocean Rising so those stories reach you each week. This is only possible thanks to a wonderfully supportive group of paying subscribers. If you find value here, please do consider joining them.

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I will be back in your ears soon.

- Luke

Wednesday 9 September was a long day. Just another day of ocean conservationing, really.

My first stop was Westminster, where Valentina Crast and the Sea Shepherd Global team were presenting their latest report on the grindadráp, the pilot whale hunts in the Faroe Islands, to MPs. My frustration came from knowing that this fight still has a very long way to go, despite all the evidence showing why the hunts should end. I hope to return to the Faroes later this year and meet some of the people who want change.

I then headed across London to Kanaloa House in Soho for the Ocean Photographer of the Year event, held by Oceanographic and Blancpain.

I walked around the photographs, lost in complete awe and wonder at what the ocean holds, until I reached Karsten Michels’ image of a mutilated pilot whale in the Faroe Islands. I was excited about the event because my day to day can be tough. I’m either campaigning to stop commercial whaling and captivity, or writing about the failing systems that are affecting the ocean.

Having that respite interrupted by an image of what I’d been talking to people about a few hours earlier was jarring, but I was also glad to see it. The ocean is, of course, filled with beauty, but it’s also full of horror, and hiding that from the people in the room wouldn’t tell its full story.

The overall prize went to Julien Anton for a photograph of a male seahorse with two tiny juveniles beside him in the waters of Mo’orea. Jenny Stock received the Female Fifty Fathoms Award, whose recipient is nominated by fellow photographers rather than entering herself.

Late that same evening, Iceland’s government published its parliamentary programme. A permanent whaling ban was in it, although not in the form some of the first headlines suggested.

That’s the lead this week. After that, two pieces of science that resurfaced in the news over the past few days: one modelling what thousands of offshore wind turbines could do to the North Sea, and another asking which organisms were actually carrying carbon down through the ocean. Two quick hits and a hard truth after that.

Deep Dives

Iceland has scheduled a review of its whaling law. A permanent ban is one of the options.

Iceland’s government has placed a full review of the country’s 1949 Whaling Act on its programme for February 2027. The official parliamentary programme says the bill will draw on a working group’s report about how whaling is governed and regulated.

It says particular consideration will be given to the group’s views on a permanent ban, and the review must consider questions under Iceland’s constitution involving freedom to work and property rights.

Those questions could affect what any ban covered, when it began, and what happened to licences already granted. The programme doesn’t say what conclusion the government has reached.

No bill has been published, and there is nothing yet showing what would be prohibited, when any ban might take effect or how the government would deal with licences already in place.

While the government prepared that review, the 2026 hunting season continued. Iceland’s Marine and Freshwater Research Institute advised catch limits that would allow up to 150 fin whales to be killed across two management areas. Around 80 fin whales (classified as Vulnerable on the International Union for Conservation of Nature’s Red List) have been killed so far this season.

The fin-whale hunt is carried out by Hvalur hf, the company run by Kristján Loftsson. In December 2024, Iceland’s outgoing government granted separate licences for fin-whale and minke-whale hunting. Hvalur received the fin-whale licence; a separate minke-whale licence went to Tjaldtangi ehf.

The government described the licences as covering a total of five years and being extended annually. It didn’t explain whether each annual extension required a new decision or happened automatically. The parliamentary programme also doesn’t say whether a future prohibition would apply to those licences.

A permanent ban has now entered Iceland’s formal parliamentary work. Whether the government will include one in its bill, and what it could mean for the current licences, remain unanswered.

Thousands of offshore wind turbines could change more than the wind above the North Sea.

Offshore wind is central to Europe’s attempt to cut the emissions warming the ocean. The turbines also stand in the sea, where their foundations and wakes can change the water around them.

Mongabay returned to that question this week, bringing two modelling studies from earlier this year back into the news.

A turbine affects the sea in two main ways. Its blades remove energy from the wind, reducing the force that the wind applies to the water below. Its foundation stands in the current like a post in a river, slowing the flow and creating turbulence. Both effects leave wakes that can travel beyond the turbine itself.

Nils Christiansen, Ute Daewel and Corinna Schrum published a study in Communications Earth & Environment on 13 January. They ran a detailed North Sea model using weather and ocean conditions from 2008 to 2017. One set of simulations represented wind farms operating or being built in 2023. Another represented a much larger possible layout in 2050. Everything that follows is model output, not a measurement of what the North Sea is doing now.

In the 2023 scenario, wind wakes reduced average surface-current speeds by around 10 per cent. Drag from turbine foundations had about half that effect. Together, the two kinds of wake produced reductions of 20 per cent or more in some areas containing several groups of turbines.

Temperature moved in both directions. Across the German Bight, reduced wind produced average summer surface warming of up to 0.05°C. Close to some wind farms, turbulence around the foundations pulled colder water upwards and produced local surface cooling of 0.15°C or more.

The 2050 scenario produced changes across a wider area. Average surface-current speeds fell by 5 to 15 per cent across much of the central and southern North Sea. The reduction exceeded 20 per cent in the German Bight, where the researchers said the combination of many turbines and naturally slow currents probably increased the effect.

Across most of the modelled area, the average sea-surface temperature rose by roughly 0.05 to 0.15°C. A few wind-farm areas in the German Bight cooled instead. The annual warming of around 0.1°C remained within the North Sea’s natural year-to-year variation of about 1°C. The authors also noted that it was roughly one tenth of the warming projected for the region from climate change this century.

A second modelling study, led by Jiayue Chen and published in the same journal on 14 March, followed the sediment. It found that wind farms could change the amount and direction of sediment moving through some places by up to 30 per cent. In the model, as much as 1.5 million tonnes of mud and 70,000 tonnes of organic carbon were redistributed each year. It also suggested that wind farms retained about 1.5 per cent of the sediment carried into the North Sea by rivers, changing where mud and carbon settled and how the open sea connected to coastal areas such as the Wadden Sea.

The results depended on water depth, currents, turbine numbers, location and the way the model represented some complicated processes. The researchers’ 3,000-metre result is therefore a comparison from one set of simulations, not a universal safe distance.

In those simulations, however, the mixing effects barely accumulated where the researchers assumed about 3,000 metres between turbines. At 1,000 metres or less, the model produced much stronger areas of turbulence. Turbines installed in the North Sea by 2023 were, on average, about 900 to 1,300 metres apart.

What reached a trap 1,000 metres below the South China Sea.

Cyanobacteria are tiny, single-celled organisms that use sunlight to make energy and take in carbon. For decades, many ocean models have treated them as poor at carrying that carbon into deep water. The usual reasoning is simple: large cells sink and small ones don’t.

The biological carbon pump is the name scientists give to the different ways carbon moves from sunlit surface water into the deep ocean. Once it gets deep enough, some of it can remain away from the atmosphere for centuries. Many models give larger phytoplankton, including diatoms, the leading role in that journey.

A paper published in AGU Advances on 30 August challenges that assumption. Eos highlighted it on 10 September, which is why an older set of samples entered the news this week.

The researchers studied one station in the northern South China Sea. A sediment trap moored at about 1,000 metres collected sinking material between June 2009 and May 2010. The team compared it with information about surface communities gathered during 19 research cruises between 2004 and 2015. This wasn’t a snapshot of the ocean today.

Different groups of phytoplankton leave different carbon signatures in the amino acids they produce. The researchers measured those signatures in the material caught by the trap and used a statistical model to estimate which groups had supplied the carbon.

The community at the surface changed with the seasons. Cyanobacteria dominated when biological production was lower, while larger microalgae became dominant when production increased. The balance was much more stable in the material collected at 1,000 metres. Cyanobacteria supplied most of the sinking carbon throughout the year, including when larger microalgae dominated closer to the surface.

The paper suggests two reasons. Carbon from larger microalgae was broken down more heavily as it passed through the ocean’s twilight zone, the dim layer between about 100 and 1,000 metres. Cyanobacteria could become caught inside larger clumps of material containing mineral particles. Those clumps helped carry the carbon down and may have protected some of it from being consumed by microbes. The researchers inferred that mechanism from their data; they didn’t watch individual cells make the journey.

This may help explain why colder parts of the ocean dominated by large phytoplankton don’t always store carbon more efficiently than warm, nutrient-poor waters filled with cyanobacteria. It doesn’t prove that the same process operates everywhere.

This was one year of trap material from one station in one basin, and the method hasn’t yet produced the same result in the North Atlantic or Southern Ocean, and the authors say its wider importance still needs to be tested.

At that northern South China Sea station, cyanobacteria supplied an estimated 67 per cent, plus or minus 2 per cent, of the sinking organic carbon collected at 1,000 metres.

Quick Hits

On 10 September, the Financial Times reported that provisional NOAA data had recorded 100 consecutive days on which the average global sea-surface temperature set a record for that date, beginning on 2 June. The report didn’t state the geographical bounds or baseline used for that calculation, so the figure should be treated as provisional. A developing El Niño is adding to the heat, while human-caused climate change remains the long-term driver. These global averages are different from marine heatwaves, which measure unusual warmth in particular places. Copernicus Marine Service reported that about 82 per cent of the global ocean had experienced marine heatwave conditions of varying strength by the end of June.

ClientEarth and Legambiente, supported by Blue Marine Foundation, have launched legal action seeking stronger protection for two Italian marine sites where they say bottom trawling continues. One lies in Tuscan waters inside the Pelagos Sanctuary. The other, Litorale di Gallipoli – Isola di Sant’Andrea, lies off Apulia and contains seagrass meadows and reef habitat. The organisations say authorities have failed to map habitats properly, assess the risks from bottom trawling and take measures to prevent damage. I haven’t seen the underlying legal filing, so those remain the organisations’ description of the case. Disclosure: I hold a retainer with Blue Marine Foundation.

Hard Truth From The Sea

So what is the thread that tirs all these stories together this week? The first description was never enough. The photography exhibition was full of beauty, and it also held an image of a mutilated pilot whale. Iceland’s programme contains a review, with a permanent ban as only one option. Offshore wind cuts emissions, while its turbines can change currents, temperature and sediment. A global heat record doesn’t describe every stretch of ocean, and the groups bringing the Italian case say bottom trawling continues inside two protected sites.

If you fancy trying a paid subscription, it opens up the full archive, every investigation and back issue. If not, that’s honestly fine. I’m glad you turn up each week for this.

Subscribe now

See you next week.

Luke

Somewhere south of the Kerguelen Islands, about as far from anywhere as you can get, elephant seals have been quietly doing oceanography for us.

I love stories like this, because an animal can go looking for dinner and, without knowing anything about climate models or how ocean water moves, end up telling us how heat and food move around one of the least visited parts of the planet.

Elsewhere this week, a study found that fish stocks can send a warning sign more than a decade before they collapse, NOAA published a list of proposed changes to American fishing rules that seems to touch almost every place where commercial fishing meets wildlife protection, the Bay of Biscay dolphin closure is back for another winter with a new design, scientists treated bleaching corals with bacteria during a real heatwave, and Jersey has closed more than a fifth of its waters to dredging and bottom trawling.

Deep Dives

Elephant seals have been showing us what happens beneath the Southern Ocean

Southern elephant seals are enormous, a big male can weigh as much as a small car, and they spend most of the year at sea, diving hundreds of metres down after squid and fish in places where sending a research ship regularly would be difficult, expensive and, for long stretches of the year, fairly miserable.

For years, scientists have been fitting some of them with sensors that record how warm and salty the water is as they dive, and a team of researchers has now gone through 133,598 of those dives, made between 2014 and 2020 in the stretch of the Southern Ocean south of Kerguelen, roughly halfway between South Africa and Australia.

The ocean is full of small patches where warmer and colder water meet and start swirling around each other, sometimes across an area one to twenty kilometres wide, and these movements don’t only push water sideways, they also push it up and down, carrying heat and nutrients between the surface and deeper water.

Scientists already knew quite a lot about what happens near the surface because satellites and ships can observe it more easily, but they knew much less about what was happening hundreds of metres down. Especially in winter, when the Southern Ocean is dark, rough and largely empty of research ships.

The seal data changed that, because the same movements were still showing up at least 500 metres below the surface, they were actually stronger down there than in the upper layer of the ocean, and their strength changed during the year too, peaking in the southern spring and falling to its lowest point in autumn.

That matters because the Southern Ocean absorbs huge amounts of heat and carbon dioxide from the atmosphere and helps move nutrients around the world’s oceans, so if more water is moving up and down far below the surface than scientists had realised, they may need to rethink some of their estimates of how heat and nutrients are being moved around.

There’s a limit to what 133,598 seal dives can tell us, because the seals went where elephant seals wanted to go, mainly where they expected to find food, rather than where a scientist designing the perfect experiment might have sent them, and this is still only one part of a very large ocean.

It’s still 133,598 measurements from a place where getting measurements is difficult, collected by animals that were mostly interested in finding squid.

Fish stocks may warn us twelve years before they collapse

Twelve years is the number that stuck out from a study published in Science Advances this week, the average gap between a fish population showing a particular warning sign and that same population later collapsing.

Mathieu Pélissié, Vincent Devictor and Vasilis Dakos at the University of Montpellier, working with Olaf Jensen in the United States, looked at 315 fish stocks from around the world with records stretching back to 1950, and instead of simply asking how many fish were left, they looked at how well each population was producing new fish.

A stock, in this context, just means one population of one species living in one area, so North Sea cod would be one stock, and the researchers had to estimate how well those populations were reproducing using fishing records and scientific surveys.

More than a quarter of the 315 stocks went through a sudden change at some point; more than half of those changes were declines, and stocks that suffered one of those sudden drops were twice as likely to collapse later, with the decline appearing, on average, about 12 years before the collapse.

That’s a long gap, particularly because the researchers also found that these declines were more common in parts of the ocean that had warmed fastest. When they compared warming with other possible explanations, including the type of fish and how heavily it was being caught, warming was the factor most closely linked to the drops.

The study doesn’t give every fishery a 12 year countdown, because it looked at 315 stocks with unusually long records and the warning sign itself has to be estimated from fishing and survey data, rather than something scientists can simply measure by putting an instrument in the water.

Boats can still be bringing in plenty of fish even when the population has already started producing fewer young fish, which means the warning can arrive while everything still looks normal.

NOAA is changing a lot more than one fishing rule

On 2 September, Eugenio Piñeiro Soler, who leads NOAA Fisheries, published a list of the rules and policies his agency intends to change, and what caught my attention wasn’t one single item so much as how many different parts of fisheries management appear once you keep reading.

The first major section says NOAA wants to move faster on removing commercial fishing bans from parts of four huge protected areas in the Pacific, including Papahānaumokuākea near Hawaii and the Mariana Trench, then there’s a rewrite of the speed rules designed to stop ships hitting North Atlantic right whales, a decision not to force lobster boats to switch to fishing gear without fixed vertical ropes, an outside review of the computer models used when deciding how to reduce whale entanglements, and another review of the models used to estimate how often humpback whales are at risk of getting caught in crab fishing gear on the west coast.

Keep reading and you reach rules protecting fish habitat, devices fitted to shrimp nets so turtles can escape, the way endangered species decisions are made, and the checks used on seafood imported into the United States.

That’s a lot of different rules moving at once, and they affect where fishing can happen, how scientists work out the danger to wildlife, what evidence regulators rely on and when those regulators decide fishing needs to be restricted.

The programme is Piñeiro Soler’s plan for carrying out President Trump’s order on Restoring American Seafood Competitiveness, and NOAA hasn’t invented the monument changes on its own, because Trump signed a proclamation on 11 June opening specified parts of the Pacific monuments to commercial fishing, while the Atlantic went first earlier this year, when a February proclamation changed the rules for Northeast Canyons and Seamounts Marine National Monument off New England and NOAA published the final change on 6 April.

Piñeiro Soler and the administration argue that some fishing businesses are dealing with rules that cost them money without delivering enough benefit, and that better science and newer technology can protect marine life without closing as much ocean to fishing. While the Western Pacific Regional Fishery Management Council had already recommended reopening some areas to commercial fishing before the June proclamation, following around 70 written and spoken public comments.

I can see the argument, particularly if a rule is genuinely outdated or based on science that has since improved, although the stakes feel rather different when you apply that logic to an animal such as the North Atlantic right whale.

The latest population estimate is 384 animals, and getting tangled in fishing gear and being hit by ships remain the two major human caused threats to the species. Decisions about ship speeds, fishing ropes and the computer models used to judge risk are being made while there are still fewer than 400 of these whales alive.

Quick Hits

The Bay of Biscay dolphin closure is back, with a twist

Five EU countries want the winter fishing closure in the Bay of Biscay, (designed to reduce common dolphin deaths in fishing gear) to run again in 2027, although this time the boats affected wouldn’t all stop fishing at once, because each vessel over eight metres would choose its own 30 consecutive days between 15 January and 27 February and tell the authorities by 8 January.

PELAGIS, the French research centre that monitors dead dolphins found on beaches, estimates around 1,900 common dolphins died after being accidentally caught in fishing gear during winter 2024 to 2025. This is compared with a revised average of roughly 4,700 per winter before the closures began, although nobody counted those dolphins directly because the figures are worked out from the bodies that reach shore and computer models estimating where dead dolphins are likely to drift.

The older figures have now been recalculated using the same method, which makes the comparison between the two periods more useful, and next winter should tell us whether allowing different boats to stop fishing at different times changes the result.

Scientists gave bleaching corals probiotics during a real heatwave

During a Red Sea heatwave in summer 2022, researchers at King Abdullah University of Science and Technology treated corals that were already bleaching with two mixtures of living bacteria thought to be helpful, as well as versions of those same mixtures where the bacteria had been killed by heat, to see whether changing the bacteria living on the coral could help it survive extreme temperatures.

After 15 days, both live treatments and one of the heat-killed treatments helped the tiny algae living inside the coral keep using sunlight to produce energy, while one live treatment and one heat-killed version also improved the researchers’ wider measure of the coral’s condition.

This is one coral species, at one site, over one fortnight, and treating individual corals by hand is a very long way from doing anything useful across an entire reef. Although it does show that researchers can test the idea on corals going through a real marine heatwave rather than only inside a laboratory.

Jersey has closed more than a fifth of its waters to trawling and dredging

On 1 September, new rules came into force around Jersey, increasing the share of the island’s waters where dredging and bottom trawling are banned from 6.5 per cent to 21.7 per cent, with the new areas covering habitats including seagrass, kelp and maerl beds, which are formed by slow-growing pink algae on the seabed.

Marine protected area percentages can be slightly deceptive because drawing a boundary around a piece of ocean doesn’t tell you very much about what people are actually allowed to do inside it. Whereas in Jersey the change is much easier to understand, because boats can no longer drag dredges or trawl nets across the seabed in those areas.

The restrictions followed three years of work involving Jersey and French fishing representatives and other groups using or trying to protect the sea.

Hard Truth From The Sea

A lot of decisions about the ocean have to be made before scientists have perfect answers, and that can mean acting while the numbers are still uncertain, whether that’s spotting trouble in a fish population years before it collapses, estimating how many dolphins died offshore from the bodies that reach the beach, or deciding how much danger fishing gear creates for a whale.

South of Kerguelen, 133,598 elephant seal dives have just made one small part of that uncertainty a little smaller.

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See you next week.

Luke

Between Tides is my personal column exclusively for paid subscribers. Think of it as an opinion column rather than one of my more rigorous science or policy pieces, where I write down what I’m thinking or feeling, and hopefully by the end of each one there’ll be something in there that’s useful to you too.

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