Como as águas mais quentes influenciam desde o sumiço das ostras à chegada precoce de baleias no Brazil

by Ana Menezes

 Pesquisadores apontam que o aumento da temperatura do mar já altera a migração de baleias, ameaça cultivos de ostras e impacta a pesca e o litoral catarinense

 

 O mar de Santa Catarina está mudando — e os impactos já começam a aparecer na economia, na biodiversidade e até em símbolos culturais do Estado, como as baleias-francas e as ostras cultivadas em Florianópolis.

 

Nos últimos anos, pesquisadores vêm observando o aumento gradual da temperatura das águas do Atlântico Sul e mudanças importantes no comportamento dos ecossistemas marinhos. Em Santa Catarina, especialistas alertam que os efeitos das mudanças climáticas já atingem a pesca, a maricultura, o turismo, a erosão costeira e os ciclos migratórios de espécies marinhas.

Em 2026, as primeiras baleias-francas chegaram ao litoral catarinense ainda em maio, antecipando novamente a temporada migratória. No mesmo cenário de mudanças no oceano, produtores de ostras enfrentaram perdas expressivas durante o verão devido à mortalidade dos animais provocada por altas temperaturas da água.

 

Pesquisadores apontam que os fenômenos ainda estão em estudo, mas que o aquecimento dos oceanos já provoca alterações perceptíveis na costa catarinense.

O que causou a morte das ostras?

 

Oceano absorve o calor do planeta

A oceanógrafa física e climatologista da Universidade Federal de Santa Catarina (UFSC), Regina Rodrigues, explica que os oceanos absorvem cerca de 90% do excesso de calor gerado pelas atividades humanas.

Segundo ela, estudos com dados de satélite analisados desde 1982 mostram uma tendência contínua de aquecimento no Atlântico Sul, incluindo o litoral de Santa Catarina.

— Estamos vendo cada vez mais períodos em que a temperatura do mar fica muito acima do normal — afirma.

 A pesquisadora explica que o aquecimento global atua junto de mudanças atmosféricas regionais. Entre elas, estão os chamados bloqueios atmosféricos, que reduzem a passagem de frentes frias, deixam o inverno mais seco e aumentam a incidência solar sobre o oceano.

 

— Santa Catarina está entrando mais no clima do Sudeste. Esses bloqueios, que antes eram mais comuns lá, estão se expandindo para o Sul — diz.

Fenômenos como o El Niño podem potencializar esse cenário, já que favorece a formação desses bloqueios atmosféricos e altera os padrões de chuva e temperatura no Sul do Brasil, conforme a pesquisadora.

Procurada pela reportagem, a Defesa Civil de Santa Catarina informou que não é possível afirmar uma relação direta entre o El Niño e o aquecimento das águas na costa catarinense.

Baleias-francas chegam mais cedo ao litoral

Os reflexos dessas mudanças também podem ser percebidos na migração das baleias-francas. A diretora de pesquisa do ProFRANCA, Karina Groch, explica que a chegada antecipada das baleias ao litoral catarinense ainda é estudada, mas que há forte relação entre alimentação, condições oceânicas e comportamento migratório.

 

As baleias-francas vêm para Santa Catarina principalmente para reprodução. As fêmeas chegam grávidas para dar à luz em águas mais abrigadas e permanecem na região até que os filhotes consigam retornar às áreas de alimentação próximas à Antártica.

Segundo Karina, a principal hipótese para a chegada antecipada desses animais envolve a disponibilidade de krill — pequeno crustáceo que serve de alimento para as baleias e depende do gelo antártico para se reproduzir.

— Quando está mais quente, há menos gelo e consequentemente menos krill. Isso influencia toda a cadeia alimentar — explica.

 Pesquisas do ProFRANCA indicam que alterações climáticas na Antártica podem gerar reflexos na população de baleias que chega ao Brasil até seis anos depois. A hipótese é que a espécie mais bem nutrida consegue completar antes o período de alimentação, iniciando a migração mais cedo.

 

— Tudo indica que o momento da chegada delas está relacionado à disponibilidade de alimento e às condições oceânicas — afirma Karina.

Ela ressalta, porém, que ainda são necessários anos de monitoramento para confirmar tendências e entender se a antecipação da temporada está diretamente ligada às mudanças climáticas ou a fenômenos específicos, como o El Niño.

 

Veja fotos das primeiras baleias-francas de 2026 no RS

Ostras sofrem com calor extremo

Enquanto as baleias antecipam a chegada, a maricultura catarinense enfrenta outro desafio: a mortalidade em massa de ostras provocada pelas altas temperaturas da água.

 

Santa Catarina é o maior produtor do marisco do Brasil, especialmente da espécie Magallana gigas, cultivada principalmente em Florianópolis. Mas a espécie, originária do Pacífico, é adaptada a águas mais frias.

Segundo o professor Rafael Diego da Rosa, do Centro de Ciências Biológicas da UFSC e coordenador do Laboratório de Biotecnologia e Saúde Marinha (LaBIOMARIS), o calor extremo registrado no verão provocou perdas expressivas na produção. No início do ano, produtores de ostras de Florianópolis enfrentam uma das maiores crises já registradas na maricultura local. A mortalidade em massa causada pelo aumento da temperatura da água do mar chegou a até 90% da produção, um índice considerado sem precedentes pelo setor.

O professor explica que o aumento da temperatura da água provoca estresse fisiológico nos animais e pode deixá-los mais suscetíveis à ação de vírus, bactérias e outros microrganismos.

Por conta disso, pesquisadores da UFSC, em parceria com instituições do Brasil, França e Chile, criaram uma rede internacional de pesquisa para investigar os fenômenos de mortalidade das ostras e a relação deles com as mudanças climáticas.

 

— Queremos entender se o que está matando as ostras é um fator ambiental, infeccioso ou uma combinação dos dois — diz Rafael.

“Ostras verdes” e novas florações

Outro fenômeno recente chamou atenção de pesquisadores e produtores: o

aparecimento

das chamadas “ostras verdes” em cultivos do Sul da Ilha.

O fenômeno ocorre quando uma microalga azul-esverdeada é filtrada pelos moluscos e pigmenta as brânquias dos animais. A mesma ocorrência já é conhecida na França, onde as ostras verdes são consideradas uma iguaria gastronômica.

Ostras esverdeadas despertaram curiosidade de produtores no Sul da Ilha (Foto: LaBIOMARIS, Divulgação)

Segundo Rafael, o evento já havia sido registrado em Santa Catarina há mais de 10 anos, mas voltou a aparecer recentemente. Pesquisadores agora tentam identificar se a microalga encontrada em Florianópolis é a mesma presente na Europa e quais fatores ambientais favoreceram a floração.

Embora essa microalga específica não apresente riscos à saúde humana, o pesquisador alerta que mudanças climáticas podem aumentar a frequência de florações de outras espécies tóxicas.

— Algumas microalgas produzem toxinas que podem inviabilizar cultivos e representar riscos para o consumo humano — explica.

Tropicalização da costa e impactos na pesca

O aquecimento do oceano também altera o comportamento de diversas espécies marinhas. Segundo Regina Rodrigues, da UFSC, pesquisadores já observam um

processo

chamado de “tropicalização” da costa catarinense: espécies típicas de águas mais quentes começam a migrar para o Sul, enquanto espécies tradicionais da pesca local podem se deslocar para águas mais frias, próximas ao Rio Grande do Sul, Uruguai e Argentina.

A mudança ameaça diretamente atividades econômicas ligadas à pesca artesanal.

— Já houve anos em que a tainha praticamente não apareceu em Santa Catarina, mas os pescadores relataram grandes cardumes mais ao sul — afirma Regina.

O NSC Total ouviu pescadores que relataram à reportagem que não sentiram diferença nos cardumes. Pelo contrário, a safra da tainha de 2026 já entrou para a história na Praia de Cima, na Pinheira, em Palhoça, por exemplo.

Em apenas um mês, o número de peixes capturados praticamente igualou todo o volume registrado ao longo da temporada de 2025. Somente em maio, foram pescadas cerca de 92.986 tainhas, segundo levantamento do grupo Informações da Pesca (IDP), de Florianópolis.

O resultado surpreendeu até os pescadores mais experientes do litoral catarinense. A expectativa inicial era de uma boa safra, mas a quantidade de cardumes que chegou às praias ficou muito acima do esperado.

 

— A Praia de Cima surpreendeu esse ano e ainda tem muita tainha chegando. Pelas informações das

embarcações

que trabalham no alto-mar, ainda existem muitos cardumes no litoral do Rio Grande do Sul subindo para Santa Catarina — afirma Marcelo Alcioni, do IDP.

Segundo Marcelo, as condições climáticas têm sido determinantes para o fenômeno. Isso porque o vento sul mais fraco estaria favorecendo a permanência dos peixes na costa catarinense por mais tempo.

— O vento sul não está sendo muito forte, então a tainha vai viajando devagarzinho e entrando nas praias. Se tivesse vento sul forte, como elas chegaram cedo, provavelmente já teriam passado por Santa Catarina rumo ao Paraná e São Paulo — explica ele.

A expectativa dos pescadores é de que os próximos dias possam registrar novos grandes lanços nas praias da região. Para Marcelo, o auge da safra ainda pode estar por vir.

 

Mais ressacas e erosão costeira

Por outro lado, os efeitos das mudanças climáticas também avançam sobre as cidades costeiras. Com temperaturas mais elevadas, aumenta a energia das tempestades, dos ventos e das ressacas, intensificando processos de erosão em praias catarinenses. Regiões como Armação, Campeche e Morro das Pedras, em Florianópolis, já convivem com episódios frequentes de avanço do mar.

Regina Rodrigues também faz um alerta sobre a ocupação urbana desordenada no litoral catarinense.

— Dunas, vegetação costeira e manguezais funcionam como proteção natural contra ressacas e erosão. Quando destruímos essas áreas, aumentamos nossa vulnerabilidade climática — afirma.

Marine heatwave over Pacific Ocean could lead to flooding in north-west. Severe ‘blob’ or marine heatwave can lead to increased inundation and wintery weather in eastern North America

People gather along the rocky bluffs of La Jolla's Windansea Beach in San Diego, California. Photograph: Kevin Carter/Getty Images

 by Eric Berger 

A marine heatwave known as a blob was especially severe this year in the north-western and central Pacific Ocean, which could lead in the coming months to increased flooding in the US Pacific north-west and especially wintery weather in eastern North America, according to climate scientists.

The temperature in August in the northern Pacific was 2.5C above preindustrial levels, according to Berkeley Earth, a non-profit that studies global warming.

That spike can lead to more thunder storms and affect marine species, according to Zeke Hausfather, a research scientist with Berkeley Earth.

“I kind of wonder, is this going to be a permanent feature?” said Nick Bond, a climatologist with the state of Washington and the University of Washington, who coined the term “blob” for the phenomenon.

 

Bond added: “A storm can come along and cool off the ocean some. You might have a sunny summer and it will warm up a little bit more than usual, so there are those kinds of fluctuations. But boy, what is out there in the central north Pacific? That is not going away anytime soon.”

Bond said he started calling such a heatwave a blob because “they are not static. They are kind of amorphous. They move around and evolve with time as the weather changes.”

Over the past decade, such heatwaves have become more severe and frequent.

“It has become appreciated that there can be these events that happen in the ocean that are significant, especially from an ecosystem point of view but also from a weather point of view,” Bond said. “It’s important to monitor them and to hopefully forecast them more effectively and just be aware that the climate is changing.”

From 2014 to 2016, there was a blob along the US west coast in which ocean temperatures were up to 3C above normal, according to the National Ocean and Atmospheric Administration.

 

“There were a lot of harmful algal blooms along the US west coast of unprecedented scope and intensity, and those shut down commercial shellfish fisheries,” Bond said.

Higher oceanic temperatures can force marine species to migrate or lead to their death, said Hausfather.

“The impacts on various marine species, on phytoplankton, which drive a lot of the food web, are quite important,” said Hausfather.

Some news organizations recently reported that the blob could cause Chicago to have the “coldest, snowiest” winter in years.

While Bond said the blob could play a role in the weather so far inland, it would probably only be a “secondary player”.

“If the air coming in off the ocean here in western Washington state is warmer than normal, then we will have less snow, all other things being equal. That effect doesn’t extend that far inland,” Bond said. “For it to impact snowfall in Chicago, it has to be causing a disruption in the weather patterns … It doesn’t mean that it has no influence whatsoever, but there are other factors that are going to be more important to how snowy it is in the midwestern US.”

Scientists also do not yet have enough data to state with confidence what impact such blobs will have and the impact can be confounded by developments such as a disruption in the polar vortex, Bond said.

In short, Bond said: “We are limited by just how many blobs we have had.”

 

Deadly algal bloom in South Australia’s Coorong an environmental ‘eye opener’, ecologist says

 

 

Dead and dying polychaete worms at the southern end of Coorong’s North Lagoon. Photograph: Glen Hill

by Petra Stock

 Among the dead in the internationally significant wetland are estuarine snails, shore crabs, baby flounder and ‘a thick stew of polychaete worms’

 

When South Australia’s algal bloom arrived in the Coorong, it stained the water like strong tea before turning it into a slurry of dead worms.

Many had hoped the storm in late May would break up the bloom of Karenia mikimotoi algae, which has killed more than 200 different marine species. Instead, high tides swept the algae into the Coorong, an internationally significant Ramsar wetland at the mouth of the Murray River.

Once there, the algae began “reproducing madly” in the nutrient rich waters of the North Lagoon, according to estuarine ecologist Faith Coleman.

Among the dead were mostly benthic species – estuarine snails, shore crabs, baby flounder and “a thick stew of dead polychaete worms” – a crucial food source for shorebirds and fish.

 

Levels had declined from their peak but the smell of rotting fish remained, along with algal spores buried in the sediment. “As soon as it warms up again, the likelihood is [the algal bloom will] be back,” Coleman said.

The marine heatwave, a contributing factor to the bloom, persisted off the coast of SA, according to an 11 June update, which showed increases in chlorophyll – an indicator of algae concentrations – along the Coorong coast and western Gulf Saint Vincent.

Fourth generation fisherman Gary Hera-Singh was one of the first to notice the lagoon’s colour turn a “dark, orangey-brown”.

“We had a big storm event, a lot of seawater got pushed around, and this algal bloom found its way into the Coorong and has just created havoc since,” he said, and there were still “massive patches – 100 acres at a time” where the bloom was flourishing.

Hera-Singh has witnessed the health of the Coorong decline in his lifetime, but said in 41 years of fishing the impact of the algal bloom was the worst event he had seen.

The Coorong, a 120km narrow band of water separated by sand dunes from the Southern Ocean, together with lakes Alexandrina and Albert, is considered a wetland of international significance, providing critical habitat for fish, water birds and many threatened species. The North Lagoon – the area affected – is an important nursery for fish such as mulloway and bream.

 Prof Peter Gell, an expert in Ramsar listed wetlands, said the wetlands had degraded over a long period of time, with barrages (structures that control water flow) added in the 1950s, higher nutrient loads and extended periods of reduced flow from the Murray.

 

Algal blooms were symptoms of broader changes, he said. “Because of this we’re seeing – both offshore and within the Coorong – substantial changes in the food web.”

As a wetland of international significance, the Australian government was obliged to report environmental changes to the Coorong under the Ramsar convention, Gell said, a process that usually triggered restoration efforts.

Federal and state governments were liaising about the situation, including any long-term impacts likely to affect the ecological character of the Coorong, a federal environment department spokesperson said.

“We understand that, given the dynamics of the North Lagoon, it is difficult to dissipate the bloom and it might remain for some time.”

Fresh water may help the situation, Coleman said, given the algae thrived at salinity levels of 18-37 grams per litre. Restoration efforts would help build the resilience of the Coorong and marine areas, she said.

The system was already under pressure, said Dr Nick Whiterod, an ecologist and science program manager at the Coorong Lower Lakes Murray Mouth Research Centre. But the recent drought and unusual algal blooms had been “eye openers” to many people, he said.

Last year, a tropical species of blue-green algal bloomed in Lake Alexandrina for the first time, and had persisted, Whiterod said. Now that karenia mikimotoi had got into the Coorong, there was concern it too would bloom again.

The Coorong was vulnerable to the impacts of climate change, like sea level rise and reduced river flows, he said.

“Ocean temperatures are heating up. It’s creating conditions that are conducive to algal blooms all around the world,” he said. “Our ecosystems are really stressed, we are getting to a period of time where some may not have the capacity to recover.”

 

'Shrinking Nemo': Smaller clownfish sound alarm on ocean heat

Clownfish are one of the most recognisable reef fish, known for their orange and white stripes

 Helen Briggs

 

Fish similar to those made famous by the movie Finding Nemo are shrinking to cope with marine heatwaves, a study has found.

The research recorded clownfish living on coral reefs slimmed down drastically when ocean temperatures rocketed in 2023.

Scientists say the discovery was a big surprise and could help explain the rapidly declining size of other fish in the world's oceans.

A growing body of evidence suggests animals are shape shifting to cope with climate change, including birds, lizards and insects.

The research took place in Kimbe Bay, a key area of marine biodiversity

"Nemos can shrink, and they do it to survive these heat stress events," said Dr Theresa Rueger, senior lecturer in Tropical Marine Sciences at Newcastle University.

The researchers studied pairs of clownfish living in reefs off Kimbe Bay in Papua New Guinea, a hot spot of marine biodiversity

The wild clownfish are almost identical to the ones depicted in the movie Finding Nemo, in which a timid clownfish living off the Great Barrier Reef goes in search of his son.

The scientific study took place in the summer of 2023, when temperatures shot up in the oceans, leading to large swathes of coral turning white.

The scientists took multiple measurements of individual clownfish coping with the heat.

They found the tiny fish didn't just lose weight but got shorter by several millimetres. And it wasn't a one-off - 75% of fish shrunk at least once during the heatwave.

Clownfish swimming on the Great Barrier Reef in Australia

Dr Rueger explained: "It's not just them going on a diet and losing lots of weight, but they're actively changing their size and making themselves into a smaller individual that needs less food and is more efficient with oxygen."

The fish may be absorbing fat and bone, as has been seen in other animals, such as marine iguanas, although this needs to be confirmed through laboratory studies.

Dr Rueger joked that a little bit of movie rewriting might be necessary, with a new chapter ahead for Nemo.

"The movie told a really good story, but the next chapter of the story surely is, how does Nemo deal with ongoing environmental change?" she told BBC News.

Mushroom soft coral on a reef in Papua New Guinea in the Pacific Ocean

Global warming is a big challenge for warm-blooded animals, which must maintain a constant body temperature to prevent their bodies from overheating.

Animals are responding in various ways: moving to cooler areas or higher ground, changing the timing of key life events such as breeding and migration, or switching their body size.

The research is published in the journal, Science Advances.

Surge in marine heatwaves costs lives and billions in storm damage – study. Floods, whale strandings and coral bleaching all more likely, say researchers, as 10% of ocean hits record high temperatures in 2023-24

 

A sperm whale died after stranding at Yeh Malet beach in Bali, in April 2023 – warmer ocean temperatures increase the risk of similar events. Photograph: Dicky Bisinglasi/AFP/Getty Images

 Sophie Kevany

 

The world’s oceans experienced three-and-a-half times as many marine heatwave days last year and in 2023 compared with any other year on record, a study has found.

The sustained spike in ocean temperatures cost lives and caused billions of dollars in storm damage, increased whale and dolphin stranding risks, harmed commercial fishing and sparked a global coral bleaching, according to the paper published on Friday in Nature Climate Change.

 

Like heatwaves on land, a marine heatwave is defined as a period of higher than normal temperature over a longer than usual time. The most recent of these were brought about by human-induced climate change and amplified by El Niño conditions, the report’s authors said, with nearly 10% of the ocean hitting record high temperatures in 2023-24.

“The more regularly our marine ecosystems are being hit by marine heatwaves, the harder it is for them to recover from each event,” said lead author Kathryn Smith from the UK’s Marine Biological Association.

Higher ocean temperatures “supercharge” evaporation, the study said, fuelling storms such as Cyclone Gabrielle which hit New Zealand in February 2023, killing 11 people and costing an estimated NZ$14.5bn (about £6.5bn).

One of the most surprising findings in the study, said Smith, was “how much [marine heatwaves] accentuated storms on land and the number of people that were hit by that – hurt, lost possessions, [suffered a] monetary impact or lost their lives”.

At least 45 people died in April last year when a dam burst in Kenya’s Rift valley, as torrential rains battered the country. Photograph: Luis Tato/AFP/Getty Images

 More worryingly, she said: “There is going to be a huge amount more [about the impacts of marine heatwaves] that we don’t know about [yet] because of the time it takes to publish in scientific literature.”

The effect on species was often devastating. Whales and dolphins venture closer to shore when the water is warm because they follow their prey, so this increased their chances of stranding, said Smith. For Mediterranean fan mussels, which have been dying in their millions since 2016, marine heatwaves may be the final nail in the coffin because the warming waters bring increased risk of diseases, the study said.

An aerial photo from February 2023 showing flooding caused by Cyclone Gabrielle in Awatoto, New Zealand. Photograph: AFP/Getty Images

Although human intervention saved some marine life from the recent heatwaves, the study found damage reduction was mostly lacking, possibly due to limited resources, disconnects between organisations and poor communication.

When there was time to prepare, successful mitigation actions included moving corals and conches in Florida to deeper, cooler water and keeping endangered Tasmanian red handfish in aquariums until they could be returned to the wild.

For corals, the study said initiatives to create new colonies using assisted sexual reproduction that increases genetic diversity showed potential, with increased resilience to bleaching “observed in trial populations of reef-building corals across the Caribbean and Mexico”.

Increased ocean temperatures can sometimes bring small wins, the study noted. In Peru, for example, while the anchovy catch was badly affected by the fish moving outside their normal range – a shift that led to commercial fishery closures and estimated losses of $1.4bn (£1.1bn) – squid landings increased.

 A juvenile queen conch. Scientists in the US moved some of the molluscs into cooler waters to protect them from the warming ocean. Photograph: Jennifer Doerr/NOAA SEFSC Galveston

 

Better forecasting, the study found, is critical to reducing damage from severe marine heatwaves, because it provides “greater confidence” for those making damage limitation decisions.

Valeria Pizarro, a scientist at America’s Perry Institute for Marine Science, who was not part of the study, said watching corals bleach “in the blink of my eyes” made her feel “very sad and frustrated”. In most cases, she said, the paper showed effective responses to marine heatwaves were lacking because “we weren’t prepared, we didn’t have the money or the manpower to do much in such a short period of time”.

More broadly, said Smith, the direct link between the climate crisis and ocean temperatures means that “until we see a switch from fossil fuels to renewable energy”, marine heatwaves, and the damage they do, will continue to increase. 

‘Catastrophic’ marine heatwaves are killing sealife and causing mass disruption to UK fisheries

 

Temperature rises in coastal seawater are affecting marine habitats and seafood production. Photograph: eye35.pix/Alamy

 Targeted research must be launched urgently to save sea creatures and plant life, oceanography centre warns

 

Robin McKie Science editor

Britain is facing a future of increasingly catastrophic marine heatwaves that could destroy shellfish colonies and fisheries and have devastating impacts on communities around the coast of the UK.

That is the stark conclusion of a new report by the National Oceanography Centre (NOC), based in Southampton, which is pressing for the launch of a targeted research programme as a matter of urgency to investigate how sudden temperature rises in coastal seawater could affect marine habitats and seafood production in the UK.

Across the planet marine heatwaves are becoming more frequent and intense as rising fossil fuel emissions force up atmospheric temperatures across the globe, causing the sea to warm.

These events not only disrupt shellfish colonies and fisheries, but also cause the bleaching of coral reefs, the spread of harmful algal blooms, the destruction of seagrass meadows, and mass mortality of fish, seabirds and marine mammals.

 

“Marine heatwaves have catastrophic impacts and we need to be prepared for them. At present, we are not and that position needs to be rectified as a matter of urgency,” said Dr Zoe Jacobs, the lead author of the NOC report, Marine heatwaves and cold spells in the Northeast Atlantic: what should the UK be prepared for?

“We need to know how these marine heatwaves are going to affect plants and animals that live in the sea and find ways to protect them, as well as the coastal communities that depend on them.”

Marine heatwaves are also causing the mass mortality of seabirds. Photograph: Jeroen van Wijk/Alamy

 

In early summer 2023 Britain was engulfed in a marine heatwave in which major rises in the temperature of sea water were experienced off the north-east coast of England and off the west of Ireland. For more than two weeks, the sea in these regions was around five degrees above normal temperatures, smashing records for late spring and early summer. The Met Office reported that the North Sea and north Atlantic experienced higher temperatures at the same time, with sea temperatures reaching an all-time high, according to records that date back to 1850.

As global temperature continues to soar, scientists believe it is inevitable that many more of these record-breaking heatwaves will affect water around Britain and Ireland in the near future, with the report by the NOC highlighting three main areas of concern.

One is in the Irish Sea between England and Ireland, one is in the North Sea off northern England and Scotland, and the last is off the coast of south-east England. “These regions are areas where marine heatwaves can coincide with extremely low oxygen concentrations in the water, which makes them especially vulnerable. It’s like a double whammy. They get the extreme heat stress and extremely low oxygen levels at the same time. And that is going to cause serious trouble for any creatures or plants that are living there.”

The problem for researchers and marine conservationists is that the long-term consequences of such jumps in temperature are still unknown, added Jacobs. “There have been stories that there were widespread die-offs of shellfish such as whelks, and disruption to many fisheries during last year’s heatwave, but there is no hard evidence to back up these because we have not carried out any detailed research into the exact effects, and that is a problem.

“Global temperatures are rising and we are going to experience more and more marine heatwaves as a result. These are already having catastrophic impacts in other parts of the world, for instance in waters off Australia and other regions where fisheries have had to be closed and hectares of seagrass have been wiped out. We need to be able to pinpoint our most vulnerable regions and monitor them very closely.”

 

A key example is provided by seagrass, which form vast meadows around the shores of the UK where they absorb high levels of carbon and provide homes for hundreds of different species of marine creatures. These have been depleted in the past and a major restoration programme is now under way.

“However, we do not know what will happen to that programme if marine heatwaves start to kill off seagrass again,” added Jacobs. “We need to understand how this will happen and investigate now to find out if there are strains that are more resilient than others and concentrate on planting these.

“At the same time, we may need to be prepared to close down fisheries at certain times or impose quotas to protect them as heatwaves start to strike. These are the kinds of actions that have had to be imposed in other parts of the world and we may have to follow suit.”