The project, Biological dynamics during marine heatwaves: rapid response analysis of samples from the English Channel and beyond, will use samples collected before, during, and after the event to measure changes across the marine food web. It will combine the MBA’s Continuous Plankton Recorder (CPR) Survey with its fish trawl surveys, allowing researchers the unique opportunity to compare present-day conditions with long-term records.
The marine heatwave began in late June 2026, with sea-surface temperatures around 3–5°C above normal levels in affected waters. It is among the most intense events recorded in the region since satellite monitoring began and is the second extreme marine heatwave to affect these seas in three years. Its arrival only a matter of weeks after an earlier warming event raises urgent questions about whether Northwest European shelf seas are entering a new climatic state.
Marine heatwaves (MHWs) are periods when ocean temperatures are unusually high for a particular place and time of year. They are becoming more frequent, longer-lasting and more severe as the climate warms, but their ecological effects in UK seas remain poorly understood. Because these events are unpredictable and short-lived, the strongest evidence can only be gathered during and immediately after them. NERC’s urgency funding enables the MBA to mobilize existing surveys, samples and expertise while this exceptional event is still unfolding.
The research team, led by MBA Research Fellow Dr. Katie Smith, will characterize changes in plankton and fish communities during the active heatwave and compare them with conditions before and after the event. Researchers will also test how biological changes relate to temperature, salinity, and nutrients, and screen samples for harmful algal bloom species, their biotoxin-producing potential, and Vibrio bacteria. The work will provide evidence relevant to marine ecosystems and fisheries, with additional implications for shellfish safety and public-health monitoring.
“Most of what we know about MHW impacts comes from other areas of the world,” explains Dr. Smith. “Seas around the UK have only recently begun experiencing MHWs of this magnitude, so how plankton and fish communities here respond remains poorly understood, a critical gap given that these events are expected to intensify.”
Around the world, marine heatwaves have caused mass die-offs of corals, kelp forests, seagrass, shellfish, fish, seabirds and marine mammals. Their effects can persist long after temperatures fall: 100 kilometers of kelp forests lost during Western Australia’s 2011 event (the first to be called a ‘marine heatwave’) have still not recovered after 15 years. The economic consequences can also be severe, with fisheries losing hundreds of millions of pounds during marine heatwaves off the west coast of the United States and more than £1 billion lost from Peru’s anchoveta fishery in a single year.
“Marine heatwaves are now one of the biggest stressors our oceans face. Entire ecosystems are being destroyed,” Dr. Smith said. “We’re seeing more of them, they’re lasting longer, and the impacts are intensifying. We’re talking about major aquaculture losses, fisheries closed for years, and billions in lost income. Warmer waters can also trigger disease outbreaks in shellfish or aquaculture, wiping out stocks. These events hit livelihoods as much as ecosystems.”
The project will use the MHW as a rare opportunity to capture ecological responses to extreme warming in near-real time. Because MHWs are unpredictable and short-lived, the ecological responses they generate can only be captured during and shortly after events. However, for this project, researchers will use existing MBA survey infrastructure—CPR and fish trawl surveys—to compare samples gathered across the currently active MHW to unique historical data, spanning multiple trophic levels. The MBA’s long-term datasets, such as the CPR Survey and fish population survey, are invaluable, allowing scientists to see how temperature changes ripple through marine ecosystems over decades.
Speaking about the vital role that data from the CPR Survey—which has been running since 1931—will play in this research, Dr. Clare Ostle, MBA, Senior Research Fellow, Pacific CPR Survey Coordinator and Chair of the Global Alliance of CPR Surveys, said: “The Survey has been sampling our seas for more than 90 years, which gives us something very few studies have: a long baseline to compare an extreme event against. By analyzing CPR samples collected before, during, and after the heatwave, we can see how plankton communities respond, and the same samples let us screen for harmful algae and Vibrio bacteria. Long-term observations like the CPR Survey are what make rapid response science possible. Because we know what normal looks like, we can measure what a marine heatwave changes, and what that means for the ecosystem and for people.”
The project will deliver preliminary findings within six months and a full analysis within 12 months. This work is essential for understanding how UK marine ecosystems and fisheries species are responding to extreme, rapid warming; information needed to anticipate impacts as such events become more frequent. It also has secondary relevance for shellfish safety and potential public health monitoring, via the Vibrio component.
The pilot dataset will also provide proof of concept for a future NERC responsive-mode proposal to embed rapid marine-heatwave monitoring within the CPR time series. Findings can be shared with government and industry through the Defra/MCCIP-funded UK Marine Heatwave Community of Practice, of which Dr. Smith is a member.
“We can’t always stop these events, but we can plan for them,” added Dr. Smith. “Forecasts and understanding rapid changes that we’re seeing in our marine species data are key to building resilience.”
Core Team
Lead:
Dr. Kathryn Smith: Marine ecologist specializing in how marine communities adapt to environmental change, particularly the ecological and socioeconomic impacts of marine heatwaves.
Project Co-Leads (UK)
Dr. Bryce Stewart: Marine ecologist and fisheries biologist specializing in evidence-based fisheries management, marine protected areas, conservation and climate change.
Dr. Clare Ostle: Marine biogeochemist specializing in plankton ecology, the marine carbonate system, ocean plastics and long-term Continuous Plankton Recorder data.
Dr. Dan Smale: Community ecologist specializing in kelp forests, marine heatwaves and the effects of global environmental change on marine biodiversity and ecosystem functioning.
David Johns: Plankton specialist focusing on macroecology, long-term dataset analysis, marine ecosystem health and quality standards for biological monitoring.
Professor Michael Cunliffe: Marine microbiologist specializing in microbial biology, ecology and evolution, including marine fungi, microbiomes and molecular approaches to biodiversity.
