Rising sea temperatures may fundamentally reshape UK marine ecosystems, study warns

A comprehensive four-year study has revealed that warming seas around the United Kingdom and the broader north-east Atlantic region could destabilize marine food webs by the middle of this century. The research indicates that these changes may weaken overall ocean health and put regional food security at risk. The findings challenge the previous scientific consensus that marine biodiversity in mid-latitude areas, such as the UK, would likely see a general increase due to climate change.

Instead of a uniform rise in species diversity, the projections point to a significant imbalance between predators and prey. Scientists argue that this shift could fundamentally reshape marine ecosystems in ways that were previously unforeseen. The seas surrounding the British Isles, with the southern North Sea being a particular concern, have been identified as marine climate hotspots. These areas are among the twenty fastest-warming marine regions globally over the past fifty years.

The study modeled the impacts of a scenario involving three degrees Celsius of warming by the year 2100. Under these conditions, while diversity among fish and seabed invertebrates is expected to rise by mid-century, key groups of plankton lower in the food chain are projected to decline. This divergence could disrupt the foundational structures of marine food webs, thereby reducing the resilience of ocean ecosystems.

Elena Couce, a marine ecologist at the Centre for Environment, Fisheries and Aquaculture Science, and co-lead author of the study, expressed surprise at the uneven nature of the changes. She noted that warming does not simply increase or decrease biodiversity across all groups. While some higher-level predators like fish may gain species in parts of the north-east Atlantic, the plankton groups that underpin these ecosystems are projected to lose species.

The research was led by Cefas, a British government agency, and published in Science Advances. It involved an international team of researchers from the University of East Anglia, the Marine Biological Association, UiT the Arctic University of Norway, the Royal Netherlands Institute for Sea Research, and the Technical University of Denmark. Couce explained that as temperatures rise, species from the equator tend to migrate north and south. The team had initially expected diversity to increase in the UK because species arriving from the south are generally more diverse than those moving northward.

Previous studies by Cefas on key fish species had suggested that warming in north-western European waters would benefit certain climate winners, such as anchovies, seabass, and sardines. Conversely, these conditions were found to be less suitable for climate losers, including Atlantic cod, haddock, and coley. The current study broadens this perspective to include the wider ecosystem, covering UK waters as well as those of Ireland and France.

Specific projections indicate that by 2050, fish and seabed invertebrate diversity could increase by approximately 12 percent. In contrast, phytoplankton diversity is expected to decline by about 3 percent, while zooplankton diversity could drop by 7 percent. Lily Greig, another marine ecologist at Cefas who co-led the study, warned that if predator diversity rises while prey diversity falls, the food chain faces potential disruption. She emphasized that gains in some groups do not necessarily mean the entire ecosystem is becoming more resilient.

The researchers stated that by identifying where biodiversity is changing fastest and which parts of the ecosystem are most at risk, the study can serve as an early warning system for potential ecological shifts. The findings have already been submitted to the government’s review of marine protected areas, which is currently examining fishery management measures. Couce noted that policymakers have a mandate to preserve or increase biodiversity and must account for these ongoing climate-driven changes before implementing other management plans.

To reach these conclusions, the scientists utilized multiple long-term datasets and advanced machine-learning techniques. These tools allowed them to determine the relationships between biodiversity and environmental change, enabling predictions of climate-driven biodiversity shifts through to 2100.