Warming oceans may affect not only where marine species live and how productive fisheries are, but also the nutritional quality of seafood. A new study published in Global Change Biology found that higher temperatures can reduce levels of omega-3 fatty acids in marine organisms.

The researchers brought together results from 489 experiments involving 132 species of algae, invertebrates and fish. Across the studies, warmer conditions were generally associated with lower concentrations of important omega-3 fatty acids. The strongest changes occurred under the highest experimental warming conditions, where reductions were observed across several parts of the marine food chain.

These changes matter because omega-3 fatty acids such as EPA and DHA play important roles in both human nutrition and the health of marine organisms. They are largely produced by marine algae and then transferred through the food chain as organisms feed on one another. Changes in their availability at lower levels of the ecosystem can therefore have consequences for species further up the food chain.

For fisheries and aquaculture, this suggests climate change could affect seafood in ways that go beyond shifts in abundance, distribution and productivity. Changes in nutritional composition may also become relevant for seafood quality, aquaculture feeds and the nutritional benefits people receive from seafood.

The study found that temperature had a clearer effect on fatty-acid composition than ocean acidification. However, the researchers also identified substantial variation between species and experimental conditions, highlighting the need for further research under longer-term and more realistic environmental conditions.

For the seafood sector, the findings add another consideration to climate adaptation: future ocean change may influence not only how much seafood can be produced and where, but also some of its nutritional characteristics.