Ocean warming could cut omega-3 levels in seafood, study finds

Global analysis finds rising ocean temperatures could reduce omega-3 fatty acids across marine food webs, with implications for seafood nutrition

Ocean warming could reduce levels of omega-3 fatty acids in fish and other marine organisms, potentially affecting the nutritional value of seafood, according to a global study.

Researchers analyzed 489 experiments from 143 published studies involving 132 marine species, including algae, invertebrates and fish. The study, published in Global Change Biology, examined how warming and ocean acidification affect fatty acids throughout marine food webs. The researchers found that warming generally reduced omega-3 fatty acids, with larger declines occurring as temperatures increased.

“Our new study shows many fish and other seafood will become less rich in omega-3s over time, due to rising ocean temperatures as the climate changes,” the researchers wrote in an article for The Conversation. “In fact, we found omega-3 could drop by 50 percent under very high warming scenarios. This is very bad news for human health but also for the health of other animals in the food web.”

Marine algae produce EPA and DHA, two important omega-3 fatty acids, and sit at the base of marine food webs. Those nutrients move through the food chain as algae are eaten by other organisms, which in turn are consumed by fish and larger animals.

“If EPA and DHA levels get disrupted along the food chain, less of those crucial fatty acids are available for animals higher up – including humans,” the researchers wrote.

The effects varied among species and experiments, but the overall analysis found warming had a stronger effect on fatty acids than ocean acidification. “We found ocean acidification had less impact on fatty acids than warming, suggesting rising temperature is the dominant driver of this problem,” the researchers wrote.

The results should not be read as a prediction that omega-3 levels in seafood will fall by 50 percent across the board. The study combined results from controlled experiments, and responses varied among species and experimental conditions. The researchers called for more long-term studies under realistic environmental conditions to improve predictions of how climate change will affect the nutritional quality of marine organisms.

The findings could have implications for fisheries and aquaculture because omega-3 availability is important to both the nutritional value of seafood and the health of marine organisms. The study’s authors said anticipating climate-driven nutritional declines will be important for fisheries management, aquaculture and food security.

Wanted: More omega-3s. But from where?

The researchers also pointed to better use of fish processing byproducts as one way to make more of existing sources of omega-3. With up to 80 percent of fish parts discarded during food processing, they suggested those parts could be used to produce omega-3-rich fish oil or as nutritional ingredients in aquaculture feed.

“Given the projected declines in nutrition into the future, these wasted fish parts could be better utilized,” the researchers said. “This might, for instance, include making fish oil products rich in omega-3 and other nutrients, or using these fish parts as nutritional aquaculture feed.

Read the full study here.