By Abbas Nazil
Climate change could reduce the concentration of essential omega-3 fatty acids in fish and other marine organisms by as much as 50 per cent under high-warming scenarios, potentially threatening both human nutrition and the health of marine ecosystems.
The finding comes from a new systematic review that examined 489 experiments involving 132 marine species, including algae, invertebrates and fish, to assess how ocean warming and acidification could affect the nutritional quality of marine life.
The researchers found that ocean warming was a more significant driver of changes in fatty acids than ocean acidification, with rising temperatures capable of substantially reducing levels of EPA and DHA, two omega-3 fatty acids that are important for brain, eye and heart health.
According to the study, warming of between zero and six degrees Celsius was associated with a 19 per cent reduction in omega-3 fatty acids in fish in experiments lasting between 24 hours and six months.
Under high-warming scenarios of more than 10 degrees Celsius, the researchers found that omega-3 levels could decline by 50 per cent in fish, 34 per cent in algae and 51 per cent in invertebrates.
At the same time, levels of saturated fats could increase by as much as 22 per cent, potentially reducing the nutritional quality of seafood and altering the balance of essential fats throughout marine food webs.
The researchers explained that marine algae, including seaweeds and diatoms, are among the main producers of EPA and DHA and form the foundation of marine food webs.
When organisms such as invertebrates consume these algae, they acquire the omega-3 fatty acids, which are subsequently transferred through the food chain as larger animals consume them.
Fish and other seafood therefore provide humans with omega-3 fatty acids that ultimately originate at the base of the marine food web.
The researchers warned that disruption of omega-3 production at lower levels of the food chain could reduce the amount available to species higher up, including humans.
The decline could be particularly concerning for populations that already have inadequate dietary intake of omega-3 fatty acids and rely heavily on seafood as a source of essential nutrients.
The researchers said the problem is occurring against a background of increasing pressure on global fish stocks from overfishing and other human activities.
They explained that marine organisms need to maintain the stability of their cell membranes as environmental conditions change.
As temperatures rise, cell membranes become more fluid, prompting organisms to replace some omega-3 fatty acids with more rigid saturated fats in a process known as homeoviscous adaptation.
Beyond its implications for human nutrition, the researchers said declining omega-3 levels could affect marine organisms themselves because the fatty acids play important roles in growth, reproduction and immune function.
The findings therefore raise concerns about the combined effects of climate change and other pressures on marine ecosystems and the communities that depend on seafood for food and nutrition.
The researchers called for urgent action to reduce greenhouse gas emissions and limit the most severe impacts of climate change on the oceans.
They also highlighted the need to strengthen food security strategies so that essential nutrients remain available to populations through traditional food sources as environmental conditions change.
With large quantities of fish currently lost or discarded during processing, the researchers suggested that more of these by-products could be recovered and used to produce omega-3-rich fish oils or nutritional feed for aquaculture.
Such measures, they said, could help reduce nutritional losses while improving the efficiency and sustainability of seafood production in a warming world.
