“Detrimental Effects of Global Warming on Nutritional Value of Fish”

Climate Change Affects Nutrient Quality of Seafood

Changes in Ocean Food Webs

Climate change is causing ocean fish populations to decline and shift their ranges. However, recent research is raising concerns that warming might also impact the very makeup of fish bodies. Warmer temperatures can transform ocean food webs by altering the amount of minerals and fats that fish get through their diet. This, in turn, can affect their metabolism and ability to excrete toxic substances. The impact of this trend is worrying since seafood provides vital nourishment to over 3 billion people worldwide, particularly in under-resourced tropical countries, where individuals rely on the ocean for more than half of their animal protein intake. Seafood is also a key source of brain and heart health-promoting omega-3 fats as well as iron and zinc.

Decline in Omega-3 Fats

The decline in omega-3 fats begins at the bottom of the food web. Marine algae called phytoplankton synthesize two types of fatty acids to develop their cell membranes. Cooler temperatures cause phytoplankton to synthesize more unsaturated fatty acids such as omega-3s, which create flexible membranes that do not freeze up. At warmer temperatures, production shifts to more structured, stiffer saturated fatty acids. This indicates that phytoplankton will make less of the healthy omega-3 fats as the ocean warms. Some studies suggest that if ocean surface temperatures increase by 2.5°C, the global phytoplankton production of docosahexaenoic acid (DHA), a type of omega-3, could decline by almost 28% by the end of the century. Everything in the food chain receives DHA from phytoplankton, which includes oceanic fish. Consequently, as fish receive less DHA, fish could become less nutritious, or even toxic, for those that consume them, including humans.

Impact on Human Health

DHA, one of the most important omega-3s for human health, connects to several benefits, including reducing inflammation, lower blood pressure, and lower risks of dying from heart disease. If the trend of decline in omega-3 fats continues, this could lead to a significant loss of one of the most essential nutrients for the human diet that prevents illness and disease.

Increase in Toxins

Increasing temperature can change the metabolism of marine fish and other species, changing the way that organisms can metabolize microelements and toxic metals. Currently, elevated toxins in some marine organisms are being reported. Heavy metals like copper, methylmercury, and arsenic, at high concentrations, can cause organ damage and neurological impairment. Following heat waves, spikes in copper have been detected in frequently-consumed species of whelks, prawns, and oysters, as well as longer-term increases in methylmercury in cod, Atlantic bluefin, and swordfish.

Future Changes in Seafood

More research is necessary to understand how future warming will affect micronutrients in fish, which likely depends on the species in question and how its environment has changed. Scientists have detected mixed results on impacts on ecosystems of climate-driven changes, as seen in the case of herbivorous fish, which were richer in iron and zinc. Changes in micronutrient concentrations seem to be varied, but research hints at future changes in seafood, such as possible protein content reductions or changes in taste and texture in specific seafood species.

Mitigating Nutritional Shortfalls in Seafood

To prevent omega-3 deficits, there are efforts in the aquaculture industry to make farmed fish more nutritious by feeding them with DHA-rich algae grown on land. However, many lower-income countries may not have the resources to do that at the necessary scale. It becomes necessary to protect existing fish populations from threats like overfishing. As the planet warms, “it is not a good situation that we’re going to be in,” says Colombo of the DHA decline. “Our ability to sustainably produce our own nutrients from aquatic ecosystems is going to be key.”

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