This process explains why predatory fish such as swordfish and sharks or birds like osprey and eagles have higher concentrations of mercury in their tissue than could be accounted for by direct exposure alone. Anything that eats these fish within the food chain also consumes the higher level of mercury that the fish have accumulated, including humans. The older that such fish become, the more mercury they may have absorbed. This results in the bioaccumulation of mercury, in a buildup in the adipose tissue of successive trophic levels: zooplankton, small nekton, larger fish, and so on. Instead, it accumulates, primarily in the viscera, although also in the muscle tissue. Methyl mercury is not soluble and therefore not excreted. Fish efficiently absorb methyl mercury, but excrete it very slowly. This algae is then eaten by fish and other organisms higher in the food chain. However, they are absorbed, usually as methyl mercury, by algae at the start of the food chain. Mercury and methyl mercury are present in only very small concentrations in seawater. The consumption of fish is by far the most significant source of ingestion-related mercury exposure in humans and animals. Cetaceans ( whales and dolphins) also bioaccumulate mercury and other pollutants, so populations that eat whale meat, such as the Japanese, Icelanders, Norwegians and the Faroese, are also vulnerable to mercury ingestion.

Species of fish that are long-lived and high on the food chain, such as marlin, tuna, shark, swordfish, king mackerel and tilefish contain higher concentrations of mercury than others. įish products have been shown to contain varying amounts of heavy metals, particularly mercury and fat-soluble pollutants from water pollution. In human-controlled ecosystems of fish, usually done for market production of wanted seafood species, mercury clearly rises through the food chain via fish consuming small plankton, as well as through non-food sources such as underwater sediment. Mercury is dangerous to both natural ecosystems and humans because it is a metal known to be highly toxic, especially due to its neurotoxic ability to damage the central nervous system. This element is known to bioaccumulate in humans, so bioaccumulation in seafood carries over into human populations, where it can result in mercury poisoning. Fish and shellfish concentrate mercury in their bodies, often in the form of methylmercury, a highly toxic organomercury compound. The presence of mercury in fish is a health concern for people who eat them, especially for women who are or may become pregnant, nursing mothers, and young children. Through the process of biomagnification, mercury levels in each successive predatory stage increase. Nearby anthropogenic sources, such as coal burning and iron mining, can contaminate water sources with methylmercury, which is efficiently absorbed in the bodies of fish.

Salmon and mercury poisoning