The environmental pioneer, Rachel Carson, first described the process of biomagnification in 1962 in her famous book “Silent Spring:” a book, which has been considered to be somewhat of an emblem of the environmental movement. Carson depicted the process of biomagnification as process by which pollutants were transferred through different trophic levels in an ecosystem. In other words, pollutants are transmitted through the food chain. The classic exampled explored in “Silent Spring” is that of the insecticide DDT (dichlorodiphenyltrichloroethane):
- DDT is dispersed throughout fields in the country side; this very same DDT arrives in aquatic ecosystems and becomes absorbed by plankton. The DDT, which plankton accumulates is then transmitted to crustaceans, small fish, and other organisms that eat plankton. Next, DDT is transmitted to bigger fish that feed on the smaller fish. This process then continues, moving up the food chain to human beings. The concentration of DDT increases in each species, as the DDT moves up the food chain because organisms that are bigger in size have slower metabolisms, slowing down their bodies’ capacity to rid itself of the DDT. As such, at each level of the food chain, species consume nutrients with greater concentrations of DDT.
Today, it seems as though a similar phenomenon is occurring with plastics. It has been recognized that plastic pollution in the world’s oceans generates grave problems for marine mammals, such as dolphins and turtles. These animals suffer from ingesting plastics and from becoming entrapped in them. Research on the impact of plastic pollution on planktivorous organisms of lower trophic levels, or species of fish and marine organisms that feed on plankton, is rather limited. There, however, have been a few studies analyzing specifically the presence of plastics in organisms and species at lower trophic levels. In 1999, the Algalita Marine Research Foundation, showed that in the North Pacific, plastics outnumbered plankton by a ratio of 6:1 (Moore et al., 2001). A study from 2010 in the same part of the North Pacific demonstrated that 35% of planktivorous fish in the area had pieces of plastic in their bodies (Boerger et al., 2010).
The alarming results of this study were not only the percentage of fish affected by plastic pollution, but also the quantity of plastics found in these organisms. In some fish, scientists found up to 83 pieces of plastic in their intestines. Since plastic disintegrates in the ocean, the fish confuse plastic for plankton. Scientists found plastics of every color in the fish. Among the colors of plastics found, were white, clear, and blue. Blue plastics were predominant in organisms (87% of the plastics found in these fish were in fact blue). Scientists
explain this predominance as related to the color of plankton in the area.
Another recent study from 2011, which was undertaken in the ocean Northeast of Brazil, had similar results. This study showed that all of the fish in the area had been exposed to plastic pollution during their lifetimes. The species studied did not measure more than 30 cm and were species eaten by bigger and more commercial fish. The study concluded that plastic ingestion among fish could have detrimental effects on the fishing industry, as it affects all types of fish species along the food chain (Possatto et al., 2011).
In general, it is difficult to measure the impact of plastic pollution on the food chain. What does remain clear, however, is that plastic has entered the food chain at lower trophic levels, potentially posing harm to human health. More research is needed on the impact of plastic pollution on both the health and the life cycles of fish. Moreover, more research is need to discover the potential effect of plastic pollution on higher trophic levels. Does plastic pollution go through the same process of biomagnification as DDT?
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