The food chain is a hierarchical series of organisms that are interrelated in their feeding habits. The chain starts when the smallest being like an insect is fed upon a larger prey species, which in turn feeds an even larger species. So if a species among the lower ranks of the chain has accumulated toxins such as pesticides or other organic chemicals, there is potential for these toxic substances to affect the species that prey upon them. This is the subject of new research conducted by the US Geological survey that found when fish feed on insects and when other wildlife species feed on fish, harmful contaminants are transferred up the line.
The food chain is a hierarchical series of organisms that are interrelated in their feeding habits. The chain starts when the smallest being like an insect is fed upon a larger prey species, which in turn feeds an even larger species. So if a species among the lower ranks of the chain has accumulated toxins such as pesticides or other organic chemicals, there is potential for these toxic substances to affect the species that prey upon them.
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This is the subject of new research conducted by the US Geological survey that found when fish feed on insects and when other wildlife species feed on fish, harmful contaminants are transferred up the line.
The potential for contaminants accumulated in wildlife to spread is a major concern because insects can transform from sedentary juveniles to winged adults, which can be carried to different locations potentially far from the pollution source.
The paper documents critical changes in insect contaminant concentrations and chemical tracers used to estimate position on the food chain during this transformation (a.k.a. metamorphosis).
"Most metals are lost during metamorphosis and are in higher concentrations in larvae than adults. Contaminants such as polychlorinated biphenyls (PCBs) are retained during metamorphosis and are in higher concentrations in adults than larvae," said Johanna Kraus, a USGS scientist based in Ft. Collins, Colorado, and lead author of the ES&T paper. "As a result, the animals that eat insects, like bats, birds and fish may be exposed to higher contaminant concentrations depending on the contaminants and whether they are eating larval or adult insects."
These results have large implications for managing and studying how far and how long it takes for contaminants to spread, and their effects on food webs across ecosystem boundaries. Metabolic regulation of contaminants generally predicts whether contaminants are excreted or concentrated in insect bodies during metamorphosis. Pollutants that magnify up the food chain tend to be retained and concentrated during metamorphosis.
This is the first paper to synthesize the general patterns and variation in contaminant transfer during a major developmental and habitat shift (e.g., water to land, ground to aerial) in animals with complex life cycles, as well as the first compilation of effects of metamorphosis on isotopic tracers used to estimate food web structure.
The study is published in Environmental Science and Technology.
See more at USGS.
Life cycle image via Shutterstock.
