What impacts may long term exposure to low level toxins have on organisms further in the food chain?

Answer 1

Toxins may have many affects on the higher level predators in food chains. When toxins are present in a predators prey, the predator develops a build up of the toxin in its system known as bio accumulation. An excellent example of a top predator being negatively affected by a toxin is the peregrine falcon. DDT (dichlorodiphenyltrichloroethane) a well-known pesticide, now banned from use in Canada, caused the thinning of the falcons eggshells. This caused fewer numbers to hatch, as the fragile shells could often break under the weight of the mother incubating them before the offspring reached the point of hatching. Organochlorines (such as DDT) are not only toxic but highly persistent in living tissues, resisting breakdown and resulting in accumulation, particularly in long-lived predator species such as the peregrine falcon. The impact of DDT in the peregrine falcon has been a dramatic decline in population, they have nearly become extinct in the wild in Canada, and the species has been listed as endangered, although with conservation efforts, captive breeding and release programs, and a ban on DDT the species is making a slow come back.