Interactions between contaminants and environmental change

Changes in environmental conditions caused by stressors, including climate change and invasive non-native species, may, in some cases, make wildlife more vulnerable to contaminants. Environmental change can increase the exposure of some aquatic species to contaminants through changes in water flow and chemistry and through changes in food webs.15, 16 Interactions may also make animals more vulnerable to the effects of contaminants. For example, salmonids in the Great Lakes have switched to a diet that includes alewife, an invasive non-native fish, leading to thiamine (vitamin B1) deficiencies that may interact with the effects of contaminants like PCBs to increase mortality rates in young fish.17

Impact of less sea ice on contaminants in seals and polar bears

Photo: bearded seal © changes in sea-ice conditions, western Hudson Bay polar bears are feeding less on
ice-associated bearded seals (which eat invertebrates) and more on open-water seals (which eat fish).18 Because fish-eating seals have higher levels of contaminants, some legacy contaminants in polar bears may not be declining as much as would be expected if their diet had not changed and levels of emerging contaminants may be increasing at a faster rate. Concentrations of brominated flame retardants (PBDEs) in western Hudson Bay polar bears are estimated to have increased 28% faster from 1991 to 2007 than would have occurred if the bears had not changed their diet.18

Impact of changes in fire regimes on mercury in fish

Photo: fireweed © in fire regimes can increase algae in lakes and contaminants in fish. A study in Jasper National Park16 found that fire in the catchment area of a lake in 2000 increased the input of nutrients to the lake over a period of several years. This led to an increase in production of algae, which led to an increase in the abundance of invertebrates, making the lake's food web more complex. The outcome was an increase in mercury accumulating in lake trout and rainbow trout.