Pollution and the food web

Oceans receive pollutants from the atmosphere and from riverine inflow. Coastal environments are more likely to be affected because they can receive pollutants from both sources. They are also less deep and can receive secondary contaminations from pollutants which were stored in the sediments. Particularly coastal areas near industrialized and highly populated areas can contain high concentrations of pollutants. If these areas have a limited mixing with water from the open ocean, like the Baltic sea, the ecosystem becomes extremely vulnerable.

The different components of the ecosystem demonstrate a different vulnerability for certain pollutants. Pollutants can bioaccumulate when they are ingested at a higher rate than excreted. Pollutants which bioacumulate can also biomagnify if the pollutant is accumulated at all levels of the food chain. Biomagnifiyng substances are typically lipophilic (meaning they tend to dissolve in fat rather than water), like organonochlorines, or have a high affinity for proteins, like methylmercury. Pollutants which are mostly water associated, like heavy metals, don't tend to biomagnify. The latter may however bioaccumulate in some organisms to very high concentrations.

Biomagnifying compounds usually affect the top of the ecosystem (sea birds, marine mammals and pelagic fishes) most, because that's where they reach the highest levels. Biomagnifying substances