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Pollution and the food web

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Versie door Daphnisd (Overleg | bijdragen) op 29 jul 2009 om 15:20

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North Sea food web © Vliz

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. [1]

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 to very high concentrations in some organisms.[2]

Biomagnifying compounds usually affect the top of the ecosystem (sea birds, marine mammals, fishes,...) most, because that's where they reach the highest levels. Compounds which don't biomagnify will first affect species with a low tolerance and those who accumulate them. Juvenile stages have been shown to be particularly sensitive towards many pollutants. Filter feeds, such as bivalves, usually have high bioacumulation rates because they acquire large amounts of pollutants from suspended particles. Pollutants with a low water solubility tend to be adsorbed to these particles. [3]

Additional hazardous characteristics of pollutants are stability and toxicity. Chemically stable pollutants, which are not biodegradable, can remain part of the ecosystem for long periods of time. Therefore their environmental concentration will continue to increase with increasing emissions. Even after emissions have stopped they can continue to contaminate the ecosystem for decades.


Below you can find some Belgian case studies of pollutants through the food web

Case studies

Case study 1: PBDE through the entire North Sea food web[4]


References

  1. Clark, R,B., 1999. Marine pollution. Oxford University press, Fourth edition, pp 161
  2. Biology of marine birds. Schreiber, E.A. & Burger, J. (Eds). 2002. Boca Raton, Florida: CRC Press. 722 pp.
  3. Kennish, M. J. (1996): Practical Handbook of Estuarine and Marine Pollution, CRC Press 524 pp
  4. Boon, J.P.; Lewis, W.E.; Tjoen-A-Choy, M.R.; Allchin, C.R.; Law, R.J.; de Boer, J.; Hallers-Tjabbes, C.C.; Zegers, B.N. (2002). Levels of polybrominated diphenyl ether (PBDE) flame retardants in animals representing different trophic levels of the North Sea food web. Environ. Sci. Technol. 36(19): 4025-4032