|Author(s)||Reijnders, P.J.H.; Borrell, P.J.H.; Franeker, J.A. van; Aguilar, A.|
|Source||In: Encyclopedia of marine mammals / Wuersig, B., Thewissen, J.G.M., Kovacs, K.M., London : Academic Press - ISBN 9780128043271 - p. 746 - 759.|
|Publication type||Chapter in scientific book|
|Abstract||Awareness of the threat of environmental contaminants to marine mammals is widespread. High concentration of certain compounds in the tissues of these animals has been associated with organ anomalies, impaired reproduction, and immune function and, as a consequence of the latter, with the occurrence of large die-offs among seal and cetacean species. This prompted alertness about the impact of pollution and stimulated research into the relationship between observed effects and pollutants. However, a clear causeand- effect relationship between residue levels of contaminants and observed effects has been might elicit a serious backlash, because in the absence of evidence, concerns expressed are easily interpreted as fear-mongering. This might lead to inertia in taking appropriate management measures, something which is undesirable for conservation and wise environmental management. The main reasons for the lack of proof of the impact of pollution on marine mammals are the difficulty or impossibility of experimenting in laboratory conditions with these animals, and
the frequent occurrence of confounding factors that hamper the establishment of cause-and-effect relationships. Examples of these factors are the fact that pollution always occurs as a mixture of a large number of chemical compounds, the lack of data on biological variables influencing tissue levels, low quality of the samples usually analyzed, the limited information on pathology and
occurrence of disease in the specimens studied, the absence of reliable population data, and the lack of information on the influence of other detrimental factors such as concurrent anthropogenic and natural changes acting as environmental, ecological, and physiological stressors.