In recent decades, a number of disease-related mass mortalities of marine mammals have occurred in populations inhabiting industrial coastal areas, suggesting that chemical contamination could have played a role. A new study has found that biological pollution could also be playing a role in the deaths of harbor seals. The study is published in the latest issue of Environmental Toxicology and Chemistry.

Considerable evidence has shown that environmental contaminants such as polychlorinated biphenyls (PCBs) contribute to marine mammal mortalities by affecting their immune systems. Marine mammals are at particularly high risk of immunotoxicity because of their high trophic levels, long life span, and limited capacity to eliminate PCBs.

The objective of the current study was to assess the impact of this chemical on the immune systems of a large group of free-ranging harbor seals. The study team found that biological pollution also appears to have an impact. Biological pollution includes bacterial pathogens in the water from human sources including sewage discharge, septic fields and storm water drainage, and agricultural activities including runoff from livestock and soil fertilization. However, the latter have only a relatively minor input compared to human sources.

The combination of PCBs and biological pollution may have lethal consequences for seals living near urban areas that receive high levels of bacterial pathogens, which are areas characterized by elevated fecal coliform counts.

To read the entire study, click here: allenpress/pdf/entc_25_1204_3110_3117.pdf

Environmental Toxicology and Chemistry is the monthly journal of the Society of Environmental Toxicology and Chemistry (SETAC). For more information about the Society, visit setac.

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