High levels of pollutants, such as industrial fluids and mercury, may have accumulated in the blubber and skin of one of the largest coastal populations of dolphins in Europe, a study in Scientific Reports indicates. Mercury concentrations found in 82 dolphins living in the English Channel are among the highest concentrations observed in the species, the work suggests.
Toxic organic pollutants, particularly those containing chlorine, were banned from most developed countries in the 1970s and 1980s; however, they can still be detected even in the deepest ocean marine life. These organic compounds are able to dissolve in fats and oils, and consist of the by-products of various industrial processes and pesticides, among others. Bottlenose dolphins are often used to study levels of environmental pollutants, as the organic compounds accumulate within their thick layer of fatty tissue.
Krishna Das and colleagues assessed levels of organic pollutants in the blubber and levels of mercury in the skin of 82 free-ranging bottlenose dolphins inhabiting the Normanno-Breton Gulf in the English Channel. They found high concentrations of pollutants in the blubber, predominantly made up of chlorine-containing compounds from industrial fluids (91% in males and 92% in females). Moreover, the levels of mercury in the skin samples were similar to concentrations previously described for bottlenose dolphins in the Mediterranean Sea and Florida Everglades, two sites already known for their high mercury contamination levels.
The authors suggest that the Normanno-Breton Gulf should become a special area of conservation to protect one of the largest costal populations of bottlenose dolphins in Europe.