Europe's largest community of coastal bottlenose dolphins threatened by industrial pollution

A study conducted by researchers from the University of Liège (UR FOCUS/MolSys Faculty of Sciences) and the Groupe d'Études des Cétacés du Corentin (GECC – Cotentin Cetacean Study Group), reveals the concentration of persistent organic pollutants and mercury in bottlenose dolphins in the Gulf of Normandy. The concentration rates observed are alarming and could have a significant impact on the last largest bottlenose dolphin community in Europe. This research is published in Scientific Reports.

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any dolphin communities live along the coasts of Europe. However, there is only one remaining community of bottlenose dolphins, called Tursiops, that lives in the Normand-Breton Gulf in Normandy. This community, which counts 400 individuals, is now threatened by human activities, and more particularly industrial activities. This is proven in any case by a recent study conducted by researchers from the University of Liège (FOCUS and MolSys Research Units / Faculty of Sciences) in collaboration with the Groupe d'Études des Cétacés du Cotentin (GECC - Cotentin Cetacean Study Group). This is due to human activity, but above all to the industrial activity of the companies that border the Gulf.

"We analyzed many samples taken from 82 dolphins living in the Gulf," explains Krishna Das, a FNRS Senior Research associate at the University of Liège’s Oceanology laboratory,"and we found very high levels of persistent organic pollutants (POPs) and mercury. "As for POPs, researchers have mainly identified polychlorinated biphenyls (PCBs), highly toxic pollutants resulting from industrial activity, which have been banned in Europe for several decades! Mercury levels in the samples were similar to those found in the Mediterranean Sea and the Everglades (Florida, USA), two sites infamous for their high levels of mercury contamination.

Mean PCB concentrations in male bottlenose dolphins from the Normanno-Breton Gulf (NBG, red bar, present study, Ʃ6 NDL-PCBs) compared to the SPCBs from other European locations.

"Persistent organic pollutants, particularly chlorine-containing PCBs," says Krishna Das,"were banned in most developed countries between the 1970s and 1990s. However, they are still detected in many species of marine organisms, even those living in the ocean depths. "Polychlorinated biphenyls have been used, among other things, as dielectrics and cooling fluids in electrical equipment and heat transfer fluids. However, despite their prohibition, PCBs still persist in the marine environment. "They are very persistent, degrade poorly and accumulate effectively in marine food webs to the dolphin. Despite current regulations, this study reveals that these organic pollutants are still present in the marine environment and accumulate infood webs up to bottlenose dolphins. "These pollutants could persist for decades, and some scientists are even considering that they could persist for centuries," says Krishna Das.

These toxic pollutants have devastating effects on the immune system but also on the reproductive capacities of these mammals. To halt this process, the research team recommends that the Gulf of Normandy-Breton could become a Special Conservation Area (SCA) to protect one of the last large populations of large coastal dolphins in Europe.

Scientific reference

Cyrielle Zanuttini, François Gally, Georges Scholl, Jean-Pierre Thomé, Gauthier Eppe, Krishna Das, High pollutant exposure level of the largest European community of bottlenose dolphins in the English Channel, Scientific Reports, Scientific Reports,volume 9, 12521 (2019). 

Contacts

Krishna DAS - FOCUS Research Unit - Faculty of Sciences

Gauthier EPPE - MolSys Research Unit - Faculty of Sciences