High pollutant exposure level of the largest European community of bottlenose dolphins in the English Channel

Abstract

The objective of this study was to assess the levels of persistent organic pollutants (POPs) and mercury (T-Hg) in the blubber and skin, respectively, of the free-ranging bottlenose dolphins, Tursiops truncatus, from the Normanno-Breton Gulf, one of the largest identified coastal population in Europe. Among all the POPs analysed in this study, the ∑NDL-PCBs were the most abundant compounds found in the blubber (mean: 1.33 × 10⁵-0.65 × 10⁵ ng.g^-1 lipid weight (lw) for males and females respectively), followed by ∑DDX (1.11 × 10⁴-4.67 × 10³ ng.g^-1 lw) > ∑DL-PCBs (8.06 × 10³-2.62 × 10³ng.g^-1 lw) > ∑PBDEs (1.95 × 10³-0.64 × 10³ng.g^-1 lw) > dieldrin (1.86 × 10³-0.18 × 10³ ng.g^-1 lw) > ∑endosulfan (405-62 ng.g^-1 lw) > HCB (86-52 ng.g^-1 lw) > ∑HCHs (47-60 ng.g^-1 lw) > ∑chlordane (24-0.97 ng.g^-1 lw) > ∑PCDFs (0.3-0.1 ng.g^-1 lw) > ∑PCDDs (0.06-0.05 ng.g^-1 lw). The T-Hg concentrations were highly variable between individuals (2.45 × 10³ ng.g^-1 to 21.3 × 10³ ng.g^-1 dry weight, dw). The reported concentrations are among the highest reported for cetaceans. We strongly recommend that the Normanno-Breton Gulf be a special area of conservation (cSAC) candidate because it contains the last large European population of bottlenose dolphins (rare or threatened within a European context) designated under the EC Habitats Directive.