Developing an indicator for persistent chemicals in Northeast Atlantic marine mammals in the framework of the OSPAR convention

The Convention for the Protection of the Marine Environment of the North‐East Atlantic (“OSPAR Convention”) established several environmental indicators to monitor persistent chemicals (PCs, e.g. PCBs and mercury) in European waters1. Due to their long lifespan, high trophic position and large blubber reservoirs, marine mammals may accumulate extremely high concentrations of PCs, often surpassing established toxicity thresholds. At the same time, they can help to assess the pollution state of the entire food web in an integrated manner2. This work aimed at collecting and harmonizing the existing data on PCs’ pollution in marine mammals across all OSPAR-managed regions in order to develop the framework for a new pollution indicator for monitoring the environmental status of the Northeast Atlantic.
Data covering all five OSPAR regions (I: Arctic waters, II: Greater North Sea, III: Celtic Sea, IV: Bay of Biscay and Iberian Coast, V: Wider Atlantic) was provided by ten OSPAR contracting parties (B, DE, DK, ES, FR, IE, NL, PT, SE, and UK) for 30 species of cetaceans and pinnipeds. Of all PCs analyzed (>200), PCBs had the widest data coverage and were selected as sentinel PCs to develop the conceptual framework of the indicator. The sum of total PCBs concentrations (ΣPCBtot) was explored, with the number of analyzed PCB congeners varying from 6 to 48. We performed a preliminary qualitative analysis of marine mammal’s pollution status, structuring the indicator’s framework in three parts: spatial, temporal and status assessment.
The highest availability of PCBs data was found for the 2009-2016 time-frame and for regions II, III and IV3. Scarce data was available for Region I and V. Small toothed cetaceans presented the highest range of the ΣPCBtot (0.20 – 820 mg/kg lipid weight, lw), followed by pinnipeds (0.01 – 226 mg/kg lw), deep-diving cetaceans (0.01 – 72 mg/kg lw), and baleen whales (0.04 – 21 mg/kg lw), all ages and sexes lumped for each group. The ΣPCBtot surpassed the established toxicity range for reproductive impairment (9 – 41mg/kg lw)4 in most small toothed cetaceans, in some deep-divers and in a few pinnipeds. Baleen whales did not surpass known toxicity thresholds.
Although data are scattered and not all species represented, the ΣPCBtot seemed to be influenced by ecological traits (e.g. diet and habitat use) rather than region or year. This preliminary assessment underlines the need for future efforts towards data harmonization at regional European level. Several parties reported that many samples are available in their tissue banks that have not been analyzed due to budget limitations. This prompts the prioritization of funding projects aiming to fill gaps at temporal and spatial scale. The next steps will include the (1) addition of legacy and emerging PCs into the spatial and temporal assessments; and (2) harmonization of this indicator with other regional sea conventions (i.e. HELCOM).