La Rochelle, France (7 jours/7)

Contaminant monitoring

Monitoring of contaminant concentrations


Since 2017, the concentrations of chemical contaminants in marine mammal populations in French waters have been monitored by the Pelagis observatory, within the framework of the Marine Strategy Framework Directive (MSFD) and the descriptor dedicated to the study of chemical contamination. Marine mammals are long-lived species, located at the top of marine food webs and therefore accumulate high concentrations of contaminants, due to the biomagnification of Persistent Organic Pollutants (POPs) and mercury. The main route of exposure of these species to contaminants is the trophic route, which is why variations in concentrations between species but also within a species linked to food preferences or feeding areas are observed. These species are therefore integrators of global contamination. Numerous studies have demonstrated the presence of a wide variety of contaminants in the tissues of marine mammals. In addition, some authors have been able to show that these toxic substances can cause alterations to the immune system, reproductive failures and disturbances to the endocrine system. As a result, these species are considered to be very sensitive to environmental disturbances and good sentinels of the health of the marine environment.

In this context, the monitoring of contaminant concentrations at the Pelagis observatory is carried out using marine mammal samples from the National Stranding Network (RNE). It is applied to each marine sub-region of mainland France (i.e. Channel – North Sea, Bay of Biscay, Celtic Seas and Western Mediterranean). For each sub-region a representative species has been chosen: the harbour porpoise (Phocoena phocoena) for the English Channel-North Sea, the common dolphin (Delphinus delphis) for the Bay of Biscay and the Celtic Seas, and the blue and white dolphin (Stenella coeruleoalba) for the Mediterranean. The bottlenose dolphin (Tursiops truncatus) which is a species common to all four sub-regions is also included in this monitoring.

Figure 1: Species and number of individuals analysed annually (n), or every two years, by marine sub-region.

Finally, within the framework of research projects or monitoring programmes in connection with the DSCMM, the quality of marine mammal prey is also monitored at the observatory, including analysis of the energy density of this prey as well as its concentrations of chemical contaminants (particularly heavy metals). This enables us to understand the exposure of these predators to contaminants via the food chain.

Résultas attendus

From these routine analyses, we will be able to establish contamination levels for the different species and populations studied, which will enable us to identify the populations or segments of populations that are most vulnerable or at highest risk from chemical contamination. What is thus done at the national level can be transposed to the international level thanks to the participation of the Pelagis observatory in European projects aimed at identifying populations at risk on the scale of European waters.

Similarly, the collection of strandings for more than 40 years on the French coast now gives us access to samples that enable us to assess the long-term temporal evolution of chemical contamination of the marine environment, through these so-called sentinel species of marine ecosystems.

Research to follow :

Studies have shown that the presence of high concentrations of POPs as well as trace elements such as certain heavy metals can cause immune and endocrine system disruption and reproductive failure in marine mammals.

However, research in this field remains difficult today in marine mammals. The main reasons for the lack of evidence of the impact of chemical pollution on marine mammals are the difficulty or impossibility of experimenting in the laboratory with these animals, the influence of numerous factors, known as confounding factors such as those already mentioned (age, sex or sexual maturity), which hinder the establishment of cause-and-effect relationships, and the difficulty of identifying, monitoring and collecting data for wildlife species such as marine mammals.

Nevertheless, at the Pelagis observatory we will seek to develop biomarkers of effects in males in relation to the population segment chosen for contaminant monitoring.

There is growing evidence that biodiversity and environmental and human health can be affected by mixtures of toxic chemicals in the environment and in food for human consumption. Today more than 350,000 chemicals are manufactured on an industrial scale, reaching the environment and food chains. As a result, currently regulated and monitored environmental contaminants represent only a fraction of the total chemical exposure of organisms. Routine testing targets known molecules that may represent only a small proportion of the total contaminant load, while many molecules not known to date may also cause potential physiological damage, yet are not considered in these targeted routine tests. Marine mammals being long-lived species, located at the top of marine food webs and with a high capacity to accumulate high concentrations of contaminants are therefore a good biological model for this type of study, and we have therefore also set up a non-targeted screening strategy (NTS) with several research laboratories (Cariou et al. 2020).

Ronan Cariou, Paula Méndez-Fernandez, Sébastien Hutinet, Yann Guitton, Florence Caurant, Bruno Le Bizec, Jérôme Spitz, Walter Vetter, and Gaud Dervilly. ACS ES&T Water Article ASAP
DOI: 10.1021/acsestwater.0c00091