Contaminants as a Conservation Threat to Marine Mammals

Abstract

Persistent Organic Pollutants (POPs) and inorganic elements like mercury (Hg) are ubiquitous environmental pollutants. Their physico-chemical properties allow them to be transported over great distances, deposited, and incorporated into aquatic food webs. As long-lived species, many high trophic level marine mammals bioaccumulate high levels of certain contaminants, and a variety of contaminant-related health effects have been reported in populations around the world. Contaminants have been identified as one of the top threats to over 80% of the marine mammal populations globally, including two of Canada’s most endangered cetacean populations, Southern Resident killer whales (orcinus orca) from the northeastern Pacific, and St Lawrence Estuary beluga whales (Delphinapterus leucas). It is therefore critical that we continue to improve upon our understanding of contaminant sources, their fate, and effects in order to better inform on marine mammal conservation measures. The collection of samples from marine mammals poses a number of challenges, however, over the past few decades novel approaches have been developed that allow for minimally invasive collection of samples (e.g., fecal). As well, the development and use of new laboratory techniques (e.g., omics) has allowed for the assessment of contaminant-related impacts at different levels of biological organization. Despite these advances, there is much to be learned about contaminant-mediated effects in marine mammals at both the individual and population levels. There is a need for long-term monitoring programmes that use multidisciplinary approaches to assess regional contaminant trends and effects in marine mammals in the context of other environmental stressors, including climate change.