Toward an integrated framework for assessing micropollutants in marine mammals: Challenges, progress, and opportunities

As apex predators, marine mammals play a key role in maintaining community structure and functioning in marine ecosystems. Hence, a decline in marine mammal populations may have negative effects on the ecosystem function and services. The discharge of anthropogenic chemicals and particles (micropollutants) into the marine environment threatens the health of marine mammals. Traditional approaches for assessing the impact of micropollutants on marine mammal populations are limited by the complexity of micropollutants (e.g., low concentrations, unknown contaminants, transformation products, and mixture effect) and marine mammals (e.g., complex physiology, life history, multiple stressors, and logistical challenges) in the environment. Recently developed (bio)analytical tools that can integrate chemical and biological assessment such as non-target and suspect screening, direct effect analysis, and multiomics (e.g., metabolomics, lipidomics, proteomics, and transcriptomics) can offer critical insights into (i) the health risks of 'known' and 'unknown' micropollutants in marine mammals, (ii) the link between exposure and population effects, and (iii) identification of priority micropollutants. This review highlights the challenges and current progress in assessing the health risk posed by micropollutants to marine mammals. A tired integrated chemical-ecological-biological framework developed from current research practices is offered for effective assessment of micropollutant risk in marine mammals.