Assessing the health of Halifax Harbour's intertidal ecosystem: Impacts of marine pollution on community structure, reproductive health of key predator populations (Nucella lapillus), and immunomodulation in blue mussels (Mytilus edulis and Mytilus trossu

A decrease in abundance of community structuring macrophytes and increased abundance of filter feeders led to an overall reduction in intertidal species richness at polluted sites in Halifax Harbour, Nova Scotia, Canada. Mytilus mussels sampled within Halifax Harbour displayed impaired immune function in the form of reduced phagocytic activity and reduced production of hydrogen peroxide by cells of the immune system when compared to mussels from a control site. Halifax Harbour sites also displayed high levels of tributyltin-mediated endocrine disruption in dogwhelks (imposex) and periwinkles (intersex), while dogwhelks were absent at sites with lowest intertidal species richness. Municipal marine pollution is a complex mixture of substances, making it difficult to choose endpoints for assessing effects of exposure on the ecological health of the receiving environment. Monitoring health at the level of the ecosystem and population, down to the cellular realms, contributes to a full understanding of effects.