Application of a weight of evidence approach utilising biological effects, histopathology and contaminant levels to assess the health and pollution status of Irish blue mussels (Mytilus edulis)

A weight of evidence (WOE) approach, integrating biological effects, mussel histopathology and tissue contaminant levels is proposed to evaluate mussel health and pollution status. Contaminant levels, histopathology and several biological effects (BEs) including Lysosomal membrane stability (LMS), acetylcholinesterase (AChe), metallothionein proteins (MT) and alkali labile phosphate (ALP), in Mytilus edulis are presented, improving the current knowledge base for these data. Potential links between histopathology, BEs and contaminants and ranking of sites are investigated with an integrated response (IR) indexing technique. Histopathological condition indices (Ih) in mussel digestive gland are used to calculate health indices. A spatial and temporal assessment is conducted at Irish coastal locations. Linear mixed effects modelling revealed effects of confounding factors such as reproductive condition on NRRT (gonad stage (p < 0.001)). Higher prevalence of inflammation, brown cells and epithelial thinning of the digestive gland was evident at Dublin and Wexford and this linked well with the Ih. Levels of contaminants were generally found to be low with few exceptions as were BE responses. Using the IR approach, Dublin was ranked as being most impacted while Shannon ranked the least impacted, this being consistent with the BE ranking.