Mapping seafloor habitats in the Bay of Fundy to assess megafaunal assemblages associated with Modiolus modiolus beds

Abstract Dense aggregations of horse mussels exist in the Bay of Fundy and are thought to be associated with high biodiversity compared to surrounding habitats. Previous research show correlations between these aggregations and long narrow flow-parallel bedforms. In this study, high resolution seafloor photographs were compared to multibeam echosounder data to investigate benthic community and biodiversity patterns across the Bay of Fundy. Biophysical seafloor types (benthoscapes) were mapped with 71% accuracy using Object Based Image Analysis (OBIA) with fuzzy c-means classification. Community patterns were found to shift gradually across benthoscapes and mega-epifaunal biodiversity was highest in areas of mixed sediments and silty gravel and anemones. Horse mussels occurred mainly within the sand benthoscape where the flow parallel bedforms exist. Community patterns were also assessed at fine scales (5 m) using a by-eye interpretation of the flow parallel bedforms, where gradational shifts across the bedforms and surrounding areas were evident and abundance of horse mussels were found to be significantly greater on the bedforms. These findings will ultimately facilitate decisions around fisheries management, marine spatial planning, and monitoring of the horse mussel habitats and the surrounding benthoscapes within the Bay of Fundy.