Benthic habitat mapping of the glass sponge (Vazella pourtalesii), and associated community composition on Sambro Bank, Scotian Shelf, Canada

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Sponges have been identified as ecosystem engineers, providing habitat structure for many other benthic organisms, but are vulnerable to the impacts of bottom contact fishing. The Sambro Bank Sponge Conservation Area (SBSCA) protects a globally unique aggregation of the glass sponge ( Vazella pourtalesii) off the east coast of Canada. Here, we present the first comprehensive, high-resolution mapping study of this site. Multispectral multibeam echosounder (MBES) mapping at three operating frequencies and 12 benthic drop camera stations were conducted at the SBSCA in 2022. Video data were analysed to record the presence and location of V. pourtalesii, and extracted still images were used to quantify all benthic fauna and sediment characteristics for each station. Using the MBES backscatter data sets as predictor variables, the study created a generalized linear mixed model of V. pourtalesii presence in the SBSCA, with 90.1% accuracy. Four seafloor benthoscape classes were identified (hard substrata, mixed substrata, sand/mud substrata, and sand/mud veneer) from the video imagery, with statistically distinct benthic macrofaunal communities associated with each class. The study creates a baseline assessment of the current community composition and habitat characteristics of the site, which can be used for future ecological monitoring and management.