AUV-based classification of benthic communities of the Ningaloo shelf and mesophotic areas

Abstract

Despite a growing understanding of the importance of mesophotic ecosystems, they remain relatively unexplored globally, and particularly in the Indian Ocean. The composition of benthic communities of the Ningaloo Marine Park in deeper water (> 20 m) was determined using autonomous underwater vehicles (AUVs). Environmental variables collected by the AUVs as well as geomorphological variables derived from high-resolution multibeam bathymetry were used to explain the distribution of these communities. Imagery was classified for benthic biota, and non-hierarchical k-means clustering was used to identify community groups. Overall, 12 community groups were identified which fell into three broad categories: (1) coral-dominated, (2) CCA-dominated; and (3) macroalgae- and filter-feeder-dominated. Specific deeper water communities (> 50 m) were characterised by the presence of sponges or other non-photosynthetic filter feeders. Corals were confined to depths < 40 m, and cover was high (29–40%). Generalised additive models identified the importance of substrate (cover of sand, rock, and gravel/pebbles), geomorphological variables (slope and bathymetric position index) and temperature in the distribution of communities.