Bathymetric patterns of sponge distribution on the Bahamian slope

Using a manned submersible equipped with a high-resolution video camera, we documented vertical patterns of species abundance, substratum usage, color, and body form of sponges living on the Bahamian slope. Sponge abundance is not linearly related to depth, but has a bimodal distribution, with peaks located on the upper slope (100 m depth) and between 400 and 500 m. Sponge fauna decreases dramatically between 100 and 230 m and remains rather depauperated to 320 m. The deep-water mode of the vertical distribution is dominated by abundant lithistids and astrophorids, whereas the shallow mode includes a wide assortment of species belonging to most of the sponge orders.