Influence of depth on bryozoan richness and distribution from the continental shelf of the northern coast of Bahia State, north-eastern Brazil.

Biological and abiotic processes influence ecosystem structure and species distribution. For bryozoan assemblages, depth, substratum and habitat structure are among the main factors influencing their distribution. Ecological studies on bryozoan fauna from Brazil are scarce and factors affecting the distribution and/or diversity of this common group are obscure. Here we attempted to verify the influence of bathymetry on bryozoan richness on the north shore of Bahia State, north-eastern Brazil. We identified 57 bryozoan taxa, comprising 35 families and 50 genera, all belonging to the Cheilostomata. Retevirgula multipunctata Winston, Vieira & Woollacott, 2014 and Tetraplaria dichotoma (Osburn, 1914) and the genus Aimulosia Jullien, 1888 were recorded for the first time from Bahia State. Species growing as encrusting sheets were dominant at all depths. There was a significant difference in richness among samples at different depths, with highest values of richness at 40 meters (Kruskal-Wallis Test). Analysis of similarities revealed a significant difference among the bryozoan assemblages, mainly when comparing assemblages from 10 and 20 meters with deeper ones. Also, shallower assemblages composition varied much than assemblages from 30 and 40 meters. Since depth is a proxy for several environmental parameters, further studies are needed to identify other factors influencing bryozoan distribution.