Effect of Depth on Sponge Assemblage Structure at Palmyra Atoll, Central Pacific

摘要

We examined the influence of depth on sponge assemblages across three lagoons at Palmyra; a remote atollsituated in the Central Pacific. The atoll is unusual in that it was heavily altered during WWII resulting in an atypicallagoon system. We conducted surveys at both 6-8m and 12-14m at 3 sites at the atoll and recorded sponge densities, areacover and available substrate for the 29 species found at these sites. Multivariate analysis of sponge densities and areacover revealed significant variability in sponge assemblages between both site and depth. Univariate analysis also showedsignificant differences in area cover between depths, but not between sites. Diversity indices and the average number ofspecies at each site showed an increase in diversity across lagoons from West to East. This study indicates that despite thesmall size of the atoll, depth is a factor that shapes sponge assemblages at Palmyra Atoll. The heavy alterations to thelagoon, particularly the area near the channel entrance may be influencing the sponge assemblage structure, however,other environmental variables still need to be investigated.