The effects of sedimentation and light on recruitment and development of a temperate, subtidal, epifaunal community.

Sedimentation has often been implicated as a factor in structuring epifaunal assemblages on hard substrata yet there are few studies that empirically test this relationship. This study investigated the effects of light and sedimentation conditions on the initial recruitment and subsequent development of an encrusting community at Lough Hyne, S.W. Ireland. Slate settlement panels were subjected to four different conditions of sedimentation and light. The five replicates of each treatment were photographed at approximately 6-week intervals over 13 months. Values for Brillouin diversity (HB) and number of recruits were greatest for shaded panels sheltered from sediment. Number of species was much higher on downward facing panels relative to upward facing panels, regardless of conditions of sedimentation and light. Sedimentation resulted in reduced cover for some species, such as Lithothamnion spp., whilst others, such as Anomia ephippium, were less affected by this variable. Total space occupied was significantly higher for inverted panels, possibly indicating geotaxic behaviour of some larvae. Number of species on each panel condition was more similar for sets of panels exposed for shorter periods relative to the 13-month experiment, implying that post-settlement mortality may differ between treatments.