The Distribution of Meiobenthic Copepods along a Sediment Gradient: Factor and Niche Analyses

The meiobenthic copepod community associated with a subtidal sedimentological gradient was investigated with the aid of diversity indices (Shannon-Wiener, species richness, and evenness), Q-mode cluster analysis, niche breadth and overlap analysis, and multiple discriminant-canonical correlation analysis.

Three broad sedimentological categories which encompass the five sampling sites were defined: a coarse sand group including the FD site, a medium sand group including the DB and SS sites, and a silt-clay group including the CB and BB sites. Diversity values indicate both spatial and temporal trends but mean values for the five sites are not significantly different. Q-mode cluster analysis showed high within groups similarity in the coarse sand group and the BB site of the silt-clay group with the other three sites showing both within and among site similarity. Four broad groupings, based on species abundance, are evident. Niche breadth and overlap values of the 14 most abundant copepods showed that species in the sand sites were characterized by narrow-medium niches which were broadly overlapping; the silt-clay sites were characterized by medium-broad niches which were slightly overlapping. Multiple discriminant-canonical analysis indicates that median grain size diameter, percent silt-clay, and organic content in the sediment are the most important physical variables in determining species distributions. Four species assemblages were indicated by the distribution of species means on the first three discriminant functions, one including species from the sand sites and three with species from the silt-clay sites.