Structure and dynamics of epifaunal assemblages on intertidal macroalgae Ascophyllum nodosum and Fucus vesiculosus in Nova Scotia, Canada

Abstract

Abundance and species composition of epifauna on Ascophyllum nodosum and Fucus vesiculosus on a rocky shore in Nova Scotia show pronounced seasonal variation. Total density of epifauna declined by 2 orders of magnitude between summer and winter. Harpacticoid copepods and their nauplii, nematodes, and halacarid mites were numerically the most important components of the assemblage throughout the 13 mo study (May 1983 to Jun 1984). Density was positively correlated with epiphytic algal biomass for most epifaunal taxa. Cluster analysis and multidimensional scaling also indicate that epifaunal sample groupings were strongly related to epiphyte biomass. There was a greater tendency for samples to cluster according to the 2 macroalgal species during the winter, when epiphyte biomass was low, suggesting that epiphytes obscure differences in morphology andlor microbial surface fllrns between A. nodosum and F. vesiculosus.