Epifaunal community structure within southern New Zealand kelp forests

Epifaunal communities associated with macroalgal forests are a key link in coastal tood webs, yet they are relatively poorly understood in terms of diversity, structure and regional variability. We quantified the biomass, density and richness of epifauna on the 7 most dominant seaweed species from 2 regions of southern New Zealand, i.e. East Otago and Stewart Island. We analysed the epifaunal community structure associated with each macroalgal species and estimated the average biomass of epifauna supported per m(2) of substrate at the shallow (2 m) and deep (10 m) extent of each reef. Significant differences in epifaunal biomass, density and richness were evident between macroalgal species in both regions, and epifaunal community structure differed significantly between regions on 2 of the 4 macroalgal species that were shared. Epifaunal biomass ranged between 5.1 and 186.8 g wet weight m(-2) and corresponded to 0.01 to 0.08% of the macroalgal biomass. Epifaunal biomass and density were not always linked to the morphological complexity of the host macroalgal species, and some of the highest values were found on species considered morphologically simple, such as the fucoid Xiphophora gladiata and laminarian kelp Ecklonia radiata. Greater macroalgal biomass at shallow depths did not always result in greater epifaunal biomass when compared to deeper depths, indicating that macroalgal community structure plays a significant role in controlling epifaunal biomass. Significant regional and host-specific factors likely influence epifaunal communities, and these should be considered when estimating secondary productivity and the effects of habitat change.