Density, biomass and productivity of animals in four subtidal rocky reef habitats: The importance of small mobile invertebrates

Abstract

Density, biomass and productivity of animals >0.5 mm were estimated in 4 shallow subtidal rocky reef habitats in temperate northeastern New Zealand. The main objective was to determine the relative contributions of mobile epifauna (0.5-10 mm) and megafauna (> 10 mm) to the flux of materials on the reef. The habitats surveyed were (1) Carpophyllum plumosum var. capillifolium forest (Phaeophyceae: Fucales), (2) Ecklonia radiate forest (Phaeophyceae: Laminariales), (3) urchin barrens, and (4) articulated coralline algal turf flats. Epifauna comprised >99.5% of individuals in each habitat. Epifauna dominated biomass (>86%) in the finely structured Carpophyllum forest and turf flats, where they contributed >97% of total secondary productivity. Although lower in the other 2 habitats, the epifaunal contribution to total secondary productivity was still ~78% on the scale of the entire reef. These results show that epifauna are major contributors to the flux of materials in rocky reef habitats, and should therefore be included in trophic models of these systems. Consumption by fish could only account for -26% of epifaunal production, with the fate of the remainder unknown. Estimated annual secondary productivity within the Carpophyllum forest and turf fiats habitats (100 to 115 g AFDW m-2 yr-1) was higher than literature values for a range of soft sediment habitats, and was exceeded only by 2 other hard-bottom communities.