Density, biomass and productivity of small mobile invertebrates in a wide range of coastal habitats

Abstract

Density, biomass and productivity of small (0.5 to 8.0 mm) mobile invertebrates were estimated within 34 diverse coastal habitats occurring along 80 km of coastline in temperate north- eastern New Zealand. These habitats ranged from the high shore to 20 m depth and included hard, soft and macroalgal substrates. The structurally complex and food-rich coralline algal turf and sandy beach seaweed wrack were the most densely populated and productive habitats, while intertidal sands tended to be most depauperate in mobile fauna. Temporal consistency in results was demon- strated for 4 habitats sampled seasonally for 2 yr. After adjusting for habitat extents, rankings of den- sity, biomass and productivity of fine-scale habitats amalgamated into broad-scale habitats were: sub- tidal rocky reef > intertidal rocky reef > subtidal soft sediments or intertidal estuary > sandy beach. Total productivity of mobile invertebrates was greater in hard- than soft-bottom habitats. Gastropods numerically dominated most hard-bottom habitats, and gammarid amphipods dominated most soft- bottom habitats. Communities of broad habitat types were reasonably discrete in multivariate space.