Response of benthic meiofauna to nutrient enrichment of experimental marine ecosystems

Abstract

he long-term (2.4 yr) response of benthic meiofauna to eutrophication of experimental marine ecosystems was studied at the Marine Ecosystems Research Laboratory, Graduate School of Oceanography, University of Rhode Island (USA). Ammonium, phosphate and silicate were added daly to the mesocosms in a logarithmic progression (OX, 1 X, 2 X, 4 X, 8 X, 16x and 32 X), with the l X addition being N = 2.88, P = 0.225, Si = 0,205 mm01 m-' d-l. Phytoplankton production and biomass in the tanks increased with increasing nutrient enrichment. The benthic community gave a quantitatively less marked response to the gradient of nutnent input. The meiofauna showed remarkably little response in terms of total biomass and abundance, but significant effects were found on major taxa, leading to a changed meiofauna community structure. Nematode and juvenile polychaete abundance increased with increasing nutrient input, especially in early summer, whereas kinorhynchs, ostracods, harpac- ticoids and juvenile bivalves decreased. The lack of a positive biomass response of the total meiofauna in the enriched tanks suggests that the meiofauna was limited not only by the availability of food, but also by biotic interactions.