Spatial variation in nutrient excretion by macrozoobenthos in a Chinese large shallow lake (Lake Taihu)

Nutrient (N and P) fluxes via excretion by macrozoobenthos were estimated in a Chinese large shallow lake (Lake Taihu). The spatial variation in nutrient fluxes and the differences of specific excretion rate among six dominant species were quantified. The distribution of dominant species varied significantly among different trophic lake areas. The maximum biomass of macrozoobenthos was calculated in phytoplankton-dominated lake areas, while the minimum occurred in macrophyte-dominated lake areas. Mass-specific excretion rate among six dominant species was significantly different. Our results indicated that nutrient flux through benthic invertebrate varied spatially, which was affected by dominant benthic species composition and biomass. Limnodrilus hoffmeisteri, Corbicula fluminea and Bellamya aeruginosa made the greatest contribution to the total nutrient fluxes in Lake Taihu. N and P fluxes excreted by macrozoobenthos were greatest in phytoplankton-dominated lake areas (1037.7 mu mol N m(-2) d(-1) and 111.74 mu mol P m(-2) d(-1)), which were almost 20times greater than in the other lake areas. Since N and P excreted by macrozoobenthos could be rapidly absorbed by algae, macrozoobenthos might be a significant nutrient source contributing to frequent algal blooms in Lake Taihu