Nutrient recycling and shifts in N:P ratio by different zooplankton structures in a South Andes lake

In South Andes lakes, zooplankton succession is characterizedby a change in the dominance from the calanoid copepod Boeckellagracilipes in winter and spring, to the cladoceran Bosmina longirostrisin midsummer, and the rotifer Polyarthra vulgaris in late summer.We performed three series of field experiments at differenttimes (late spring, summer and late summer) to examine the roleof zooplankton constitution in the released nitrogen:phosphorus(N:P) ratio. We observed that changes in the zooplankton constitutionover the annual cycle may change the nutrient supply ratio.In South Andes lakes, Boeckella gracilipes would decrease theP limitation, lowering the N:P ratio, whereas Bosmina longirostristends to increase the N:P ratio and therefore increase the Plimitation during summer.