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

Abstract

In South Andes lakes, zooplankton succession is characterized by a change in the domin- ance from the calanoid copepod Boeckella gradlipes in winter and spring, to the cladoceran Bosmina longirostris in midsummer, and the rotifer Polyarthra vulgaris in late summer. We performed three series of field experiments at different times (late spring, summer and late summer) to examine the role of zooplankton constitution in the released nitrogen:phosphorus (N:P) ratio. We observed that changes in the zooplankton constitution over the annual cycle may change the nutrient supply ratio. In South Andes lakes, Boeckella gradlipes would decrease the P limitation, lowering the N:P ratio, whereas Bosmina longirostris tends to increase the N:P ratio and therefore increase the P limitation during summer.