Copepod and cladoceran success in an oligotrophic lake

Cladocerans have proved to be much less successful members of the Lake Tahoe limnetic community than the calanoid copepods. An analysis of temporal and spatial heterogeneity of the cladoceran Bosmina longirostris and the herbivorous calanoid copepod Diaptomus tyrrelli revealed important differences between the two types of zooplankton. Although the productivity of both species is limited to varying degree by the abundance of certain algal species and the availability of particulate nitrogen, they differ strongly in the mechanisms responsible for mortality. Correlation analysis suggests that B. longirosris is severely limited temporally and spatially by predation from the omnivorous calanoid copepod Epischura nevadensis . In contrast, D. tyrrelli is not noticeably limited by predators. Instead, abiotic seasonal events and starvation control its population dynamics. Mortality and natality differences between Bosmina and Diaptomus in Lake Tahoe help to explain the general lack of success of cladocerans in oligotrophic lakes.