The size-abundance distribution and taxonomic composition of plankton in an oligotrophic, high mountain lake (La Caldera, Sierra Nevada, Spain)

In this paper we describe the main features of the size-abundance distribution and taxonomic structure of plankton in an oligotrophic, high mountain lake (La Caldera, Sierra Nevada, Spain). The distribution is characterized by a discontinuity in the size range between ˜2000 and 32 000 μm 3 (cell volume). Phytoplankton are numerically dominated by the cyanobacteria Cyanarcus sp., followed by the chrysophyte Chromulina nevadensis and the diatom Cyclotella ocellata . Some microplanktonic species such as the diatom Navicula radiosa were observed sporadically. The size spectrum and composition of the zooplanktonic community are dominated by the copepod Mixodiaptomus laciniatus . On considering biomass, however, the maximum values are associated with the largest size classes, dominated by the cladoceran Daphnia pulex . Both the size structure and taxonomic composition of the planktonic community studied are consistent with expectations based on theories relating the pattern of energy flow and trophic status in lakes.