Small-and large-celled phytoplankton during a strong disturbance period

While natural aquatic communities are characterized by high time-space variability, a variety of statistical methods produce highly sophisticated and efficient tools for analyses of ecological problems. Community-level modeling has earned growing attention as an alternative to and enhancement of studies focusing on individual species. Our aim was to compare the size structure of several components of Lake Kinneret (Israel) phytoplankton assemblage, using a long-term monitoring period made up of both stable years and years with great disturbances. Statistical descriptors of specific size classes identify zones of different variability within the lake phytoplankton spectra. While the annual succession change was most evident through the phytoplankton biomass variability, very conspicuous changes also characterized the small-celled part of the assemblage. At the same time that ataxonomic size spectra and allometries have produced very efficient tools of modern ecology, community-level taxonomic models augment such studies with the help of specific taxonomic group analyses providing diagnostically important information on the health of the studied ecosystem. Species abundances and occurrence rates produce common patterns that attract much interest in macroecology and help us derive simple diagnostic estimates for the assemblage disturbance level. Problems of assemblage-component (sensitive-size regions and phyla) selection and processing, that can amplify the diagnostic value of size spectra, are discussed. Such models deserve attention as efficient numerical tools applicable in theoretical ecology and monitoring.