Stability of Lake Kinneret phytoplankton structure as evidenced by several types of size spectra

Stability analysis of the aquatic community is among the most important and complicated fields in modern ecology. Application of statistical approaches and modern automated tools has introduced new operational methods for the comparative analyses of aquatic assemblage structure. While much work has been done on two types of biomass size distributions or size spectra (BSS and NBS), the size-frequency distribution of taxonomic units, called here the traditional taxonomic size spectrum (TTSS), has been given much less attention. The composite size spectrum (CSS) described here compares several types of size structures. Two of them (NBS and TTSS) evidenced consistent patterns for Lake Kinneret phytoplankton. The high similarity level of the discussed patterns was estimated quantitatively by cluster analysis. While typical patterns were evident and consistent even during two extremely abnormal years (1997-1998), the fine structure of all size spectra was susceptible to strong environmental impacts. Several types of size spectra used simultaneously provide more comprehensive information describing community structural change.