Influence of basin scale on structure of natural aquatic communities

The aim of the study was to analyze the influence of aquatic ecosystem size on community structure. Analysis is based on quantitative indices, describing integral communities and comparison of their biomass size spectra with standard patterns. Comparative analysis of widely differing aquatic communities shows that certain characteristics of the community structure withstand considerable changes of many important parameters of the abiotic environment and taxonomic composition of the community. At the same time, there are some changes in fine structure of the community size spectra, which can now be documented and measured with relatively high precision due to development of modern automated means of data acquisition. In this study, application of spectral descriptions is discussed as applied to communities of River Jordan-Lake Kinneret aquatic system. It follows from the theoretical scheme developed that, for analysis, the most important part of the community size spectrum is its right extreme, i.e. body size of the largest species of the ecosystem. In the case of Lake Kinneret, that is fish. The fish biomass size spectra were obtained using dual-beam hydro-acoustics techniques. The parameter comparison shows that for riverine systems (i.e. ecological systems with a high role of allochtonous organic matter in the total energy influx of the community), both the water area and the watershed basin (including its terrestrial part) deserve attention as the appropriate scaling parameter.