Complex Interactions in the Lake Kinneret Ecosystem

Abstract

Published models indicate that phytoplankton density, and consequently water quality is dependent on grazing capacity by herbivore zooplankton (small and large Cladocera and Rotifera). Moreover, the top-down eco-force, cascading effect, produced by zooplanktivore fishes, Cyclopoid predator zooplankton, or both, attributes the principal pressure. Nevertheless, complex interactions within the ecosystem have also indicated an impact induced by other factors such as nutrients (bottom-up eco-force), which affect the major food resource of herbivore zooplankton, and grazeable algae (Chlorophyta, Diatoms) density. Temperature significantly affects zooplankton density as well as lake water residence time and Water Level. Two methods of statistical analyzes were utilized aimed at the evaluation of a multivariate comprised ecosystem: Principal Component Analyzes (PCA) and its illustrated plot (Biplot). Results conclusively indicate that zooplanktivore fishes (Sardines) and temperature are the Principal Components. Seclude of isolated single factor as a unique impacting parameter on zooplankton density, either predator Cyclopoida or Sardine fishes is therefore misleading.