Dramatic Change in the Kinneret Phytoplankton Community Structure—Peridinium Out, Cyanobacteria in (POCI): Perennial or Disposable

Abstract

A comprehensive compilation of long-term data records about the dynamics of nutrient migration and availability in the Kinneret epilimnion was statistically evaluated. A replacement of Peridinium spp. domination by cyanobacteria in Lake Kinneret (Israel) was documented. Nitrogen outsourcing is a significant factor within the Kinneret ecosystem structure. Part of the Kinneret watershed, the Hula Valley, which was covered by a shallow lake and swampy wetlands was drained. The result was the conversion of the nitrogen supply, as ammonium and organic forms, into nitrate. Nevertheless, nutrients supplied from aquaculture (fish ponds) and raw sewage partly compensated for the ammonium deficiency. After sewage removal and fish pond restrictions (the early 1990s), the majority of nitrogen migration became nitrate, dependent on climate conditions (rainfall, river discharges). The preference for ammonium by the bloom-forming Peridinium spp. caused a reduction in the efficiency of nitrogen utilization and cyanobacteria replaced phytoplankton for domination.