Algal indicator system of environmental variables in the Hadera River basin, central Israel

We identified 126 species of algae and cyanoprokaryotes from seven divisions in 21 samples of plankton and periphyton collected at 8 stations over the Hadera River in 2003 - 2005. The chlorophytes strongly prevail. Of these, 110 species are indicators of environmental conditions. The indicators of saprobity (Watanabe's scale) show a medium level of organic pollution. The saprobity index S (Sládecek's scale) varies from 1.73 to 2.80, corresponding to II - IV classes of water quality. The environmental pollution index (EPI) varies from 2 to 5 indicating a range of slightly to strongly polluted water of classes III and IV. The Water Ecosystem State Index, WESI = 0.6, testifies to a toxic impact on the algae in the middle reaches. The River Pollution Index for saprobity (RPIs = 2.35 - 2.42), temperature (RPIt = 17.1 in winter), conductivity (RPI? = 3.31 - 4.5), nitric nitrogen (RPI N = 15.3), and pH (RPI pH = 7.6 - 8.3) indicate alkaline, moderately mineralized waters with an occasional input of nitrates all year round, corresponding to classes III - IV of water quality, and the beta- to alfa-mesosaprobic self-purification zone. According to our results, the self-purification capacity of the Hadera River ecosystem is rather high. This study shows the potential of the algal bioindication method for aquatic ecosystems of Israel.