Original paper

Diversity and ecology of phytoplankton and periphyton of the Nahal Oren, Alon Natural Park, Northern Israel

Barinova, Sophia S.; Anissimova, Olga V.; Nevo, Eviatar; Wasser, Solomon P.

Abstract

We studied algal diversity of Nahal Oren, the least polluted coastal river of Israel that can be used as a model of a regional aquatic ecosystem. In 94 samples of periphyton and phytoplankton we found 221 taxa of species and subspecies ranks belonging to 9 divisions of algae and cyanoprokaryotes. The diatoms, chlorophytes, and cyanoprokaryotes prevail. Most of the species are cosmopolitan or widespread in both the Mediterranean and Boreal realms; only two species, the Gloeothece violacea and Chroococcidiopsis kashayi, have relatively narrow Mediterranean ranges. In the ecological analysis, the algal species of Nahal Oren are divided in respect to their habitats, temperature conditions, water dynamics, oxygenation, salinity, acidity, and saprobity (concentrations of organic pollutants). The algal assemblage comprises the indicators of warm, temperate and cool waters, as well as eurythermics. The indicators of organic pollution include 108 species. The indices of saprobity fall in the range of oligo to betamesosaprobic self-purification grades (1.20 to 2.41). The indicators of salinity (125 species, 57%) are assigned to five ecological groups. The most numerous among them are the oligohalobien-indifferents of a broad tolerance of salinity fluctuations. Alkaliphiles predominate among the indicators of acidity, with few acidophiles confined to the aerophytic communities. Ecologically, the majority of algal species are the typical inhabitants of temperate alkaline waters of low mineralization. Several types of algal communities are described for the stream and still water habitats. Diatom communities prevail on chalk cliffs of the upper reaches. In the middle reaches, the chlorophytes and cyanoprokaryotes are added to the dominant algal species, the overall diversity fluctuates between 8 to 101 species. The lower reaches contain the most heterogeneous habitats supporting the algal communities dominated by chlorophytes, cyanoprokaryotes, and diatoms. Rare species of red algae Audouinella pygmaea and charophytes Chara tenuispina are found for the first time in the Nahal Oren, which is the southernmost occurrence for the latter species. These pollution-sensitive species add to the ecological significance of Nahal Oren as a model of natural aquatic ecosystems in the coastal zone of Israel. Species richness is positively correlated with the ranges of saprobity indices indicating the heterogeneity of habitats in respect to concentration of nutrients. The diversity decreases with saprobity and further falls with periodic desiccation.

Keywords

freshwater algaediversityalgal communitiesecologyphytogeographyisrael