ALGAL VEGETATIVE ACTIVITY IN THE UPPER JORDAN RIVER (NORTHERN ISRAEL): AN IN VITRO GLASS SLIDE EXPERIMENT

Algal vegetative activity and intensity of self purification processes were determined via a two stage in vitro artificial substrates (glass slides) occupation experiment, conducted during winter 2006-2007 and summer 2007 in the streams of the Upper Jordan River Basin. Daily measurement of temperature, conductivity, mineralization and pH were performed. Once a week algal species where identified, snd their Abundance (cells/cm(2)), Cell volumes (mu m(3)/cm(2)) and richness of species (taxa encountered/600 algal cells) tabulated for each taxon. Algal communities where richer in the summer in all stations and contained mainly Diatoms or Diatoms/green algae mix. Only the Banias station winter community was dominated by the green algae. Highest self-purification activity was observed during the summer in the upper part of the basin (Banias station). Species richness grew with anthropogenic influence and self-purification intensity. Self-purification proceeded faster in conditions of high temperature and solar radiation. The Shannon index positively correlated with species richness in both winter and summer experiments. The artificial colonization of substrates by algae took 2-3 weeks; formation of small celled green algae encouraged by high temperatures and solar radiation conditions increased colonization speed in the summer. Statistically significant factors influencing algal activity were found to be pH and Total Dissolved Solids concentration.