Heterotrophic and anoxygenic photosynthetic bacteria

This chapter reviews the current knowledge of the heterotrophic and anoxygenic photosynthetic bacteria in Lake Kinneret. Morphological and phylogenetic diversity of bacteria and archaea as well as data from routine total bacterial cell counts are summarized. From 2001 to 2011, there was a definite, significant trend to lower the annual average cell counts that coincided with a significant decrease in bacterial productivity. Additional information is provided on anoxygenic phototrophic bacteria prevailing in Lake Kinneret. The most abundant of these phototrophs is the green sulfur bacterium (GSB) Chlorobium phaeobacteroides Pfennig. It forms (almost consistently) a prominent layer in the metalimnion from June through October. The spatial distribution of BChl e, an indicator of C. phaeobacteroides, was fairly heterogeneous, and its peak values often exceeded the record of chlorophyll a peaks. C. phaeobacteroides was identified as a major contributor to the sedimenting material in the lake in the summer, making up on average 27 % of the carbon settling towards the bottom.