Solar Lake (Sinai). 3. Bacterial distribution and production1

The relations between photosynthetic and nonphotosynthetic (chemoorganotrophic and chemolithotrophic) microorganisms in Solar Lake were studied during the annual limnological cycle. Six different bacterial plates were observed during stratification by direct and viable bacterial counts, light and dark CO 2 incorporation, chlorophyll a , protein, ATP, and ETS determinations. A maximal dark CO 2 incorporation of 1,014 mg C m −3 d −1 may represent as much as 16,900 mg C m −3 d −1 of chemoorganotrophic bacterial production, on the assumption that these bacteria assimilate an average of 6% CO 2 of their total carbon uptake. This calculated production is very high in comparison to the recorded photosynthetic maximum of 4,960 mg C m −3 d −1 . The organic carbon needed for such a high chemoorganotrophic production may be supplied by the benthic cyanobacterial mats. Extremely high specific activities of ATP and ETS for the layer immediately above the thermocline indicate a very active bacterial plate at this layer.