Solar Lake (Sinai). 4. Stromatolitic cyanobacterial mats1

Abstract

Cyanobacterial mats of Solar Lake, studied in the field and by microscopic methods, are classified into four types: flat shallow‐water mat, pinnacle mat on the upper slope, cyanobacterial and other photosynthetic bacterial films on the lower slope, and flocculose mat at the bottom. The annual cycle and development of the four types are described. Measurements of photosynthesis by the flat shallow‐water mat in the field and the laboratory yielded an average value of 10 g C m−2 d−1. In the flocculose anaerobic bottom mat 5 g C m−2 d−1 was measured. Total accretion rates including organogenic material for the four mat types range between 5 and 50 cm 100 yr−1; aerobic and anaerobic degradation of the organic production of the shallow‐water mat remineralizes more than 99% of the biomass. In the deeper parts of the mat, organic matter is transformed into carbonates. The role of bacteria in this process is demonstrated by ultramorphological analyses and by comparison to laboratory experiments with bacterial isolates.