The ecology of photosynthetic bacteria in Burton Lake, Vestfold Hills, Antarctica

Abstract

Photosynthetic bacteria in Burton Lake, a seasonally tidal, meromictic lake of maximum depth 18 m, located in the Vestfold Hills, Antarctica, were studied throughout 1983. The dominant species were Chlorobium vibrioforme and Chlorobium limicola (up to 5.4 × 10⁶ cells ml⁻¹) and minor species were Thiocapsa roseopersicina (< 1.25 × 10⁵ cells ml⁻¹) and Rhodopseudomonas palustris (< 100 cells ml⁻¹). The Chlorobium spp. and T. roseopersicina were found throughout the anoxic water, which ranged in temperature from −0.5°C to −2.2°C, but did not form discrete layers at the O₂−H₂S interface. The growth zone, however, of the Chlorobium spp. was delineated by the presence of light and H₂S and was restricted to less than 3 m below the O₂−H₂S interface. R. palustris was found in oxic and anoxic water. Available light, which varied from 0–4.9µE m⁻² s⁻¹ at the O₂−H₂S interface, was considered to be the major environmental factor controlling growth of the bacterial phototrophs. Growth was initiated in spring in low light levels (< 1 µE m⁻² s⁻¹) following 3 months of darkness during winter. It is concluded that the dominance of the Chlorobium spp. was a result of their more efficient maintenance metabolism in winter and of their greater efficiency in utilizing low intensity light.