The growth of
Chromatium sp. in Lake Kaiike, a small coastal lake on the Kamikoshiki Island, was considered from the viewpoint of growth responses of
Chromatium sp. in culture to different gradients of environmental factors such as temperature, light, pH and H
2S. In July, 1978,
Chromatium sp. densely populated the upper part of the H
2S layer and the density and assimilation rate of the bacterium attained to 2×10
6 cells/ml and 700 mg C m
-3 day
-1, respectively. Incident light and H
2S concentration at the habitat, being less than 1% of that just beneath the surface and less than 3 mg S/l, lay within the ranges where the growth of laboratory-cultured
Chromatium sp. increased in proportion to their quantities. But the fact that the habitat of
Chromatium sp. is confined to a depth below the algal compensation depth indicates that light condition does not exert such a pronounced effect on the
in situ growth of
Chromatium sp. On the contrary, the supply of H
2S to the habitat supposedly would have an important effect on the growth of this bacterium.
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