Microstratified vertical distribution and migration of phototrophic microorganisms during a diel cycle in Lake Arcas-2 (Spain)
Rodrigo, María A.; Camacho, Antonio; Vicente, Eduardo; Miracle, María R.
Archiv für Hydrobiologie Volume 145 Number 4 (1999), p. 497 - 512
published: Jul 26, 1999
ArtNo. ESP141014504004, Price: 29.00 €
During the study of a diel cycle in Lake Arcas-2 by means of a fine-layer sampler, dense populations of phototrophic microorganisms have been detected sequentially and sharply layered from the metalimnion-hypolimnion interface to the lake bottom. The predominant purple sulphur bacterium was Chromatium weissei which formed a dense plate at the oxic-anoxic boundary. The mean biovolume of C. weissei was statistically different in the cells forming the plate and those located below it, with the former 22 % larger than the latter. Two other Chromatiaceae species, Thiocapsa sp., and Amoebobacter sp. were members of this phototrophic community, although their abundances were much lower. Green sulphur bacteria (mainly Pelodictyon clathratiforme) were also present in low numbers below the purple bacteria. Maximum concentration of Oscillatoria cf. ornata filaments was observed very close to the populations of phototrophic bacteria within the microaerobic and anoxic layers. Motile cryptomonads (mainly Cryptomonas erosa) were observed at high densities in the vicinity of phototrophic prokaryotes. Several members of the photosynthetic community moved vertically about 40 cm during the diel cycle. Most microorganisms were concentrated at the oxic-anoxic boundary during the day (showing lower niche breadth) and dispersed through the hypolimnion at night (higher niche breadth). Diel changes in physical and chemical factors such as light penetration, oxygen and sulphide profiles are related with the complex and structured community of phototrophic microorganisms.