Control of primary productivity and the significance of photosynthetic bacteria in a meromictic kettle lake. Mittlerer Buchensee, West-Germany

Abstract

During 1986 planktonic primary production and controlling factors were investigated in a small (Ao = 11.8-103 m 2, Zmax = 11.5 m) meromictic kettle lake (Mittlerer Buchensee). Annual phytoplankton productivity was estimated to ca 120 gC. m -2. a -t (1,42 tC-lake 1. a-l). The marked thermal stratification of the lake led to irregular vertical distributions of chlorophylla concentrations (Chla) and, to a minor extent, of photosynthesis (Az). Between the depths of 0 to 6m low Chla concentrations (< 7mg. m -3) and comparatively high background light attenuation (kw = 0,525 m -~, 77 % of total attenuation due to gelbstoff and abioseston) was found. As a consequence, light absorption by algae was low (mean value 17,4 %) and self-shading was absent. Because of the small seasonal variation of Chla concentrations, no significant correlation between Chla and areal photosynthesis (ZA) was observed. Only in early summer (June-July) biomass appears to influence the vertical distribution of photosynthesis on a bigger scale. Around 8 m depth, low-light adapted algae and phototrophic bacteria formed dense layers. Due to low ambient irradiances, the contribution of these organisms to total primary productivity was small. Primary production and incident irradiance were significantly correlated with each other (r 2 = 0.68). Although the maximum assimilation number (Popt) showed a clear dependence upon water temperature (Qa0 = 2.31), the latter was of minor importance to areal photosynthesis.

Seasonal change in microbial sulfur cycling in monomictic Lake Fukami‐ike, Japan

“…The predominant bacterial phylotype through all depths was FK-01, which was closely related to the previously described anoxygenic phototroph, green sulfur bacterium Chlorobium phaeoclathratiforme sp. (Y08108) (Overmann and Tuschak 1997) within the genus Chlorobium. Other than the abundant bacterial phylotype of potentially sulfur-oxidizing phototrophic bacteria, only the bacterial phylotype (FK-07) that was moderately related to a sulfate-reducing bacterium Algodomarina propionica sp.…”

“…For the first possibility, decreasing levels of the oxic-anoxic boundary would enhance anoxygenic photosynthesis at the lake bottom. Previous studies showed that the rate of anoxic photosynthesis is highest just below the oxic-anoxic boundary (Parkin and Brock 1980;Overmann et al 1991). In Lake Fukami-ike, Yagi et al (1983) studied the rate of carbon uptake by green sulfur bacteria and suggested that the uppermost 1 m below the oxic-anoxic boundary showed a rate 10 times higher than that in the other depth in the anoxic layer.…”

Diel dynamics of vertical changes of chlorophyll and bacteriochlorophyll in small humic lakes

“…Bacteriochlorophyll d+e was determined in the same samples using Overmann's formulae (Overmann 1987, cited in Overmann andTilzer 1989). At the same time, the temperature, pH, oxygen, and conductivity in situ were measured throughout the whole water column at 1 m intervals and air temperature was determined with a YSI 610-DM sensor.…”

Gas vesicle formation and buoyancy regulation in Pelodictyon phaeoclathratiforme (Green sulfur bacteria)

“…m -2 9 s -1 (Overmann and Tilzer 1989). At this illumination, a growth rate of lower than 0.1 d -1 (equal to a doubling time of 14 d at a 12-h light period) was measured in pure cultures (Fig.…”