Vertical distribution of bacteria and intensity of microbiological processes in two stratified gypsum Karst Lakes in Lithuania

Abstract

Key-words:bacteria, microbial processes, karst lakes Physical-chemical parameters and the vertical distribution of bacteria and organic matter production-destruction processes were studied during midsummer stratification in two karst lakes (Kirkilai and Ramunelis) located in northern Lithuania. The lakes were characterized by high sulfate concentrations (369−1248 mg·L −1 ). The O 2 /H 2 S intersection zone formed at 2−3 m depth. In Lake Kirkilai, the highest bacterial densities (up to 8.7 × 10 6 cell·mL −1 ) occurred at the O 2 /H 2 S intersection zone, whereas in Lake Ramunelis the highest densities were observed in the anoxic hypolimnion (up to 11 × 10 6 cell·mL −1 ). Pigment analysis revealed that green sulfur bacteria dominated in the microaerobic-anaerobic water layers in both lakes. The most intensive development of sulfate-reducing bacteria was observed in the anaerobic layer. Photosynthetic production of organic matter was highest in the upper layer. Rates of sulfate reduction reached 0.23 mg S 2− ·dm 3 ·d −1 in the microaerobic-anaerobic water layer and 1.97 mg S 2− ·dm 3 ·d −1 in sediments. Karst lakes are very sensitive to organic pollution, because under such impact in the presence of high sulfate amounts, sulfate reduction may become very intensive and, consequently, the increase in hydrogen sulfide and development of sulfur cycle bacteria may reduce the variety of other hydrobionts. Article published by EDP SciencesA. Krevs and A. Kucinskiene: Knowl. Managt. Aquatic Ecosyst. (2011) 402, 02 anoxiques (jusqu'à 0,23 mg S 2− ·dm 3 ·jour −1 ) et dans les sédiments (jusqu'à 1,97 mg S 2− ·dm 3 ·jour −1 ). Ces lacs karstiques sont très sensibles à la pollution organique, parce que, dans ce cas, en présence de fortes concentrations en sulfates, la réduction des sulfates peut devenir très intense et, en conséquence, l'augmentation du sulfure d'hydrogène et le développement des bactéries du cycle du soufre peuvent réduire la biodiversité.

Phytoplankton Community Structure in Highly-Mineralized Small Gypsum Karst Lake (Russia)

“…These lakes are mainly small, but relatively deep and often stratified. The hydrochemical facies of these water bodies are typical complexes of predominating solutes, pointing toward definite climatic and, accordingly, geochemical (weathering), soil, and hydrogeological and hydrobiological conditions, under which lake waters acquire their concentrations and compositions [3,4]. Gypsum karst lakes are characterized as sulphate lakes, as they are rich in gypsum or calcium sulphate, and they have elevated conductivity values [5].…”

“…These lakes are brackish (dissolve salts up to 2.0 g/L) and often cold water. Some have powerful springs of underground water pressure, specific water balances, amplified water exchanges, high transparency, and azure (ultramarine) water colors [4,6]. On the global scale, surface outcrops of gypsiferous strata appear quite limited [7].…”

“…On the global scale, surface outcrops of gypsiferous strata appear quite limited [7]. In this regard, such lakes are often considered as endemic [8] or unique [4][5][6]9].…”

Exploring Viral Diversity in a Gypsum Karst Lake Ecosystem Using Targeted Single-Cell Genomics

“…depth 6-7 m), nutrient-and organic matter-rich water body with high concentrations of Ca 2+ and SO 4 2− ions [27]. During summer stratification, the lake exhibits a pronounced chemocline at approximately 2 m deep, which is noticeable due to the depletion of oxygen, changes in water conductivity, and the presence of hydrogen sulfide (H 2 S) [28][29][30]. These conditions are also accompanied by a significant shift in water temperature and density.…”

“…These conditions are also accompanied by a significant shift in water temperature and density. Previous studies based on pigment analysis and partial 16S rRNA gene sequences obtained from the enrichment cultures revealed that members of genera Chlorobium (green sulfur-oxidizing bacteria; GSB) and Desulfovibrio (sulfate-reducing bacterium; SRB) are prevalent in the euxinic water layers of Lake Kirkilai [28][29][30]. At present, however, the relative abundance and distribution of these species, and any associations with other members of the lake bacterial or viral communities, are unknown.…”