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  • Title: Microbial processes of the carbon and sulfur cycles in an ice-covered, iron-rich meromictic lake Svetloe (Arkhangelsk region, Russia).
    Author: Savvichev AS, Kokryatskaya NM, Zabelina SA, Rusanov II, Zakharova EE, Veslopolova EF, Lunina ON, Patutina EO, Bumazhkin BK, Gruzdev DS, Sigalevich PA, Pimenov NV, Kuznetsov BB, Gorlenko VM.
    Journal: Environ Microbiol; 2017 Feb; 19(2):659-672. PubMed ID: 27862807.
    Abstract:
    Biogeochemical, isotope geochemical and microbiological investigation of Lake Svetloe (White Sea basin), a meromictic freshwater was carried out in April 2014, when ice thickness was ∼0.5 m, and the ice-covered water column contained oxygen to 23 m depth. Below, the anoxic water column contained ferrous iron (up to 240 μμM), manganese (60 μM), sulfide (up to 2 μM) and dissolved methane (960 μM). The highest abundance of microbial cells revealed by epifluorescence microscopy was found in the chemocline (redox zone) at 23-24.5 m. Oxygenic photosynthesis exhibited two peaks: the major one (0.43 μmol C L-1  day-1 ) below the ice and the minor one in the chemocline zone, where cyanobacteria related to Synechococcus rubescens were detected. The maximum of anoxygenic photosynthesis (0.69 μmol C L-1  day-1 ) at the oxic/anoxic interface, for which green sulfur bacteria Chlorobium phaeoclathratiforme were probably responsible, exceeded the value for oxygenic photosynthesis. Bacterial sulfate reduction peaked (1.5 μmol S L-1  day-1 ) below the chemocline zone. The rates of methane oxidation were as high as 1.8 μmol CH4  L-1  day-1 at the oxi/anoxic interface and much lower in the oxic zone. Small phycoerythrin-containing Synechococcus-related cyanobacteria were probably involved in accumulation of metal oxides in the redox zone.
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