AB - Vol. 14 No. 2 - Feature article

Hypoxia strongly influences microbial community of Lake Vesij√§rvi, Finland. Inset: epifluorescence micrograph of APP cells (red), and DAPI signals of DNA containing cells (blue); scale bar = 10 μm). Photos: G. Bręk-Laitinen

Bręk-Laitinen G, López Bellido J, Ojala A


Response of a microbial food web to prolonged seasonal hypoxia in a boreal lake


Hypolimnetic hypoxia is a common phenomenon in many antrophogenically affected lakes. Bręk-Laitinen and co-workers determined the response of the microbial food web to changes in environmental conditions in boreal Lake Vesij√§rvi. They found ciliate community creating a characteristic species distribution pattern along the water column as a response to changes in temperature and oxygen concentration. Bacterivorous taxa dominated in the hypoxic zone, while in the epilimnion bacterivorous, algivorous and predatory taxa were present. Moreover, the close coupling between seasonal dynamics of bacteria and productivity of phytoplankton, including autotrophic picoplankton, suggests that the smallest phytoplankton species are an important source of carbon for bacteria. These results serve to characterize carbon transfer pathways in microbial communities of hypoxic freshwaters.


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