Alteration of lake bacterioplankton diversity and community composition during lake stratification and gradual oxygen depletion
(English)Manuscript (preprint) (Other academic)
Hypolimnetic waters of many stratifying lakes experience gradual oxygen depletion and seasonal hypoxia as organic matter is degraded with oxygen as terminal electron acceptor. Such changes are known to have dramatic effects on larger organisms, but also resident microbiota are likely to be affected by altered availability of oxygen, nutrients and other chemical constituents. We explored how such seasonal shifts in water mass characteristics influenced the resident bacterioplankton in a mesotrophic temperate lake by tracing the temporal dynamics of bacterial communities and populations at different phylogenetic resolution across the entire period of summer stratification. Compared to the epilimnion, bacterial richness was significantly higher in the hypolimnion where varying hypoxia was also reflected in higher beta diversity. Many abundant groups of freshwater bacteria, such as Actinobacteria acI, Polynucleobacter and freshwater SAR11 (LD12), were abundant in both the epi- and hypolimnion, with distinct temporal and vertical population shifts observed at the 97% population identity level. The mechanisms that lead to closely related populations partitioning into ecotypes are not well understood, but are probably due to fine-tuned physiological adaptions towards oxygen and nutrient concentrations in the lake. The existence of ecotypes partitioned by oxygen availability and the seasonal succession in hypolimnetic bacteria driven by gradual oxygen depletion and associated changes in water chemistry merits further studies on their implications for biogeochemical cycles.
hypolimnion, Bacteria, Community Composition, Diversity, Hypoxia, Dynamics, Indicator, Habitat
Research subject Biology with specialization in Evolutionary Genetics; Biology with specialization in Limnology
IdentifiersURN: urn:nbn:se:uu:diva-245068OAI: oai:DiVA.org:uu-245068DiVA: diva2:790351