AME 79:63-78 (2017)  -  DOI: https://doi.org/10.3354/ame01813

ABSTRACT: Recently discovered submerged sinkholes in Lake Huron are high-sulfur, low-oxygen extreme environments for microbial life. In order to understand the relationship between the physical environment, photophysiology and community composition, we measured the physical conditions, photophysiological indices, and genetic diversity at 3 microbial mat sites bathed in high conductivity groundwater under a natural light gradient during 2012 and 2013. A strong seasonal trend prevailed at all sites, characterized by decreased photosynthetic yield (F_v’/F_m’; 0.25 to 0.40) during the summer (April to August) and increased yield (0.70 to 0.75) during the winter (November to March). Chlorophyll a content varied seasonally in a similar manner to photosynthetic yield. All sites were dominated by >80% abundance of one cyanobacterial group, most closely related to Phormidium sp. Phycobilins (phycocyanin and phycoerythrin) were consistently higher in concentration than chlorophyll. Photosynthetic yield was statistically indistinguishable between sites, suggesting that these mat communities are able to acclimate across a wide range of photosynthetically active radiation (PAR). Interestingly, these cyanobacteria carried out oxygenic photosynthesis in the presence of in vitro H₂S, further suggestive of their versatile photophysiologies under variable redox conditions. Collectively, our study provides insight into the adaptive capabilities of cyanobacteria by revealing how they photophysiologically respond to changes in light climate and redox conditions, and are thereby able to inhabit a wide range of physico-chemical environments. Such versatile physiologies may have enabled their ancestors to thrive across a range of habitats on early Earth.

KEY WORDS: Cyanobacteria · Sinkhole · Photophysiology · Photopigments · Photosynthesis

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Cite this article as: Snider MJ, Biddanda BA, Lindback M, Grim SL, Dick GJ (2017) Versatile photophysiology of compositionally similar cyanobacterial mat communities inhabiting submerged sinkholes of Lake Huron. Aquat Microb Ecol 79:63-78. https://doi.org/10.3354/ame01813 Export citation Share:    Facebook - - linkedIn