For a large part of earth's history, cyanobacterial mats thrived in low‐oxygen conditions, yet our understanding of their ecological functioning is limited. Extant cyanobacterial mats provide windows into the putative functioning of ancient ecosystems, and they continue to mediate biogeochemical transformations and nutrient transport across the sediment–water interface in modern ecosystems. The structure and function of benthic mats are shaped by biogeochemical processes in underlying sediments. A modern cyanobacterial mat system in a submerged sinkhole of Lake Huron (
Seasonal changes in light and physicochemical conditions have strong impacts on cyanobacteria, but how they affect community structure, metabolism, and biogeochemistry of cyanobacterial mats remains unclear. Light may be particularly influential for cyanobacterial mats exposed to sulphide by altering the balance of oxygenic photosynthesis and sulphide‐driven anoxygenic photosynthesis. We studied temporal shifts in irradiance, water chemistry, and community structure and function of microbial mats in the Middle Island Sinkhole (MIS), where anoxic and sulphate‐rich groundwater provides habitat for cyanobacteria that conduct both oxygenic and anoxygenic photosynthesis. Seasonal changes in light and groundwater chemistry were accompanied by shifts in bacterial community composition, with a succession of dominant cyanobacteria from
- NSF-PAR ID:
- 10443962
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Environmental Microbiology
- Volume:
- 25
- Issue:
- 11
- ISSN:
- 1462-2912
- Format(s):
- Medium: X Size: p. 2516-2533
- Size(s):
- ["p. 2516-2533"]
- Sponsoring Org:
- National Science Foundation
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Desulfocapsa , and eukaryotic algae. The least diverse particle‐associated assemblages occurred near the lower oxycline boundary, where microbial activities and abundances were highest, and anoxygenic photoautotrophs were enriched. The low‐diversity particle‐associated heterotrophs likely remineralize complex organic substrates, releasing simpler organic substrates to free‐living assemblages during transit, thereby influencing surrounding microbial diversity and function. Our results challenge the paradigm that phytoplankton from the shallow photic zone are the primary contributor to the vertical flux. We suggest that photoautotrophic prokaryotes from the deep photic zone contribute significantly to deep‐water carbon in this environment, and possibly in other oxygen‐deficient waters with sulfidic photic zones. Furthermore, results suggest that seasonally variable terrestrial carbon and metal inputs also influence microbial diversity and function in similar systems. -
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