Exploring The Relative Importance Of Surficial Cyanobacteria Communities Versus Physical, Chemical And Bioloigical Processes At Depth On Sulfur Cycling In Two Microbial Mat Environments
ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY(2018)
摘要
Microbial mats are multi-layered structures built by morphol. and metabolically diverse consortiums of microorganisms.
In many mats, the predominant fabric and biovolume of the structures are primarily generated by Cyanobacteria, which
carry out photosynthesis at or near the mat surface. Both the mat-building and mat-dwelling communities shape the
morphol. and geochem. gradients with depth in the mat. After dioxygen, redox transformations of sulfur fuel mat
biogeochem. and provide a useful window into understanding community structure and biogeochem. cycling in the mat.
In particular, it has been shown that the top of the zone of sulfide accumulation migrates through the day in response diel
light cycles: it lies at a greater depth in the day when dioxygen is produced by photosynthetic Cyanobacteria, and moves
towards the surface at night when photosynthesis is no longer active and oxygen accumulation is limited by rates of
diffusion through the mat surface. We analyzed sulfur isotope patterns in pore water sulfide in order to understand how
different types of microbial communities and environmental conditions influence microbial-driven geochem. reactions in
two Cyanobacteria-rich systems:. (1) saline microbial mats lining a shallow lagoon at Little Ambergris Cay, Turks and
Caicos Islands, and. (2) benthic microbial mats underlying brackish, low-O_2 waters in Middle Island Sinkhole in Lake
Huron, near Alpena, Michigan. We find that diel variations in pore water sulfide sulfur isotope gradients penetrate to
depths of up to 8cm below the zone of active photosynthetic activity. This implies that, although photosynthetic activity
may play a role in influencing vertical migrations of the top of the zone of sulfide accumulation, other phys., chem. and
biol. processes influence sulfur cycling at greater depths. By comparing these two sites, we provide insight into how both
environmental conditions and microbial communities shape biogeochem. patterns in microbial mats.
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关键词
Microbial mat,Sulfide,Benthic zone,Diel vertical migration,Photosynthesis,Sulfur,Cyanobacteria,Brackish water,Environmental chemistry,Environmental science
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