The metabolic activities of cable bacteria and the associated microbial e-community can enable remote oxidation of H2S to SO42- in anoxic deposits through long distance electron transport coupled to O2 and NO3-/NO2- reduction at the sediment-water interface. The spatial separation of oxidation and reduction half-reactions requires modification of diagenetic models that electron donors and acceptors are required to react with each other locally in sedimentary deposits. In this dissertation, an irreversible planar optical H2S sensor was developed and applied in studies of cable bacteria dynamics, and 2D cable bacteria colonization dynamic patterns have been revealed by using this sensor and planar optical pH sensors. The development dynamics of cable bacteria were studied in Fe/Mn depleted carbonate muds with only dissolved phase sulfide available (Florida Bay, FL) and Fe rich coastal lithogenic muds with apparently only solid phase sulfide available (Great Peconic Bay, NY) for the electrogenic redox reactions. Results demonstrate that cable bacteria can become established and remain active in the two types of sediment but with the dynamics of electrogenic redox reactions varying significantly between them. In both cases, a range of compositional features consistent with cable bacteria activity developed, including sediment surface pH maximum zones, anodic pore water Ca2+ enrichments, H2S consumptions, and increases in the abundance of cable bacteria filaments.
As revealed by the planar pH optical sensors, the highly characteristic sediment surface pH maximum zone can start to develop from a small, isolated region and subsequently spread horizontally across the entire sediment surface. Cable bacteria activity can develop with only dissolved phase sulfide, and does not necessarily demand redox reactive metals (Fe, Mn). By inserting physical barriers at different depths thus manipulating the maximum lengths the cable bacteria filaments can extend, results showed that the characteristic fingerprints of cable bacteria activity (e.g. anodic carbonate dissolution) were different among experimental groups, suggesting that cable bacteria activity and the associated effects on sediment early diagenetic reactions are impacted by the scales of the redox reactive critical zone.
Sediment disturbance as a result of sediment reworking by infauna has a negative effect on the integrity of cable bacteria filaments. Here, I employed pH sensitive planar optodes to investigate cable bacteria activity dynamics associated with different bioturbation features. Data reveals that mobile bioturbators like nereid polychaetes inhibit cable bacteria activity in vicinity of active burrows with a collapse of local sediment surface pH maximum zone. However, near abandoned structures, electrogenic metabolism fingerprints regenerated as quickly as within 13 hours. For infauna who build stable tubes (e.g. spinoid polychaetes), once stable tubes are built, cable bacteria activity fingerprints (pH elevation) can be detected around the subsurface stable redox domains. Long cable bacteria filaments were also found aggregating near Sabaco tubes. Heterogeneous distributions and activities of cable bacteria were evident in sediment with different sizes of animal tubes suggesting the generality of cable bacteria aggregating with subsurface stable redox domains. These findings suggest a complex, highly dynamic interaction between cable bacteria distributions and bioturbation patterns, and a substantial, time and spatially-dependent impact of electrogenic metabolism and subsurface pH maxima on sediment early diagenetic reactions.
|Advisor:||Zhu, Qingzhi, Aller, Robert C.|
|Commitee:||Cochran, J. Kirk, Aller, Josephine Y., Fike, David A.|
|School:||State University of New York at Stony Brook|
|Department:||Marine and Atmospheric Science|
|School Location:||United States -- New York|
|Source:||DAI-B 82/4(E), Dissertation Abstracts International|
|Subjects:||Biogeochemistry, Sedimentary Geology, Hydrologic sciences, Microbiology|
|Keywords:||Cable bacteria, Sulfur cycle, Bioturbated sediments, Microbial e-community, Metabolic activities, Remote oxidation, Sediment-water interface, Florida Bay, Great Peconic Bay, New York, Coastal lithogenic muds, Electrogenic redox reactions, Sediment disturbance, Sabaco tubes, Electrogenic metabolism|
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