Particle-Associated Biogeochemical Processes in Fayetteville Green Lake, a High Sulfur, Permanently Anoxic Lake
There have been many projects that have studied the geochemistry of size-fractionated particulate matter and PA versus FL microbiology, but few have studied both in parallel. Here I present δ13CPOC, δ15N and the molecular biology data of particulate matter operationally defined as PA (> 2.7 μ)and FL (0.2 – 2.7 μ) from Fayetteville Green Lake, NY- a meromictic lake with similar concentrations of dissolved inorganic carbon and sulfate to marine anoxic basins.
PA δ13CPOC ranged from -27 to -43 with a minimum at 20.5m (upper monimolimnion). FL δ13CPOC reached a minimum of -41 at the lower redoxcline boundary, followed by a positive excursion to -34 in the upper monimolimnion. The greatest difference between PA and FL δ13CPOC occurred in the upper monimolimnion, where δ15N reached a minimum of -6, consistent with complete denitrification. These features coincided with the maximum concentration of RuBisCO-II, which was predominantly PA. This was unexpected, as carbon fixation via RuBisCO-II results in δ13CPOC between 9 and -13. The most abundant OTUs at these depths were Sulfuricurvum kujiense, a sulfur-oxidizing denitrifier, Desulfobulbaceaand purple sulfur bacteria (PSB). TheDesulfobulbaceaare known ectosymbionts of the PSB, and both are typically particle-associated. Sulfuricurvum kujiensefixes carbon through the reverse citric acid (rTCA) cycle and is common in free-living assemblages.