| Distinct biogeochemical gradients at small spatial scales have been observed near the sediment-water interface and in surface sediments of many aqueous systems. The interactions between minerals and oxygen with organic matter in these surficial zones are affected by a variety of factors such as sediment accumulation and electron acceptor availability, variations in local hydrology, amount of organic matter, and microorganism activity. At the sediment-water interface these factors determine whether biogeochemical reactions will result in the dissolution of minerals or in the formation of new solid or amorphous phases of minerals. This study evaluated the spatial variability in indicators of biogeochemical processes including iron II, sulfate, sulfide, nitrate, and alkalinity using samplers known as "peepers." Peepers were used to collect water samples at 1 cm intervals for profiles spanning the interface between surface water and underlying sediments to a depth of 60 cm from reservoir sediments. The reservoir system was studied during the onset of a wet season after an extensive period of dryness (no standing water for ---5 months) in December, 2009. Two locations were studied that varied in 1) amount of visible submerged vegetation, 2) proximity to local run-off sources, and 3) initial surface water conditions. Sediment cores were also collected and sampled for carbon content and magnetic susceptibility. The resulting data identified steep biogeochemical gradients in the pore-water analyzed from both peepers with dominant biogeochemical processes varying between the two locations. |
