State Water Resources Research Institute Program


Project Id: 2010OH157B
Title: Nitrogen Removal by Microbial-Mediated Processes Under Hypoxic Conditions in Lake Erie
Project Type: Research
Start Date: 3/01/2010
End Date: 2/28/2011
Congressional District: 17
Focus Categories: Nutrients, Nitrate Contamination
Keywords: anaerobic ammonia oxidation, anammox, denitrification, nitrogen loss, bacteria, nitrogen, hypoxia, algal bloom, eutrophication
Principal Investigators: Mou, Xiaozhen (Kent State University); Bade, Darren; Heath, Robert; Leff, Laura
Federal Funds: $ 22,832
Non-Federal Matching Funds: $ 45,666
Abstract: Accumulating evidence suggests that in Lake Erie N and P are often co-limiting to phytoplankton. Given that N-loading is increasing while P-loading in the Great Lakes is relatively static, one would expect to see greater P-limitation instead of less, but that is not what is seen. We hypothesize that seasonal hypoxia and post-phytoplankton bloom conditions promote active growth of anammox and denitrifying bacteria, which converts available N to N2 gas leading to significant N-loss from the lake and subsequently to N- and P-co-limitation. The goal of this research is to examine the N-dynamics and especially the activity and diversity of anammox and denitrifying bacteria in Lake Erie near regions experiencing hypoxia or phytoplankton blooms. The project has three objectives: 1) to measure the anammox and denitrification potentials in the lake water and sediments before, under hypoxic and post phytoplankton bloom conditions, 2) to determine the taxonomic diversity of anammox and denitrifying bacteria using molecular approaches, and 3) to identify environmental factors that affect the distribution and activity of anammox and denitrifying bacteria. The N2 producing potential of anammox and denitrifying bacteria will be measured using the widely accepted isotope incubation procedure. Three incubations will be made for each sample with addition of 15NO3- only, 15NH4+ only, or 15NO3 and 14NH4+. Anammox and denitrification process through distinct routes to produce 15N14N and 15N15N, respectively. The identity and diversity of anammox and denitrifying bacteria will be assessed by PCR-based clone library analysis using anammox- and denitrifying bacteria-specific primers. Standard limnological parameters, including temperature, dissolved oxygen, pH and etc., will be measured using a Hydrolab H2O multi-datasonde. Nutrients, including total dissolved organic carbon (DOC), dissolved organic nitrogen (DON), NH4+, NO2-, NO3-, soluble reactive phosphors (SRP), total soluble phosphorus (TSP) will be determined following standard APHA protocols. The abiotic measurement and biotic species data will be statistically analyzed to identify environmental factors that may affect the activity and distribution of anammox and denitrifying bacteria in Lake Erie water and sediments. The results of this project will provide a more complete understanding of the dynamics of N and mechanisms underlying those processes. Multiple beneficial outcomes are expected, including: 1) explanation on unexpected N and P co-limitation in Lake Erie, 2) validation of using PCR-based genetic methods to identify the distribution of anammox and denitrifying bacteria and estimate their in situ activities and 3) promotion on wise N management, including whether it should be should be managed and if so how.

Progress/Completion Report, 2010, PDF

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