Education | Research Interests | PCB4048/5445 | Current Projects | Publications | Photogallery
Effect of Diurnal and Weekly Water Column Hypoxic Events on Nitrification and Nitrogen Transformations in Estuarine Sediments.

Funding by National Science Foundation, Chemical Oceanography. 2004-2008. Nitrogen is essential for plant growth in terrestrial and aquatic environments. However, use of too much nitrogen in agriculture and on residential lawns, as well as nitrogen from sewage treatment plants runs off into lakes, rivers and estuaries. This excess nitrogen in aquatic environments causes algal blooms and can lead to depletion of oxygen (anoxia) in the water column and sediments. Nitrification contributes to removing fixed nitrogen from ecosystems; it is a centrally important process modulating ecosystem productivity and the global nitrogen budget. In anoxic estuaries, nitrification is compromised, reducing the removal of fixed nitrogen. Bottom water anoxia leads to increased HS-concentrations in pore waters that can lead to extended inhibition of aerobic nitrifying bacteria. We believe loss of nitrification activity during week long hypoxic events will reduce denitrification rates, although N2 production by anaerobic NH4+ oxidation (anammox) may be enhanced. Six estuaries selected for sampling for this grant span a gradient from infrequent hypoxia (< 3% of the year) to frequent and extended hypoxia (78% of the year) at monitoring sites. Weeks Bay, AL and Apalachicola Bay, FL have infrequent hypoxia. Sapelo Ilsand, GA has an intermediate frequency of hypoxic events, with median summer DO concentrations of 3.5 mg/L. Pensacola Bay, FL and Rookery Bay, FL have extended summer hypoxia. While Elkhorn Slough, CA has a predictable pattern of hypoxic and anoxic events.