3 research outputs found
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Nitrogen cycling in Sabine Lake
As a part of continuing efforts to investigate nitrogen cycling in Texas estuaries, denitrification, nitrogen fixation, dissimilatory nitrate reduction to ammonium (DNRA), and sediment oxygen demand were measured in Sabine Lake, Texas. Estuarine phytoplankton production can be limited by N availability, and sediments often are an important source of dissolved inorganic N ... . Denitrification transforms combined N to gaseous forms ... . These end-products represent unavailable nutrient sources to most estuarine producers (e.g., phytoplankton and bacteria; Howarth et al. 1988). Thus, denitrification may drive systems toward N limitation (Seitzinger 1990). The purposes of this study were to evaluate the importance of denitrification in nitrogen cycling and examine environmental conditions influencing nitrogen cycling in Sabine Lake. A membrane inlet mass spectrometer (MIMS) for dissolved gas measurement and high performance liquid chromatography (HPLC) system for ammonium isotope measurements were used to quantify denitrification, N-fixation, DNRA, and sediment oxygen demand. Four sampling trips to Sabine Lake were made in June, September, December 2000 and March 2001. Here, we report water column measurements and incubation experiment results.Final report submitted to: The Texas Water Development Board, contract #2000-483-337July 2001Marine Scienc
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Nitrogen cycling in Laguna Madre and Baffin Bay
Estuarine phytoplankton production can be limited by N availability (Ryther & Dunstan 1971, Hecky & Kilham 1988) and sediments often serve as an important source of dissolved inorganic N ... . Denitrification is the only biological process that transforms combined N to gaseous forms ... . These gaseous end-products represent unavailable nutrient sources to most estuarine producers (e.g., phytoplankton and bacteria; Howarth et al. 1988). Benthic denitrification has proven to be a significant sink for combined N in systems where detailed studies of denitrification have been completed. This process may drive systems toward N limitation (Seitzinger 1990). The purposes of this study were to evaluate the importance of denitrification in nitrogen cycling and to examine environmental conditions influencing nitrogen cycling in Laguna Madre and Baffin Bay. A membrane inlet mass spectrometer (MIMS) system for dissolved gas measurement and a high performance liquid chromatography (HPLC) system for ammonium isotope measurement, that are available at the University of Texas Marine Science Institute, allowed us to measure dissimilatory nitrate reduction to ammonium (DNRA) as another major nitrate reduction pathway in addition to denitrification.Submitted to: The Texas Water Development Board, contract no. 99-483-278July 2000Marine Scienc
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Nitrogen cycling in East Matagorda Bay
As a part of continuing efforts to investigate nitrogen (N) cycling in Texas bays and estuaries, denitrification, N fixation, dissimilatory nitrate reduction to ammonium (DNRA), and sediment oxygen demand (SOD) were measured in East Matagorda Bay, Texas. ... The purposes of this study were to measure nutrient fluxes, denitrification, N fixation, evaluate the relative importance of NO₃⁻ reduction pathways (denitrification and DNRA) in N cycling, and examine environmental conditions influencing N cycling in East Matagorda Bay. A membrane inlet mass spectrometer (MIMS) for dissolved gas measurement and high performance liquid chromatography (HPLC) system for NH₄⁺ isotope measurements were used to quantify denitrification, N fixation, DNRA, and SOD. Six sampling trips to East Matagorda Bay were made in June, July, and October 2001 and January, April, and July 2002. Here, we report water column measurements and incubation experiment results.Final report submitted to: The Texas Water Development Board, contract # 2001-483-387October 2002Marine Scienc