This study was designed to assess the importance of dissolved free amino acids (DFAA) as a nitrogen source for the scleractinian coral Stylophora pistillata. For this purpose, experiments were performed using (15)N-enriched DFAAs, and %(15)N enrichment was measured both in animal tissue and zooxanthellae at different DFAA concentrations, incubation time and light levels. As previously observed ...

Dissolved organic nitrogen (DON) and carbon (DOC) often dominate the dissolved nitrogen and organic carbon fluxes from rivers, yet they are not considered to affect coastal water quality because of their assumed refractory nature. The objective of this study was to quantify DON and DOC bioavailability to bacteria in 9 rivers on the east coast of the United States during a 6 d dark bioassay expe...

In two montane watersheds that receive minimal deposition of atmospheric nitrogen, 15–71% of dissolved organic nitrogen (DON) was bioavailable in stream water over a 2-year period. Discharge-weighted concentrations of bulk DON were between 102 and 135 lg/l, and the C:N ratio differed substantially between humic and non-humic fractions of DON. Approximately 70% of DON export occurred during snow...

Nitrate uptake in the epilemnetic waters of a small eutrophic Canadian Shield lake was studied by using a 15N method during summer stratification. Concurrent with inhibition of primary production, 3-(3,4-dichlorophenyl)-1,1-dimethylurea inhibited NO3- assimilation. Nitrate up to 1 mg of N/liter did not affect the rate of primary production during 3 h of incubation. The NO3- fertilizer added to ...

Groundwater is connected to the landscape above and is thus affected by the overlaying land uses. This study evaluated the impacts of land uses upon groundwater quality using trilinear analysis. Trilinear analysis is a display of experimental data in a triangular graph. Groundwater quality data collected from agricultural, septic tank, forest, and wastewater land uses for a 6-year period were u...

Dissolved organic nitrogen (DON) derived from wastewater effluent can participate in reactions that lead to formation of nitrogenous chlorination by-products, membrane fouling, eutrophication, and nitrification issues, so management of DON is important for both wastewater reuse applications and nutrient-sensitive watersheds that receive discharges from treated wastewater. This study documents D...

[1] The preformed nitrate distribution throughout the subtropical North Pacific is characterized by a negative anomaly between 100 m and the 25.4 sq surface. Its presence indicates that nitrogen remineralization in the upper thermocline deviates significantly from Redfield stoichiometry. It has been previously suggested that this feature is created during the degradation of nitrogen-poor dissol...

We document an example of a forested watershed at the Coweeta Hydrologic Laboratory with an extraordinary tendency to retain dissolved organic matter (DOM) generated in large quantities within the ecosystem. Our objectives were to determine fluxes of dissolved organic C, N, and P (DOC, DON, DOP, respectively), in water draining through each stratum of the ecosystem and synthesize information on...