Dissolved organic nitrogen (DON) and phosphorus (DOP) represent themost abundant formof their respective nutrient pool in the surface layer of the oligotrophic oceans and play an important role in nutrient cycling and productivity. Since DOP is generally more labile than DON, it provides additional P that may stimulate growth of nitrogen-fixing diazotrophs that supply fixed nitrogen to balance ...

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 ...

The eutrophication of freshwaters is a global health concern as lakes with excess nutrients are often subject to toxic cyanobacterial blooms. Although phosphorus is considered the main element regulating cyanobacterial biomass, nitrogen (N) concentration and more specifically the availability of different N forms may influence the overall toxicity of blooms. In this study of three eutrophic lak...

Major fluxes of sulphur and dissolved inorganic nitrogen were estimated in Central European mountain ecosystems of the Bohemian Forest (forest lakes) and Tatra Mountains (alpine lakes) over the industrial period. Sulphur outputs from these ecosystems were comparable to inputs during a period of relatively stable atmospheric deposition (10-35 mmol m-2 yr-1) around the 1930s. Atmospheric inputs o...

The subarctic North Pacific is one of three major high nitrate, low chlorophyll (HNLC) oceanic regions, along with the Southern Ocean and the eastern equatorial Pacific. In these regions, uptake of nitrogen by phytoplankton is widely thought to be regulated by the availability of dissolved iron. The supply of dissolved iron is twofold: via atmospheric deposition of dust and via upward transport...

a randomized complete block design with three replications was performed in rice research institute of iran, rasht in 2008, to find the effect of supplement foliar application of nitrogen and potassium on ’daylam‘ hybrid rice grain yield, its components and grain protein percentage. foliar application of 20 kg nitrogen (5 percent n) and 15 kg potassium (3 percent k2o) in different pre-anthesis ...

Nitrite and nitrous oxide made up 40% of the hypolimnetic dissolved inorganic nitrogen in mesotrophic Lake Rotoiti, New Zealand, prior to hypolimnetic anoxia. Up to 120 mg of N m-3 as nitrite and 20 mg of N m-3 as nitrous oxide accumulated, whereas dissolved-oxygen concentrations remained between 1.0 and 0.2 g m-3 and were totally consumed when the hypolimnion became completely anoxic. Assays o...

‘Ihe Ipswich River is a low-gradient, coastal river in northeastem Massachusetts. It is about 55 km long and drains an area of 401 km’. Previous observations and studies indicate high levels of dissolved inorganic nitrogen (DIN) in the headwaters of the river due to urban and residential land use (1). However, concentrations drop quickly with distance downstream, presumably due to biological pr...