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...

Experiments were carried out over 15 mo to assess the net exchange of dissolved inorganic nitrogen (DIN) by the symbiotic coral Acropora palmata (Lamarck) under near-natural environmental conditions. Specimens were enclosed in situ in transparent acrylic chambers and changes in the ambient seawater concentrations of nitrate, nitrite and ammonium determined over 1 h closed incubat ion~ . There w...

conclusions it was shown that the removal efficiency of nitrate was directly proportional to the amount of chaff, temperature, and contact time but inversely to the ph. this study showed that nitrate removal by chaff is a promising technique. results the result of this study revealed that chaff as an absorbent could remove nitrate from solutions, and the efficiency of adsorption increased as co...

Type II methanotrophs produce polyhydroxybutyrate (PHB), while Type I methanotrophs do not. A laboratory-scale fluidized bed reactor was initially inoculated with a Type II Methylocystis-like dominated culture. At elevated levels of dissolved oxygen (DO, 9 mg/L), pH of 6.2-6.5 with nitrate as the N-source, a Methylobacter-like Type I methanotroph became dominant within the biofilms which did no...

The method of Parsons et al. (1984) for measuring dissolved free amino acids (DFAA) in coastal seawater was modified. We found considerable interference in DFAA determination from ammonia dissolved in coastal seawater, although the interference of urea could be ignored. For DFAA analysis for coastal seawater samples, ammonia determinations for the same sample are needed to correct DFAA values. ...

Until recently, studies of the fate of primary production in coastal upwelling systems have focused mainly on export through sinking of particulate organic matter (POM). In week-long deck incubations conducted during the upwelling season off Oregon, a large accumulation of carbonrich (C:N ≥ 16) dissolved organic matter (DOM) occurred following nitrate depletion by diatom blooms. The response of...

Results: The increase in mass of the tunic became lower as the region was closer to the bottom of Halocynthia roretzi. However, the decrease in mass caused by the mechanical stimuli was not different between the adjacent regions. Also, the tunic of the siphon, the tubular tissue for influx and efflux of the seawater, increased the mass more slowly after the stimuli. The size of the layer coveri...

The effects of dissolved oxygen on simultaneous nitrification and denitrification were evaluated in polyurethane foam contact oxidation reactors in a municipal wastewater treatment process. It was observed that nitrate could be removed at low dissolved oxygen levels, but the removal rate was gradually reduced as the dissolved oxygen concentration increased to a higher level of 6.0 mg/L. Nitroge...

A 20-month pilot-scale study was conducted to examine the impact of temperature on the performance of an anaerobic biological contractor used to treat perchlorate-contaminated water. The contractor was successfully acclimated with indigenous microorganisms. Influent temperatures varied from 1.4 to 30 degrees C. The objectives of the study were to investigate the effects of temperature on perchl...

We studied storm discharges of nitrate and dissolved and particulate forms of ammonium, organic N, phosphate, and organic P from four adjacent small watersheds of differing land use on the Atlantic Coastal Plain in Maryland. We used V-notch weirs and automated storm samplers to measure discharges and collect samples at flow intervals during 76 storms. The watershed aquifers are perched on an im...