Life Sciences Commons^™

Nitrogen Isotope Dynamics Of The Cariaco Basin, Venezuela, Robert C. Thunell, Daniel M. Sigman, Frank E. Muller-Karger, Yrene Astor, Ramon Varela

Marine Science Faculty Publications

We report ¹⁵N/¹⁴N measurements of water column nitrate and ammonium, sinking particles, and sediments from the Cariaco Basin, an anoxic marine basin off the coast of Venezuela. Water column denitrification occurring in the basin has only a very small isotopic imprint on nitrate in the basin because nitrate consumption is nearly complete in the actively denitrifying water near the oxic/anoxic interface (∼275 m). Being free of a large denitrification signal, the δ¹⁵N of shallow thermocline nitrate is ∼3.5‰, significantly lower than the mean deep ocean nitrate δ¹⁵N of 5‰. This may be due …

Isolation And Characterization Of Aerobic Denitrifiers From Agricultural Soil, Ebru Çelen, Mehmet Aki̇f Kiliç

Turkish Journal of Biology

Denitrification is generally considered an anaerobic process. However, in recent years it has been shown that bacteria can also reduce nitrate to nitrite under aerobic conditions. The characterization of biologically available nitrogen forms and their biological cycling mechanisms is important for ecological and agricultural implications. In this study, aerobic nitrate reducers were isolated from greenhouse soil. Using a nitrate reduction assay, it was found that 39 out of 60 isolates can reduce nitrate to nitrite under aerobic conditions. Five of those 39 isolates were selected for further characterization of their aerobic nitrate reduction activity. Four of those 5 isolates were …

Hydrologic Variability, Organic Matter Supply, Anddenitrification In The Garonne River Ecosystem, Michelle A. Baker, P. Vervier

Biology Faculty Publications

1. Groundwater nitrate contamination has become a worldwide problem as increasing amounts of nitrogen fertilisers are used in agriculture. Alluvial groundwater is uniquely juxtaposed between soils and streams. Hydrological connections among these subsystems regulate nutrient cycling.

2. We measured denitrification using an in situ acetylene‐block assay in a nitrate‐contaminated portion of the Garonne River catchment along a gradient of surface water–ground water mixing during high (snowmelt) and low flow.

3. During high flow (mid‐April to early June) the water table rose an average of 35 cm and river water penetrated the subsurface to a great extent in monitoring wells. Denitrification …