The influence of burrow spacing on sedimentary nitrification and denitrification was simulated experimentally using sediment plugs of different thicknesses immersed in aerated seawater reservoirs. Different plug thicknesses mimic different distances between oxygenated burrow centers and produce similar changes in aerobic–anaerobic reaction balances as a function of diffusive transport scaling. ...

The diagenetic behavior of proteins, defined as large polypeptides, was examined over a 2-yr period at a mudflat site subject to intense bioturbation. Protein concentrations in the surface sediment correlated well with deposition of algal detritus from the water column. Cellular biomass made up a significant, though likely not a major, component of protein in the sediments; likewise, changes in...

Bacillus subtilis grows in the absence of oxygen using nitrate ammonification and various fermentation processes. Lactate, acetate, and 2,3-butanediol were identified in the growth medium as the major anaerobic fermentation products by using high-performance liquid chromatography. Lactate formation was found to be dependent on the lctEP locus, encoding lactate dehydrogenase and a putative lacta...

Invasion by the African grass Andropogon gayanus is drastically altering the understory structure of oligotrophic savannas in tropical Australia. We compared nitrogen (N) relations and phenology of A. gayanus and native grasses to examine the impact of invasion on N cycling and to determine possible reasons for invasiveness of A. gayanus. Andropogon gayanus produced up to 10 and four times more...

Spontaneous ethylenediamine-resistant mutants of Azospirillum brasilense were selected on the basis of their excretion of NH(4). Two mutants exhibited no repression of their nitrogenase enzyme systems in the presence of high (20 mM) concentrations of NH(4). The nitrogenase activities of these mutants on nitrogen-free minimal medium were two to three times higher than the nitrogenase activity of...

Subterranean estuaries are highly dynamic in processing dissolved inorganic nitrogen (DIN). Here we investigate DIN turnover surface sediments (0–20 cm depth) at the higher, medium and lower intertidal of a seepage face, i.e., outer “mouth” subterranean estuary, during four consecutive seasons Sanggou Bay, China. Throughout studied period, ammonium (NH4+) nitrite (NO2−) concentrations sampled p...

Estuarine sediments are the location for significant bacterial removal of anthropogenically derived inorganic nitrogen, in particular nitrate, from the aquatic environment. In this study, rates of benthic denitrification (DN), dissimilatory nitrate reduction to ammonium (DNRA), and anammox (AN) at three sites along a nitrate concentration gradient in the Colne estuary, United Kingdom, were dete...

Salt-affected soils contain high levels of soluble salts (saline soil) and exchangeable sodium (alkali soil). Globally, about 932 million ha (Mha), including 831 Mha agricultural land, is salt-affected. Salinity sodicity adversely affect soil microbial diversity enzymatic activities, thereby carbon nitrogen dynamics greenhouse gas (GHG) emissions from soils. In this review article, we synthesiz...

Over the past decade, the environmental impact of wastes discharged from high-density flow-through fish-production systems has been viewed with increasing concern. Recirculating aquaculture systems are gaining wider acceptance because of their ability to reduce waste discharges, improve quality control, and reduce costs. The crucial processes that must be addressed in treating recirculating wat...

A field study was conducted to determine nitrogen (N) mineralization from broiler litter (EL) in two Coastal Plain soils of differing texture, sandy (Tifton loamy sand) or clayey (Greenville sandy clay loam). These soils represented the broad range in surface textures conmlOnly found in soils used {or agricultural production in the southeastern Coastal Plain. Published protocols used for the st...