Accumulation Of Inorganic Nitrogen Research Articles

Microbial assemblages and associated biogeochemical processes in Lake Bonney, a permanently ice-covered lake in the McMurdo Dry Valleys, Antarctica

BackgroundLake Bonney, which is divided into a west lobe (WLB) and an east lobe (ELB), is a perennially ice-covered lake located in the McMurdo Dry Valleys of Antarctica. Despite previous reports on the microbial community dynamics of ice-covered lakes in this region, there is a paucity of information on the relationship between microbial genomic diversity and associated nutrient cycling. Here, we applied gene- and genome-centric approaches to investigate the microbial ecology and reconstruct microbial metabolic potential along the depth gradient in Lake Bonney.ResultsLake Bonney is strongly chemically stratified with three distinct redox zones, yielding different microbial niches. Our genome enabled approach revealed that in the sunlit and relatively freshwater epilimnion, oxygenic photosynthetic production by the cyanobacterium Pseudanabaena and a diversity of protists and microalgae may provide new organic carbon to the environment. CO-oxidizing bacteria, such as Acidimicrobiales, Nanopelagicales, and Burkholderiaceae were also prominent in the epilimnion and their ability to oxidize carbon monoxide to carbon dioxide may serve as a supplementary energy conservation strategy. In the more saline metalimnion of ELB, an accumulation of inorganic nitrogen and phosphorus supports photosynthesis despite relatively low light levels. Conversely, in WLB the release of organic rich subglacial discharge from Taylor Glacier into WLB would be implicated in the possible high abundance of heterotrophs supported by increased potential for glycolysis, beta-oxidation, and glycoside hydrolase and may contribute to the growth of iron reducers in the dark and extremely saline hypolimnion of WLB. The suboxic and subzero temperature zones beneath the metalimnia in both lobes supported microorganisms capable of utilizing reduced nitrogens and sulfurs as electron donors. Heterotrophs, including nitrate reducing sulfur oxidizing bacteria, such as Acidimicrobiales (MAG72) and Salinisphaeraceae (MAG109), and denitrifying bacteria, such as Gracilimonas (MAG7), Acidimicrobiales (MAG72) and Salinisphaeraceae (MAG109), dominated the hypolimnion of WLB, whereas the environmental harshness of the hypolimnion of ELB was supported by the relatively low in metabolic potential, as well as the abundance of halophile Halomonas and endospore-forming Virgibacillus.ConclusionsThe vertical distribution of microbially driven C, N and S cycling genes/pathways in Lake Bonney reveals the importance of geochemical gradients to microbial diversity and biogeochemical cycles with the vertical water column.

Soil Characteristics and the Accumulation of Inorganic Nitrogen in an Arid Urban Ecosystem

Urbanization represents the extreme case of human influence on an ecosystem. Biogeochemical cycling of nitrogen (N) in cities is very different from that of non-urban landscapes due to the large input of reactive forms of N and the heterogeneous distribution of various land uses that alters landscape connections. To quantify the likely effects of human activities on soil N and other soil properties in urban ecosystems, we conducted a probability-based study to sample 203 plots randomly distributed over the 6,400 km2 Central Arizona-Phoenix Long-Term Ecological Research (CAP LTER) area, which encompasses metropolitan Phoenix with its 3.5 million inhabitants. Soil inorganic N concentrations were significantly higher in urban residential, non-residential, agricultural, transportation, and mixed sites than in the desert sites. Soil water content and organic matter were both significantly higher under urban and agricultural land uses, whereas bulk density was lower compared to undeveloped desert. We calculated that farming and urbanization on average had caused an accumulation of 7.23 g m−2 in soil inorganic N across the CAP study area. Average soil inorganic N of the sampled desert sites (3.23 g m−2) was much higher than the natural background level reported in the literature. Laboratory incubation studies showed that many urban soils exhibited net immobilization of inorganic N, whereas desert and agricultural soils showed small, but positive, net N mineralization. The large accumulation of inorganic N in soils (mostly as nitrate) was highly unusual in terrestrial ecosystems, suggesting that in this arid urban ecosystem, N is likely no longer the primary limiting resource affecting plants, but instead poses a threat to surface and groundwater contamination, and influences other N cycling processes such as denitrification.

Abundance of Alnus incana ssp. rugosa in Adirondack Mountain shrub wetlands and its influence on inorganic nitrogen

The purpose of this research was to determine the abundance of the nitrogen-fixing shrub, Alnus incana ssp. rugosa (speckled alder), in shrub wetlands of the Adirondack Mountain region of New York State and to determine whether its abundance affects the concentration or accumulation of inorganic nitrogen in wetland substrates. Alder/willow wetlands are the second most common wetland type in the Adirondack region. The Adirondack Park Agency's digital GIS database of wetland types was used to determine the areal extent of alder/willow wetlands in the Adirondacks. Randomly selected wetlands were sampled to determine the size and abundance of alder. Alder densities averaged ∼7000 stems ha −1 and alder was present in 75% of the wetlands. As an indication of short-term accumulation of NO 3 − and NH 4 + in wetland substrates, ion exchange resins were used to sample ground water in high and low alder density wetlands as well as from wetlands lacking alder and dominated by conifers. Additionally, NO 3 − and NH 4 + concentrations in ground water samples were measured. NH 4 + accumulation levels from exchange resins were low for all wetland types while groundwater NH 4 + concentration was highest in the low-density alder sites. Wetlands with high alder density had approximately six times higher NO 3 − accumulation than other wetlands. Substrate groundwater NO 3 − concentrations in wetlands of high-density alder exceeded by three times levels in low or no alder wetlands, showing the importance of alder to local N budgets. To assess the recovery of shrub wetlands from acidification, future studies should determine the fate of fixed N in wetland systems.

Oxygen consumption and ammonia accumulation in the hypolimnion of Walker Lake, Nevada

Walker Lake (area = 140 km2, Zmean = 19.3 m) is a large, terminal lake in western Nevada. As a result of anthropogenic desiccation, the lake has decreased in volume by 75% since the 1880s. The hypolimnion of the lake, now too small to meet the oxygen demand exerted by decaying matter, rapidly goes anoxic after thermal stratification. Field and laboratory studies were conducted to examine the feasibility of using oxygenation to avoid hypolimnetic anoxia and subsequent accumulation of ammonia in the hypolimnion, and to estimate the required DO capacity of an oxygenation system for the lake. The accumulation of inorganic nitrogen in water overlaying sediment was measured in laboratory chambers under various DO levels. Rates of ammonia accumulation ranged from 16.8 to 23.5 mg-N m−2 d−1 in chambers with 0, 2.5 and 4.8 mg L−1 DO, and ammonia release was not significantly different between treatments. Beggiatoa sp. on the sediment surface of the moderately aerated chambers (2.5 and 4.8 mg L−1 DO) indicated that oxygen penetration into sediment was minimal. In contrast, ammonia accumulation was reversed in chambers with 10 mg L−1 DO, where oxygen penetration into sediment stimulated nitrification and denitrification. Ammonia accumulation in anoxic chambers (18.1 and 20.6 mg-N m−2 d−1) was similar to ammonia accumulation in the hypolimnion from July through September of 1998 (16.5 mg-N m−2 d−1). Areal hypolimnetic oxygen demand averaged 1.2 g O2 m−2 d−1 for 1994–1996 and 1998. Sediment oxygen demand (SOD) determined in experimental chambers averaged approximately 0.14 g O2 m−2 d−1. Continuous water currents at the sediment-water interface of 5–6 cm s−1 resulted in a substantial increase in SOD (0.38 g O2 m−2 d−1). The recommended oxygen delivery capacity of an oxygenation system, taking into account increased SOD due to mixing in the hypolimnion after system start-up, is 215 Mg d−1. Experimental results suggest that the system should maintain high levels of DO at the sediment-water interface (∼10 mg L−1) to insure adequate oxygen penetration into the sediments, and a subsequent inhibition of ammonia accumulation in the hypolimnion of the lake.

Effect of variations in daily feeding frequency and ration size on growth of shrimp, Litopenaeus vannamei (Boone), in zero-water exchange culture tanks

It is generally believed that increasing feeding frequency has immediate benefits, including reduced nutrient leaching and increased shrimp growth. In this study, static-water ecoassays were conducted to determine the effect of feeding frequency and percentage of daily ration on growth of Litopenaeus vannamei and accumulation of inorganic nitrogen and phosphorus in the culture water. Shrimp were fed a semi-purified diet containing 19.5% crude protein. Experiment 1 tested five feeding frequencies (3, 5, 8, 11 and 15 feedings day −1) evenly spaced in time during 24 h. Daily ration was divided in similar amounts for each feeding frequency. Mean shrimp survival was 98.6% for all treatments. No significant differences were found either on shrimp growth or accumulation of total inorganic nitrogen (TIN) or total reactive phosphorus (TRP) regardless of feeding frequency. In experiment 2 daily rations were offered manually 1 (100% at 0800 h), 2 (50% each at 0800 and 2000 h), 3 (33% each at 0800, 1400 and 2000 h), 3 + (45, 20 and 35% at 0800, 1400 and 2000 h, respectively), 4 (25% each at 0800, 1200, 1600 and 2000 h), 4 + (40, 15, 15 and 30% at 0800, 1200, 1600 and 2000 h, respectively) and 6 (16.6% each at 0800, 1030, 1300, 1600, 1800 and 2000 h) times day −1; and with automatic feeders 15 times day −1 (every 96 min). Shrimp survival was 100% for all treatments. Although mean shrimp growth was highest at 2 feedings day −1 no significant differences were found among feeding treatments. Accumulation of TIN in the culture water was significantly lower for tanks receiving feed 2 times day −1 compared to 1 and 3 times day −1. Levels of TIN were not significantly different among the other feeding treatments. Accumulation of TRP was not significantly different regardless of feeding treatment. These data indicated that under these culture conditions increasing feeding frequency or manipulating ration size did not significantly improve shrimp survival or growth. The only significant environmental effect detected in the culture water was a reduction of TIN at a feeding frequency of 2 compared to 1 and 3 times day −1 in experiment 2. The authors suggest that multiple feedings may not be advantageous for some static culture systems, and that the cost-effectiveness of multiple feedings be evaluated for different feeds and culture systems.

Control and utilization of inorganic nitrogen in intensive fish culture ponds

One of the main obstacles toward the intensification of aquaculture systems is the accumulation of inorganic nitrogen in the water, A solution demonstrated in this work is to control inorganic nitrogen levels through the induction of microbial protein synthesis. This is achieved by adding a carbonaceous substrate, adjusted in a way so as to supply the needed carbon to immobilize all the non-utilized nitrogen. Inorganic nitrogen levels are reduced due to the resulting production of microbial protein. The in situ produced microbial protein is a substitute to the protein added with the feed. Fish growth in the treated ponds was higher than the growth in conventionally fed ponds. Protein utilization was doubled due to the recycling of nitrogen in the pond system, leading to diminution of the deleterious inorganic nitrogen accumulation. The price of feed was reduced to 50-67% of that common in conventional ponds, due both to replacement of protein and limited wash-out of feed.

Carbon‐nitrogen relationships in soil. IV.—Mineralization of Carbon and Nitrogen

AbstractProduction of carbon dioxide and accumulation of inorganic nitrogen have been studied in a group of 27 soils differing widely in origin. Samples of each soil were incubated for 28 days at 23.5° and 30°. Further batches of soil were incubated at 23.5° after partial sterilization by steaming, and others after air‐drying and re‐moistening.Significant relationships were found between the carbon and nitrogen mineralized under each of the experimental conditions tested. Steaming and air‐drying the soils generally increased the mineralization of both carbon and nitrogen, as compared with untreated soils incubated at the same temperature, and resulted in a lower ratio of carbon to nitrogen mineralized.The amounts of nitrogen and carbon mineralized were significantly correlated with the total nitrogen and organic carbon contents of the soils. Evidence was obtained that the organic matter of intensively cultivated soils is more resistant than that of maiden soils to further microbiological decomposition.

Mineralization of the nitrogen of urea‐formaldehyde compounds in relation to soil ph

AbstractMineralization of the nitrogen of two urea‐formaldehyde compounds has been studied in twenty soils having initial pH values ranging from 3·9 to 7·8. The results show highly significant negative correlations between soil pH and the accumulation of inorganic nitrogen throughout the experiments. For comparison, the initial rates of decomposition of a sample of hoof were also studied in the same soils. In contrast to the urea‐formaldehyde compounds, mineralization of the nitrogen of hoof was markedly retarded in three of the most acid soils, the results for the remaining soils showing no significant relationship to soil pH.