Potential Nitrogen Source Research Articles

Tiger Nut (Cyperus esculentus) Milk Byproduct and Corn Steep Liquor for Biosurfactant production by Yarrowia lipolytica

The use of agroindustrial wastes for biosurfactant production is advantageous since the raw material represents a great part of the costs to obtain this bio-product. Low cost raw materials (Tiger nut fibre – TNF and corn steep liquor – CSL) were evaluated as potential carbon and nitrogen sources for biosurfactant production by Yarrowia lipolytica IMUFRJ 50682. It was demonstrated that it is possible to produce biosurfactant using corn steep liquor or tiger nut fiber in medium containing ammonium sulfate, with emulsification indexes (EI) around 40% for each residue. The culture medium containing ammonium sulfate, corn steep liquor and tiger nut fiber presented the same EI (60%) as the medium containing glucose, yeast extract, glycerol and ammonium sulfate (Control medium). This is the first report of the use of tiger nut by-product for biosurfactant production. It was estimated that the cost for ammonium sulfate, corn steep liquor and tiger nut fiber medium is one third the cost of control medium.

Metagenomic analysis reveals potential interactions in an artificial coculture

Disentangling the interactions between cyanobacteria and associated bacterial community is important for understanding the mechanisms that mediate the formation of cyanobacterial blooms in freshwater ecosystems. Despite the fact that a metagenomic approach enables researchers to profile the structure of microbial communities associated with cyanobacteria, reconstructing genome sequences for all members remains inefficient, due to the inherent enormous microbial diversity. Here, we have established a stable coculture system under high salinity, originally from a mixture of an axenic cyanobacterium Synechococcus sp. PCC 7002 and a non-axenic bloom-forming cyanobacterium Microcystis colony. Metagenomic analysis showed that the coculture consists of S. sp. PCC 7002 and two heterotrophic bacteria, designated as Pseudomonas stutzeri TAIHU and Mesorhizobium sp. TAIHU, respectively. And near-complete genome sequences of both bacteria were reconstructed from the metagenomic dataset with an average completeness of 99.8%. Genome-wide pathway analysis revealed that M. sp. TAIHU carried all the genes involved in the de novo biosynthesis of cobalamin, which is required by S. sp. PCC 7002 for growth. To cope with the high salinity in the coculture, experimental evidence demonstrated that S. sp. PCC 7002 would synthesize the compatible solutes including sucrose and glucosylglycerol, which are supposed to be exploited by both heterotrophic bacteria as potential carbon and/or nitrogen sources. Furthermore, the genes encoding for the biosynthesis of the ectoine, another common osmolyte are found exclusively in P. stutzeri TAIHU, while the genes responsible for the catabolism of ectoine and its derives are present only in M. sp. TAIHU. These genomic evidence indicates beneficial interaction between three members in the coculture. Establishment of the coculture system with relative simplicity provides a useful model system for investigating the interspecies interactions, and genome sequences of both bacteria associated with Microcystis bloom described here will facilitate the researcher to elucidate the role of these heterotrophic bacteria in the formation and maintenance of cyanobacterial bloom in freshwater ecosystem.

Aqueous Reaction of Dicarbonyls with Ammonia as a Potential Source of Organic Nitrogen in Airborne Nanoparticles.

Nitrogen-containing organic species such as imines and imidazoles can be formed by aqueous reactions of carbonyl-containing compounds in the presence of ammonia. In the work described here, these reactions are studied in airborne aqueous nanodroplets containing ammonium sulfate and glyoxal, methylglyoxal, or glycolaldehyde using a combination of online and offline mass spectrometry. N/C ratios attributed to the organic fraction of the particles (N/Corg) produced from glyoxal and methylglyoxal were quantified across a wide relative humidity (RH) range. As the RH was lowered, glyoxal was found to increase N/Corg, attributed to "salting-in" with increasing solute concentration, while methylglyoxal led to a decrease in N/Corg, attributed to "salting-out". Glycolaldehyde was found to evaporate from the droplets rather than react in the aqueous phase and did not form particulate-phase organic matter from aerosol drying under any of the conditions studied. The results are discussed in the context of ambient nanoparticle composition measurements and suggest that aqueous chemistry may significantly impact nanoparticle composition and growth during new particle formation in locations where emissions of water-soluble dicarbonyls are high, such as the eastern United States.

Selective Nitrate-to-Ammonia Transformation on Surface Defects of Titanium Dioxide Photocatalysts

Ammonia (NH3) is an essential chemical in modern society, currently manufactured via the Haber–Bosch process with H2 and N2 under extremely high pressure (>200 bar) and high-temperature conditions (>673 K). Toxic nitrate anion (NO3–) contained in wastewater is one potential nitrogen source. Selective NO3–-to-NH3 transformation via eight-electron reduction, if promoted at atmospheric pressure and room temperature, may become a powerful recycling process for NH3 production. Several photocatalytic systems have been proposed, but many of them produce nitrogen gas (N2) via five-electron reduction of NO3–. Here, we report that unmodified TiO2, when photoexcited by ultraviolet (UV) light (λ > 300 nm) with formic acid (HCOOH) as an electron donor, promotes selective NO3–-to-NH3 reduction with 97% selectivity. Surface defects and Lewis acid sites of TiO2 behave as reduction sites for NO3–. The surface defect selectively promotes eight-electron reduction (NH3 formation), while the Lewis acid site promotes nonselect...

Freshwater Contributions and Nitrogen Sources in a South Texas Estuarine Ecosystem: a Time-Integrated Perspective from Stable Isotopic Ratios in the Eastern Oyster (Crassostrea virginica)

Freshwater inflows to Texas estuaries vary widely due to regional climate fluctuations and are being substantially altered by human activities. The natural abundance stable isotope ratios of carbon and nitrogen in oyster adductor muscle were used to acquire a time-integrated view of freshwater and nitrogen contributions to the Mission-Aransas National Estuarine Research Reserve in South Texas. The study objective was to determine the influence of inputs from the San Antonio and Guadalupe rivers, which deliver approximately 1.6 km3 of water to the mid-Texas coastal region annually. A transect of sampling stations extending from the head of San Antonio Bay (northeast of the Reserve boundary) to the Aransas Pass ship channel (roughly 70 km to the southwest) was visited multiple times between 2009 and 2011. Carbon isotopic values increased from approximately −25 to −17‰ while δ15N values decreased from approximately +16 to +10‰ between the bay and ship channel. This range of carbon isotope values translates into time-integrated freshwater fractions as high as 0.8 (1 = 100% fresh) at the most inland sampling station to freshwater fractions around zero approaching the Gulf of Mexico. Contributions from the San Antonio and Guadalupe rivers to waters of the reserve vary between wet and dry years, but overall, the data suggest that these rivers are persistent and substantial sources of fresh water and nitrogen to the reserve. This study emphasizes the importance of connectivity and lateral exchanges among bays/lagoons when considering potential sources of fresh water and nitrogen that control ecosystem structure and function.

Characteristics of amino acids during the process of algae-originated particles decomposition in Lake Taihu

在实验条件下研究了高浓度蓝藻堆积后水体中的藻源性颗粒物中氨基酸的分解速率、分解量和氨基酸态氮形态的变化情况.在自然光照组中，颗粒态氨基酸（PAA）的浓度从实验前的0.46 mmol/L降至实验后的0.30 mmol/L；而在无光分解组中PAA从0.44 mmol/L降至0.06 mmol/L.两种处理下PAA的降解速率常数分别为0.03916和0.17424 d^-1.溶解态氨基酸（DAA）在分解过程中浓度比较低，随时间的变化表现出先增大后减小的趋势，在两种不同的处理下，最大值分别为10.94和7.94 μmol/L，21 d后减小到与实验开始时持平，甚至低于初始值.实验初期，PAA所占比例高达74%~80%，但迅速被分解转化为DAA和铵态氮（NH₄⁺-N），随着实验的进行NH₄⁺-N又逐渐转化为硝态氮，其中无光分解组中的分解更为彻底，而自然光照组中PAA分解量小于无光分解组.实验结果表明，氨基酸作为水体中浮游植物的潜在氮源，可以被分解为水华过程中藻类所需的NH₄⁺-N，对水华的维持具有一定的促进作用.;The characteristics of decomposition rate and quantity of amino acids, as well as the change of nitrogen forms, were explored during the process of decomposition of high-density cyanobacterial particles in this study. The results showed that the initial concentrations of particulate amino acids (PAA) were 0.46 mmol/L in natural light group and 0.44 mmol/L in the aphotic group. At the end of the experiment, the PAA was much stable with a concentration of 0.30 mmol/L in natural light group, while decreased dramatically to 0.06 mmol/L in the aphotic group. The degradation rate constants were 0.03916 and 0.17424 d^-1, respectively. The concentration of dissolved amino acids (DAA) was much lower in comparison to PAA in the process of decomposition. In detail, the DAA increased gradually and peaked at 10.94 and 7.94 μmol/L for the two groups, respectively, and then declined to around the initial value in the end of the 21st day. At the beginning of the experiment, PAA accounted for 74%-80% of the total amino acids, then PAA was transformed to DAA and ammonia (NH₄⁺-N) quickly, and finally the NH₄⁺-N was transformed gradually to NO₃^--N by nitrification. Compared with the natural light group, the decomposition of particles in aphotic group was more complete. Algal photosynthesis inhibited the decomposition of cyanobacterial particles in the natural group. Our results demonstrated that amino acids are potential nitrogen sources of phytoplankton and could be demineralized to NH₄⁺-N to support phytoplankton growth during cyanobacterial blooms. Therefore, the decomposition of high-density algal particles plays a key role in the maintenance of cyanobacterial blooms.

Combining multi-source data to explore a mechanism for the effects of micrometeorological elements on nutrient variations in paddy land water

Paddy land plays a key role in global crop production. Thus, paddy land water is a potential source of nitrogen and phosphorus; both nutrients largely contribute to non-point source pollution because they usually vary closely with micrometeorological elements (MEs) during the growth period. However, few studies have focused on the mechanism of co-variation between nutrients and MEs at the field scale. The relationships between nutrients in the paddy land water and MEs as well as soil water content, soil temperature, and the normalized difference vegetation index (NDVI) are still unclear. In this paper, an in situ experiment was designed to obtain 5 years of meteorological data and nutrient data (nitrogen and phosphorus); the size of the experiment plot is in accordance with the spatial resolution of NDVI data. Multi-source meteorological and satellite data were integrated to explore the mechanism of co-variation. The results show that precipitation, air temperature, and solar radiation are the three MEs significantly affecting the nitrogen concentration in the paddy land water during the growth period. The air temperature is the most important ME influencing the phosphorus concentration. At the same time, the NDVI, as an effective indicator of the photosynthetic potential of rice used to explore the relationship between nutrients, has a prominent influence on soluble nutrients, especially on dissolved phosphorus. These findings could significantly improve our understanding about the responses of paddy land nutrients during the growth period to the surrounding drivers, inclusive of MEs, soil water, soil temperature, and NDVI. Undoubtedly, it is a potentially helpful means to monitor the sources of non-point pollution.

Field Evaluation of Nitrogen Treatment by Conventional and Single-Pass Sand Filter Onsite Wastewater Systems in the North Carolina Piedmont

Excess nitrogen loading has contributed to the impairment of major watersheds across North Carolina. Onsite wastewater systems (OWS) are a potential source of nitrogen to water resources, but more research is needed to determine their actual contributions, especially in the Piedmont region of the state. The objective of this study was to determine the total dissolved nitrogen (TDN) treatment efficiency of four OWS in clayey soils of the North Carolina Piedmont. Two OWS were conventional style, and two were single-pass sand filters. The four volunteered sites with OWS were instrumented with piezometers (27 total) for groundwater collection and analyses. Piezometers were installed within 1.5 m of each OWS and downgradient from the conventional OWS. Septic tank effluent, groundwater from the piezometers, sand filter effluent, and adjacent surface waters were sampled bimonthly (five times) during 2015. Samples were analyzed for TDN, NO3 −-N, NH4 +-N, chloride, dissolved organic carbon, and physical and chemical parameters on each sampling event. Groundwater samples collected 35 m downgradient from the two conventional OWSs had TDN concentrations and masses, on average, of 98 and 70 %, respectively, lower than septic tank effluent. Isotopic analysis of the natural abundance of δ15N and δ18O in NO3 − in groundwater collected at the conventional OWS sites suggests that denitrification was a mass removal mechanism. The sand filter OWS reduced TDN concentrations by an average of 80 % and mass loading by 50 % prior to discharge to surface waters. Nitrogen management regulations in nutrient-sensitive watersheds should consider the contributions from OWS, especially direct discharge systems like sand filters. Improvements in the TDN treatment efficiency of direct discharge OWS would result in immediate surface water quality improvements.

Use of corn steep liquor as an economical nitrogen source for biosuccinic acid production by Actinobacillus succinogenes

Expensive raw materials are the driving force that leads to the shifting of the petroleum-based succinic acid production into bio-based succinic acid production by microorganisms. Cost of fermentation medium is among the main factors contributing to the total production cost of bio-succinic acid. After carbon source, nitrogen source is the second largest component of the fermentation medium, the cost of which has been overlooked for the past years. The current study aimed at replacing yeast extract- a costly nitrogen source with corn steep liquor for economical production of bio-succinic acid by Actinobacillus succinogenes 130Z. In this study, a final succinic acid concentration of 20.6 g/L was obtained from the use of corn steep liquor as the nitrogen source, which was comparable with the use of yeast extract as the nitrogen source that had a final succinate concentration of 21.4 g/l. In terms of economical wise, corn steep liquor was priced at $ 200 /ton, which was one fifth of the cost of yeast extract at $ 1000 /ton. Therefore, corn steep liquor can be considered as a potential nitrogen source in biochemical industries instead of the costly yeast extract.

Drained coastal peatlands: A potential nitrogen source to marine ecosystems under prolonged drought and heavy storm events—A microcosm experiment

Over the past several decades there has been a massive increase in coastal eutrophication, which is often caused by increased runoff input of nitrogen from landscape alterations. Peatlands, covering 3% of land area, have stored about 12–21% of global soil organic nitrogen (12–20Pg N) around rivers, lakes and coasts over millennia and are now often drained and farmed. Their huge nitrogen pools may be released by intensified climate driven hydrologic events—prolonged droughts followed by heavy storms—and later transported to marine ecosystems. In this study, we collected peat monoliths from drained, natural, and restored coastal peatlands in the Southeastern U.S., and conducted a microcosm experiment simulating coupled prolonged-drought and storm events to (1) test whether storms could trigger a pulse of nitrogen export from drought-stressed peatlands and (2) assess how differentially hydrologic managements through shifting plant communities affect nitrogen export by combining an experiment of nitrogen release from litter.During the drought phase, we observed a significant temporal variation in net nitrogen mineralization rate (NMR). NMR spiked in the third month and then decreased rapidly. This pattern indicates that drought duration significantly affects nitrogen mineralization in peat. NMR in the drained site reached up to 490±110kgha−1year−1, about 5 times higher than in the restored site. After the 14-month drought phase, we simulated a heavy storm by bringing peat monoliths to saturation. In the discharge waters, concentrations of total dissolved nitrogen in the monoliths from the drained site (72.7±16.3mgL−1) was about ten times as high as from the restored site. Our results indicate that previously drained peatlands under prolonged drought are a potent source of nitrogen export. Moreover, drought-induced plant community shifts to herbaceous plants substantially raise nitrogen release with lasting effects by altering litter quality in peatlands.

Evolution and adaptation of SAR11 and Cyanobium in a saline Tibetan lake.

Lake Qinghai is a unique lacustrine ecosystem located on the Tibetan Plateau and exhibits oligotrophic, alkaline, and saline conditions. Previous studies have focused on the community phylogenetic diversity of bacterioplankton in the ecosystem. This study aimed to address the ecotype diversity of bacterioplankton populations in the unique microbial habitat, using metagenomic sequencing and analysis. Phylogenetic analysis revealed two major bacterial populations: SAR11 IIIa (14% of the total) and Cyanobium (14%). Although the two populations shared high 16S rRNA gene sequence identity (> 98% identity) with their closest marine counterparts, they displayed substantial genomic divergence (≤ 80% average amino acid sequence identity). Comparative genomic analysis identified conservation of carbon and energy storage metabolism (biosynthesis of polyphosphate and polyhydroxyalkanoate) gene operons in the SAR11 IIIa and a cyanate (potential nitrogen source in alkaline conditions) transporter gene operon in the Cyanobium. We further identified genetic signature of positive selection acting on an exodeoxyribonuclease gene of the SAR11 IIIa population, which is potentially associated with DNA repair responsive to strong UV radiation on the high altitude mountain. Taken together, our results revealed the ecosystem-specific gene content of the bacterioplankton populations and provided new insights into their adaptations unique to the Tibetan lake.

Sediment amino acids as indicators of anthropogenic activities and potential environmental risk in Erhai Lake, Southwest China

Total hydrolysable amino acids (THAAs) constitute the most important fraction of labile nitrogen. Anthropogenic activities directly influence various biogeochemical cycles and then accelerate lake ecosystem deterioration. This is the first study that has established the relationship between sediment THAAs and anthropogenic activities using dated sediment cores, and evaluated the possibility of THAAs release at the sediment interface based on changes in environmental conditions in Erhai Lake. The results showed that historical distribution and fractions of THAAs could be divided into three stages: a stable period before the 1970s, a clear increasing period from the 1970s to 1990s, and a gradually steady period that started after the 1990s. The chemical fraction, aromatic and sulfur amino acids (AAs) accounted for only ≤3% of THAAs. Basic AAs accounted for 5–17% of THAAs, and remained at a relatively stable level. However, acidic and neutral AAs, which accounted for 19–44% and 35–69% of THAAs, respectively, were the predominant factors causing THAAs to increase due to rapid agricultural intensification and intensification of contemporary sedimentation of phytoplankton or macrophytes since the 1970s. These trends were closely related to both anthropogenic activities and natural processes, which implied that sediment THAAs could act as an effective indicator that reflects anthropogenic activities and aquatic environmental characteristics. The current contributions of sediment THAAs on TN and TOC were <5% and 1.5%, respectively. However, the dramatic increase in THAAs in the sediment cores indicated that there was a huge potential source of labile nitrogen for the overlying water under certain environmental conditions. Correlation analysis suggested that the release of THAAs was negatively correlated with pH, whereas positively correlated with bacterial number and degree of OM mineralization, which particularly depend on the stability of HFOM. Therefore, the risk of sediment THAAs release might increase when the sediment environment continuously changes.

Distributions, Early Diagenesis, and Spatial Characteristics of Amino Acids in Sediments of Multi-Polluted Rivers: A Case Study in the Haihe River Basin, China.

The Haihe River Basin, which is one of the most water-scarce and polluted river basins in China, has abnormally high nitrogen levels. In this study, total hydrolyzable amino acids (THAAs) were measured in surface sediment and sediment core samples in the Haihe River Basin to determine if amino acids were potential sources of ammonium, organic nitrogen, and organic carbon. The rivers were found to be in a state of hypoxia and contain abnormally high levels of ammonium and organic nitrogen. Additionally, NH3-N was the predominant form of inorganic nitrogen in the surface sediments, while organic nitrogen accounted for 92.53% of sedimentary nitrogen. THAAs-C accounted for 14.92% of the total organic carbon, while THAAs-N accounted for more than 49.59% of organic nitrogen and 45.68% of total nitrogen. The major fraction of THAAs were protein amino acids. Three sediment cores of the most heavily polluted rivers also showed high levels of THAAs. Evaluation of the degradation index (DI) of sedimentary organic matter in sediments evaluated based on the THAAs revealed that most positive DI values were found in the downstream portion of the Ziya River Watershed. Additionally, the DI of surface sediment was correlated with THAAs (r2 = 0.763, p < 0.001), as was the DI of sediment cores (r2 = 0.773, p < 0.001). Overall, amino acids in sediments were found to be an important potential source of ammonium, organic nitrogen, and organic carbon.

Identification of Potential Culture Conditions for Enhancing the Biomass Production of Microalga Chlorella minutissima

Identification of Potential Culture Conditions for Enhancing the Biomass Production of Microalga Chlorella minutissima Microalgae have been considered as appropriate source of various commercial products due to their enormous potential of growth, higher content of biochemical product like sugars, lipids, proteins and pigments, high CO2 tolerance etc. But these organisms are easily affected by environmental factors due to their minute size. So it is necessary to find potential culture conditions of microalgae so maximum biomass can be achieved in short duration of time under lab settings. In this study, effects of various components of culture conditions on biomass of microalga Chlorella minutissima were recorded. Based on the result of biomass production, potential culture conditions have been summarized for microalgae Chlorella minutissima. Among six different media tested, N-11, BBM and BG-11 media were found suitable for this microalga. Although with nitrogen starvation, BBM and BG-11 were found to be the potential media. Potential source of nitrogen, phosphorus and carbon were sodium & potassium nitrate, di-potassium hydrogen phosphate & potassium di hydrogen phosphate and glycerol respectively. The suitable concentration of nitrate, phosphate, and glycerol were 0.375 g/l, 0.16 g/l and 12.5 g/l. Alkaline pH was found suitable for this microalgae to provide higher biomass. Chlorella minutissima has shown better biomass production in 24 hours of illumination of white light of 20 W tube light and shaking period of 2 hours in Erlenmeyer flasks.

Fate of Effluent‐Borne Nitrogen in the Mounded Drainfield of an Onsite Wastewater Treatment System

Core Ideas Water filled porosity (WFP) controlled N dynamics in the drainfields. Sand layer was hotspot for nitrification due to 0.07–0.32 WFP. Soil layer was hotspot for denitrification due to 0.55–0.91 WFP. Organic N was mobile in the vadose zone and leached below drainfields. Onsite wastewater treatment systems (OWTS), commonly known as septic systems, are increasingly recognized as a potential source of nitrogen in the shallow groundwater. Our objective was to investigate the effect of hydrological and biogeochemical factors in the vadose zone on the fate of effluent‐borne N in the drainfields of a drip‐dispersal OWTS. Three lysimeters (152.4 cm long, 91.4 cm wide, and 91.4 cm high) were constructed using pressure‐treated wood to mimic OWTS drainfields. Each lysimeter had three distinct layers of gravel–sand mixture, soil, and commercial sand. A drip tube, which was covered with commercial sand before planting St. Augustine grass (Stenotaphrum Trin.) on the top and sides of the lysimeters, dispersed 9 L of septic tank effluent (STE) per day on top of the stacked layers. Each lysimeter was instrumented with 10 multi‐probe sensors to determine the water content, electrical conductivity (EC), and temperature in the center and sides of sand and soil layers. Leachate samples were collected over 67 events, which consisted of one sample every 24 h for 15 d (n = 15) and weekly flow‐weighted composite samples (n = 52). In all events, the pH, EC, and chloride were lower in the leachate than STE. Daily multi‐probe data showed that EC was greater in the center than sides of the lysimeters due to more STE interaction. Sensor water content data were used to calculate water filled porosity (WFP), which was greater in the soil (0.55–0.9) than sand (0.07–0.32) due to the textural differences. Mean total N was 70 mg L−1 in the STE, which reduced to 27.4 mg L−1 in the leachate likely due to the denitrification in the soil layer. The dominance of NOx–N in the leachate (61%) as compared to STE (0.6%) was attributed to the nitrification in the sand layer. Higher proportion of organic N in the leachate (39%) than STE (16%) suggests that organic N was mobile in the vadose zone and leached below the drainfields. We conclude that hydrological and biogeochemical controls in the vadose zone play an important role in N transformations and transport of NOx–N and organic N below OWTS drainfields.

The composition, seasonal variation, and potential sources of the atmospheric wet sulfur (S) and nitrogen (N) deposition in the southwest of China.

The composition, seasonal variation, and potential sources of sulfate (S) and nitrogen (N) deposition in precipitation in the southwest of China from 2003 to 2013 were investigated. The results showed that the concentration of SO4 (2-), NO3 (-), and NH4 (+) in rainwater were 10.57-1360, 7.16-523.71, and 7.54-1020 μeq l(-1), with an annual volume-weighted mean (VWM) concentration of 103.99, 46.73, and 97.30 μeq l(-1), respectively. The annual wet deposition of SO4 (2-), NO3 (-), and NH4 (+) was 21.66, 8.16, and 17.49 kg S (N) ha(-1), respectively. The temporal variations of the ions showed that the abrupt decreasing breakpoints were in 2008 for SO4 (2-) and in 2009 for NO3 (-) and NH4 (+), and increasing trends were observed after 2010 for the three ions. These trends reflected the effect of economy recession and the policy of controlling SO2 and NOx emissions. The acid rain type of precipitation was shifted from sulfur to a mixed one. The ions of SO4 (2-), NO3 (-), and NH4 (+) presented high values in winter and spring and low values in autumn and summer. A highly positive linear correlation between SO4 (2-) and NO3 (-) (R(2) = 0.71), SO4 (2-) and NH4 (+) (R(2) = 0.74), and NO3 (-) and NH4 (+) (R(2) = 0.84) existed while a strong negative correlation was found between the three main ionic concentrations and precipitation. The SO4 (2-) was mainly from fossil fuel combustion (60.53%), aged sea salt (19.03%), agriculture (11.38%), crust (6.66%), and biomass burning (2.40%); the NO3 (-) was mainly from fossil fuel combustion (75.41%), biomass burning (9.67%), aged sea salt (7.97%), and agriculture (6.96%); and the NH4 (+) was mainly from agriculture (86.38%), fossil fuel combustion (10.52%), and aged sea salt (3.09%).

Alfalfa juice as a nitrogen source or supplement for acetone–butanol–ethanol production by Clostridium acetobutylicum

The conversion of agricultural and agro-industrial wastes and residues into a spectrum of marketable products and energy is of great importance to the environment and to sustainable development. The objective of this study is to assess the feasibility of using alfalfa juice to substitute or supplement expensive nutrients in an acetone–butanol–ethanol (ABE) fermentation medium. Three batches of early-bloom alfalfa harvested at different periods have been pressed, analyzed and their properties compared. Based on the composition of the juice extracted from each sample in terms of C:N ratio and nutrient content, the most appropriate juice was selected to be used as a fermentation enhancer. To investigate the effect of nitrogen supplementation on Clostridium growth and butanol production, the fermentation experiments were first carried out using a synthetic standard medium in the presence of 60g/L of xylose as a carbon source and different concentrations of yeast extract. Alfalfa juice was subsequently used to replace yeast extract in the medium or to supplement it at different proportions: 10, 25 or 50% v/v. When replacing the yeast extract by the alfalfa juice at a nitrogen concentration of 0.9g/L, the butanol production was 3.52g/L, a value close to that obtained with the standard synthetic medium. The supplementation of the medium with alfalfa juice at 10% v/v enhanced butanol production to a concentration of 5g/L. The results showed that the C:N ratio improving butanol production should be comprised between 21 and 35. This work clearly demonstrates the efficiency of using alfalfa juice as a potential nitrogen source to enhance butanol production from xylose as a carbon source.

Potential omnivory in the sea urchin Diadema antillarum?

Sea urchins are one of the most important herbivores of shallow-water reefs in the Western Atlantic, capable of controlling seaweed communities. One of them, Diadema antillarum Philippi, 1845 has been target of several studies due to its capacity to control algal communities, and it has been considered a generalist herbivore species. Nevertheless, the assimilation process in D. antillarum using stable isotopes remains unclear. Our main goals were to characterize isotopically the sea urchin D. antillarum with the surrounding macroalgae communities, determine its trophic position, and calculate the contribution of the primary producers using stable isotopes. We collected samples of sea urchin and their potential food resources at four shallow water reefs of Puerto Rico Archipelago during February and October of 2013. The δ13C isotopic ratio of D. antillarum did not vary on site and in time, but it varied spatial and temporally in term of δ15N. The Trophic level (TL) ranged from 2.35 ±0.11 to 3.24 ±0.17, and exhibited spatial and temporal significant differences. The lack of congruent polygons found in this study, and the high TL values support the conclusion that D. antillarum produced isotopic ratios not adequately explained by the algal data. Our findings reinforce the importance of benthic invertebrates as potential nitrogen sources for D. antillarum. Further studies including benthic invertebrates may help to quantify the contribution of those species to the diet of D. antillarum.

Preliminary evidence of effects of Phragmites australis growth on N2O emissions by laboratory microcosms

Abstract Denitrification has been found to play a significant role in the nitrogen (N) biogeochemical cycle of riparian wetland systems; however, there is little understanding of the role of emergent macrophytes in sediment denitrification. In this study, laboratory culture experiments were conducted to examine how Phragmites australis growth affected N 2 O emissions. Additionally, preliminary investigations into the variability of carbon and available NO 3 − –N fractions were conducted. The N 2 O emission rate was quantified based on the high-resolution N 2 O microprofiles in acetylene-inhibited sediment cores. Seasonal-dependence of N 2 O emission was remarkable throughout incubation of both P. australis rooted sediments and control with no P. australis , and increased significantly with biomass steady accumulation (p 2 O m −2 day −1 at day 180 (in late autumn) in the P. australis rhizosphere . Simultaneously, N 2 O emissions were more highly influenced by fine-root biomass, belowground biomass and plant height than total biomass, root activity and relative growth rate in the Spearman rank correlation model. More specifically, based on the strong and significant (p 2 O emission flux, the rapid transformation indicated that changes in the HWC (ranging from 720 to 3564 mg kg −1 ) with plant growth could reflect a 14-fold variation in N 2 O emissions during the growth stage, and that N 2 O emissions were highly dependent on fine-root biomass and its delivery of organic carbon. The ion exchangeable form NO 3 -N (IEF-NO 3 -N) in sediments was found to be the predominant transferable form involved in denitrification, while the iron-manganese oxide form NO 3 -N (IMOF-NO 3 -N) can be considered as a potential source of nitrogen for denitrification. This study highlights that emergent macrophyte communities dominate riparian ecosystem denitrification and that the metabolic mechanisms of emergent macrophytes can have positive feedbacks on the HWC fraction and available NO 3 -N combined with sediment components in rhizosphere sediments.

Urea as a potential nitrogen source for harmful algal blooms in San Francisco Bay, California

Urea as a potential nitrogen source for harmful algal blooms in San Francisco Bay, California