Distribution and Significance of Fecal Indicator Organisms in the Upper Chesapeake Bay

Total viable aerobic, heterotrophic bacteria, total coliforms, fecal coliforms, and fecal streptococci were enumerated in samples collected at five stations located in the Upper Chesapeake Bay, December 1973 through December 1974. Significant levels of pollution indicator organisms were detected at all of the stations sampled. Highest counts were observed in samples collected at the confluence of the Susquehanna River and the Chesapeake Bay. The indicator organisms examined were observed to be quantitatively distributed independently of temperature and salinity. Counts were not found to be correlated with concentration of suspended sediment. However, significant proportions of both the total viable bacteria (53%) and fecal indicator organisms (>80%) were directly associated with suspended sediments. Correlation coefficients (r) for the indicator organisms examined in this study ranged from r = 0.80 to r = 0.99 for bottom water and suspended sediment, respectively. Prolonged survival of fecal streptococci in most of the sediment samples was observed, with concomitant reduction of the correlation coefficient from r = 0.99, fecal streptococci to total coliforms in water, to r = 0.01, fecal streptococci to fecal coliforms in sediments. The results of this study compared favorably with fecal coliforms: fecal streptococci ratios for the various sample types. Characterization of organisms beyond the confirmed most-probable-number procedure provided good correlation between bacterial indicator groups.     

An exploration of how litter controls drainage water DIN, DON and DOC dynamics in freely draining acid grassland soils

Surface and subsurface litter fulfil many functions in the biogeochemical cycling of C and N in terrestrial ecosystems. These were explored using a microcosm study by monitoring dissolved inorganic nitrogen (DIN) (NH₄ ⁺–N?+?NO₃ ^?–N), dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) concentrations and fluxes in drainage water under ambient outdoor temperatures. Subsurface litter remarkably reduced the DIN concentrations in winter, probably by microbial N uptake associated with higher C:N ratio of added litter compared with soil at 10–25?cm depth. Fluxes of DIN were generally dominated by NO₃ ^?–N; but NH₄ ⁺–N strongly dominated DIN fluxes during freeze–thaw events. Appreciable concentrations of NH₄ ⁺–N were observed in the drainage from the acid grassland soils throughout the experiment, indicating NH₄ ⁺–N mobility and export in drainage water especially during freeze–thaw. Litter contributed substantially to DOC and DON production and they were correlated positively (p?<?0.01) for all treatments. DOC and DON concentrations correlated with temperature for the control (p?<?0.01) and surface litter (p?<?0.001) treatments and they were higher in late summer. The subsurface litter treatment, however, moderated the effect of temperature on DOC and DON dynamics. Cumulative N species fluxes confirmed the dominance of litter as the source of DON and DOC in the drainage water. DON constituted 42, 46 and 62% of cumulative TDN flux for control, surface litter and subsurface litter treatments respectively.     

Nitrite oxidation in the upper water column and oxygen minimum zone of the eastern tropical North Pacific Ocean

Nitrogen (N) is an essential nutrient in the sea and its distribution is controlled by microorganisms. Within the N cycle, nitrite (NO₂⁻) has a central role because its intermediate redox state allows both oxidation and reduction, and so it may be used by several coupled and/or competing microbial processes. In the upper water column and oxygen minimum zone (OMZ) of the eastern tropical North Pacific Ocean (ETNP), we investigated aerobic NO₂⁻ oxidation, and its relationship to ammonia (NH₃) oxidation, using rate measurements, quantification of NO₂⁻-oxidizing bacteria via quantitative PCR (QPCR), and pyrosequencing. ¹⁵NO₂⁻ oxidation rates typically exhibited two subsurface maxima at six stations sampled: one located below the euphotic zone and beneath NH₃ oxidation rate maxima, and another within the OMZ. ¹⁵NO₂⁻ oxidation rates were highest where dissolved oxygen concentrations were <5 μM, where NO₂⁻ accumulated, and when nitrate (NO₃⁻) reductase genes were expressed; they are likely sustained by NO₃⁻ reduction at these depths. QPCR and pyrosequencing data were strongly correlated (r²=0.79), and indicated that Nitrospina bacteria numbered up to 9.25% of bacterial communities. Different Nitrospina groups were distributed across different depth ranges, suggesting significant ecological diversity within Nitrospina as a whole. Across the data set, ¹⁵NO₂⁻ oxidation rates were decoupled from ¹⁵NH₄⁺ oxidation rates, but correlated with Nitrospina (r²=0.246, P<0.05) and NO₂⁻ concentrations (r²=0.276, P<0.05). Our findings suggest that Nitrospina have a quantitatively important role in NO₂⁻ oxidation and N cycling in the ETNP, and provide new insight into their ecology and interactions with other N-cycling processes in this biogeochemically important region of the ocean.     

The effect of nutrient concentrations,nutrient ratios and temperature on photosynthesis and nutrient uptake by Ulva prolifera: implications for the explosion in green tides

The green-tide macroalga, Ulva prolifera, was tested in the laboratory to determine its nutrient uptake and photosynthesis under different conditions. In the nutrient concentration experiments U. prolifera showed a saturated uptake for nitrate but an escalating uptake in the tested range for phosphorus. Both N/P and NO₃ ^?/NH₄ ⁺ ratios influenced nutrient uptake significantly (p?<?0.05) while the PSII quantum yield [Y(II)] (p?>?0.05) remained unaffected. The maximum N uptake rate (33.9?±?0.8 μmol g^?1 DW h^?1) and P uptake rate (11.1?±?4.7) was detected at N/P ratios of 7.5 and 2.2, respectively. U. prolifera preferred NH₄ ⁺-N to NO₃ ^?-N when the NO₃ ^?-N/NH₄ ⁺-N ratio was less than 2.2 (p?<?0.05). But between ratios of 2.2 and 12.9, the uptake of NO₃ ^?-N surpassed that of NH₄ ⁺-N. In the temperature experiments, the highest N uptake rate and [Y(II)] were observed at 20 °C, while the lowest rates were detected at 5 °C. P uptake rates were correlated with increasing temperature.     

Growth and uptake of caesium,rubidium, and potassium by ectomycorrhizal and saprotrophic fungi grown on either ammonium or nitrate as the N source

After the accident at the Fukushima Dai-ichi Nuclear Power Plant in 2011, high activities of radiocaesium have been reported in wild mushrooms in Japan. Fungi play an important role in the dynamics of radiocaesium in forest ecosystems. We examined the contents of caesium (Cs), rubidium (Rb), and potassium (K) in the mycelium of 15 isolates of ectomycorrhizal (EM) fungi and nine isolates of saprotrophic (SA) fungi in a synthetic medium with either ammonium chloride (NH₄Cl) or sodium nitrate (NaNO₃), supplemented with 1 ppm caesium chloride and rubidium chloride. The mycelia were harvested after 8 weeks of incubation, and the contents of Cs, Rb, and K were measured by inductively coupled plasma mass spectrometry. The dry weight of the mycelium in the medium with NH₄ was significantly higher than that with NO₃, although some EM species, Hebeloma, Astraeus, Scleroderma, and Pisolithus, grew well in the medium with NO₃. Among SA species, Crucibulum and Cyathus grew in the medium with NO₃. The uptakes of Cs, Rb, and K by Suillus, Pisolithus, and Rhizopogon were higher than that in other EM and SA species when they grew on the medium with NH₄, while the uptakes of these elements by Astraeus and Scleroderma were higher than those by other species grown on the medium with NO₃. The content of Rb was positively correlated with Cs (r = 0.85, p < 0.001) and K (r = 0.51, p < 0.001). The accumulation of Cs, Rb, and K was differently affected by the N source and fungal species.     

Riverine nitrogen export in Swedish catchments dominated by atmospheric inputs

We present the first estimates of net anthropogenic nitrogen input (NANI) in European boreal catchments. In Swedish catchments, nitrogen (N) deposition is a major N input (31–94%). Hence, we used two different N deposition inputs to calculate NANI for 36 major Swedish catchments. The relationship between riverine N export and NANI was strongest when using only oxidized deposition (NO_y) as atmospheric input (r² = 0.70) rather than total deposition (i.e., both oxidized and reduced nitrogen, NO_y + NH_x deposition, r² = 0.62). The y-intercept (NANI = 0) for the NANI calculated with NO_y is significantly different from zero (p = 0.0042*) and indicates a background flux from the catchment of some 100 kg N km^?2 year^?1 in addition to anthropogenic inputs. This agrees with similar results from North American boreal catchments. The slope of the linear regressions was 0.25 for both N deposition inputs (NO_y and NO_y + NH_x), suggesting that on average, 25% of the anthropogenic N inputs is exported by rivers to the Baltic Sea. Agricultural catchments in central and southern Sweden have increased their riverine N export up to tenfold compared to the inferred background flux. Although the relatively unperturbed northernmost catchments receive significant N loads from atmospheric deposition, these catchments do not show significantly elevated riverine N export. The fact that nitrogen export in Swedish catchments appears to be higher in proportion to NANI at higher loads suggests that N retention may be saturating as loading rates increase. In northern and western Sweden the export of nitrogen is largely controlled by the hydraulic load, i.e., the riverine discharge normalized by water surface area, which has units of distance time^?1. Besides hydraulic load the percent total forest cover also affects the nitrogen export primarily in the northern and western catchments.     

Ecological indicators of nutrient enrichment, freshwater wetlands, Midwestern United States (U.S.)

Vegetation and soil indicators of nutrient condition were evaluated in 30 wetlands, 10 each in 3 Nutrient Ecoregions (NE) (VI-Corn Belt and Northern Great Plains, VII-Mostly Glaciated Dairy Region, IX-Temperate Forested Plains and Hills) of the Midwestern United States (U.S.) to identify robust indicators for assessment of wetland nutrient enrichment and eutrophication. Nutrient condition was characterized by surface water inorganic N (NH₄-N, NO₃-N) and P (PO₄-P) concentrations measured seasonally for 1 year, plant available and total soil N and P, and aboveground biomass, leaf N and P and species composition of emergent vegetation measured at the end of the growing season. Aboveground biomass, nutrient uptake and species composition were positively related to surface water NH₄-N (N) but not to PO₄-P or NO₃-N. Aboveground biomass and biomass of aggressive species, Typha spp. plus Phalaris arundinacea, increased asymptotically with surface water N whereas leaf P, senesced leaf N and senesced leaf P increased linearly with N. And, species richness declined with surface water N. Soil total P was positively related to surface water PO₄-P but it was the only soil indicator related to wetland nutrient condition. Individual regressions for each NE generally were superior to a single regression for all NEs. In NE VI (Corn Belt), few indicators were related to surface water N because of the high degree of anthropogenic disturbance (85% of the landscape is cleared) as compared to NEs VII and IX (24–53% cleared). Of the indicators evaluated, stem height (r² = 0.42 for all NEs, r² = 0.56 for NE VII + IX) and percent biomass of aggressive species, Typha spp. plus Phalaris, (r² = 0.46 for all NEs, r² = 0.54 for NE VII + IX), were the best predictors of wetland nutrient enrichment. Vegetation-based indicators are a promising tool for assessment of wetland nutrient condition but they may not be effective in NEs where landscape disturbance is intense and widespread.     

Bioremediation of aquaculture wastewater using macroalgae and Artemia

Aquaculture produces a significant amount of wastes, consisting of metabolic by-products, leading to general deterioration of water quality. An alternative for reducing nutrient excess is the use of biofilters that can effectively remove nutrients from the water. A laboratory study was conducted to test the efficacy of the macroalgae Gracilaria caudata and the microcrustacean Artemia franciscana to remove nutrients from aquaculture effluents. The experiment consisted of three treatments: macroalgae (1) macroalgae and Artemia (2), and only Artemia (3). The results indicated that the treatment 2 was the most efficient in removing the nitrogenated forms. The maximum reduction values were: NH₄ = 29.8%; NO₂ = 100%; NO₃ = 72.4% and DIN = 44.5%. In contrast, the nutrients concentration was significantly higher at the end of the experiment in the treatment 3 than in the other treatments (ANOVA: p < 0,001). PO₄ showed a significant increase during the experiment, especially in treatments 2 and 3 (ANOVA: p < 0.001). The results showed that G. caudata and A. franciscana performed well in absorbing nitrogenated forms. This indicates that the use of these organisms as biofilters has the potential for being an ecologically correct practice and may contribute to improving the water quality of coastal regions.     

Factors affecting the performance of membrane bioreactor for piggery wastewater treatment

This study was conducted to identify the factors affecting the performance of membrane bioreactor (MBR) for piggery wastewater treatment. The change of organic and nitrogen concentrations in piggery wastewater was studied to investigate the treatment efficiency. The increase of COD, BOD and NH₃–N from 1150 to 2050 mg/L, 683 to 1198 mg/L and 154 to 248 mg/L has led to the decrease of treatment efficiency. Removal efficiencies of COD, BOD and NH₃–N have decreased from 96.0% to 92.0%, 97.0% to 92.7% and 93.2% to 69.5%, respectively. The effects of biomass characteristics on membrane fouling were determined based on Pearson’s correlation coefficient (r_p). It was found that MLSS had a negative correlation with permeate flux (r_p = −0.745, at significant level of 0.05) while sludge floc size a positive correlation (r_p = 0.731, at significant level of 0.05). MLSS and sludge floc size were found to be the dominant factors that controlled the membrane filterability while sludge viscosity, EPS, SMP and SV₃₀ have taken as the sub-factors affecting membrane fouling.     

Pore water N:P and NH4 +:NO3 ? alter the response of Phragmites australis and Glyceria maxima to extreme nutrient regimes

Phragmites australis and Glyceria maxima are fast-growing littoral grasses often competing for similar wetland habitats. Eutrophication affects their competitiveness, but the outcome is not generally predictable due to the complexity of interrelated factors. We hypotheses that pore water N:P and NH₄ ⁺:NO₃ ^? modify their growth and metabolic responses to the trophic status of the habitat. The hypothesis was tested under standardized conditions of long-term sand cultures. Application of N?+?P up to extreme levels in combination with N:P?<?10 and NH₄ ⁺:NO₃ ^??<?1 triggered positive growth response in both species. In contrast, similar N levels applied in N:P?>?90 and NH₄ ⁺:NO₃ ^??=?4 caused lower productivity, changes in resource allocation, morphology and metabolic relations (e.g. high shoot density, low shoot diameters and heights, reduced root and rhizome growth). Observed signs of stress resembled the factors associated with the reed retreat at the die-back sites. Unbalanced N levels obviously alter plant susceptibility to stresses (altering, e.g. ventilation efficiency, plant anchorage or below-ground storage capacity). The positive effect of sufficient P supply was pronounced in Glyceria. It might therefore favour Glyceria in competition with Phragmites at highly fertile habitats rich in P.     

Anthropogenic nutrient enrichment of seagrass and coral reef communities in the Lower Florida Keys: discrimination of local versus regional nitrogen sources

Land-based nutrient pollution represents a significant human threat to coral reefs globally. We examined this phenomenon in shallow seagrass and coral reef communities between the Content Keys (southern Florida Bay) and Looe Key (south of Big Pine Key) in the Lower Florida Keys by quantifying the role of physical forcing (rainfall, wind, tides) and water management on mainland South Florida to nutrient enrichment and blooms of phytoplankton, macroalgae, and seagrass epiphytes. Initial studies (Phase I) in 1996 involved daily water quality sampling (prior to, during, and following physical forcing events) at three stations (AJ, an inshore area directly impacted by sewage discharges; PR, a nearshore patch reef located inshore of Hawk Channel; and LK, an offshore bank reef at Looe Key) to assess the spatial and temporal patterns in advection of land-based nutrients to the offshore reefs. Concentrations of dissolved inorganic nitrogen (DIN=NH₄⁺+NO₃⁻+NO₂⁻), soluble reactive phosphorus (SRP), and chlorophyll a increased at PR and LK following a wind event (∼15 knots, northeast) in mid-February. The highest DIN (mostly NH₄⁺) and SRP concentrations of the entire study occurred at the inshore AJ during an extreme low tide in March. Following the onset of the wet season in May, mean NH₄⁺ and chlorophyll a concentrations increased significantly to maximum seasonal values at PR and LK during summer; relatively low concentrations of NO₃⁻ and a low f-ratio (NO₃⁻/NH₄⁺+NO₃⁻) at all stations during summer do not support the hypothesis that the seasonal phytoplankton blooms resulted from upwelling of NO₃⁻. A bloom of the seagrass epiphyte Cladosiphon occidentalis (phaeophyta) followed the onset of the rainy season and increased NH₄⁺ concentrations at LK, resulting in very high epiphyte:blade ratios (∼3:1) on Thalassia testudinum. Biomass of macroalgae increased at all three stations from relatively low values (<50 g dry wt m⁻²) in winter and early spring to higher values (∼100-300 g dry wt m⁻²) typical of eutrophic seagrass meadows and coral reefs following the onset of the rainy season. The mean δ¹⁵N value of Laurencia intricata (rhodophyta) during 1996 at AJ (+4.7‰) was within the range reported for macroalgae growing on sewage nitrogen; lower values at the more offshore PR (+3.1‰) and LK (+2.9‰) were at the low end of the sewage range, indicating an offshore dilution of the sewage signal during the 1996 study. However, transient increases in δ¹⁵N of Cladophora catanata (chlorophtyta) from ~+2% to +5% at LK concurrent with elevated NH₄⁺ concentrations following rain and/or wind events in May and July suggest episodic advection of sewage nitrogen to the offshore LK station. The Phase II study involved sampling of macroalgae for δ¹⁵N along a gradient from the Content Keys through Big Pine Key and offshore to LK in the summer wet season of 2000 and again in the drought of spring 2001. During the July 2000 sampling, macroalgae in nearshore waters around Big Pine Key had elevated δ¹⁵N values (~+4‰) characteristic of sewage enrichment; lower values (~+2‰) at LK were similar to values reported for macroalgae in upstream waters of western Florida Bay influenced by nitrogen-rich Everglades runoff. That pattern contrasted with the drought sampling in March 2001, when δ¹⁵N values of macroalgae were elevated (+6‰) to levels characteristic of sewage enrichment over a broad spatial scale from the Content Keys to LK. These results suggest that regional-scale agricultural runoff from the mainland Everglades watersheds as well as local sewage discharges from the Florida Keys are both significant nitrogen sources supporting eutrophication and algal blooms in seagrass and coral reef communities in the Lower Florida Keys. Hydrological and physical forcing mechanisms, including rainfall, water management on the South Florida mainland, wind, and tides, regulate the relative importance and variability of these anthropogenic nitrogen inputs over gradients extending to the offshore waters of the Florida Reef Tract.     

Water Stress Effects on Nitrogen Assimilation and Growth of Trifolium subterraneum L. Using Dinitrogen or Ammonium Nitrate

The relative effects of water stress on growth parameters of subterranean clover (Trifolium subterraneum L. cv. Woogenellup) dependent on either N₂ or 8 millimolar NH₄NO₃ for N were examined. Whole-plant carbon exchange rate (CER), acetylene reduction (AR), dry matter production, and Kjeldahl N accumulation were measured on uniform, intact swards of clover that were maintained under adequately watered conditions or were subjected to three cycles of water stress (leaf water potential ≤−30 bar) over an 18-day period. In the absence or presence of water stress, growth rate, net N accumulation rate, and total N concentration of plants dependent on N₂ were 25 to 26, 45 to 50, and 20 to 21% less, respectively, than plants supplied with 8 millimolar NH₄NO₃. The water stress treatment produced less than a 50% decrease in CER regardless of plant N source, a 90% inhibition of AR in plants dependent on N₂, and a 41% decline in dry matter production on both N sources. Water stress decreased reduced N accumulation 55% in N₂-dependent plants and 50% in NH₄NO₃-dependent plants. Changes in growth and N accumulation caused a 10 to 11% decrease in total plant N concentration of water-stressed plants compared to adequately irrigated controls, but water stress decreased the N concentration of tissue synthesized during the 18-day treatment period in N₂-grown plants more than in plants supplied 8 millimolar NH₄NO₃. Thus, the relative effect of water stress on growth under the two N regimes was similar, but N accumulation by N₂-dependent clover was inhibited to a slightly greater extent (P ≤ 0.001) than in NH₄NO₃-dependent plants.     

Nitrogen nutrition of Salvinia natans: Effects of inorganic nitrogen form on growth,morphology, nitrate reductase activity and uptake kinetics of ammonium and nitrate

In this study we assessed the growth, morphological responses, and N uptake kinetics of Salvinia natans when supplied with nitrogen as NO₃⁻, NH₄⁺, or both at equimolar concentrations (500 μM). Plants supplied with only NO₃⁻ had lower growth rates (0.17 ± 0.01 g g⁻¹ d⁻¹), shorter roots, smaller leaves with less chlorophyll than plants supplied with NH₄⁺ alone or in combination with NO₃⁻ (RGR = 0.28 ± 0.01 g g⁻¹ d⁻¹). Ammonium was the preferred form of N taken up. The maximal rate of NH₄⁺ uptake (V_max) was 6–14 times higher than the maximal uptake rate of NO₃⁻ and the minimum concentration for uptake (C_min) was lower for NH₄⁺ than for NO₃⁻. Plants supplied with NO₃⁻ had elevated nitrate reductase activity (NRA) particularly in the roots showing that NO₃⁻ was primarily reduced in the roots, but NRA levels were generally low (<4 μmol NO₂⁻ g⁻¹ DW h⁻¹). Under natural growth conditions NH₄⁺ is probably the main N source for S. natans, but plants probably also exploit NO₃⁻ when NH₄⁺ concentrations are low. This is suggested based on the observation that the plants maintain high NRA in the roots at relatively high NH₄⁺ levels in the water, even though the uptake capacity for NO₃⁻ is reduced under these conditions.     

A study of the microbial quality of grey water and an evaluation of treatment technologies for reuse

The reuse of grey water for non-potable water applications is a potential solution for water-deprived regions worldwide. Adequate treatment of grey water prior to reuse is important to reduce the risks of pathogen transmission and to improve the efficacy of subsequent disinfection. This study investigated the presence of common pathogens in grey water and compared the pathogen removal performance of leading contender treatment technologies. The opportunistic pathogens Pseudomonas aeruginosa and Staphylococcus aureus were detected in the grey water tested. Three configurations of constructed wetland, a membrane bioreactor (MBR), and a membrane chemical reactor (MCR) were evaluated for indicator bacteria (total coliforms, Escherichia coli, Enterococci, Clostridia, and heterotrophs) removal over a period of 2 years under conditions of low and high strength grey water influent. Total coliforms were found to be good indicators for P. aeruginosa, showing strong and significant Spearman's rank correlations in the influent grey water (r_s = 0.77, P = 0.005) and treated effluents (r_s = 0.81, P ≤ 0.001). The MBR provided the highest quality treated effluent and was the most robust treatment technology, remaining unaffected by an increase in influent grey water strength. Of the three constructed wetlands, the VFRB was the most reliable performer under low and high strength influent conditions, indicating aerobic unsaturated wetland to be the most suitable form of the technology for pathogen removal.     

Nitrogen uptake and assimilation in Enteromorpha intestinalis (L.) Link (Chlorophyta): using N to determine preference during simultaneous pulses of nitrate and ammonium

We investigated the ability of Enteromorpha intestinalis (L.) Link to take up pulses of different species of nitrogen simultaneously, as this would be an important mechanism to enhance bloom ability in estuaries. Uptake rates and preference for NH₄⁺ or NO₃⁻ following 1, 3, 6, 9, 12 or 24 h of exposure to either ¹⁵NH₄NO₃ or NH₄¹⁵NO₃ were determined by disappearance of N from the medium. Differences in assimilation rates for NH₄⁺ or NO₃⁻ were quantified by the accumulation of NH₄⁺, NO₃⁻, and atom % ¹⁵N in the algal tissue. NH₄⁺ concentration was reduced more quickly than water NO₃⁻ concentration. Water column NH₄⁺ concentration after the longest time interval was reduced from 300 to 50 μM. Water NO₃⁻ was reduced from 300 to 150 μM. The presence of ¹⁵N or ¹⁴N had no effect on uptake of either NH₄⁺ or NO₃⁻. ¹⁵N was removed from the water at an almost identical rate and magnitude as ¹⁴N. Differences in accumulation of ¹⁵NH₄⁺ and ¹⁵NO₃⁻ in the tissue reflected disappearance from the water; ¹⁵N from NH₄⁺ accumulated faster and reached an atom % twice that of ¹⁵N from NO₃⁻. This outcome suggested that when NH₄⁺ and NO₃⁻ were supplied in equal concentrations, more NH₄⁺ was taken up and assimilated. The ability to take up high concentrations of NH₄⁺, and NO₃⁻ simultaneously is important for bloom-forming species of estuarine macroalgae subject to multiple nutrient species from various sources.     

Organic matter quality and management effects on enrichment of soil organic matter fractions in contrasting soils in Zimbabwe

Spatial variability of soil total nitrogen (N), available N (KCl extractable NH₄⁺ and NO₃⁻), and spatial patterns of N mineralization and nitrification at a stand scale were characterized with geostatistical and univariate analysis. Two extensive soil spatial samplings were conducted in an evergreen broadleaf forest in Sichuan province, southwestern China in June and August 2000. In a study area of 90 × 105 m², three soil samples were collected from each 5 × 5 m² plot (n = 378) in June and August, and were analyzed for total N and available N contents. Net N mineralization and nitrification were measured by in situ core incubation and the rates were estimated based on the difference of NH₄⁺ and NO₃⁻ contents between the two sampling dates. Total N, NH₄⁺, and NO₃⁻ were all spatially structured with different semivariogram ranges (from high to low: NH₄⁺, NO₃⁻, and total N). The semivariograms of mineralization and nitrification were not as spatially structured as available N. NH₄⁺ was the dominant soil inorganic N form in the system. Both NH₄⁺ and NO₃⁻ affected spatial patterns of soil available N, but their relative importance switched in August, probably due to high nitrification as indicated by greatly increased soil NO₃⁻ content. High spatial auto-correlations (>0.7) were found between available N and NH4⁺, available N and NO₃⁻ on both sampling dates, as well as total N measurements between both sampling dates. Although significant, the spatial auto-correlation between NH₄⁺ and NO₃⁻ were generally low. Topography had significant but low correlations with mineralization (r = −0.16) and nitrification (r = −0.14), while soil moisture did not. The large nugget values of the calculated semivariograms and high-semivariance values, particularly for mineralization and nitrification, indicate that some fine scale (<5 m) variability may lie below the threshold for detection in this study.     

Proton production from nitrogen transformation drives stream export of base cations in acid-sensitive forested watersheds

The biogeochemical cycles of nitrogen (N) and base cations (BCs), (i.e., K⁺, Na⁺, Ca²⁺, and Mg²⁺), play critical roles in plant nutrition and ecosystem function. Empirical correlations between large experimental N fertilizer additions to forest ecosystems and increased BCs loss in stream water are well demonstrated, but the mechanisms driving this coupling remain poorly understood. We hypothesized that protons generated through N transformation (PPR_N)—quantified as the balance of NH₄⁺ (H⁺ source) and NO₃⁻ (H⁺ sink) in precipitation versus the stream output will impact BCs loss in acid-sensitive ecosystems. To test this hypothesis, we monitored precipitation input and stream export of inorganic N and BCs for three years in an acid-sensitive forested watershed in a granite area of subtropical China. We found the precipitation input of inorganic N (17.71 kg N ha⁻¹ year⁻¹ with 54% as NH₄⁺–N) was considerably higher than stream exported inorganic N (5.99 kg N ha⁻¹ year⁻¹ with 83% as NO₃⁻–N), making the watershed a net N sink. The stream export of BCs (151, 1518, 851, and 252 mol ha⁻¹ year⁻¹ for K⁺, Na⁺, Ca²⁺, and Mg²⁺, respectively) was positively correlated (r = 0.80, 0.90, 0.84, and 0.84 for K⁺, Na⁺, Ca²⁺, and Mg²⁺ on a monthly scale, respectively, P < 0.001, n = 36) with PPR_N (389 mol ha⁻¹ year⁻¹) over the three years, suggesting that PPR_N drives loss of BCs in the acid-sensitive ecosystem. A global meta-analysis of 15 watershed studies from non-calcareous ecosystems further supports this hypothesis by showing a similarly strong correlation between ∑BCs output and PPR_N (r = 0.89, P < 0.001, n = 15), in spite of the pronounced differences in environmental settings. Collectively, our results suggest that N transformations rather than anions (NO₃⁻ and/or SO₄²⁻) leaching specifically, are an important mediator of BCs loss in acid-senstive ecosystems. Our study provides the first definitive evidence that the chronic N deposition and subsequent transformation within the watershed drive stream export of BCs through proton production in acid-sensitive ecosystems, irrespective of their current relatively high N retention. Our findings suggest the N-transformation-based proton production can be used as an indicator of watershed outflow quality in the acid-sensitive ecosystems.     

Tear staining in pigs: a potential tool for welfare assessment on commercial farms

Tear staining or chromodacryorrhea refers to a dark stain below the inner corner of the eye, caused by porphyrin-pigmented secretion from the Harderian gland. It has been shown to be a consistent indicator of stress in rats and to correlate with social stress and a barren environment in pigs. The current study was, to our knowledge, the first to test it on commercial pig farms as a potential welfare indicator. The study was carried out on three commercial farms in Finland, in connection to a larger study on the effects of different types of manipulable objects on tail and ear biting and other behavioural parameters. Farm A was a fattening farm, on which 768 growing-finishing pigs were studied in 73 pens. Farm B had a fattening unit, in which 656 growing-finishing pigs were studied in 44 pens, and a farrowing unit, in which 29 sows and their litters totalling 303 piglets were studied in 29 pens. Farm C was a piglet-producing farm, on which 167 breeder gilts were studied in 24 pens. Data collection included individual-level scoring of tear staining; scoring of tail and ear damage in the growing-finishing pigs and breeder gilts; a novel object test for the piglets; and a novel person test for the growing-finishing pigs on Farm B and the breeder gilts on Farm C. On Farm A, tear staining was found to correlate with tail damage scores (n=768, r_s=0.14, P<0.001) and ear damage scores (n=768, r_s=0.16, P<0.001). In the growing-finishing pigs on Farm B, tear staining of the left eye correlated with tail damage (n=656, r_s=0.12, P<0.01) and that of the right eye correlated with ear damage (n=656, r_s=0.10, P<0.01). On Farm A, tear-staining sores were lower in the treatment with three different types of manipulable objects as compared with controls (mean scores 3.3 and 3.9, respectively, n=31, Fs₂₉=4.2, P<0.05). In the suckling piglets on Farm B, tear staining correlated with the latency to approach a novel object (n=29, r_p=0.41, P<0.05). Although correlations with tail and ear damage were low, it was concluded that tear staining has promising potential as a new, additional welfare indicator for commercial pig farming. Further research is needed on the mechanisms of tear staining.     

The global nitrogen cycle in the twenty-first century

Global nitrogen fixation contributes 413 Tg of reactive nitrogen (N_r) to terrestrial and marine ecosystems annually of which anthropogenic activities are responsible for half, 210 Tg N. The majority of the transformations of anthropogenic N_r are on land (240 Tg N yr⁻¹) within soils and vegetation where reduced N_r contributes most of the input through the use of fertilizer nitrogen in agriculture. Leakages from the use of fertilizer N_r contribute to nitrate (NO₃⁻) in drainage waters from agricultural land and emissions of trace N_r compounds to the atmosphere. Emissions, mainly of ammonia (NH₃) from land together with combustion related emissions of nitrogen oxides (NO_x), contribute 100 Tg N yr⁻¹ to the atmosphere, which are transported between countries and processed within the atmosphere, generating secondary pollutants, including ozone and other photochemical oxidants and aerosols, especially ammonium nitrate (NH₄NO₃) and ammonium sulfate (NH₄)₂SO₄. Leaching and riverine transport of NO₃ contribute 40–70 Tg N yr⁻¹ to coastal waters and the open ocean, which together with the 30 Tg input to oceans from atmospheric deposition combine with marine biological nitrogen fixation (140 Tg N yr⁻¹) to double the ocean processing of N_r. Some of the marine N_r is buried in sediments, the remainder being denitrified back to the atmosphere as N₂ or N₂O. The marine processing is of a similar magnitude to that in terrestrial soils and vegetation, but has a larger fraction of natural origin. The lifetime of N_r in the atmosphere, with the exception of N₂O, is only a few weeks, while in terrestrial ecosystems, with the exception of peatlands (where it can be 10²–10³ years), the lifetime is a few decades. In the ocean, the lifetime of N_r is less well known but seems to be longer than in terrestrial ecosystems and may represent an important long-term source of N₂O that will respond very slowly to control measures on the sources of N_r from which it is produced.     

Assessing reproductive biology of Macrobrachium lamarrei in the Ganges River (NW Bangladesh) in relation to environmental parameters

Macrobrachium lamarrei (H. Milne-Edwards, 1837) is a well-known freshwater prawn species of Bangladesh. The aim of the research is to explore various reproductive aspects (size at sexual maturity, reproductive period and fecundity) of M. lamarrei in the Ganges River, Bangladesh through October 2012 to September 2013. We also study the environmental parameters and their impact on reproduction of M. lamarrei. A total 391 (ovigerous = 141, non-ovigerous = 250) female specimens were collected using Drag net. The TL₅₀ (the TL at which 50% of individuals become mature) was calculated by a logistic equation as 5.20 cm. Based on the availability of ovigerous females the spawning season was February-November with the peak June-July. Further, 50% and 90% ovigerous females were observed when Fulton’s condition factor (K_F) was 0.85 and 1.03, respectively. The total fecundity (F_T) was ranged from 65 to 370 where TL was 4.20–6.40 cm and BW was 0.84–2.50 g. Fecundity was found to be highly correlated with TL (r² ≥ 0.96, r_s = 0.96, p < 0.0001) and BW (r² ≥ 0.88, r_s = 0.93, p < 0.0001). Temperature (r_p = 0.82, p = 0.009), dissolved oxygen (DO) (r_p = −0.83, p = 0.0007), pH (r_p = 0.80, p = 0.0014) and total alkalinity (r_p = −0.87, p = 0.0002), were highly correlated with ovigerous females. The average temperature on peak spawning season was 32 °C. Also, the spawning period connected with the peak rainfall and showed a notable relation between rainfall and ovigerous females. In addition, exploration of long data series pointed that yearly average air temperature is rising by 0.029 °C yr⁻¹, whereas yearly average rainfall is falling by 2.96 mm yr⁻¹. Therefore, the result will be helpful for the sustainable management and conservation of M. lamarrei through fixed permissible mesh size and establishment of a ban period in the Ganges River, Bangladesh and adjoining ecosystems.