Chemical characteristics of soils and pore waters of three wetland sites dominated by Phragmites australis: relation to vegetation composition and reed performance

Chemical characteristics of soils and soil pore waters, plant species composition and horizontal stand structure were investigated for three reed stands in the Třeboň Basin (Czech Republic): Branná sand pit and two littoral stands of Rožmberk fishpond (Rožmberk East and Rožmberk West). Phragmites stands were expanding, stable and retreating at the three sites, respectively. The elemental soil composition (especially of C, N, P, and K) indicated the lowest trophic conditions at Branná, intermediate at Rožmberk East and the highest at Rožmberk West. This corresponded well also with concentrations of ammonium nitrogen, dissolved reactive phosphate and total phosphorus in the soil pore water. In contrast, Branná had by far the highest level of total nitrogen, determined by nitrate nitrogen (20 mg l⁻¹), and the highest level of total dissolved solids (concentrations of NO₃⁻, SO₄²⁻, Ca²⁺ and Mg²⁺) of all three sites. No conspicuous differences were found among the three stands in biomass and its allocation. The vegetation composition corresponded more closely to elemental soil composition than to total nitrogen or total dissolved solids in the pore water. It is concluded that Branná provides an example of a site subjected to an initiating but dramatic and fast eutrophication while conditions at the two Rožmberk sites indicate a slower but longer lasting eutrophication. Owing to continuous heavy organic loading, Rožmberk West represents a hypertrophic site characterised by the highest levels of organic matter and associated characteristics (soil C, N, P, K, dissolved P), but also by the most severe lack of oxygen of the three sites.     

Effect of nutrient pulses on photosynthesis of Chaetomorpha linum from a shallow Mediterranean coastal lagoon

The influence of nitrogen and phosphorus pulses on Chaetomorpha linum (Muller) Kutzing growth and photosynthesis was studied in laboratory experiments. Photosynthesis and growth of C. linum from Tancada lagoon seems limited by both nitrogen and phosphorus, as indicated by the high rate (4.7–11.6 mg O₂ g⁻¹ dry weight h⁻¹) of light-saturated photosynthesis (P_m) and growth rates observed under nitrogen plus phosphorus enrichment in relation to enrichment by nitrogen alone (2.9–7.6 mg O₂ g⁻¹ dry weight h⁻¹). Significant increase in nitrogen and phosphorus content as percentage of dry weight was observed in C. linum fertilized with a single nutrient or with nitrogen plus phosphorus. In Tancada lagoon, when availability of nitrogen to primary producers is by pulses, an increase of nitrate concentration in the water column (from 6 to 100 μM) has a greater effect on growth of C. linum (growth rate: 0.13 day⁻¹) than an increase in ammonium concentration (from 20 to 100 μM and growth rate: 0.11 day⁻¹). For a given thallus nitrogen content (0.6–1.4% N), both P_m and the photosynthetic efficiency (α) normalized to dry weight were correlated (r² = 0.73, p < 0.005) indicating that variations in electron transport were coupled to variations in C-fixation capacity. Optimizing both α and P_m may be a general characteristic of thin-structured opportunistic algae in more variable estuarine environments.     

Statistical analysis and optimization of nitrogen,phosphorus, and inoculum concentrations for the biodegradation of petroleum hydrocarbons by response surface methodology

In order to optimize and evaluate the influence of nitrogen, phosphorus, and inoculum concentrations on the biodegradation of hydrocarbon contaminated effluents, experiments based on central composite design (CCD) method were carried out for 3 days, employing C1 mixed culture and intermittent aeration. The independent variables were nitrogen concentration (X ₁), phosphorus concentration (X ₂), and inoculum concentration (X ₃) and the removal of total petroleum hydrocarbons (TPH) was the dependent variable. The optimized nutrients ratio (C:N:P = 100:20:2.7) and inoculum concentration (1.32 g/l) provided TPH removal of 71.8% after processing for three days. Analysis using gas chromatography identified five hydrocarbons classes: paraffins, isoparaffins, olefins, naphthenics, and aromatics. The naphthenic compounds did not degrade as readily as the other hydrocarbons that were identified. The following degradation percentages were obtained: 87.1% for the paraffins, 77.7% for the isoparaffins, 78.6% for the olefins, 38.4% for the naphthenics, and 71.7% for the aromatics.     

Characterization of a toxic Pseudo-nitzschia spp. bloom in the Northern Gulf of Mexico associated with domoic acid accumulation in fish

A toxic bloom of Pseudo-nitzschia spp. was observed in the Alabama coastal waters of the northern Gulf of Mexico (NGOM) in June 2009 that resulted in the accumulation of domoic acid (DA) in fish. The bloom initiated following a large storm event that likely caused increased groundwater discharge 16–20 days prior to peak densities. Eleven sites, located in littoral shoreline waters and inshore embayments spanning the entire Alabama NGOM coastline, were sampled during peak densities to assess Pseudo-nitzschia species composition and toxicity, and associated water-quality parameters. Small fish (0.27–11.9 g body weight) were collected at six of these sites for analysis of DA content. High Pseudo-nitzschia spp. densities (8.27 × 10⁴–5.05 × 10⁶ cell l⁻¹) were detected at eight sites located in the littoral shoreline and particulate DA was detected at six of these littoral sites (48.0–540 pg ml⁻¹). The bloom consisted primarily (>90%) of Pseudo-nitzschia subfraudulenta, a species previously characterized as forming only a minor component of Pseudo-nitzschia assemblages and not known to produce DA. Pseudo-nitzschia spp. were at low densities or not detected at the inshore sites and DA was detected at these sites. Pseudo-nitzschia spp. density varied along an estuarine gradient, with greater densities occurring in the most saline, clear, and nutrient-poor waters. Cell density was strongly and negatively correlated with silicate (Si) concentrations and the ratios of silicate to dissolved inorganic nitrogen and phosphate (Si:DIN and Si:PO₄). Cell toxin quota was negatively correlated with phosphate, and strongly and positively correlated with the ratio of total nitrogen to total phosphorus (TN:TP). These relationships are consistent with previous observations that indicate Pseudo-nitzschia spp. density and toxicity are likely to be greater in high salinity, high irradiance, and nutrient-poor waters. DA was detected in 128 of 131 (98%) of the fish collected, which included seven primary and secondary consumer species. This is the first demonstration of trophic transfer of DA in this region of the NGOM, indicating that toxic blooms of Pseudo-nitzschia spp. in Alabama coastal waters have the potential to transfer DA to recreationally and commercially important fish species.     

Seasonal Variations of Dissolved Nitrogen and DOC:DON Ratios in an Intermittent Mediterranean Stream

Seasonal variations of dissolved inorganic nitrogen (DIN) (NO₃–N and NH₄–N) and dissolved organic nitrogen (DON) were determined in Fuirosos, an intermittent stream draining an unpolluted Mediterranean forested catchment (10.5 km²) in Catalonia (Spain). The influence of flow on streamwater concentrations and seasonal differences in quality and origin of dissolved organic matter, inferred from dissolved organic carbon to nitrogen ratios (DOC:DON ratios), were examined. During baseflow conditions, nitrate and ammonium had opposite behaviour, probably controlled by biological processes such as vegetation uptake and mineralization activity. DON concentrations did not have a seasonal trend. During storms, nitrate and DON increased by several times but discharge was not a good predictor of nutrient concentrations. DOC:DON ratios in streamwater were around 26, except during the months following drought when DOC:DON ratios ranged between 42 and 20 during baseflow and stormflow conditions, respectively. Annual N export during 2000–2001 was 70 kg km⁻¹ year⁻¹, of which 75% was delivered during stormflow. The relative contribution of nitrogen forms to the total annual export was 57, 35 and 8% as NO₃–N, DON and NH₄–N, respectively.     

Growth and nutrient removal properties of a freshwater microalga Scenedesmus sp. LX1 under different kinds of nitrogen sources

Microalgae have received much attention for the inorganic nutrient removal in tertiary treatment of domestic wastewater. Effect of different kinds of nitrogen sources on the growth and nitrogen/phosphorus removal properties of a newly isolated freshwater microalga, Scenedesmus sp. LX1, from a low-nutrient environment condition was studied and reported in this paper. The order of specific growth rate of the microalga with different nitrogen sources was NH₄-N > urea-N > NO₃-N. With nitrate or urea as nitrogen source, the microalga could grow well and remove both nitrogen and phosphorus efficiently (90% nitrogen and nearly 100% phosphorus were removed). However, with ammonium as the nitrogen source, the maximum algal density was relatively low, and the nitrogen and phosphorus removal efficiencies were as low as 31.1% and 76.4%, respectively. This was caused by the inhibitory effect of algal culture's acid pH due to H⁺ releasing from NH₄⁺ during algal cultivation process.     

Contrasting contributions to inorganic nutrient recycling by the co-occurring jellyfishes, Catostylus mosaicus and Phyllorhiza punctata (Scyphozoa, Rhizostomeae)

The rhizostome jellyfishes, Catostylus mosaicus and Phyllorhiza punctata abound in estuaries in New South Wales, Australia. P. punctata contains symbiotic zooxanthellae but C. mosaicus contains few or no zooxanthellae. Our experiment measured the rates at which NH₃, PO₄ and NO_x were taken up or excreted by each species and in two controls: a “water only” control and a “mucus” control. Rates of uptake or excretion were measured as changes in the nutrient concentration of the water in the containers housing the animals over periods of 6 h. Experiments were repeated twice during the day and twice at night, under both ambient and enriched nutrient conditions. Under ambient nutrient conditions, the flux of NH₃ in the P. punctata treatment did not differ from the controls but under enriched conditions P. punctata excreted NH₃ during the night (49 μg kg⁻¹ WW (wet weight) h⁻¹) and took up NH₃ during the day (123 μg kg⁻¹ WW h⁻¹). In contrast, C. mosaicus excreted NH₃ at a rate of 1555 μg kg⁻¹ WW h⁻¹ during the day and 1004 μg kg⁻¹ WW h⁻¹ during the night under both enriched and ambient nutrient conditions. P. punctata neither took up nor excreted PO₄ but C. mosaicus excreted PO₄ at a faster rate during the day than night (173 μg kg⁻¹ WW h⁻¹ cf. 104 μg kg⁻¹ WW h⁻¹). Both C. mosaicus and P. punctata excreted NO_x and, although the rate of excretion for P. punctata varied between the two experiments conducted during the day, the rate of excretion was consistently greater than for C. mosaicus (52 and 80 μg kg⁻¹ WW h⁻¹ cf. 26 μg kg⁻¹ WW h⁻¹⁾. Tubs containing P. punctata had a much greater concentration of dissolved oxygen at the end of the experiments conducted during the day (152% saturation) than night (60% saturation) but tubs containing C. mosaicus had a greater dissolved oxygen concentration during the night (47% saturation) than day (39%). Overall, C. mosaicus appears to recycle more inorganic nutrients to estuaries than P. punctata. Calculations of the importance of inorganic nitrogen excreted by this species during times of peak biomass in Lake Illawarra suggest that it can meet about 8% of the phytoplankton primary production requirements of N and that its inorganic N excretion rate is about 11% of measured inorganic ammonia fluxes from sediments in that system. Since the biomass of C. mosaicus often exceeds several thousand tonnes, the contribution of inorganic nutrients by this species is substantial.     

Effects of experimental warming and nitrogen enrichment on leaf and litter chemistry of a wetland grass,Phragmites australis

As global climate is warming and the nitrogen cycle accelerates, plants are likely to respond not only by shifting community composition, but also by adjusting traits such as tissue chemistry. We subjected a widespread wetland plant, Phragmites australis, to increased nitrate supply and elevated temperature in enclosures that were established in a littoral permanently submerged freshwater marsh. The nitrogen (N) and phosphorus (P) concentrations in green leaves ranged from 11.4 to 13.8 mg N and from 1.5 to 2.0 mg P g⁻¹ dry mass. While the N concentration changed little in brown litter, the P concentration decreased to 0.53–0.65 mg P g⁻¹ litter dry mass. Neither experimental warming of the water and sediment surface, nor nitrate enrichment during the growing season affected nitrogen or phosphorus concentrations in green leaves. Concentrations of the two major structural carbon compounds in plant litter, cellulose and lignin, were also unaffected, ranging from 32.1 to 34.2% of dry mass for cellulose and from 16.3 to 17.7% of dry mass for lignin. Warming, however, significantly increased the nitrogen concentration of fully brown leaf litter. Thus, temperature appears to be more important than the supply of dissolved N in the water, especially in affecting leaf litter N concentrations in P. australis, even when only water but not air temperature is increased. This result may have implications for decomposition processes and decomposer food webs, which both depend on the quality of plant litter.     

Metabolism of glucosinolate-derived isothiocyanates to glutathione conjugates in generalist lepidopteran herbivores

The defensive properties of the glucosinolate-myrosinase system in plants of the order Brassicales have been attributed to the formation of toxic isothiocyanates generated upon tissue damage. Lepidopteran herbivores specialised on brassicaceous plants have been shown to possess biochemical mechanisms preventing the formation of isothiocyanates. Yet, no such mechanisms are known for generalist lepidopterans which also occasionally but successfully feed on plants of the Brassicales. After feeding on Arabidopsis thaliana plants, faeces of Spodoptera littoralis larvae contained glutathione conjugate derivatives (cysteinylglycine- and cysteinyl-isothiocyanate-conjugates) of the plant's major glucosinolate hydrolysis product, 4-methylsulfinylbutyl isothiocyanate. When caterpillars fed on leaves of A. thaliana containing [¹⁴C]₄-methylsulfinylbutyl glucosinolate, more than half of the ingested radioactivity was excreted as the unmetabolised corresponding isothiocyanate, and only 11% as glutathione conjugate derivatives. However, these conjugates were demonstrated to be the major metabolites of isothiocyanates in S. littoralis, and their abundance was shown to correlate with the amount of isothiocyanates ingested. Analysis of larval faeces from several species of generalist lepidopterans (Spodoptera exigua, S. littoralis, Mamestra brassicae, Trichoplusia ni and Helicoverpa armigera) fed on different Brassicaceae revealed that glutathione conjugates arise from a variety of aliphatic and aromatic isothiocyanates derived from dietary glucosinolates.     

Net and gross incorporation of nitrogen by marine copepods fed on N-labelled diatoms: Methodology and trophic studies

The stable isotope of nitrogen (¹⁵N) and an appropriate three-compartment model were used in two 24-h lasting feeding experiments to trace the flow of N through the copepod Acartia discaudata and Calanus helgolandicus fed on ¹⁵N-labelled Skeletonema costatum and Thalassiosira weissflogii, respectively. Details of the labelling technique and principles of the computation of N transport rates are given. At the end of a single 24-h feeding period only about one third of the total amount of N ingested by A. discaudata was incorporated into the copepod's body N; we refer to this rate as net incorporation. Most of the N ingested was lost as ammonium (48% of total N ingested), followed by losses in the form of eggs + fecal pellets (13%) and dissolved organic N (DON, 9%). The sum of net incorporation and the latter losses is defined as gross incorporation. Net incorporation by C. helgolandicus and N losses did not vary over time during a 24 h lasting time-series feeding experiment. On average, 79% of total N ingested was actually incorporated by the copepod whereas mean N losses as ammonium, eggs + fecal pellets represented only 12 and 9%, respectively. After a 24-h feeding period only 2% of N ingested was lost as DON. Inspection of individual DON pathways showed that both A. discaudata and C. helgolandicus highly contributed to total DON production via direct excretion (79 and 64%, respectively). The remaining DON appearing in the DON pool was derived from phytoplankton via direct release and/or indirect release (copepod ‘sloppy feeding’).     

Anaerobic Oxalate Degradation: Widespread Natural Occurrence in Aquatic Sediments

Significant concentrations of oxalate (dissolved plus particulate) were present in sediments taken from a diversity of aquatic environments, ranging from 0.1 to 0.7 mmol/liter of sediment. These included pelagic and littoral sediments from two freshwater lakes (Searsville Lake, Calif., and Lake Tahoe, Calif.), a hypersaline, meromictic, alkaline lake (Big Soda Lake, Nev.), and a South San Francisco Bay mud flat and salt marsh. The oxalate concentration of several plant species which are potential detrital inputs to these aquatic sediments ranged from 0.1 to 5.0% (wt/wt). In experiments with litter bags, the oxalate content of Myriophyllum sp. samples buried in freshwater littoral sediments decreased to 7% of the original value in 175 days. This suggests that plant detritus is a potential source of the oxalate within these sediments. [¹⁴C]oxalic acid was anaerobically degraded to ¹⁴CO₂ in all sediment types tested, with higher rates evident in littoral sediments than in the pelagic sediments of the lakes studied. The turnover time of the added [¹⁴C]oxalate was less than 1 day in Searsville Lake littoral sediments. The total sediment oxalate concentration did not vary significantly between littoral and pelagic sediments and therefore did not appear to be controlling the rate of oxalate degradation. However, depth profiles of [¹⁴C]oxalate mineralization and dissolved oxalate concentration were closely correlated in freshwater littoral sediments; both were greatest in the surface sediments (0 to 5 cm) and decreased with depth. The dissolved oxalate concentration (9.1 μmol/liter of sediment) was only 3% of the total extractable oxalate (277 μmol/liter of sediment) at the sediment surface. These results suggest that anaerobic oxalate degradation is a widespread phenomenon in aquatic sediments and may be limited by the dissolved oxalate concentration within these sediments.     

Nitrogen partitioning and blood meal utilization by Aedes aegypti (Diptera Culicidae)

The utilization of the blood meal by mosquitoes was investigated by first feeding females quantities of blood ranging from 1 to 5 mg, and then analyzing the faeces for the various by-products of protein catabolism that were subsequently eliminated. The nitrogeneous waste products in order of importance were uric acid, histidine, ammonia and arginine. Only traces of the other amino acids were excreted.The total amount of each faecal substance varied linearly with the quantity of blood ingested, however their relative proportions did not change. Regardless of blood meal size the quantily of uric acid and ammonia produced indicates that about 80% of the non-histidine and arginine amino acids are deaminated and utilized for metabolic purposes other than egg protein synthesis.Most of the histidine and about one half of the arginine content of the blood were excreted as free amino acids, but the other amino acids were lost in trace amounts.Nineteen per cent of the total ingested amino acids was incorporated into soluble yolk proteins and this proportion was constant even for small blood meals that result in a reduction in the numbers of eggs produced.The comparative aspects of nitrogen partitioning and blood meal utilization by haematophagous insects, as well as the factors that affect blood meal utilization and fecundity in A. aegypti are discussed.     

Heterologous expression of Anabaena PCC 7120 all3940 (a Dps family gene) protects Escherichia coli from nutrient limitation and abiotic stresses

This study presents first hand data on the cloning and heterologous expression of Anabaena PCC 7120 all3940 (a dps family gene) in combating nutrients limitation and multiple abiotic stresses. The Escherichia coli transformed with pGEX-5X-2-all3940 construct when subjected to iron, carbon, nitrogen, phosphorus limitation and carbofuron, copper, UV-B, heat, salt and cadmium stress registered significant increase in growth over the cells transformed with empty vector under iron (0%), carbon (0.05%), nitrogen (3.7 mM) and phosphorus (2 mM) limitation and carbofuron (0.025 mg ml⁻¹), CuCl₂ (1 mM), UV-B (10 min), heat (47 °C), NaCl (6% w/v) and CdCl₂ (4 mM) stress. Enhanced expression of all3940 gene measured by semi-quantitative RT-PCR at different time points under above mentioned treatments clearly demonstrates its role in tolerance against aforesaid abiotic stresses. This study opens the gate for developing transgenic cyanobacteria capable of growing successfully under above mentioned stresses.     

Colonization of acidic mining lakes: <Emphasis Type="Italic">Chydorus sphaericus</Emphasis> and other Cladocera within a dynamic horizontal pH gradient (pH 3−7) in Lake Senftenberger See (Germany)

Spatio-temporal distribution of nitrogen was examined along the gradient from open water to lakeshore in Lake Taihu, China. Two types of undulating littoral zones were selected: natural reed belt and bare lakeshore. The reed belt affected nitrogen transformation and was sink for internal-lake nitrogen, whereas the bare lakeshore showed little effect. During the growing season, NO ₃ ⁻ -N concentration increased by up to 3–5 times from open water to reed belt, while NH ₄ ⁺ -N concentration decreased. It suggested that nitrification was the main nitrogen process in reed belt. Total dissolved nitrogen (TDN) showed little spatial variation, indicating that most of nitrogen released from sediment did not move into open water again. Significant temporal variation of dissolved nitrogen occurred and was similar in both the littoral zone and the open water. Maximum TDN and NH ₄ ⁺ -N concentrations occurred in January, and NO ₃ ⁻ -N in March. Minimum NH ₄ ⁺ -N and NO ₃ ⁻ -N concentrations occurred in July and August, respectively. An increasing total soil nitrogen was found in the surface sediments from reed belt to open water. This further suggested that the reed-covered littoral zone had strong nitrogen transformation potential.     

15N fractionation between vegetation, soil, faeces and wool is not influenced by stocking rate

Understanding stable isotope fractionation in trophic networks is important for the interpretation of stable isotope composition of ecosystem components. This work explores the influence of grazing pressure on the nitrogen isotope composition (?? ¹⁵N) of vegetation (standing biomass), soil, and sheep??s faeces and wool in a three-years (2005?C2007) experiment with different stocking rates (0.375?C2.25 sheep ha^-1 year^-1) in semi-arid Inner Mongolia grassland. The ¹⁵N of wool (from a yearly shearing) reflects vegetation at the whole-year grazing grounds-scale while faeces reflect that of the area grazed within a few days. Stocking rate had no effect on ?? ¹⁵N of vegetation and soil, and sheep??s faeces and wool, although nitrogen content of bulk vegetation increased with stocking rate. Furthermore, ?? ¹⁵N of vegetation and diet did not differ between stocking rates. Hence, ¹⁵N fractionations between vegetation and faeces (??_veg-faeces), vegetation and wool (?? _veg-wool), faeces and soil (?? _faeces-soil) and soil and vegetation (?? _soil-veg) were constants, with ?? _veg-faeces?=?3.0?? (±0.1??, 95% confidence interval), ?? _veg-wool?=?5.3?? (±0.1??), ?? _faeces-soil?=?1.1?? (±0.4??) and ?? _soil-veg?=?-4.1?? (±0.3??). This finding is useful as it means that ?? ¹⁵N of wool or faeces can be used to estimate the ¹⁵N of grazed vegetation, even if grazing pressure is unknown.     

Influence of freshwater macrophytes on the littoral ecosystem structure and function of a young Colorado reservoir

The presence of rooted macrophytes, mostly the milfoil Myriophyllum sibiricum, was manipulated in enclosures in the littoral zone of a Colorado reservoir. The presence of macrophytes significantly increased the abundance of major invertebrate taxa by 70–1725% and increased the emission of methane 127%. The increase in abundance of most invertebrates was probably due to the habitat and surfaces provided by milfoil as stable isotope analyses indicated that milfoil was an insignificant carbon source for all of the invertebrate taxa, except for the milfoil midge Cricotopus myriophylli. Cricotopus is known to specialize on milfoil (other members of the genus specialize on Hydrilla or are generalists), had an isotopic signature that indicated a diet of milfoil, and was about 15 times more abundant when milfoil was present than when it was absent. Milfoil had no detectable effect on the total particulate phosphorus (TPP), soluble reactive phosphorus (SRP), total dissolved phosphorus (TDP), dissolved organic phosphorus (DOP), and Chl a of water within the enclosures. However, enclosures containing milfoil had higher concentrations of SRP in the pore water of surface sediments than enclosures that had milfoil removed. SRP in pore water dropped below 2 μg/L at >2 cm sediment depth and DOP increased progressively from nearly zero at the surface to about 150 μg/L at 15 cm depth, regardless of vegetation. Thus, milfoil had significant effects on many, but not all, measures of littoral ecosystem structure and function that were monitored.     

Enhancement of nitrogen removal in towery hybrid constructed wetland to treat domestic wastewater for small rural communities

Efforts to protect watercourses, especially sources of drinking water, particularly in rural areas, are now underway in China. Nitrogen present in wastewater, due to its role in eutrophication and potential toxicity to aquatic species, is a focus of primary concern. Constructed wetlands (CWs), a simpler, less costly treatment alternative, have been used to treat domestic wastewater for small communities. Although showing great promise for removing carbonaceous materials from wastewater, wetland systems have not been successful in removing nitrogen mainly due to lack of dissolved oxygen (DO). To enhance nitrogen removal, a novel CW configuration with three stages, towery hybrid constructed wetland (THCW), was designed. The first and third stages were rectangle subsurface horizontal flow CWs, and the second stage was a circular three-layer free-water flow CW. Increased DO by passive aeration of a tower type cascade overflow from the upper layer into the lower layer in the second stage of the wetland enhanced nitrification rates. Denitrification rates were also improved by additional organic matter supplied as a result of bypass influent directly into the second stage. Evergreen tree Pond Cypress (Taxodium ascendens), industrial plants Mat Rush (Schoenoplectus trigueter) and Wild Rice shoots (Zizania aquatica), ornamental floriferous plants Pygmy Waterlily (Nymphaea tetragona) and Narrow-leaved Cattail (Typha angustifolia) were planted in the wetland. The average percentage of removal was 89%, 85%, 83%, 83% and 64% for total suspended solid, chemical oxygen demand, ammonia nitrogen, total nitrogen and total phosphorus, respectively. There was no significant difference (p < 0.05) at low and high hydraulic loads (16 cm/d and 32 cm/d) for performance of THCW. Nitrifying and denitrifying bacteria as well as potential nitrification activity and potential denitrification rates measured have shown that nitrification–denitrification is the main mechanism for nitrogen removal in the wetland. THCW also provided additional aesthetic benefits.     

Effects of fumonisin B1 on growth and metabolism of larvae of the yellow mealworm, Tenebrio molitor

The chronic and acute toxicity of fumonisin B₁ (FB₁), a mycotoxin from Fusarium moniliforme, to the larvae of the yellow mealworm, Tenebrio molitor, was assessed. The toxin was administered via the diet or injected directly into the larvae. Young T. molitor larvae fed on a diet containing 450 µg FB₁ per g diet exhibited reduced growth performance but only after consuming the fumonisin-contaminated diet for several weeks. FB₁-contaminated diet also reduced the rate of carbon dioxide production, food consumption and protein metabolism. The concentrations of FB₁ in the diet did not increase mortality, even when tested at the highest dose of 450 µg FB₁ per g of diet. Injection of 25 ng FB₁ per larva decreased the CO₂ production, but became significant only 11 days after the injection and was reversible with time. A parallel analysis of the retention of FB₁ by the larvae indicated that about 40% of the ingested FB₁ was excreted in the faeces.     

Export of Nitrogen,Phosphorus, and Suspended Solids from a Southern New England Watershed to Little Narragansett Bay

The Pawcatuck River watershed (764 km²) is a mainly forested drainage basin with a low population density (80 people km⁻²) that discharges to a shallow estuary, Little Narragansett Bay (RI and CT, USA). In order to quantify the nitrogen (N) and phosphorus (P) flux to the estuary, we measured all forms of nitrogen and phosphorus, as well as suspended solids at the mouth of the river above tidal influence, on more than 80 occasions over an annual cycle. The annual export of total nitrogen, total phosphorus, and total suspended solids amounted to 16.0×10⁶ mol y⁻¹, 0.97×10⁶ mol y⁻¹, and 1.4×10⁶ kg y⁻¹, respectively. Nitrogen export was equally divided between dissolved inorganic (83% NO₃⁻) and organic forms, with particulate nitrogen comprising 17% of the total flux. Phosphorus export was dominated by particulate forms (67%), with dissolved inorganic phosphate contributing 30% and dissolved organic phosphorus contributing 8% of the annual flux. Preliminary nutrient budgets for the Pawcatuck watershed suggest that only about 10% of the nitrogen and phosphorus inputs are exported from the system. Strong regressions between water discharge and TN enabled us to extrapolate the data collected during the relatively dry study period to a long term average discharge year. Under normal river discharge conditions, the N flux would be approximately 26.0×10⁶ mol y⁻¹ or about 20% of the nitrogen inputs to the watershed. This value is very close to the N flux predicted by a regression developed by others from a wide range of larger watersheds. The relatively large size of the Pawcatuck watershed relative to the estuary (9.6 km²), makes Little Narragansett Bay one of the most intensively nitrogen loaded estuaries on the Atlantic coast in spite of the dominant forest cover of the watershed.     

Low degradable protein supply to increase nitrogen efficiency in lactating dairy cows and reduce environmental impacts at barn level

Generally, <30% of dairy cattle’s nitrogen intake is retained in milk. Large amounts of nitrogen are excreted in manure, especially in urine, with damaging impacts on the environment. This study explores the effect of lowering dietary degradable nitrogen supplies – while maintaining metabolisable protein – on dairy cows’ performance, nitrogen use efficiency and gas emissions (NH₃, N₂O, CH₄) at barn level with tied animals. Two dietary N concentrations (CP: 12% DM for LowN; 18% DM for HighN) were offered to two groups of three lactating dairy cows in a split-plot design over four periods of 2 weeks. Diets were formulated to provide similar metabolisable protein supply, with degradable N either in deficit or in excess (PDIN of 84 and 114 g/kg DM for LowN and HighN, respectively). Cows ingested 0.8 kg DM/day less on the LowN diet, which was also 2.5% less digestible. Milk yield and composition were not significantly affected. N exported in milk was 5% lower (LowN: 129 g N/day; HighN: 136 g N/day; P<0.001) but milk protein yield was not significantly affected (LowN: 801 g/day; HighN: 823 g/day; P=0.10). Cows logically ingested less nitrogen on the LowN diet (LowN: 415 g N/day; HighN: 626 g N/day; P<0.001) resulting in a higher N use efficiency (N milk/N intake; LowN: 0.31; HighN: 0.22; P<0.001). N excreted in urine was almost four times lower on the LowN diet (LowN: 65 g N/day; HighN: 243 g N/day; P<0.001) while urinary urea N concentration was eightfold lower (LowN: 4.6 g/l; HighN: 22.9 g/l; P<0.001). Ammonia emission (expressed in g/h in order to remove periods of the day with potential interferences with volatile molecules from feed) was also lower on the LowN diet (LowN: 1.03 g/h per cow; HighN: 1.25 g/h per cow; P<0.05). Greenhouse gas emissions (N₂O and CH₄) at barn level were not significantly affected by the amount of dietary N. Offering low amounts of degradable protein with suitable metabolisable protein amounts to cattle improved nitrogen use efficiency and lowered ammonia emissions at barn level. This strategy would, however, need to be validated for longer periods, other housing systems (free stall barns) and at farm level including all stages of manure management.