Removal of nitrogen from wastewaters by anaerobic ammonium oxidation (ANAMMOX) using granules in upflow reactors

Nitrogen pollution of waters has sometimes caused severe eutrophication, leading to the death of fishes and most aquatic life. There is therefore a need for efficient and cost-effective methods to remove nitrogen from ammonium-rich wastewaters. Anaerobic ammonium oxidation (ANAMMOX) is a promising process to remove nitrogen because this process directly oxidizes ammonium (NH₄ ⁺) to dinitrogen gas (N₂) under anoxic condition. Nonetheless, a challenge of this process is that chemolithoautotrophic Anammox bacteria grow slowly at the beginning, thus resulting in low Anammox biomass and instability of reactors. Such issues can be overcome by granulation of the Anammox sludge. Here, we review the characteristics of the Anammox bacteria, and the formation, structure and flotation of Anammox granules under high hydraulic loadings. We also evaluate the performances of full-scale granular Anammox processes. The major points are: 1) Anammox bacteria secrete a large amount of extracellular polymeric substances (EPS), up to 415 mg g^?1 of volatile suspended solids (VSS), containing many hydrophobic functional groups that facilitate biomass granulation. 2) Granulation enhances the sludge settling property and retention time, which contributes to the extremely high nitrogen removal rate of 77 kg m^?3 d^?1 of Anammox upflow reactors. 3) Flotation of Anammox granules frequently occurs under nitrogen removal rate higher than 10 kg m^?3 d^?1, which is mainly due to the overproduction of EPS under high hydraulic conditions.     

Effects of mussel aquaculture on the nitrogen cycle and benthic communities in Kenepuru Sound,Marlborough Sounds,New Zealand

Nitrogen pools and transformations and benthic communities at a Perna canaliculus farm and a nearby reference site without direct influence of marine farming in Kenepuru Sound, New Zealand, were compared on four dates between September 1982 and May 1983. The organic nitrogen pool in the top 12 cm sediment was 7.4 to 10.8 mol m^-2 at the mussel farm and 6.1 to 8.9 mol m^-2 at the reference site. The nitrate and nitrite pools were similar in both sediments, but the ammonium pool in the mussel farm sediment was about twice as high as in the reference sediment. In January, the sediment ammonium concentrations ranged from 418 nmol cm^-3 (surface) to 149 nmol cm^-3 (12 cm depth) at the mussel farm and from 86 to 112 nmol cm^-3 at the reference site. The molar C:N ratio of the sediment organic matter was 6.2 to 7.2 at the mussel farm and 7.9 to 10.0 at the reference site. The molar N:P ratio of the sediment organic matter was 4.3 to 7.2 and 3.3 to 6.1 at mussel farm and reference site, respectively. The total nitrogen mineralisation rate in the top 12 cm sediment ranged from 21.7 to 37.1 mmol m^-2 d^-1 at the mussel farm and from 8.5 to 25.0 mmol m^-2 d^-1 at the reference site. Ammonium excretion by mussels was about 4.7% (January) and 7.4% (May) of the combined nitrogen mineralisation by mussels and sediment. The sediment-denitrification rate was 0.7 to 6.1 mmol m^-2 d^-1 at the mussel farm and 0.1 to 0.9 mmol m^-2 d^-1 at the reference site. In January, 76 and 93% of the nitrate reduced in the sediments were denitrified at the mussel farm and reference site, respectively. The denitrification rate on the mussel lines (determined on detritus-covered mussels) was twice the mussel farm sediment-denitrification rate and 10 times the reference sediment-denitrification rate. Total denitrification at the mussel farm was 21% higher than at the reference site. The loss of nitrogen through mussel harvest and denitrification was 68% higher at the mussel farm. The surface layers of both sediments contained about 75 mg m^-2 chlorophyll a. Sediment phaeophytin levels were 52 mg m^-2 at the reference site and 137 mg m^-2 at the mussel farm. While the benthic infauna of the mussel-farm sediment consisted only of polychaete worms, the reference sediment contained also bivalve molluscs, brittle stars and crustaceans.     

Spatial distribution of copper in relation to recreational boating in a California shallow-water basin

The overall effect of the number of boats on the copper (Cu) levels in the water column and sediment, along with their spatial variability within Shelter Island Yacht Basin (SIYB), San Diego Bay, California was examined. We identified a horizontal gradient of increasing dissolved Cu and Cu in sediment from outside to the head of SIYB which was coincident with the increasing number of boats. Spatial models of Cu distribution in water and sediment indicated the presence of ‘hotspots’ of Cu concentration. From outside to the head of SIYB, dissolved Cu ranged from 1.3 μ g L^?1 to 14.6 μ g L^?1 in surface water, and 2.0 μ g L^?1 to 10.2 μ g L^?1 in bottom water. Cu in sediment exceeded the Effect Range Low of 34 mg kg^?1 (i.e. where adverse effects to fauna may occur), with a peak concentration of 442 mg kg^?1 at the head of the basin. Free Cu⁺⁺ in surface water was several orders of magnitude higher than in sediment porewater. High-resolution data of Cu species together with probability maps presented in this paper will allow managers to easily visualise and localise areas of impaired quality and to prioritise which areas should be targeted to improve Cu-related conditions.     

Selenium speciation in wheat grain varies in the presence of nitrogen and sulphur fertilisers

This study investigated whether selenium species in wheat grains could be altered by exposure to different combinations of nitrogen (N) and sulphur (S) fertilisers in an agronomic biofortification experiment. Four Australian wheat cultivars (Mace, Janz, Emu Rock and Magenta) were grown in a glasshouse experiment and exposed to 3 mg Se kg^?1 soil as selenate (Se^VI). Plants were also exposed to 60 mg N kg^?1 soil as urea and 20 mg S kg^?1 soil as gypsum in a factorial design (N + S + Se; N + Se; S + Se; Se only). Plants were grown to maturity with grain analysed for total Se concentrations via ICP-MS and Se species determined via HPLC-ICP-MS. Grain Se concentrations ranged from 22 to 70 µg Se g^?1 grain (dry mass). Selenomethionine (SeMet), Se-methylselenocystine (MeSeCys), selenohomolanthionine (SeHLan), plus a large concentration of uncharacterised Se species were found in the extracts from grains. SeMet was the major Se species identified accounting for between 9 and 24 µg Se g^?1 grain. Exposure to different N and S fertiliser combinations altered the SeMet content of Mace, Janz and Emu Rock grain, but not that of Magenta. MeSeCys and SeHLan were found in far lower concentrations (<4 µg Se g^?1 grain). A large component of the total grain Se was uncharacterisable (>30 % of total grain Se) in all samples. When N fertiliser was applied (with or without S), the proportion of uncharacterisable Se increased between 60 and 70 % of the total grain Se. The data presented here indicate that it is possible to alter the content of individual Se species in wheat grains via biofortification combined with manipulation of N and S fertiliser regimes. This has potential significance in alleviating or combating both Se deficiency and Se toxicity effects in humans.     

Nitrogen cycling in microbial mats: rates and patterns of denitrification and nitrogen fixation

Spatial and temporal variations in nitrogen fixation and denitrification rates were examined between July 1991 and September 1992 in the intertidal regions of Tomales Bay (California, USA). Microbial mat communities inhabited exposed mudflat and vegetated marsh surface sediments. Mudflat and marsh sediments exhibited comparable rates of nitrogen fixation. Denitrification rates were higher in marsh sediments. Nitrogen fixation rates were lowest during January at both sites, whereas highest rates occurred during summer and fall. Denitrification rates were highest during fall and winter months in marsh sediments, while rates in mudflat sediments were highest during summer and fall. In mudflat sediments, nitrogen fixation and denitrification rates, integrated over 24 h, ranged from 6 to 79 mg N m^-1 d^-1 and 1 to 10 mg N m^-2 d^-1, respectively. Rates of denitrification represented between 6 and 20% of nitrogen fixation rates during the day, but exceeded or were equivalent to nitrogen fixation rates at night. The highest integrated rates of both nitrogen fixation and denitrification occurred during July, whereas, the highest percent loss occurred during spring when denitrification rates amounted to 20% of nitrogen fixation rates during the day. Over an annual cycle, inputs of fixed N to mudflat communities occurred exclusively during daylight. These results underscore the importance of determining integrated diel rates of both nitrogen fixation and denitrification when constructing N budgets. Using this approach, it was shown that microbial denitrification can represent a significant loss of combined nitrogen from mats on daily as well as monthly time scales.     

Mesocosm and in situ observations of the burrowing shrimp Calocaris templemani (Decapoda: Thalassinidea) and its bioturbation activities in soft sediments of the Laurentian Trough

In vivo observations in laboratory mesocosms and aquaria, accompanied with in situ photographic surveys, have shown that the burrowing shrimp Calocaris templemani has a significant impact on bottom sediment dynamics and geochemistry in the St. Lawrence Estuary. This burrowing shrimp establishes and maintains complex semi-permanent burrows made up of several interconnected, ‘U-shaped’ galleries with generally four or more openings to the sediment surface. In the Estuary, at 345 m depth, Calocaris average density was estimated at 3.4 individuals m^?2. Observed individual burrows reached a maximum volume of 0.54 L. C. templemani displaces this volume of mostly anoxic sediments from the subsurface layers (down to 15 cm) to the sediment surface, thereby obscuring some of the natural stratification patterns. With an estimated turnover rate of about 8 L m^?2 year^?1 of sediment, our calculations suggest that over a period of about 18.75 years, all the sediment to a depth of 15 cm will have been reworked by C. templemani alone.     

Photosynthetic and growth responses of Japanese sasabamo (Potamogeton wrightii Morong) under different photoperiods and nutrient conditions

Controlled laboratory experiments were conducted to examine how photosynthesis and growth occur in Potamogeton wrightii Morong under different photoperiods and nutrient conditions. The experiment was based on a 3×2 factorial design with three photoperiods (16, 12 and 8 h) of 200 μE · m^?2·s^?1 irradiance and two nutrient conditions, high (90 μmol N · L^?1·d^?1 and 9 μmol P · L^?1·d^?1) and low (30 μmol N L^?1·d^?1 and 3 μmol P · L^?1·d^?1). After 14, 28, 56 and 70 days of growth, plants were harvested to determine net photosynthesis rate and various growth parameters. Above- and below-ground biomass were investigated on days 56 and 70 only. Plants under low nutrient conditions had greater leaf area, more chlorophyll a, a higher rate of net photosynthesis and accumulated more above- and below-ground biomass than plants in the high nutrient condition. Plants with an 8 h photoperiod in the low nutrient condition had a significantly higher rate of net photosynthesis, whereas 8 h photoperiod plants in the high nutrient condition had a lower rate of net photosynthesis and their photosynthetic capacity collapsed on day 70. We conclude that P. wrightii has the photosynthetic plasticity to overcome the effects of a shorter photoperiod under a tolerable nutrient state.     

Spatial variations in the N2O emissions and denitrification potential of riparian buffer strips in a contaminated urban river

Spatial variations in the N₂O emissions and denitrification potential of riparian buffer strips (RBS) in a polluted river were examined. The river received large pollutant inputs from urban runoff and wastewater discharge, resulting in impaired water quality in the river and downstream reservoir. The potential for nitrogen removal by RBS was evaluated by measuring in situ N₂O emission fluxes in static closed chambers and sediment denitrification potentials with acetylene inhibition techniques. The results showed that N₂O emission fluxes decreased from the upstream (16.39 μg/(m²·h)) to downstream (0.30 μg/(m²·h)) sites and from the water body to upland sites. The trend in decreasing N₂O emission fluxes in the downstream direction was mainly associated with sediment/soil textures (clay loam→sandy soil) and sediment/soil water contents and was also related to the vegetation along the RBS and nutrients in the sediments/soils. The correlation coefficient was highest (r=0.769) between the N₂O emission flux and sediment/soil water content. Sediment/soil denitrification potentials under N-amended and ambient conditions were higher (highest 32.86 mg/(kg·h)) for the upstream sites, which were consistent with in situ N₂O flux rates.     

Diffusive boundary layers and photosynthesis of the epilithic algal community of coral reefs

The effects of mass transfer resistance due to the presence of a diffusive boundary layer on the photosynthesis of the epilithic algal community (EAC) of a coral reef were studied. Photosynthesis and respiration of the EAC of dead coral surfaces were investigated for samples from two locations: the Gulf of Aqaba, Eilat (Israel), and One Tree Reef on the Great Barrier Reef (Australia). Microsensors were used to measure O₂ and pH at the EAC surface and above. Oxygen profiles in the light and dark indicated a diffusive boundary layer (DBL) thickness of 180–590 μm under moderate flow (~0.08 m s^?1) and >2,000 μm under quasi-stagnant conditions. Under light saturation the oxygen concentration at the EAC surface rose within a few minutes to 200–550% air saturation levels under moderate flow and to 600–700% under quasi-stagnant conditions. High maximal rates of net photosynthesis of 8–25 mmol O₂ m^?2 h^?1 were calculated from measured O₂ concentration gradients, and dark respiration was 1.3–3.3 mmol O₂ m^?2 h^?1. From light–dark shifts, the maximal rates of gross photosynthesis at the EAC surface were calculated to be 16.5 nmol O₂ cm^?3 s^?1. Irradiance at the onset of saturation of photosynthesis, E _k, was <100 µmol photons m^?2 s^?1, indicating that the EAC is a shade-adapted community. The pH increased from 8.2 in the bulk seawater to 8.9 at the EAC surface, suggesting that very little carbon in the form of CO₂ occurs at the EAC surface. Thus the major source of dissolved inorganic carbon (DIC) must be in the form of HCO₃ ^?. Estimates of DIC fluxes across the DBL indicate that, throughout most of the daytime under in situ conditions, DIC is likely to be a major limiting factor for photosynthesis and therefore also for primary production and growth of the EAC.     

Characterisation and classification of hoarfrost samples collected in Poland (2003–2005) by discriminant analysis

Discharges of nutrients, urea, dissolved organic matter and heavy metals by a sewage underwater pipeline are analysed in comparison to environmental conditions in a shallow coastal zone. Variable thermo-haline stratifications of the water column and currents in upper (2.62–34.97 cm s^?1) and deeper (0.83–10.91 cm s^?1) layers drive vertical diffusion and lateral transport of wastewaters. Loads of reactive phosphorus (0.13 tons d^?1) and ammonium (1.62 tons d^?1) by the pipeline are not negligible compared to the major river loads in the gulf. High concentrations of urea (≤11.51 μmol N dm^?3) were found in the area of wastewater release. Ammonium uptake (6.14–534 nmol N dm^?3 h^?1) strongly exceeded nitrate uptake (0.19–138 nmol N dm^?3 h^?1), indicating that discharges of ammonium by the pipeline are actively assimilated by plankton community even at low levels of light. Distribution of Zn (≤27.7 ppb), Cu (≤25.6 ppb), Cd (≤0.80 ppb) and Pb (≤13.5 ppb) in the water column and the measurement of their complex-forming capacity in seawater did not indicate a persistent perturbation of the pelagic environment due to heavy metals.     

Assessment of heavy metals in a soil contaminated by oil spill: a case study in Nigeria

Surface and subsurface soil samples contaminated with crude oils were collected from an impacted site at Bodo City in the Niger Delta, Nigeria, after a field reconnaissance survey. An uncontaminated soil sample collected 100 m from the impacted site, but within the same geographical area, was used as a control. Trace elements such as, As, Cu, Cr, Cd, Fe, Pb, Ba, Ni, V, Hg and cation-exchange capacity constituents of the contaminated and uncontaminated soils were determined by atomic absorption spectroscopy. Trace element concentrations were: Cu, 0.5–13.4 mg kg^{? 1}; Cr, 0.2–0.8 mg kg^{? 1}; Fe, 6.2–8.7 mg kg^{? 1}; Ba 80.0–108.0 mg kg^{? 1}; Ni, 0.6–4.8 mg kg^{? 1}; and V, 4.0–9.4 mg kg^{? 1}; cation-exchange capacity ranged from 43.6 to 57.2 mg kg^{? 1} in surface and subsurface soils. Results showed that eigenvalues for the two first principal components represent up to 49% of the total variance. A positive correlation of the first principal component with Cu, Cr and cation-exchange capacity shows pollution from oil spillage, while a positive correlation of the second principal component with Cr, Fe, V, and dissolved oxygen (DO) shows both oil pollution and allochthonous inputs.     

Sediment load and timing of sedimentation affect spore establishment in Macrocystis pyrifera and Undaria pinnatifida

Although the frequency and magnitude of sedimentation often varies across coastal landscapes creating patches with different mean sediment loads, duration of sedimentation and rates of sediment resuspension, few studies have documented the emergent effects of spatio-temporal variability in sedimentation. Here, we conducted two laboratory experiments to evaluate such effects on the establishment of Macrocystis pyrifera and Undaria pinnatifida spores. In the first experiment, spore establishment was significantly affected by sediment load (the effective dose required for a 40 % reduction in establishment ranged between 16 and 60 mg sediment l^?1) and sediment regime (relative sedimentation occurring before spore settlement, ~3 times more sediment was required for 20 % reduction in spore establishment when sedimentation occurred after spore settlement). The second experiment demonstrated that the effects of sediment depended on sediment load (spore establishment was 2–4 times greater when sediment load was 200 mg l^?1 relative to 400 mg l^?1), variability in sedimentation (spore establishment was 1.36 times greater with variable than fixed sediment loads), repeated pulses of sedimentation (pulsed sedimentation decreased spore establishment by 59–91 % relative to a single sedimentation event) and timing of sedimentation relative to spore settlement (sedimentation before spore settlement decreased establishment by 51–95 % relative to sedimentation after spore settlement). These results have important implications for ecologists and resource managers attempting to predict the consequences of sedimentation, suggesting that it is not only important to consider sediment load, but also fine-scale temporal variability in sedimentation relative to key life-history events of the impacted organisms.     

Relationships between loading rates and nitrogen removal effectiveness in subsurface flow constructed wetlands

Nitrogen removal of wetlands under 40 different inflow loadings were studied in the field during 15 months. The removal efficiency of four different sets of beds, namely the reed bed, the Zizania caduciflor bed, the mixing planting bed, and the control bed were studied. The outflow loading and total nitrogen (TN) removal rate of these beds under different inflow loadings and pollution loadings were investigated. The inflow loadings of 4 subsurface flow systems (SFS) ranged from 400 to 8000 mg·(m²·d)^?1, while outflow loadings were less than 7000 mg·(m²·d)^?1. The results showed that the inflow and outflow loading of TN removal rate in SFS presented an obvious linear relationship. The optical inflow loading to run the system was between 2000 to 4000 mg·(m²·d)^?1. Average removal rate was between 1062 and 2007 mg·(m²·d)^?1. SFS with plant had a better removal rate than the control. TN removal rates of the reed and Zizania caduciflora bed were 63% and 27% higher than the control bed, respectively. The results regarding the TN absorption of plants indicated that the absorption amount was very limited, less than 5% of the total removal. It proved that plants clearly increase TN removal rates by improving the water flow, and increasing the biomass, as well as activities of microorganisms around the roots. The research provided a perspective for understanding the TN removal mechanism and design for SFS.     

The influence of solid matrices on arsenic toxicity to Corophium orientale

In marine ecosystems, benthic organisms are really important because they are the first step in the transfer of contaminants from environment to biota. To this end, this study focused on biological assays with the amphipod Corophium orientale exposed to two different molecules of arsenic: arsenate (As^V), the most abundant form in sediments, and dimethyl-arsinate (DMA), expected to be moderately toxic as an intermediate in the process of detoxification. The toxicity of arsenic compounds was measured after exposure to three different matrices: water, spiked natural sediment and inert spiked quartz sand. LC₅₀ values were calculated for each exposure, and the results confirmed the highest toxicity of As^V, in addition to underlining the importance of matrix of exposure. Water exposure was the matrix which presented the highest toxicity for inorganic arsenic (As^V LC₅₀=3.51 mg L^?1 vs DMA LC₅₀=54.65 mg L^?1), spiked natural sediment demonstrated its capability to chelate arsenate toxicity (As^V LC₅₀=34.27 mg kg^?1 vs. DMA LC₅₀=52.19 mg kg^?1) and spiked quartz sand presented intermediate values for As^V (LC₅₀=25.26 mg kg^?1), whereas for DMA a lower toxicity was registered (LC₅₀=872.35 mg kg^?1). This study can provide some useful data linked with chemical speciation of arsenic and exposure matrix, for improving the correct management of contaminated sediment.     

Respiration and lipid content of the Arctic copepod<Emphasis Type="Italic"> Calanus hyperboreus</Emphasis> overwintering 1 m above the seafloor at 2,300 m water depth in the Fram Strait

In August 2000 high concentrations of the dominant herbivorous copepod Calanus hyperboreus were detected in the Arctic Fram Strait, west of Spitsbergen, 1 m above the seafloor at 2,290 m water depth. Individuals from that layer were sampled by a hyper-benthic net attached to the frame of an epi-benthic sledge. For comparison, the vertical distribution of C. hyperboreus in the water column was studied simultaneously by a multiple opening/closing net haul from 2,250 m depth to the surface. Maximum abundance was found close to the surface with 6.6 and 10.0 ind. m^?3 at 0–50 m and 50–100 m depth, respectively. However, the major fraction of the population (>40%) occurred between 1,000 and 1,500 m depth. In the deepest layer (2,000–2,250 m) abundance measured 2.2 ind. m^?3 and was twice as high as between 100 and 1,000 m depth. In comparison to individuals from surface waters, copepods from the hyper-benthic layer were torpid and did not react to mechanical stimuli. Stage CV copepodids and females from the deep sample contained 4–10% less lipid and showed significantly reduced respiration rates of 0.24 and 0.26 ml O₂ h^?1 g^?1 dry mass (DM) as compared to surface samples (0.49 and 0.43 ml O₂ h^?1 g^?1 DM). All these observations indicate that the hyper-benthic part of the population had already started a dormant overwintering phase at great depth. Based on the lipid deposits and energy demands, the potential maximum duration of the non-feeding dormant phase was estimated at 76–110 days for females and at 98–137 days for CV copepodids, depending on what indispensable minimum lipid content was assumed. In any case, the estimated times could not meet the necessary requirements for a starvation period of >6 months until the next phytoplankton bloom in the following spring. The ecological implications of these results are discussed with respect to the life cycle and eco-physiological adaptations of C. hyperboreus to its high-Arctic habitat.     

Contaminated lead environments of man: reviewing the lead isotopic evidence in sediments,peat, and soils for the temporal and spatial patterns of atmospheric lead pollution in Sweden

Clair Patterson and colleagues demonstrated already four decades ago that the lead cycle was greatly altered on a global scale by humans. Moreover, this change occurred long before the implementation of monitoring programs designed to study lead and other trace metals. Patterson and colleagues also developed stable lead isotope analyses as a tool to differentiate between natural and pollution-derived lead. Since then, stable isotope analyses of sediment, peat, herbaria collections, soils, and forest plants have given us new insights into lead biogeochemical cycling in space and time. Three important conclusions from our studies of lead in the Swedish environment conducted over the past 15 years, which are well supported by extensive results from elsewhere in Europe and in North America, are: (1) lead deposition rates at sites removed from major point sources during the twentieth century were about 1,000 times higher than natural background deposition rates a few thousand years ago (~10 mg Pb m^?2 year^?1 vs. 0.01 mg Pb m^?2 year^?1), and even today (~1 mg Pb m^?2 year^?1) are still almost 100 times greater than natural rates. This increase from natural background to maximum fluxes is similar to estimated changes in body burdens of lead from ancient times to the twentieth century. (2) Stable lead isotopes (²⁰⁶Pb/²⁰⁷Pb ratios shown in this paper) are an effective tool to distinguish anthropogenic lead from the natural lead present in sediments, peat, and soils for both the majority of sites receiving diffuse inputs from long range and regional sources and for sites in close proximity to point sources. In sediments >3,500 years and in the parent soil material of the C-horizon, ²⁰⁶Pb/²⁰⁷Pb ratios are higher, 1.3 to >2.0, whereas pollution sources and surface soils and peat have lower ratios that have been in the range 1.14–1.18. (3) Using stable lead isotopes, we have estimated that in southern Sweden the cumulative anthropogenic burden of atmospherically deposited lead is ~2–5 g Pb m^?2 and ~1 g Pb m^?2 in the “pristine” north. Half of this cumulative total was deposited before industrialization. (4) In the vicinity of the Rönnskär smelter in northern Sweden, a major point source during the twentieth century, there is an isotopic pattern that deviates from the general trends elsewhere, reflecting the particular history of ore usage at Rönnskär, which further demonstrates the chronological record of lead loading recorded in peat and in soil mor horizons.     

Effect of waterborne boron and molybdenum on survival,growth and feed intake of Indian major carp,Cirrhinus mrigala (Hamilton)

The effect of either boron (B) or molybdenum (Mo) on survival, growth and feed intake of Indian major carp, Cirrhinus mrigala (Hamilton), advanced fry was studied in two separate experiments. Survival rates of C. mrigala fry (2.78±0.14 g) following 50 days’ exposure to B at 0.01 (control), 0.5, 1.0, 2.0, 4.0 and 8.0 mg·L ^?1 were 100% at all concentrations except 8.0 mg·L ^?1 where the survival rate 87.5±7.5%. We observed 100% survival of mrigala fry at all concentrations of Mo, 0.02 (control), 0.5, 1.0, 2.0, 4.0 and 8.0 mg·L ^?1. Both B and Mo at 0.5 mg·L ^?1 showed significantly (p<0.05) higher growth of the fish compared with control and other concentrations. B exposure at 1.0, 2.0 and 4.0 mg·L ^?1 had no significant effect on growth rate, whereas at 8.0 mg B·L ^?1 growth of the fish almost ceased. Mo exposure at 1.0, 2.0, 4.0 and 8.0 mg·L ^?1 caused no significant effect on growth rate of the fish compared to control. Both B and Mo at all concentrations had no significant effect on feed intake of the fish compared with control, except at the highest concentration of boron (8.0 mg·L ^?1).     

Stable isotope variation in the northern Gulf of Mexico constrains bottlenose dolphin (Tursiops truncatus) foraging ranges

Site-specific differences were found in consumer isotope values among ten sites examined in the northern Gulf of Mexico. Average δ¹³C values among sites ranged ?21.7 to ?15.7 ‰, δ¹⁵N ranged <3 ‰: from 9.8 to 11.5 ‰, and δ³⁴S ranged from 5.9 to 18.3 ‰. Isotope variation among these sites provided insight into the ranging habits of bottlenose dolphins (Tursiops truncatus) sampled in St. George Sound (29.8N, 84.6W), a nearshore seagrass habitat, during May of 2005. Isotope comparisons suggest that the majority of dolphins sampled (average ± one standard deviation: δ¹³C = ?17.5 ± 0.8, δ¹⁵N = 14.5 ± 0.9, and δ³⁴S = 10.6 ± 1.5) did not forage significantly on offshore species which are significantly ³⁴S-enriched, nor is it likely that they ranged either eastward or westward along the coast within the sampling region. Despite their capability for ranging, these dolphins occupied a restricted home range, during the spring before our sampling efforts. These results demonstrate significant fine-scale isotope variation among coastal habitats explained by differences in freshwater inputs, organic matter loading, and modes of primary production that may be used to constrain the foraging ranges of a highly mobile apex predator.     

Concentrations,input prediction and probabilistic biological risk assessment of polycyclic aromatic hydrocarbons (PAHs) along Gujarat coastline

A comprehensive investigation was conducted in order to assess the levels of PAHs, their input prediction and potential risks to bacterial abundance and human health along Gujarat coastline. A total of 40 sediment samples were collected at quarterly intervals within a year from two contaminated sites—Alang-Sosiya Shipbreaking Yard (ASSBRY) and Navlakhi Port (NAV), situated at Gulf of Khambhat and Gulf of Kutch, respectively. The concentration of ΣPAHs ranged from 408.00 to 54240.45 ng g^?1 dw, indicating heavy pollution of PAHs at both the contaminated sites. Furthermore, isomeric ratios and principal component analysis have revealed that inputs of PAHs at both contaminated sites were mixed-pyrogenic and petrogenic. Pearson co-relation test and regression analysis have disclosed Nap, Acel and Phe as major predictors for bacterial abundance at both contaminated sites. Significantly, cancer risk assessment of the PAHs has been exercised based on incremental lifetime cancer risks. Overall, index of cancer risk of PAHs for ASSBRY and NAV ranged from 4.11 × 10^?6–2.11 × 10^?5 and 9.08 × 10^?6–4.50 × 10^?3 indicating higher cancer risk at NAV compared to ASSBRY. The present findings provide baseline information that may help in developing advanced bioremediation and bioleaching strategies to minimize biological risk.