Moderate stoichiometric homeostasis in the sea urchin Lytechinus variegatus: effects of diet and growth on C:N:P ratios

The influence of dietary elemental contents on consumer stoichiometry was investigated in selected and combined soft tissues (as a proxy of the whole individual) of the omnivorous sea urchin, Lytechinus variegatus. We raised urchins for 4 months in controlled seawater tanks using three different diets with different nutritional contents (from lower to higher: seagrass, red macroalgae, and a formulated diet). Individuals fed the different diets varied an average of 19.7, 19.4, and 38 % in C:N, C:P, and N:P ratios, respectively, with stronger temporal variability for C:P and N:P ratios across tissues and whole individuals. This resulted in homeostasis parameters (1/H) of ?0.45, 0.09, and 0.38, respectively, for C:N, C:P, and N:P, indicative of homeostatic to weakly homeostatic organisms, at least for C:P and N:P ratios. Individuals fed the nutrient-rich formulated diet had higher growth rates (14 ± 0.83 g WW month^?1) than those fed macroalgae or seagrass (9.3 ± 0.57 and 3.4 ± 0.33 g WW month^?1, respectively). However, rapid body increments in more nutritional diets caused both a decrease in the %N and an increase in the %P of soft tissues, which resulted in significant but opposite effects of diet stoichiometry and growth in sea urchin C:N (R = ?0.74 and R = 0.93, for diet and growth effects, respectively) and N:P ratios (R = 0.60 and R = ?0.63, also, respectively, for diet and growth effects). Among potential compensatory mechanisms helping to preserve certain levels of homeostasis, ingestion rates (g WW diet per g WW of urchin) were higher for seagrass and macroalgae diets than for the nutrient-rich formulated diet. In contrast, absorption and growth efficiencies displayed significant negative associations with nutrient contents in diets and did not exhibit nutritional compensation. Overall, our results suggest that resource stoichiometry strongly determines the growth rate of individuals (R = 0.88, P < 0.01), and moderate variability in C:N:P ratios of sea urchins possibly arise from differences in the allocation of proteins and RNA to body components, similarly to what has been proposed by the growth rate hypothesis.     

Estimation and validation of biomass of a mountainous agroecosystem by means of sampling,spectral data and QuickBird satellite image

Biomass estimation in agroecosystems (AESs) is important to understand their role in carbon exchange for a sustainable environment. We used field spectra and sampled biomass of an AES including cultivated and abandoned croplands to develop a simple biomass estimation model. The digital number (DN) of a QuickBird (QB) satellite image was converted to a reflectance factor using the dark object subtraction method and the spectral reflectance of asphalt. The relationship between the reflectance factor of field-based spectra and the QB image obtained in early July 2007 was insignificant in the blue (R ² = 0.15) and green (R ² = 0.18) bands but was significant (p < 0.05) in the red (R ² = 0.57) and near-infrared (NIR, R ² = 0.45) bands in the AES. Better correlations were obtained between field-based and QB-based vegetation indices (VIs). The best correlations were obtained with the normalized difference vegetation index (NDVI) (R ² = 0.97, p < 0.001) and the ratio vegetation index (RVI) (R ² = 0.99, p < 0.001). Biomass was significantly correlated with both field-based NDVI and RVI (R ² = 0.79 and 0.72, respectively, p < 0.001). Although RVI saturated at higher biomass densities (>600 g m^?2), NDVI showed a linear relationship. Other field-based VIs showed poorer correlations with biomass. The model was evaluated by incorporating it into high-resolution QB images to obtain the observed biomass. The relationship between field-estimated and QB-observed biomass appeared to be a one-to-one linear relationship (R ² = 0.79). Thus, models using field spectra and sampled biomass can be applied to QB images for remote estimation of biomass in an AES.     

Evaluation of rare earth elements in groundwater of Lagos and Ogun States,Southwest Nigeria

Rare earth elements in our environment are becoming important because of their utilization in permanent magnets, lamp phosphors, superconductors, rechargeable batteries, catalyst, ceramics and other applications. This study was conducted to evaluate the level of rare earth elements (REE) and the variability of their anomalous behavior in groundwater samples collected from Lagos and Ogun States, Southwest, Nigeria. REE concentrations were determined in 170 groundwater samples using inductively coupled plasma-mass spectrometry, while the physicochemical parameters were determined using standard methods. Lagos State groundwater is enriched with REE [sum REEs range (mean ± SD)]; [0.365–488 (69.5 ± 117)] µg L^?1 than Ogun State groundwater [sum REEs range (mean ± SD)]; [1.14–232 (22.6 ± 41.1)] µg L^?1. Boreholes are more enriched with REEs than wells. Significant (P < 0.05) positive correlation (R = Pearson) was recorded in Lagos State groundwater between sum REEs and Fe (R = 0.55). However, there were no significant correlations between sum REEs, pH (R = 0.073) and HCO₃ ^2? (R = 0.157) in Ogun State groundwater. Chondrite-normalized plot shows that Lagos groundwater exhibits positive Ce anomaly, while Ogun State groundwater does not. The source of REE in Lagos State may be from the ocean and leaching from wastes dumpsites, while the source in Ogun State groundwater may be from the rocks.     

Forest cover dynamics in the Selva Maya of Central and Southern Quintana Roo,Mexico: deforestation or degradation?

ABSTRACT

Forest cover dynamics (1993-2018) was assessed in two regions on the Yucatan Peninsula: Zona Maya (ZM), 67% indigenous with shifting cultivation and community forestry; and Bacalar–Rio Hondo (BRH), mainly commercial agriculture and pastureland. Degradation (12,915 ha y^?1) exceeded deforestation (5882 ha y^?1) and was worse in BRH. In BRH there was a net forest loss (?1.6% y^?1) associated with pastureland and commercial agriculture. In ZM, mature forest recovery (1.4% y^?1) and dynamic forest cover (continuous loss and gain) were associated with shifting cultivation. Changes were more intense during 2011–2018 and gains of mature forest in ZM and deforested areas in BRH targeted secondary vegetation. Fragments of mature and secondary vegetation decreased, and connectivity improved in ZM, but opposite trends occurred in BRH. Reporting and monitoring deforestation using Global Forest Watch data is inadequate since 62% of forest cover loss represent degrading or recovering forest cover.     

Preconcentration of samarium with modified yeast cells for its determination by atomic emission spectroscopy

A chelating-modified biosorbent is produced by coupling of a dye, procion red, to yeast cells. The resulting modified cells have been characterized by Fourier transform infrared, elemental analysis and thermogravimetric analysis and studied for preconcentration and determination of trace Sm(III). The optimum pH value for sorption of the samarium ions is 6.2. The sorption capacity of functionalized modified yeast cells is 7.2 mg g^?1. Recovery was 99% when Sm(III) was eluted with an aqueous solution of 0.1 mol L^?1 ethylenediaminetetraacetic acid. Scatchard analysis suggested that binding sites were homogeneous. The equilibrium data were analyzed using Langmuir, Freundlich, Temkin, and Redlich–Peterson isotherm models, and the respective constants were determined as 1.0 (L mg^?1), 2.9 [(mg g^?1) (L mg^?1)^1/n], 2.4 × 10⁸ (L g^?1), and 30 (dm³ g^?1) at 20 °C. The method was applied for an Sm(III)-containing sample of ceramic industry effluent.     

Seasonal variations in physicochemical characteristics and cyanobacterial diversity of a lake in Northern India

Physicochemical analyses and cyanobacterial diversity of Ramgarh Lake water were performed at five sampling sites during winter, summer, and monsoon seasons. Higher load of solids, carbon, and nutrients were persistent throughout the analysis that indicates the conversion of lake from oligotrophic to eutrophic nature. High nutrients load enhanced cyanobacterial biomass, while low nutrients load produced relatively less biomass. The physicochemical parameters of water samples revealed minimum 2.9 mg L^?1 dissolved oxygen (DO) at site-1 during summer, while maximum (5.6 mg L^?1) at site-4 in monsoon season. Maximum biochemical oxygen demand (BOD) (40 mg L^?1) and chemical oxygen demand (COD) (126 mg L^?1) were recorded at site-1 during summer, whereas minimum BOD (18 mg L^?1) and COD (52 mg L^?1) were evident at site-3 in monsoon season. Minimum concentration of nitrate (0.72 mg L^?1) was recorded at site-3 in summer, whereas maximum 2.7 mg L^?1 was present at site-5 in winter season. The phosphate concentration was maximum (0.52 mg L^?1) at site-5 in summer, and minimum (0.18 mg L^?1) was observed at site-4 in monsoon season. Cyanobacterial diversity was higher during all the seasons, and dominated by the species of Microcystis at all the five sampling sites.     

Adsorptive removal of rhodamine B from textile wastewater using water chestnut (Trapa natans L.) peel: adsorption dynamics and kinetic studies

Water chestnut peel, an agricultural bio-waste, was used as a biosorbent for removal of rhodamine B (RhB), basic textile dye, from an aqueous solution. The effects of various experimental parameters were studied. The equilibrium data correlated well with a Freundlich isotherm (R² = 0.98–0.99) followed by a Halsey isotherm model (R² = 0.98–0.99) which indicated heterogeneity of the adsorbent surface and multilayer adsorption of RhB dye onto the water chestnut peel waste (WCPW). High correlation coefficients (R² = 0.99) together with close agreement between experimental q_e (0.4–1.7 mg g^?1) and calculated q_e (0.4–2.5 mg g^?1) suggested that the adsorption process followed pseudo-second-order kinetics, with k₂ values in the range of 52–3.4 × 10^?1 g mg^?1 min^?1 at different concentrations. The overall mechanism of adsorption was controlled by both liquid-film and intra-particle diffusions. The negative values of change in Gibb's free energy (?ΔG⁰ = 19.2–29.2 kJ mol^?1) and positive values of change in enthalpy (ΔH⁰ = 30.9–117.6 kJ mol^?1) revealed the process to be spontaneous and endothermic. WCPW was found to be an effective adsorbent for removal of RhB, a cationic dye, from an aqueous solution.     

Impacts of vineyard area dynamics on soil erosion in a Mediterranean catchment (1950-2011)

The Mediterranean basin has undergone widespread land cover change. Urbanization of coastal areas, land abandonment of steeper slopes, and agricultural intensification in alluvial plains are recurrent themes. The objective of this study was to examine how vineyard land cover changes have affected agricultural soil erosion in a 50 year period (1950–2011). The study area covers a 235 km² catchment located near the Gulf of St Tropez. Aerial photographs were used to map land cover in 1950, 1982, 2003 and 2011, and the RUSLE soil erosion model was run to estimate soil erosion.

Between 1950 and 2011, vineyard went from about 2,426 ha to 1,561 ha. Mean soil erosion increased as vineyard slopes became steeper (11.8 T ha^?1, 13.2 T ha^?1, 14.4 T ha^?1 and 13.5 T ha^?1 for 1950, 1982, 2003 and 2011). Total erosion decreased after 1982: 28,621 T y^?1 in 1950, 29,030 T y^?1 in 1982, 22,848 T y^?1 in 2003, and 21,074 T y^?1 in 2011. Total soil loss in 2011 is about 75% of values in 1950–1982, so impacts on water pollution and channel dredging have evolved positively over time.     

Environmental modeling of uranium interstitial compositions of non-stoichiometric oxides: experimental and theoretical analysis

Study of uranium interstitial compositions of non-stoichiometric oxides UO_2+x (x ∈ 0.1–0.02) in gas and condense phases has been presented, using various soft-ionization mass spectrometric methods such as ESI-, APCI-, and MALDI-MS at a wide dynamic temperature gradient (∈ 25–300 °C). Linearly polarized vibrational spectroscopy has been utilized in order to assign unambiguously, the vibrational frequencies of uranium non-stoichiometric oxides. Experimental design has involved xUO_2.66·yUO_2.33, xUO_2.66·yUO_2.33/SiO₂, xUO_2.66·yUO_2.33/SiO₂ (NaOH) and SiO₂/x′NaOH·y′UO₂(NO₃)₂·6H₂O, multicomponent systems (x = 1, y ∈ 0.1–1.0 and x′ = 1, y′ ∈ 0.1–0.6) as well as phase transitions UO₂(NO₃)₂·6H₂O → {U₄O₉(UO_2.25)} → U₃O₇(UO_2.33) → U₃O₈(UO_2.66) → {UO₃}, thus ensuring a maximal representativeness to real environmental conditions, where diverse chemical, geochemical and biochemical reactions, including complexation and sorption onto minerals have occurred. Experimental factors such as UV-irradiation, pH, temperature, concentration levels, solvent types and ion strength have been taken into consideration, too. As far as uranium speciation represents a challenging analytical task in terms of chemical identification diverse coordination species, mechanistic aspects relating incorporation of oxygen into UO _2+x form the shown full methods validation significantly impacts the field of environmental radioanalytical chemistry. UO₂ is the most commonly used fuel in nuclear reactors around the globe; however, a large non-stoichiometric range ∈ UO_1.65–UO_2.25 has occurred due to radiolysis of water on UO₂ surface yielding to H₂O₂, OH^·, and more. Each of those compositions has different oxygen diffusion. And in this respect enormous effort has been concentrated to study the potential impact of hazardous radionuclide on the environment, encompassing from the reprocessing to the disposal stages of the fuel waste, including the waste itself, the processes in the waste containers, the clay around the containers, and geological processes. In a broader sense, thereby, this study contributes to field of environmental analysis highlighting the great ability of various soft-ionization MS methods, particularly, MALDI-MS one, for direct assay of complex multicomponent heterogeneous mixtures at fmol–attomol concentration ranges, along with it the great instrumental features allowing, not only meaningful quantitative, but also structural information of the analytes, thus making the method indispensable for environmental speciation of radionuclides, generally.     

Effects of ethyl 2-methyl acetoacetate (EMA) on the growth of Phaeodactylum tricornutum and Skeletonema costatum

We investigated the effects of ethyl 2-methyl acetoacetate (EMA) on growth of the marine diatom algae Phaeodactylum tricornutum (P. tricornutum) and Skeletonema costatum (S. costatum). Growth of P. tricornutum was significantly inhibited by the minimum concentration (3.5 mmol·L ^?1) of EMA at lower initial algal densities (IADs) (3.6×10⁴ and 3.3×10⁵ cells·mL ^?1). However, at the highest IAD, significant growth inhibition was found at above 7 mmol·L ^?1 of EMA exposure. In S. costatum, EMA concentrations of 10.5 mmol·L ^?1 or more significantly inhibited growth at lower IAD (3×10⁴ and 1.8×10⁵ cells·mL ^?1); at the highest IAD, only EMA concentrations above 14 mmol·L ^?1 obviously inhibited the growth of S. costatum. Changes in specific growth rates and pigment were consistent with algal growth, but only at higher EMA concentrations or lower IAD values was the ratio of chlorophyll a (Chla) to carotenoid significantly lower than the control. Medium effective concentration (EC ₅₀) values were in the order 4.07, 8.03 and 12.27 mmol·L ^?1 for P. tricornutum and 7.48, 11.92 and 17.22 mmol·L ^?1 for S. costatum. All these results show that the effect of EMA on the growth of algae was species specific and mainly depended on IAD, which might be an important factor to influence algal growth.     

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.     

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.     

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.     

The effects of temperature,body size and growth rate on energy losses due to metabolism in early life stages of haddock (<Emphasis Type="Italic">Melanogrammus aeglefinus</Emphasis>)

Rates of routine respiration (R _R, μl O₂ fish⁻¹ h⁻¹) and total ammonia nitrogen excretion (E _R, μg NH₄–N + NH₃–N fish⁻¹ h⁻¹) were measured on larval and juvenile haddock (Melanogrammus aeglefinus) to ascertain how energy losses due to metabolism were influenced by temperature (T), dry body mass (M _D, mg) and specific growth rate (SGR, % per day). R _R and E _R increased with M _D according to y = a  · M _D ^b with b-values of 0.96, 0.98, 1.14, and 0.89, 0.78, 0.74, respectively, at 10, 7, and 4°C, respectively. Multiple regressions explained 98% of the variability in the combined effects of M _D and T on R _R and E _R in larval haddock: R _R = 0.97 · M _D ^0.98  · e^0.092 · T ; E _R = 0.06 · M _D ^0.79  · e^0.092 · T . In young juvenile (24–30 mm standard length) haddock, R _R tended to decline (P = 0.06) and E _R significantly declined (P = 0.02) with increasing SGR. O:N ratios significantly increased with increasing SGR suggesting that N was spared in relatively fast-growing individuals. Our results for young larval and juvenile haddock suggest: (1) nearly isometric scaling of R _R with increasing body size, (2) allometric scaling of E _R with increasing body size, (3) Q ₁₀ values of 2.5 for both R _R and E _R, (4) metabolic differences in substrate utilization between relatively fast- and slow-growing individuals, and (5) that rates of routine energy loss and growth were not positively related. The measurements in this study will provide robust parameter estimates for individual-based models that are currently being utilized to investigate how variability in climatic forcing influences the vital rates of early life stages of haddock. Our results also stress that inter-individual differences in rates of energy loss should not be overlooked as a factor influencing growth variability among individuals.     

Determination of persistent organic pollutants in sediment and fish of the western coast of Alexandria,Egypt

Persistent organic pollutants (POPs) were recorded in sediment and fish samples collected from the western coast of Alexandria. Total hydrocarbons (aliphatic+PAHs ) in sediment ranged from 683.8 to 34670.1 ng g ^?1 with an average of 9286.9 ng g ^?1. The sum of C16–C34 of aliphatic fractions was<4000?ng g;^?1, indicating the presence of a fresh petroleum source. For all sediments, the anthracene/phenanthrene ratio was>0.1, suggesting the dominance of a pyrolytic source. Total aliphatics in different fish species ranged from 253 to 11?132 ng g;^?1, while total PAHs ranged from 3862 to 35?746 ng g;^?1 wet weight. Benzo[a]pyrene was the most dominant PAH fraction ranged from 1902.7 to 32 905.5 with an average of 9464.5?ng g;^?1 wet weight in all fish species. Concentrations of polychlorinated biphenyls (PCBs) ranged from 0.79 to 64.9?ng g;^?1 with an average 12.14?ng g;^?1 wet weight. The concentrations of organochlorines in fish species (Euthynnus alleferatus, Scomberomorus commerson, Sphyraena Sphyraena, Diplodus vulgaris, and Alepes djedaba) decreased following the order: PCBs>DDTs>HCHs>total cyclodienes. Concentrations of DDTs in fish tissues ranged from 4.89 to 36.37 ng g^?1 with an average of 16.4?ng g;^?1 wet weight. The concentrations of total HCHs ranged from 0.3 to 65.7?ng g;^?1 with an average of 16.35?ng g;^?1. The present study indicates: (1) fresh petroleum input where Pr/Ph>1; (2) PAHs in sediment<4000 ng g ^?1; (3) BaP concentration exceeded the permissible levels in Alepes djedaba species; (4) DDTs in sediment were below the effective range low level; (5) PCBs>effective range low and相似文献   

Insulative capacity of the integument of the dugong (Dugong dugon): thermal conductivity,conductance and resistance measured by in vitro heat flux

Extant sirenians are restricted to warm waters, presumably due to their low metabolism and poor thermoregulatory capacity, including thin blubber. When subjected to winter waters, Florida manatees (Trichechus manatus latirostris) migrate to warm areas, but dugongs (Dugong dugon) do not and instead live year-round in winter waters as cool as 15–18 °C. Dugongs appear to be more active than manatees and may have higher metabolic rates, but little is known about thermal energetics or the insulative properties of their integument. This study investigated the physical and thermal properties of whole samples of dugong integument, i.e. epidermis, dermis and hypodermis (blubber) sampled from fresh dugong carcasses collected from 2004 to 2012 in Moreton Bay (27.21°S, 153.25°E). Physico-chemical properties (thickness, density and lipid content) of each component tissue layer were measured. Thermal conductance (C) and conductivity (k) were measured for each tissue layer through in vitro temperature flux experiments within an insulated chamber. C and k were higher for dermis (25.7 ± 1.2 W m^?2 K^?1, 0.43 ± 0.02 W m^?1 K^?1, respectively, n = 21) than blubber (24.3 ± 2.4 W m^?2 K^?1, 0.31 ± 0.01 W m^?1 K^?1, n = 21), suggesting that blubber, with higher density and lipid content, affords better insulation. However, because the dermis contributes 65 % of integumentary thickness, both layers contribute significantly to insulation. The integument of dugongs is a poorer insulator compared to many cold-water marine mammals, but the greater thickness of its dermal layer means that despite its relatively thin blubber, its integumentary insulation is similar to warm-water dolphins of similar body size.     

Biological effects of water soluble fraction of crude oil on the Arctic sea ice amphipod Gammarus wilkitzkii

With increasing petroleum related activity in the Barents Sea and the subsequent risk of accidents, there is a demand for knowledge about the effect of oil pollution in Arctic ecosystems. In the present study, the sea ice amphipod Gammarus wilkitzkii was exposed to a water soluble fraction (WSF) of oil in two experiments, using a rock column system. First, three groups of adult females were exposed for 36 days for control (n=9), low dose (n=10) (initial and final oil concentration: 14, 115 and 120 μ g/l) and high dose (n=10) (initial and final oil concentration: 78, 764 and 395 μ g/l). Total oxyradical scavenging capacity (TOSC), malondialdehyde (MDA), catalase activity (CAT), respiration rate and mortality were measured. In the second experiment, moulting rate was measured in immature individuals of two groups, control (n=10) and exposed (n = 20), over 113 days. No mortality was observed in either of the experiments. There was a dose-related significant increase in respiration rate (40.69 (±22.82), 55.63 (±20.98), 94.57 (±22.80)) mg O₂ h^?1g ww^?1 in control, low dose and high dose, respectively. A higher MDA level was detected in the low dose group (25.04 (±6.00) nmol g^?1 of tissue) compared to both control (20.44 (±2.62) nmol g^?1 of tissue) and high dose groups (20.93 (±4.79) nmol g^?1 of tissue). Likewise, the low dose group had the highest value of TOSC towards hydroxyl (727.74 (±475.58), 1157.58 (±278.62), 1067.30 (±369.22) TOSC unit value mg^?1 of protein for control, low and high dose, respectively). Although no difference in the catalase activity between control and exposed groups was detected, higher activity was measured at 0 °C (average: 248 μ mol^?1 min^?1 mg^?1 of protein) than at the standard temperature for catalase measurement of 25 °C (average: 140 μ mol^?1 min^?1 mg^?1 of protein), indicating a need to optimise the standard operational procedure when working with Arctic organisms. No effect of WSF exposure on moulting rate was detected. In conclusion, little mortality was observed during the experiments, indicating some degree of tolerance levels. However, the biomarker results indicated sub-lethal effects in G. wilkitzkii after exposure to WSF.     

Biodegradation of carbofuran in sequencing batch reactor augmented with immobilised Burkholderia cepacia PCL3 on corncob

The performance of sequencing batch reactors (SBRs) augmented with immobilised Burkholderia cepacia PCL3 on corncob for biodegradation of carbofuran in basal salt medium (BSM) was studied. A 2.0-L SBR with a working volume of 1.5 L was operated for a total cycle of 48 h, consisting of 1.0 h fill phase, 46 h react phase and 1.0 h decant phase. The initial pH of the feed medium was 7.0. Air was fed into the reactor at a controlled flow rate of 600 mL·min ^?1. The effect of hydraulic retention time (HRT) (14 to 6 days) on carbofuran-degradation efficiency was investigated at a carbofuran concentration in the feed medium of 20 mg·L ^?1. The shortest HRT resulting in complete degradation of carbofuran was 8 days. At 75% of the optimum HRT (6 days), the effects of biostimulation using organic amendments, i.e. molasses, cassava pulp, rice bran and spent yeast, and the effect of carbofuran concentration in the feed medium (20–80 mg·L ^?1) were investigated. The optimum conditions for SBRs were an initial carbofuran concentration of 40 mg·L ^?1 and 0.1 g·L ^?1 of rice bran as a biostimulated amendment. Complete degradation of carbofuran with a first-order kinetic constant (k ₁) of 0.044 h^?1 was achieved under these optimum conditions.     

Photoelectrochemical treatment of ammonium using seawater as a natural supporting electrolyte

In the present study, a photoelectrochemical process containing seawater as a natural low-cost supporting electrolyte was used to remove ammonium from wastewater in a continuous flow mode. Based on central composite design (CCD), response surface methodology (RSM) was employed to evaluate the performance of the process in ammonia removal. The effect of four main independent parameters, including initial ammonium concentration, hydraulic retention time (HRT), current intensity and initial pH on the removal of ammonia was evaluated by the model. The optimal initial ammonium concentration, HRT, current intensity and initial pH were 917 mg NH ₄? N;·L ^?1, 108 min, 1.8 A and 8.4, respectively. The high coefficients (R ²=0.97 and adjusted R ²=0.94) obtained by the analysis of variance (ANOVA) demonstrated close correlation between predicted and experimental values. Also, treating the reject water from the sludge dewatering unit as an ammonium-rich wastewater showed the effectiveness of the process for treating real wastewaters (86% ammonium removal). The results revealed that the present process can be an efficient method for ammonium removal from polluted effluents in coastal areas based on the availability of seawater as a cost-efficient supporting electrolyte.     

In vitro genotoxicity of extracellular extract from Nostoc piscinale

The extracellular extract obtained from 3 weeks incubation of the soil isolate cyanobacterium strain Nostoc piscinale GT-319 in BG-11 broth medium showed cytotoxic activity against Chinese Hamster Ovary (CHO) cells. Based on comet assay, a concentration of 333 µg mL^?1 (IC₅₀) produced DNA breakages in CHO cells. The concentration of 481 mg kg^?1 (LD₅₀) produced acute toxicity in mice at 48 h.