The objective of this study was to explore the relationships between the distribution of some meroplanktonic species and water temperature. Meroplankton larvae abundance of bivalves, and barnacles and water temperature fluctuations were studied from February 2011 to January 2012 at five stations in Ghar El Melh lagoon (GML) Mediterranean Sea, northern Tunisia). According to redundancy analysis (RDA), a significant difference was found in the distribution of larvae among the seasons (F = 10.28, p < 0.001); summer and autumn appear to be the period of bivalve larvae development, whereas the arrival of barnacle larvae coincided with winter and spring. The generalized additive models (GAMs) show strong correlation of bivalve larvae with high temperature (F = 23.2; p < 0.001) and the affinity of barnacle larvae to low temperature values (F = 8.41; p = 0.004). This environmental parameter accounted for 26 % of the deviance in variability in larvae abundance. The development process of many generations of larvae may therefore have been predetermined by temperature.

Cd²⁺-induced oxidative stress and its effects on the expression of stress biomarkers and on macromolecule damage in the skin and blood of common carp were studied. Both tissues play important roles in the defence mechanisms against external hazards, serving as an anatomical barrier and as connecting tissue between the organs. In the skin, the production of peroxynitrite anion and hydrogen peroxide was almost doubled after exposure to 10 mg/L Cd²⁺. The accumulation of these oxidant molecules suggests an intensive production of superoxide anion and nitrogen monoxide and the development of oxidative and/or nitrosative stress. Although the metallothioneins and the components of the glutathione redox system were activated in the skin, the accumulation of reactive intermediates led to the enhanced damage of lipid molecules after 24 h of metal exposure. In the blood, the basal levels of metallothionein messenger RNAs (mRNAs) were 2–2.5-fold of that measured in the skin. This high level of metallothionein expression could be the reason that the blood was less affected by an acute Cd²⁺challenge and the metallothionein and glutathione systems were not activated.

Nonpoint source (NPS) pollution is considered as the main reason for water quality deterioration; thus, to quantify the NPS loads reliably is the key to implement watershed management practices. In this study, water quality and NPS loads from a watershed with limited data availability were studied in a mountainous area in China. Instantaneous water discharge was measured through the velocity-area method, and samples were taken for water quality analysis in both flood and nonflood days in 2010. The streamflow simulated by Hydrological Simulation Program-Fortran (HSPF) from 1995 to 2013 and a regression model were used to estimate total annual loads of various water quality parameters. The concentrations of total phosphorus (TP) and total nitrogen (TN) were much higher during the flood seasons, but the concentrations of ammonia nitrogen (NH₃-N) and nitrate nitrogen (NO₃-N) were lower during the flood seasons. Nevertheless, only TP concentration was positively correlated with the flow rate. The fluctuation of annual load from this watershed was significant. Statistical results indicated the significant contribution of pollutant fluxes during flood seasons to annual fluxes. The loads of TP, TN, NH₃-N, and NO₃-N in the flood seasons were accounted for 58–85, 60–82, 63–88, 64–81 % of the total annual loads, respectively. This study presented a new method for estimation of the water and NPS loads in the watershed with limited data availability, which simplified data collection to watershed model and overcame the scale problem of field experiment method.

The role of chemical interactions in shaping microbial communities has raised increasing interest over the last decade. Many benthic microorganisms are known to develop chemical strategies to overcome competitors, but the real importance of chemical interactions within freshwater biofilm remains unknown. This study focused on the biological and chemical mechanisms of an interaction involving two benthic microorganisms, an allelopathic filamentous green alga, Uronema confervicolum, and a common diatom, Fistulifera saprophila. Our results showed that functions critical for benthic phototrophic microorganisms were inhibited by U. confervicolum extracts. Growth, cell motility, adhesion, and photosynthetic activity were impaired at extract concentrations ranging between 5 and 20 μg ml⁻¹. The adhesion inhibition was mediated by intracellular nitric oxide (NO) induction. A bioassay-guided fractionation of the extract with HPLC helped to identify two C18 fatty acids present in the growth-inhibiting fractions: linoleic (LA) and α-linolenic (LNA) acids. These compounds represented 77 % of the total free fatty acids of U. confervicolum and were present in the culture medium (1.45 μg l⁻¹ in total). Both could inhibit the diatom growth at concentrations higher than 0.25 μg ml⁻¹, but had no effect on cell adhesion. The discrepancy between the effective concentrations of fatty acids and the concentration found in culture medium may be explained by the presence of high-concentration microenvironments. The compounds involved in adhesion inhibition remain to be identified. Though further experiments with complex biofilms are needed, our results suggest that U. confervicolum may participate to the control of biofilm composition by inhibiting diatom adhesion.

Persistence of delltamethrin, endosulfan, and triazophos in egg plant and tomato was studied following application of two ready mix formulations of insecticides viz. deltametrhin and endosulfan (Cobra 5000; 0.75 % deltamethrin + 29.5 % endosulfan) and deltamethrin and triazophos (Annaconda Plus; 1 % deltamethrin + 35 % triazophos) at recommended (1.0 L/ha and double dose 2.0 L/ha). The residues of deltamethrin persisted till 7 and 5 days in tomato and egg plant fruits, respectively, in the ready mix formulation of Cobra 5000 whereas endosulfan persisted till 15 and 10 days in tomato and egg plant fruits, respectively. Dissipation of the insecticides followed first-order kinetics with half-life values of deltamethrin and endosulfan ranged from 2.6 to 4.7 and 1.4 to 1.7 days, respectively, for both the vegetables. In case of combination mix of deltamethrin and triazophos (Annaconda Plus), deltamethrin persisted beyond 5 days in both tomato and egg plant fruits, while triazophos persisted till 10 days in both the vegetables. Residues of deltamethrin and triazophos dissipated with half-life of 2.6–4.2 and 1.7–4.1 days, respectively, on tomato and egg plant fruits. Based on the Codex MRL limits, a safe waiting period of 5 and 3 days is suggested for tomato and egg plant, respectively, for the ready mix formulation of deltamethrin and endosulfan (Cobra 5000), and 5-day waiting period is suggested for tomato and egg plant for the combination mix of deltamethrin and triazophos.

Spatial and temporal distributions of concentrations of polycyclic aromatic hydrocarbons (PAHs) in surface sediments and dated sediment core from Taihu Lake in eastern China were determined. The sum of concentrations of PAHs (sum of total 16 USEPA priority PAH (∑PAHs)) of the entire Taihu Lake ranged from 2.9 × 10²to 8.4 × 10² ng/g dry mass (dm). Concentrations of ∑PAHs in surface sediments near more urbanized regions of the lake shore were greater than those in areas more remote from the urban centers. Temporal trends in concentrations of ∑PAHs ranged from 5.1 × 10²to 1.5 × 10³ ng/g dm, increasing from deeper layers to surface sediments with some fluctuations, especially in the past three decades after the inception of China’s Reform and Opening Up Policy, in which China’s economy and urbanization underwent rapid development. Forensic analysis of surface sediments indicates that PAHs originated primarily from combustion of grass/wood/coal except for the special function water area, which was most likely influenced by petroleum products of traveling vessels. Vertical profiles of relative concentrations of PAHs suggested that the contribution of lesser-molecular-weight PAHs was gradually decreasing, while due to the heavier consumption of petroleum products, the proportion of greater-molecular-weight PAHs was increasing. When assessed by use of the rather conservative, apparent effect threshold method, concentrations of ∑PAHs in sediments from most locations in Taihu Lake are predicted to pose little risk of harm to benthic invertebrates.

Metallic contamination is a widespread phenomena, particularly in areas impacted by human activities, and has become a relevant environmental concern. However, the toxicity of metals on fish requires full characterization in terms of short- and long-term effects. Thus, the purpose of this study was to determine the acute and chronic oxidative stress response in liver and gills of Gambusia holbrooki exposed to copper and cadmium. To assess the effects of these two metals, we adopted a strategy of analyzing the pollution effects caused by salts of the two metallic elements, and we quantified the oxidative stress biomarkers catalase, glutathione reductase, glutathione-S-transferases, and lipid peroxidation after exposure (4 and 28 days) to ecologically relevant concentrations, thus simulating actual conditions of exposure in the wild. Our results showed that copper elicited strong effects in all tested biomarkers for both acute and chronic challenges. Cadmium caused a similar response and was shown to cause significant changes particularly in catalase and glutathione-S-transferases activities. These findings evidence that ecologically relevant concentrations of common anthropogenic contaminants are causative agents of serious imbalances (namely oxidative stress) that are likely to trigger life-threatening events.

Compared to soil pollution by heavy metals and organic pollutants, soil pollution by fluorides is usually ignored in China. Actually, fluorine-contaminated soil has an unfavorable influence on human, animals, plants, and surrounding environment. This study reports on electrokinetic remediation of fluorine-contaminated soil and the effects of this remediation technology on soil fertility. Experimental results showed that electrokinetic remediation using NaOH as the anolyte was a considerable choice to eliminate fluorine in contaminated soils. Under the experimental conditions, the removal efficiency of fluorine by the electrokinetic remediation method was 70.35 %. However, the electrokinetic remediation had a significant impact on the distribution and concentrations of soil native compounds. After the electrokinetic experiment, in the treated soil, the average value of available nitrogen was raised from 69.53 to 74.23 mg/kg, the average value of available phosphorus and potassium were reduced from 20.05 to 10.39 mg/kg and from 61.31 to 51.58 mg/kg, respectively. Meanwhile, the contents of soil available nitrogen and phosphorus in the anode regions were higher than those in the cathode regions, but the distribution of soil available potassium was just the opposite. In soil organic matter, there was no significant change. These experiment results suggested that some steps should be taken to offset the impacts, after electrokinetic treatment.

Nitrogen (N) loss from vegetable cropping systems has become a significant environmental issue in China. In this study, estimation of N balances in both open-air and greenhouse vegetable cropping systems in China was established. Results showed that the total N input in open-air and greenhouse vegetable cropping systems in 2010 was 5.44 and 2.60 Tg, respectively. Chemical fertilizer N input in the two cropping systems was 201 kg N ha⁻¹ per season (open-air) and 478 kg N ha⁻¹ per season (greenhouse). The N use efficiency (NUE) was 25.9 ± 13.3 and 19.7 ± 9.4 % for open-air and greenhouse vegetable cropping systems, respectively, significantly lower than that of maize, wheat, and rice. Approximately 30.6 % of total N input was accumulated in soils and 0.8 % was lost by ammonia volatilization in greenhouse vegetable system, while N accumulation and ammonia volatilization accounted for 19.1 and 11.1 %, respectively, of total N input in open-air vegetable systems.

Pesticide contamination in the rice fields has manifested into a serious global environmental concern. Application of pesticides in the rice fields has deleterious effects on non-target organisms including nitrogen-fixing cyanobacteria which help to maintain the rice field fertility. In the present research endeavor, the effect of lambda cyhalothrin (5 % EC), a synthetic pyrethroid insecticide, has been studied on the growth and pigments content of Calothrix sp. (GUEco 1001), an indigenous strain isolated from rice grown areas of Brahmaputra floodplain. To study the toxic effect of lambda cyhalothrin, the test organism was exposed to varying concentrations of the insecticide i.e., 20 ppm, 40 ppm, 80 ppm, and 160 ppm based upon the determination of LC₅₀ for a period of 20 days. The result obtained in the laboratory showed a progressive decrease in the growth and pigments content by the test organism with increasing concentrations of the lambda cyhalothrin against time dose-dependent manner. At high dose (160 ppm), the test organism showed significant decrease in dry weight biomass (54.5 %), chlorophyll-a (68 %), carotenoids (38 %), phycocyanin (80 %), and nitrogen contents (55 %) over the control. A little but insignificant stimulatory effect on growth and chlorophyll-a contents was recorded in 20 ppm treatment of the insecticide that, however, was reversed in case of carotenoids and phycocyanin contents.