An integrative approach to assess ecological risks of surface water contamination for fish populations

Mesoporogen free synthesis of CuO/TiO2 heterojunction for ultra-trace detection of catechol in water samples

Creating mesoporous architecture on the surface of metal oxides without using pore creating agent is significant interest in electrochemical sensors because these materials act as an efficient electron transfer process between the electrode interface and the analytes. Recent advances in mesoporous titanium dioxide (TiO₂)-based materials have acquired extraordinary opportunities because of their interconnected porous structure could act as a host for doping with various transition metals or heteroatoms to form a new type of heterojunction. Herein, a simple method is developed to synthesize mesoporous copper oxide (CuO) decorated on TiO₂ nanostructures in which homogenous shaped CuO nanocrystals act as dopants decorated on the mesoporous structure of TiO₂, resulting in p-n heterojunction nanocomposite. The TiO₂ particles exhibit a mesoporous structure with a pore volume of about 0.117 cm³/g is capable to load CuO nanocrystals on the surface. As a result, large pore volume 0.304 cm³/g is obtained for CuO-TiO₂ heterojunction nanocomposite with the loading of uniform-shaped CuO nanocrystals on the mesoporous TiO₂. The resulting CuO-TiO₂ nanocomposite on modified glassy carbon (GC) electrode exhibits good electrochemical performance for oxidation of catechol with the observation of strong enhancement in the anodic peak potential at +0.36 V. The decrease in the overpotential for the oxidation of catechol when compared to TiO₂/GC is attributed to the presence of CuO nanocrystals providing a large surface area, resulting in wide linear range 10 nM to 0.57 μM. Moreover, the resultant modified electrode exhibited good sensitivity, selectivity and reproducibility and the sensor could able to determine the presence of catechol in real samples such as lake and river water. Therefore, the obtained CuO-TiO₂ nanocomposite on the modified GC delivered good electrochemical sensing performance and which could be able to perform a promising strategy for designing various metal oxide doped nanocomposites for various photochemical and electrocatalytic applications.

Endocrine disrupting chemicals entering European rivers: Occurrence and adverse mixture effects in treated wastewater

In the present study on endocrine disrupting chemicals (EDCs) in treated wastewater, we used chemical and effect-based tools to analyse 56 wastewater treatment plant (WWTP) effluents from 15 European countries. The main objectives were (i) to compare three different receptor-based estrogenicity assays (ERα-GeneBLAzer, p-YES, ERα-CALUX®), and (ii) to investigate a combined approach of chemical target analysis and receptor-based testing for estrogenicity, glucocorticogenic activity, androgenicity and progestagenic activity (ERα-, GR-, AR- and PR-GeneBLAzer assays, respectively) in treated wastewater. A total of 56 steroids and phenols were detected at concentrations ranging from 25 pg/L (estriol, E3) up to 2.4 μg/L (cortisone). WWTP effluents, which passed an advanced treatment via ozonation or via activated carbon, were found to be less contaminated, in terms of lower or no detection of steroids and phenols, as well as hormone receptor-mediated effects. This result was confirmed by the effect screening, including the three ERα-bioassays. In the GeneBLAzer assays, ERα-activity was detected in 82 %, and GR-activity in 73 % of the samples, while AR- and PR-activity were only measured in 14 % and 21 % of the samples, respectively. 17β-estradiol was confirmed as the estrogen dominating the observed estrogenic mixture effect and triamcinolone acetonide was the dominant driver of glucocorticogenic activity. The comparison of bioanalytical equivalent concentrations (BEQ) predicted from the detected concentrations and the relative effect potency (BEQ_chem) with measured BEQ (BEQ_bio) demonstrated good correlations of chemical target analysis and receptor-based testing results with deviations mostly within a factor of 10. Bioassay-specific effect-based trigger values (EBTs) from the literature, but also newly calculated EBTs based on previously proposed derivation options, were applied and allowed a preliminary assessment of the water quality of the tested WWTP effluent samples. Overall, this study demonstrates the high potential of linking chemical with effect-based analysis in water quality assessment with regard to EDC contamination.

Spatially structured freshwater fish population dynamics at the River Basin District scale: Implication for environmental management and fish conservation

European Union environmental policy has created a unique regulatory framework to favour aquatic ecosystem management and biodiversity conservation across European countries. Identifying the spatial structure of freshwater fish population dynamics is crucial to define region-specific management and conservation planning. To implement evidence-driven management and conservation decisions at a regional scale we assessed spatial heterogeneity in common freshwater fish population dynamics in France with a focus on trends in River Basin Districts (RBDs). The abundance and biomass growth rates of 18 common European freshwater fish species were estimated with state-space models on 546 sites distributed across the 5 main RBDs sampled in France between 1990 and 2011. Anguilla anguilla, Rutilus rutilus, Salmo trutta fario and Esox spp. exhibited large scale decline in abundance and/or biomass in several RBDs. The other species showed spatial heterogeneity in population growth rates. The main declines were observed in the Adour-Garonne and Loire-Bretagne RBDs, where management and conservation measures are urgently needed to halt the erosion of freshwater fish populations. In each of the 5 investigated RBDs, our results highlight areas where most of the common species we studied exhibited negative population growth rates. Freshwater fish surveys provide the fundamental information necessary to inform the European environmental policies and local environmental management needed to restore freshwater biodiversity. The next steps are to identify the main drivers of freshwater biodiversity erosion in the areas where we demonstrated major declines and to define the most cost-effective restoration measures.

Risk assessments of emerging contaminants in various waters and changes of microbial diversity in sediments from Yangtze River chemical contiguous zone, Eastern China

Over recent decades, increasing chemical contamination has greatly affected aquatic life and human health, even though most contaminants are present at low concentrations. The large-scale chemical industrial parks (CIPs) concentrated in the Yangtze River Delta account for over half of the total in China, and Jiangsu Province occupies one fifth of the Yangtze River Delta. Inevitably, the ecosystems could be affected by these CIPs. In this study, we collected 35 water and 12 sediment samples from the Yangtze River (Taizhou section) surrounding waters adjacent to concentrated CIPs and determined their cumulative chemical levels to be 0.2 to 28.4 μg/L and cumulative detections to be 11 to 39 contaminants with a median of 20 contaminants. 61 out of 153 screened chemicals were detected from at least one sampling site, and 6 contaminants, mostly semi-volatile organic compounds, appeared at all sites. Among these detected chemicals, di-n-octyl phthalate and dibutyl phthalate were at the highest levels. Ecological assessment revealed that 4-chloroaniline, phenol and dibutyl phthalate possibly would induce adverse effects on Yangtze River (Taizhou) ecosystems. Further aided with an evaluation of integrated biomarker response (IBR) index, it was found that site W06 (downstream of Binjiang CIP wastewater inlet) was the location in greatest need of urgent action. As a result, the microbial diversity of sediments in the Yangtze River mainstream was significantly higher than that of tributaries, where CIPs wastewater entered.

Assessing the Quality of Amazon Aquatic Ecosystems with Multiple Lines of Evidence: The Case of the Northeast Andean Foothills of Ecuador

We assessed the quality of Andes-Amazonia streams in Ecuador impacted by gold mining (GM), discharges from inefficient sewage network in urban areas (UA), wastes from fish farming (FF) and from non-functional landfill (LF) and other few threats (FT). We selected three lines of evidence (LOE) that were used separately and integrated into a index: water quality (WQI) and macroinvertebrate community (AAMBI) indices and phytotoxicity tests. Streams affected by UA and LF had the lowest scores to WQI and phytotoxicity, and by GM had the lowest scores to AAMBI. Macroinvertebrate absence in GM should be considered as a warning signal of long-term mining impacts in the area. The integrated LOE index showed that sites with identified threats had 30%-53% stream quality decline compared to FT sites. The use of the selected LOE seems to be a useful tools for long-term monitoring and evaluation of this sensitive aquatic ecosystem.

Joint toxic impacts of cadmium and three pesticides on embryonic development of rare minnow (Gobiocypris rarus)

Although rare minnow (Gobiocypris rarus) has been employed in many toxicological investigations, most of them have only assessed the impacts of single chemical. In our current work, we investigated the single and joint toxic impacts of heavy metal cadmium (Cd) and three pesticides (thiamethoxam, bifenthrin, and tebuconazole) on G. rarus embryos. Results from the 96-h semi-static toxicity assay exhibited that bifenthrin possessed the highest intrinsic toxic effect on rare minnows with an LC₅₀ value of 1.86 mg L^-1, followed by tebuconazole with LC₅₀ values of 4.07 mg L^-1. Contrarily, thiamethoxam elicited the least toxic effect with an LC₅₀ value of 351.9 mg L^-1. Seven chemical mixtures (four binary mixtures of Cd-bifenthrin, thiamethoxam-bifenthrin, thiamethoxam-tebuconazole, and bifenthrin-tebuconazole, two ternary mixtures of Cd-thiamethoxam-tebuconazole and thiamethoxam-bifenthrin-tebuconazole, and one quaternary mixture of Cd-thiamethoxam-bifenthrin-tebuconazole) displayed synergistic impacts with equivalent concentration and equitoxic ratio on G. rarus. Our results offered valuable insights into ecological risk assessment of these chemical combinations to aquatic vertebrates. The simultaneous existence of a few chemicals in the aquatic ecosystem might result in elevated toxicity, leading to severe harm to the non-target organisms compared with single compound. The observed synergistic interactions underlined the necessity to revise water quality standards, in which the detrimental joint effects of these chemicals are likely to be underestimated.

Stress responses in fish: From molecular to evolutionary processes

In the context of global changes, fish are increasingly exposed to multiple stressors that have cascading effects from molecules to the whole individual, thereby affecting wild fish populations through selective processes. In this review, we synthetize recent advances in molecular biology and evolutionary biology to outline some potentially important effects of stressors on fish across biological levels. Given the burgeoning literature, we highlight four promising avenues of research. First, (1) the exposure to multiple stressors can lead to unexpected synergistic or antagonistic effects, which should be better taken into account to improve our predictions of the effects of actual and future human activities on aquatic organisms. Second, (2) we argue that such interactive effects might be due to switches in energy metabolism leading to threshold effects. Under multiple stress exposure, fish could switch from a "compensation" strategy, i.e. a reallocation of energy to defenses and repair to a "conservation" strategy, i.e. blocking of stress responses leading to strong deleterious effects and high mortality. Third, (3) this could have cascading effects on fish survival and population persistence but multiscale studies are still rare. We propose emerging tools merging different levels of biological organization to better predict population resilience under multiple stressors. Fourth (4), there are strong variations in sensitivity among populations, which might arise from transgenerational effects of stressors through plastic, genetic, and epigenetic mechanisms. This can lead to local adaptation or maladaptation, with strong impacts on the evolutionary trajectories of wild fish populations. With this review, we hope to encourage future research to bridge the gap between molecular ecology, ecotoxicology and evolutionary biology to better understand the evolution of responses of fishes to current and future multiple stressors in the context of global changes.

Physiological impacts of pollution exposure in seabird's progeny nesting in a Mediterranean contaminated area

Aquatic wildlife is exposed through trophic transfer of hazardous substances to several threats inducing physiological impairments. We aimed at assessing the impact of contamination in one of the hot spots of pollution along Mediterranean coasts, the gulf of Gabes in Tunisia, on Common tern Sterna hirundo, a piscivorous top predator bird. Firstly, we compared the reproductive effort of breeding adults through clutch size distribution in three sites with different levels of pollution. Then, a battery of genotoxicity and oxidative stress biomarkers was carried out to assess physiological impairments in chicks. While defense mechanisms showed a depletion, lipid peroxidation and genotoxicity increased significantly according to pollution level. The multi-biomarker approach used here, discriminated chicks according to contamination degree of their nesting sites. Increases in genotoxicity and oxidative stress were correlated to a decrease in chick body mass known to lead to long-term impacts on juvenile survival and recruitment in birds.

IMPROVEMENT OF THE MODEL OF TRANSFORMATION OF NITROGEN-CONTAINING SUBSTANCES IN A WATER BODY FOR THE SOLUTION OF NATURE MANAGEMENT PROBLEM

In the article is considered the one of aspects of nature management regulation – an account of successive transformation of pollutants in a water body, that come with waste waters of industrial, municipal and agricultural enterprises. It is necessary at the determination of permissible pollutants emission with waste waters that doesn’t allow the excess of the permissible level of substances content in the control point of a water body. This problem is considered on the example of successive transformation of nitrogen-containing substances in the following transformation order: organic nitrogen – ammonium nitrogen - nitrite nitrogen – nitrate nitrogen. The topicality of the modeling of nitrogen-containing substances is conditioned by their role in water ecosystems functioning. At that existent mathematical models of natural water quality formation that take into account substances transformation contain the large number of unknown parameters. So, the use of such models in problems of nature management regulation is problematic, because identification of model parameters is a separate very complicated scientific problem. And existent models with relatively small number of parameters don’t take into account the natural pollution of water bodies, caused by the life activity of organisms; substance losses in the transformational chain are also possible. The improved matrix mathematical model of nitrogen-containing substances transformation without the indicated shortcomings is offered.