Implications For Environmental Monitoring Research Articles

Advanced AIE Materials for Environmental Monitoring: Selective Sensing of Thorium(IV) in Aquatic Systems.

Thorium (Th) is commonly used in various applications, but its long-term exposure poses health risks, necessitating its detection in aqueous environments. Traditional methods such as inductively coupled plasma mass spectrometry are sensitive but require complex instrumentation. Optical sensors, particularly fluorometry-based methods, are simpler, cost-effective, and selective. However, developing effective aggregation-induced emission (AIE) turn-on sensors for Th(IV) requires water-soluble fluorophores with a low background fluorescence. In the present work, we report a turn-on detection method for Th(IV) based on the AIE of the fluorophore tetra(4-sulfophenyl) ethylene (SuTPE). Th(IV)-induced aggregation of SuTPE and the simultaneous drastic enhancement of the emission property of SuTPE have been utilized for the selective sensing of Th(IV) in 100% aqueous media. The sensing mechanism was explored using ground-state absorption, steady-state and time-resolved emission, FTIR, DLS, SEM, AFM and quantum chemical studies of the SuTPE-Th(IV) complex. The selectivity of the present probe toward Th(IV) ions has been established by studying the interference of several metal ions, including lanthanides and uranyl ions. The LOD for Th(IV) was estimated to be 240 nM (56 ppb). The performance of the probe was demonstrated in tap water and diluted seawater matrixes. This work provides a significant advance for Th(IV) detection in aqueous environments, with implications for environmental monitoring and health safety.

Response of benthic diatom assemblages to environmental heterogeneity in an urban river: implications for environmental monitoring

Response of benthic diatom assemblages to environmental heterogeneity in an urban river: implications for environmental monitoring

Investigation of a DNA tagged aerosol tracer method for In Situ evaluation of germicidal UV air cleaner effectiveness

Transmission of respiratory pathogens occurs primarily in indoor settings, interventions to reduce the risk of their transmission include increases in outdoor air introduction, filtration, and ultraviolet germicidal irradiation (UVGI). However, validating these interventions is challenging, particularly in actual applications. This study introduces an aerosol tracer system utilizing DNA as tracer molecule, aimed at quantitative characterization of the performance of indoor air cleaning systems. Two DNA tracers, designed one to be relatively UV-resistant and another relatively UV-sensitive, were employed to assess air quality changes related to filtration and ventilation and the contributions of UVGI fixtures in various built environments. We conducted controlled UV exposure experiments of DNA-tagged tracers on foil coupons, aerosolization studies in a test chamber, and in a commercial building conference room. The DNA tracer results provided insights at the point of sampling into the effects of complex airflow dynamics. Additionally, a way to scale the DNA tracer results to MS2 bacteriophage is proposed. Four distinct UV devices challenged with MS2 in a chamber test produced equivalent clean airflow rates of 13–147 CFM. Scaled equivalent clean airflow rates in a commercial building setting using the UV-sensitive tracer varied from 47 percent less to 101 percent more than the chamber results, possibly due to differences in airflow patterns, equipment configuration, and other factors. Our findings provide quantitative understanding of the interaction between UV-sensitive aerosols and the built environment, with implications for environmental monitoring, measuring UVGI fixture impact in field settings, and addressing current technologies limitations for assessing UVGI disinfection efficacy.

Ultra-selective pyrene-based fluorescent sensor for detection of Fe+3 in neat aqueous medium

Transition metals, particularly Fe+3, play vital roles in biological and environmental systems, yet their chronic elevation can lead to severe diseases. Early detection of Fe+3 is crucial for diagnosing associated ailments. While traditional detection methods have drawbacks, fluorescent sensors offer promising alternatives due to their ease of use, cost-effectiveness, and real-time monitoring capability. Pyrene-based sensors have demonstrated notable sensitivity and selectivity for Fe+3, but challenges remain in achieving applicability in neat aqueous systems. We present two novel turn-off pyrene-based sensors, APTS (sodium 8-aminopyrene-1,3,6-trisulfonate) and APSS (sodium (E)-4-hydroxy-3-((pyren-1-ylimino)methyl)benzenesulfonate), incorporating sulfonate groups to enable their use in pure water samples and achieve nanomolar-level detection limits. Through meticulous experimental and characterization efforts, we elucidate the significance of the imine linkage in enhancing selectivity towards Fe+3 ions. Our sensors exhibit exceptional selectivity and sensitivity, with LODs of 45.6 nM and 45.9 nM for APTS and APSS, respectively, surpassing environmental protection guidelines. Additionally, binding stoichiometry studies reveal insights into the interaction mechanisms, supported by fluorescence lifetime analysis and DFT studies. APSS particularly stands out for its lack of interference from other metal ions, notably Cu2+ as well as Fe2+, offering promising potential for real-time applications and development of paper strip tests. The practical applicability of our sensors is demonstrated through successful Fe+3 detection in various water samples with recoveries ranging from 94 % to 104 %. Overall, our study highlights the effectiveness of APTS and APSS as robust fluorescent probes, with implications for environmental monitoring and biomedical diagnostics.

Screen-Printed Bimetallic Cobalt-Manganese Metal-Organic Framework Electrodes for Electrochemical Detection of Dichlorvos

Organophosphate pesticides are extremely hazardous to human health and the environment, discerning the development of sensitive and selective detection technologies. In this paper, we describe a novel technique for detecting dichlorvos (DDVP), an organophosphate pesticide, using a modified screen-printed electrode (SPE). The metal-organic framework (MOF) containing cobalt and manganese ions in an equimolar ratio was synthesised using a solvothermal method. The synthesized material was characterized using various techniques: FE-SEM, XRD, XPS, BET, Raman spectroscopy, and FTIR. The electro-catalytic behavior of the material was studied utilizing electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The insightful behaviour of the material towards dichlorvos had been investigated through differential pulse voltammetry (DPV) in the concentration range of 1–10 nM with a detection limit of 0.645 nM. Furthermore, we tested our proposed sensor’s selectivity and applicability using real-world samples. Our findings provide insight into the development of highly sensitive and selective detection systems for organophosphate pesticides, which might have implications for environmental monitoring and public health.

Revealing the urban heat Island: Investigating spatiotemporal surface temperature dynamics, modeling, and interactions with controllable and non-controllable factors

The unchecked growth of urban populations has spurred rapid and unsustainable urban expansion, exacerbating environmental degradation both locally and globally. This research offers a comprehensive analysis of the Urban Heat Island (UHI) phenomenon in Bangalore and Hyderabad, India, focusing on its spatial and temporal distribution and its correlation with air pollutants. Conducted over the course of summer and winter seasons from 2001 to 2021, this study advances our understanding of UHI dynamics in rapidly urbanizing regions, shedding light on the complex interplay between urbanization, climate, and air quality. The primary objective of this study is to assess and compare the predictive performance of baseline Random Forest (RF) and Extreme Gradient Boosting (XGBoost) models for forecasting Land Surface Temperature (LST) in Hyderabad, India, while examining the impact of integrating spatial information into these models. Incorporating an extensive array of input variables, ranging from spectral indices to terrain features, land use/land cover (LULC) data, atmospheric parameters, and spatial data, the analysis reveals significant relationships between LST and various factors. Notably, Aerosol Optical Depth (AOD) and Normalized Difference Built-up Index (NDBI) exhibit strong positive correlations with LST, while Enhanced Vegetation Index (EVI) demonstrates a pronounced negative correlation. Similarly, Modified Normalized Difference Water Index (MNDWI) displays the strongest positive correlation with LST (r = 0.49), whereas EVI exhibits the most notable negative correlation (r = −0.67). Additionally, Modified Bare Soil Index (MBI) demonstrates a noteworthy negative correlation (r = −0.48) with LST for Bangalore. Atmospheric components such as CO, NO2, and O3 also show significant positive correlations with LST, with NO2 displaying the highest correlation during winter in urban areas. XGBoost emerges as the superior model, achieving high R2 values of 0.84 for Bangalore and 0.88 for Hyderabad. Integration of spatial information consistently enhances the performance of both RF and XGBoost models, resulting in reduced Mean Squared Error (MSE) and Root Mean Squared Error (RMSE) values. However, predictions over water bodies tend to be underestimated. The study underscores the importance of incorporating spatial data for accurate LST prediction, with implications for environmental monitoring and management. Despite the advancements made, further research is needed to elucidate the specific mechanisms through which spatial information improves model performance, suggesting avenues for future investigation and refinement of modeling methodologies. At the intersection of rapid urban growth and environmental conservation, these findings are poised to inform policymakers, urban planners, and researchers, guiding them towards innovative and sustainable urban development strategies aimed at mitigating the adverse impacts of rapid urban expansion while promoting ecosystem well-being. The study contributes to spatial modeling strategies and refines LST prediction methodologies, offering valuable insights for addressing the challenges posed by urbanization and climate change in rapidly urbanizing regions.

Predicting large-scale spatial patterns of marine meiofauna: implications for environmental monitoring

Predicting large-scale spatial patterns of marine meiofauna: implications for environmental monitoring

Mediation of arsenic mobility by organic matter in mining-impacted sediment from sub\u2010Arctic lakes: implications for environmental monitoring in a warming climate

Arsenic (As) is commonly sequestered at the sediment–water interface (SWI) in mining-impacted lakes through adsorption and/or co-precipitation with authigenic iron (Fe)-(oxy)hydroxides or sulfides. The results of this study demonstrate that the accumulation of organic matter (OM) in near-surface sediments also influences the mobility and fate of As in sub-Arctic lakes. Sediment gravity cores, sediment grab samples, and porewaters were collected from three lakes downstream of the former Tundra gold mine, Northwest Territories, Canada. Analysis of sediment using combined micro-X-ray fluorescence/diffraction, K-edge X-ray Absorption Near-Edge Structure (XANES), and organic petrography shows that As is associated with both aquatic (benthic and planktonic alginate) and terrestrially derived OM (e.g., cutinite, funginite). Most As is hosted by fine-grained Fe-(oxy)hydroxides or sulfide minerals (e.g., goethite, orpiment, lepidocrocite, and mackinawite); however, grain-scale synchrotron-based analysis shows that As is also associated with amorphous OM. Mixed As oxidation states in porewater (median = 62% As (V), 18% As (III); n = 20) and sediment (median = 80% As (-I) and (III), 20% As (V); n = 9) indicate the presence of variable redox conditions in the near-surface sediment and suggest that post-depositional remobilization of As has occurred. Detailed characterization of As-bearing OM at and below the SWI suggests that OM plays an important role in stabilizing redox-sensitive authigenic minerals and associated As. Based on these findings, it is expected that increased concentrations of labile OM will drive post-depositional surface enrichment of As in mining-impacted lakes and may increase or decrease As flux from sediments to overlying surface waters.

Geochemistry of Negombo Lagoon sediments in Sri Lanka: implications for environmental monitoring

Negombo Lagoon is one of the largest lagoons in Sri Lanka. This study focuses on the geochemical evaluation of poorly understood tropical subtidal sediments of the western coast, Sri Lanka. Geochemical characteristics of sediments were examined using δ13C and δ15N stable isotopes, X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR) analyses. The chronology was determined using accelerated mass spectrometry (AMS) 14C dates for undamaged two shells. Stratigraphic observations suggested grey to blackish fine-grained muddy clay sediments in the subtidal mudflat. The calculated organic matter and carbonate contents decrease slightly from bottom to surface sediments. Bulk C/N ratios and δ13C values suggested terrestrial organic matter dominant sediments such as from mangrove swamps mixed with marine dissolved organic carbon. XRD identified the crystalline phases present in sediments and thereby chemical composition can be identified by the software as illite, montmorillonite, and quartz. It indicates the deposition of limited chemical weathering materials from near distance sources. FTIR identified several functional groups such as carboxylic, polysaccharide, carboxylate ions, and aliphatic substances in the lagoon sediments. The variations of carboxylic groups/carboxylate ions indicate a slow rate of decomposition of organic matter during early diagenesis. Humification and decomposition proxies also indicate slow rates of decomposition under an anoxic condition. However, Negombo Lagoon still acts as a healthy ecosystem under the minor influence of sewage/agricultural nutrient contamination.

Intra-lake response of Arcellinida (testate lobose amoebae) to gold mining-derived arsenic contamination in northern Canada: Implications for environmental monitoring

Arcellinida (testate lobose amoebae) were examined from 40 near-surface sediment samples (top 0.5 cm) from two lakes impacted by arsenic (As) contamination associated with legacy gold mining in subarctic Canada. The objectives of the study are two folds: quantify the response of Arcellinida to intra-lake variability of As and other physicochemical controls, and evaluate whether the impact of As contamination derived from two former gold mines, Giant Mine (1938–2004) and Tundra Mine (1964–1968 and 1983–1986), on the Arcellinida distribution in both lakes is comparable or different. Cluster analysis and nonmetric multidimensional scaling (NMDS) were used to identify Arcellinida assemblages in both lakes, and redundancy analysis (RDA) was used to quantify the relationship between the assemblages, As, and other geochemical and sedimentological parameters. Cluster analysis and NMDS revealed four distinct arcellinidan assemblages in Frame Lake (assemblages 1–4) and two in Hambone Lake (assemblages 5 and 6): (1) Extreme As Contamination (EAC) Assemblage; (2) High calcium (HC) Assemblage; (3) Moderate As Contamination (MAC) assemblages; (4) High Nutrients (HN) Assemblage; (5) High Diversity (HD) Assemblage; and (6) Centropyxis aculeata (CA) Assemblage. RDA analysis showed that the faunal structure of the Frame Lake assemblages was controlled by five variables that explained 43.2% of the total faunal variance, with As (15.8%), Olsen phosphorous (Olsen-P; 10.5%), and Ca (9.5%) being the most statistically significant (p < 0.004). Stress-tolerant arcellinidan taxa were associated with elevated As concentrations (e.g., EAC and MAC; As concentrations range = 145.1–1336.6 mg kg−1; n = 11 samples), while stress-sensitive taxa thrived in relatively healthier assemblages found in substrates with lower As concentrations and higher concentrations of nutrients, such as Olsen-P and Ca (e.g., HC and HM; As concentrations range = 151.1–492.3 mg kg−1; n = 14 samples). In contrast, the impact of As on the arcellinidan distribution was not statistically significant in Hambone Lake (7.6%; p-value = 0.152), where the proportion of silt (24.4%; p-value = 0.005) and loss-on-ignition-determined minerogenic content (18.5%; p-value = 0.021) explained a higher proportion of the total faunal variance (58.4%). However, a notable decrease in arcellinidan species richness and abundance and increase in the proportions of stress-tolerant fauna near Hambone Lake’s outlet (e.g., CA samples) is consistent with a spatial gradient of higher sedimentary As concentration near the outlet, and suggests a lasting, albeit weak, As influence on Arcellinida distribution in the lake. We interpret differences in the influence of sedimentary As concentration on Arcellinida to differences in the predominant As mineralogy in each lake, which is in turn influenced by differences in ore-processing at the former Giant (roasting) and Tundra mines (free-milling).

Effects of Parasite Infection and Host Body Size on Habitat Associations of Invasive Aquatic Snails: Implications for Environmental Monitoring.

The Comal River, a spring-fed system in central Texas, was invaded in the 1960s by two Asian aquatic snails (Thiaridae: red-rimmed melania Melanoides tuberculata and quilted melania Tarebia granifera) and subsequently by three of their trematode parasites (the avian eye-fluke Philophthalmus gralli in the 1960s; the gill trematode Centrocestus formosanus in the 1990s; and the intestinal fluke Haplorchis pumilio in the 2000s). Previous snail collections (2001-2002) established that habitat conditions significantly affect the distribution of both snail species. However, the effects of snail size (known to influence infection prevalence) and habitat conditions (known to influence snail size) on trematode infection patterns in this system were not evaluated. In a re-evaluation of this data set, logistic regression analyses with individual snails showed that for both M. tuberculata and T. granifera populations, large snails were more likely to be infected than small snails, and habitat conditions were significantly related to infection in T. granifera. However, only snail size was significant in explaining the probability of infection in M. tuberculata. This result was confirmed by linear regression models, which showed that both infected and noninfected M. tuberculata used similar habitats, as large individuals in both infection categories were found in patches dominated by fine substrates and high levels of aquatic vegetation and detritus. For the large size-class of T. granifera, noninfected individuals were found primarily in habitats with silt/sand substrates and high vegetation and detritus cover, while infected individuals occurred among all available habitats. Using these results, we suggest that targeted sampling of large individuals of M. tuberculata in habitats with high detritus and vegetation and large individuals of T. granifera in any habitat can be used to efficiently ascertain parasite "hot spots" and to evaluate changes in parasite prevalence or detect the invasion of new parasites in these thiarid snails.

Earthworms and cadmium – Heavy metal resistant gut bacteria as indicators for heavy metal pollution in soils?

Preservation of the soil resources stability is of high importance for ecosystems, particularly in the current era of environmental change, which presents a severe pollution burden (e.g. by heavy metals) to soil fauna. Gut microbiomes are becoming recognized as important players in organism health, with comprehension of their perturbations in the polluted environment offering new insights into the nature and extent of heavy metal effects on the health of soil biota. Our aim was to investigate the effect of environmentally relevant heavy metal concentrations of cadmium (Cd) on the earthworm (Lumbricus terrestris) gut microbiota. Our results revealed that Cd exposure led to perturbations of earthworm gut microbiota with an increase in bacteria previously described as heavy metal resistant or able to bind heavy metals, revealing the potential of the earthworm-gut microbiota system in overcoming human-caused heavy metal pollution. Furthermore, an ‘indicator species analysis’ linked the bacterial genera Paenibacillus, Flavobacterium and Pseudomonas, with Cd treatment, suggesting these bacterial taxa as biomarkers of exposure in earthworms inhabiting Cd-stressed soils. The results of this study help to understand the impact of anthropogenic disturbance on soil fauna health and will have implications for environmental monitoring and protection of soil resources.

Forthcoming risk of Prosopis juliflora global invasion triggered by climate change: implications for environmental monitoring and risk assessment.

Climate is a determinant factor in species distribution and climate change will affect the species abilities to occupy geographic regions. Prosopis juliflora is one of the most problematic invasive species and its biological invasion causes various negative effects in tropical, arid, and semi-arid regions of the world. As eradication efforts subsequent to the establishment of an alien invasive species are costly and time-consuming, assessing patterns of the introduction of an invasive species to new regions is among the most cost-effective means of monitoring and management of natural ecosystems. In this study by using the concept of species distribution modeling (SDM) and maximum entropy (MaxEnt) method, the effect of climate change on the current and future distribution of P. juliflora has been assessed at a global scale. Bioclimatic variables in current condition and 2050 regarding two global circulation models (GCM) and two climate change scenarios were considered as explanatory variables. Our results showed that annual mean temperature (BIO1), annual precipitation (BIO12), and temperature mean diurnal range (BIO2) represented more than 87% of the variations in the model, and with an AUC of 0.854 and TSS of 0.51, the model showed a good predictive performance. Our results indicate that on a global scale, suitable ranges for P. juliflora increase across all the GCM and RCP scenarios. In a global scale, Mediterranean Basin, Middle East, and North America are regions with the highest risk of range expansion in the future. Regarding the negative impacts of P. juliflora on structure and function of natural habitats in the invaded areas, findings of this study could be considered as a warning appliance for the environmental monitoring of the regions highly sensitive to the global invasion of the species. We suggest that assessing impacts of climate change on the global distribution of the invasive species could be used as an efficient tool to implement broad-scale and priority-setting monitoring programs in natural ecosystems.

Sediment grain size measurements are affected by site-specific sediment characteristics and analysis methods: implications for environmental monitoring

ABSTRACTSediment grain size, and specifically changes in the percent mud content (i.e. the fraction <63 µm) over time is often used as an indicator of estuarine environmental health. Using sediment samples from three distinct estuarine systems, we determined that different analytical methods (laser diffraction and wet sieving) gave significantly different results in terms of percent mud content. These differences are also ecologically meaningful when considering the influence of mud on estuarine macrofauna. We propose an approach to measuring sediment grain size termed Environmentally Available Sediment (EAS), which advocates for the measurement of the sediment that biota are directly exposed to. For the purposes of environmental monitoring, it is also essential to monitor sediment grain size in a repeatable way which is likely to be achieved using consistent (or no) pre-treatment and the use of a measurement technique that is unlikely to change over time, e.g. wet sieving.

Geochemical soil anomalies: Assessment of risk to human health and implications for environmental monitoring

Areas with natural geochemical anomalies are not normally included when defining geochemical backgrounds for metals. However, it is important to understand the distribution and extent of anomalous geochemical values when assessing the risks associated with metal contamination to the ecosystem. This study measured the concentrations of Cd, Cr, Cu, Hg, Ni, Pb, and Zn in pedogenetic soil horizons with geochemical anomalies. The factors that control the vertical distribution of these elements (pH, organic carbon, cation exchange capacity, lithogenic metals, granulometry) were also examined. Except to Cd and Hg, the average surface concentrations of the metals studied exceeded the expected background levels for the region. The concentrations of Cr, Cu, and Ni were higher in soils developed from basalt, while Cd, Hg, Pb and Zn exhibited concentrations with no direct relation to the type of parent material. All the metals are of natural origin with the exception of Zn, which was influenced by anthropogenic activities in two soil profiles. With an exception of the Cd and Hg contents that were low for all analyzed soils, samples showed geochemical anomalies for all the metals, in particular Cr, Ni, and Pb, with values high enough to warrant investigation due to the possible impairment of soil functions and potential risks to human health. However, when samples were evaluated using sequential extraction analyses, results showed at least 84% of the total content of Cr, Ni e Pb was associated with the residual fraction, indicating a low potential for mobility and availability in the environment. Measures of the hazard quotient and the hazard index showed that adverse impacts on human health are not likely to result from the high concentrations of Cr, Ni, and Pb, even in more sensitive organisms. These results have important implications for the definition of trigger values for investigative or remedial measures in areas with geochemical anomalies.

Diversity and Abundance of High-Molecular-Weight Azaarenes in PAH-Contaminated Environmental Samples.

Azaarenes are N-heterocyclic polyaromatic pollutants that co-occur with polycyclic aromatic hydrocarbons (PAHs) in contaminated soils. Despite the known toxicity of some high-molecular-weight azaarenes, their diversity, abundance, and fate in contaminated soils remain to be elucidated. We applied high-resolution mass spectrometry and mass-defect filtering to four PAH-contaminated samples from geographically distant sites and detected 232 azaarene congeners distributed in eight homologous series, including alkylated derivatives and two hitherto unknown series. Four- and five-ring azaarenes were detected among these series, and the most abundant nonalkylated congeners groups (C13H9N, C15H9N, C17H11N, C19H11N, and C21H13N) were quantified. The profiles of congener groups varied among different sites. Three-ring azaarenes presented higher concentrations in unweathered sites, while four- and five-ring azaarenes predominated in weathered sites. Known toxic and carcinogenic azaarenes, such as benzo[c]acridine and dibenzo[a,h]acridine, were detected along with their multiple isomers. Our results highlight a previously unrecognized diversity and abundance of azaarenes in PAH-contaminated sites, with corresponding implications for environmental monitoring and risk assessment.

Size effect on the mineralogy and chemistry of Mytilus trossulus shells from the southern Baltic Sea: implications for environmental monitoring

Mussels have the ability to control biomineral production and chemical composition, producing shells with a range of functions. In addition to biological control, the environment also seems to influence the process of biomineralization; thus, shells can be used as archives of ambient water parameters during the calcium carbonate deposition. Past and present environmental conditions are recorded in the shells in the form of various proxies including Mg/Ca or Sr/Ca ratios. For such proxies to be accurate and robust, the influence of biological effects including the size of studied organism must be examined and eliminated or minimized, so that the environmental signal can be efficiently extracted. This study considers mineralogy and elemental composition of shells representing four size classes of Mytilus trossulus from the Baltic Sea. Obtained results suggest that mineralogy and chemical composition change throughout the shell development due to most likely a combination of environmental and biological factors. The content of aragonite increases with increasing shell size, while the bulk concentrations of Na, Cd, Cu, U, V, Zn and Pb were found to decrease with increasing height of the shells. Therefore, using mussels for environmental monitoring requires analysis of individuals in the same size range.

Oxygen‐depleted bottom waters along the west coast of South Africa, 1950–2011

AbstractAs part of the southern Benguela upwelling ecosystem, South Africa's west coast represents a very productive marine habitat. Decadal‐scale environmental and ecosystem regime shifts have been documented based on wind and ocean temperature data, as well as biota. This study analyses the variability of oxygen‐depleted (&lt;2 mL L−1) bottom waters on South Africa's west coast shelf using data from St Helena Bay, the most productive embayment in the ecosystem, from 1957, data from demersal and pelagic fisheries surveys since the 1980s, and monthly observations from a fixed transect off St Helena Bay from 2000 to 2011. Oxygen‐depleted waters are generally restricted to bottom depths &lt;150 m, and occur regularly during austral summer and autumn, albeit with variable severity. The high spatial variability makes it impossible to define any single station as an indicator station for the extent of oxygen depletion. We provide estimates of the shelf area, 30–33°S, covered by oxygen‐depleted bottom water in austral summer and autumn, and show a parabolic relationship between oxygen depletion and upwelling strength. The results suggest that the cumulative upwelling divergence from the onset of the upwelling season (September) to the establishment of oxygen depletion (January) can be used as a proxy indicator for oxygen depletion in summer. Periods of better bottom ventilation are indicated for the second half of the 1960s to the early 1980s; more extensive oxygen depletion at the beginning of the 1950s, and the mid‐1990s to the mid‐2000s. Implications for environmental monitoring and marine living resources are discussed.

Optimization of effects‐assessment of greenside darter (Etheostoma blennioides) exposed to tertiary treated municipal wastewater based on seasonal changes of reproductive endpoints

The present study describes the seasonal changes in reproductive endpoints of the greenside darter (Etheostoma blennioides) and its implications for environmental monitoring. Fish collections conducted at the appropriate time for the site-specific sentinel fish species can provide a wide variety of population-level information including recruitment, reproduction, and energy storage. The objectives of the present study were to: 1) characterize seasonal changes in reproductive endpoints of the greenside darter (both sexes) to determine the appropriate period for monitoring of this sentinel species; and 2) evaluate the effect of exposure of this sentinel species to tertiary treated municipal effluent at the selected monitoring period. Based on the selected parameters (gonadosomatic index [GSI], liver somatic index [LSI], condition factor, and in vitro gonadal steroid production [testosterone (T) in both sexes; estradiol (E2) in females; and 11-ketotestosterone (11KT) in males]), the present study provides evidence for the value of collecting darters during recrudescence (late fall/early winter) to ensure temporal stability, minimum variability, and stable steroid production capacity. Darters exposed to tertiary treated municipal effluent tended to be larger and heavier relative to reference fish but did not demonstrate any consistent responses in terms of condition or relative liver size. No effect on gonadal development was observed, even though these tertiary-effluent-exposed fish demonstrated a significant reduction in the ability to produce hormones. The present study suggests that although fish exposed to tertiary treated effluent demonstrate no population-level effects, they are still responding at a physiological level. Documentation of the reproductive cycle of sentinel species allows for selection of the most appropriate sampling period to reduce variability and greatly enhances the reliability and interpretation of biological responses.

Effects of Temperature in Juvenile Seabass (Dicentrarchus labrax L.) Biomarker Responses and Behaviour: Implications for Environmental Monitoring

The effects of temperature on European seabass (Dicentrarchus labrax L.) juveniles were investigated using a 30-day bioassay carried out at 18 and 25 °C in laboratory conditions. A multiparameter approach was applied including fish swimming velocity and several biochemical parameters involved in important physiological functions. Fish exposed for four weeks to 25 °C showed a decreased swimming capacity, concomitant with increased oxidative stress (increased catalase and glutathione peroxidase activities) and damage (increased lipid peroxidation levels), increased activity of an enzyme involved in energy production through the aerobic pathway (isocitrate dehydrogenase) and increased activities of brain and muscle cholinesterases (neurotransmission) compared to fish kept at 18 °C. Globally, these findings indicate that basic functions, essential for juvenile seabass surviving and well performing in the wild, such as predation, predator avoidance, neurofunction and ability to face chemical stress may be compromised with increasing water temperature. This may be of particular concern if D. labrax recruitment phase in northwest European estuaries and coastal areas happens gradually in more warm environments as a consequence of global warming. Considering that the selected endpoints are generally applied in monitoring studies with different species, these findings also highlight the need of more research, including interdisciplinary and multiparameter approaches, on the impacts of temperature on marine species, and stress the importance of considering scenarios of temperature increase in environmental monitoring and in marine ecological risk assessment.