Protection Of Aquatic Ecosystems Research Articles

An analysis of McMurdo Dry Valleys’ lotic habitats within Antarctica’s protected area network and addressing gaps in biodiversity protection

ABSTRACT The McMurdo Dry Valleys (MDV), Antarctica’s largest ice-free region, hosts unique terrestrial ecosystems, with biodiversity concentrated in the aquatic environments and surrounding soils. Despite being a scientific hub, the creation of the MDV Antarctic Specially Managed Area (ASMA) made significant steps toward protecting the environment from degradation from human usage. However, with sustained human presence within the MDV, increasing human activity across Antarctica, and aquatic ecosystems subject to environmental change, the effectiveness of current protections for biodiversity conservation requires evaluation. This study employs spatial analysis of MDV protected areas, streams, lakes, research camps, and tourist sites to assess the robustness of current protections, identify underprotected areas, and outline steps for future protection. Within the MDV ASMA, five smaller Antarctic Specially Protected Areas (ASPAs) exist. Only two ASPAs contain streams, and only one with a full hydrologic catchment. With roughly 6% of the lotic habitat area protected by ASPAs, the MDV fall short of global goals for freshwater protection. Past successful management of the MDV shows the effectiveness of collaboration and early action, and amongst calls for ASPA network expansion and restructuring, the MDV has the opportunity to be at the forefront again and increase the protection of Antarctic aquatic ecosystems.

Assessment of carbonized himalayan chir pine biomass as an eco-friendly adsorbent for effective removal of industrial dyes

This study investigates the use of carbonized Himalayan Chir Pine Biomass, known as Chir Pine Activated Carbon (CPAC), as an eco-friendly and cost-effective adsorbent for efficient industrial dye removal, with a focus on environmental sustainability. By applying different additive treatments, four adsorbents (C1, C2, C3, and C4) were formulated. CPAC was synthesized through pyrolysis and characterized using various analytical techniques including FE-SEM, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). The adsorption capacity of CPAC was evaluated using Malachite Green (MG) dye as a model contaminant. FE-SEM images revealed high porosity (~ 10 µm) and a high surface area (119.886 m2/g) as confirmed by BET testing. CPAC effectively removed MG dye within 30 min at a solution pH of 7. Langmuir and Freundlich isotherm models indicated both monolayer and multilayer adsorption, while kinetic models suggested chemisorption. The regeneration efficiency was assessed using 0.1 N HCl over five consecutive cycles, with C4 demonstrating a high regeneration tendency of 85% and only a 9% reduction in adsorption ability after the fifth cycle. The developed CPAC shows excellent potential for use in the textile, paper, and leather industries for industrial dye adsorption, contributing to the protection of aquatic ecosystems. Additionally, CPAC can be utilized in other water and air purification applications.

Ecotoxicity threshold values for 4-hydroxychlorothalonil, carbendazim, dimethoate and methoxyfenozide in fresh and marine waters: Part 1. Derivation of threshold values

Pesticide active ingredients are frequently detected in the rivers, creeks, wetlands, estuaries, and marine waters of the Great Barrier Reef (GBR) region and are one of the main contributors to poor water quality. Pesticide concentrations detected in the environment through water quality monitoring programs can be compared against estimates of ecologically “safe” concentrations (i.e., water quality guidelines) to assess the potential hazard and risk posed to aquatic ecosystems. Water quality guidelines are also required to estimate the aquatic risk posed by pesticide mixtures, which is used for the Reef 2050 Water Quality Improvement Plan pesticide target. Seventy-four pesticide active ingredients and their degradates are frequently detected in GBR catchment waterways, however many do not have water quality guidelines in the Australian and New Zealand Guidelines for Fresh and Marine Water Quality. The current study derives ecotoxicity threshold values (ETVs) as unendorsed guideline values for active ingredients in two fungicides (4-hydroxychlorothalonil (fungicide degradate) and carbendazim) and two insecticides (dimethoate and methoxyfenozide) that are commonly detected in GBR catchment waterways. The proposed ETVs have been derived using species sensitivity distributions, as recommended in the Australian and New Zealand nationally endorsed method for deriving water quality guidelines for aquatic ecosystem protection. Four ETVs were derived for each chemical with values that should theoretically protect 99, 95, 90 and 80 % of species (i.e., PC99, PC95, PC90, PC80, respectively). The PC99 and PC95 values for 4-hydroxychlorothalonil, carbendazim, dimethoate and methoxyfenozide were 0.49 μg/L and 4 μg/L, 0.029 μg/L and 0.45 μg/L, 0.11 μg/L and 5.8 μg/L and 0.19 μg/L and 2 μg/L, respectively. The ETVs will be used in an ecological hazard and risk assessment across GBR waterways in part two of this study. The ETVs can also be used to assess potential risk across Australia and internationally where monitoring data are available.

Water-Energy-Food-Forest Nexus in The Amazon Conservation Unit

Objective: The general objective of this research is to analyze the integration of forests into the water-energy-food nexus in a Conservation Unit in the Brazilian Amazon, aiming to verify how traditional populations, in whose areas they inhabit, use two natural and non-wood resources for their survival. Theoretical Framework: The approach to the water-energy-food nexus emerged in the last decade around concerns such as global trends in population growth, economic growth and climate changes that place pressure on water, energy, food and forest resources. Method: The adopted methodology uses a qualitative approach, given the importance of understanding how the water, energy, food and forest resources in the Lago do Cuniã Extractive Reserve are explored. An exploratory-descriptive type of research, with a central concern in carrying out a preparatory analysis of a known context, meanwhile little explored in the Amazon. The collection of data was carried out by means of interviews with the application of questionnaire and application of non-participant observation techniques. Results and Discussion: The results demonstrate that studies with a nexus approach with four elements provide no understanding of the exploration of sustainable development in the environment of conservation units. Furthermore, the study reveals that maintaining forest resources improves water quality not only, but also controls erosion and resilience against droughts and floods; Contributing to the energy supply, in addition, contributes to the safety of feeding the residents of the conservation unit. Research Implications: For public policy makers, the results demonstrate the need for management practices for the conservation of forests, protection of the quantity and quality of existing rivers and lakes in the conservation unit and protection of aquatic and agricultural ecosystems. Originality/Value: The originality of the article is in the analysis of the role of addressing water, energy and food within an area of ​​environmental protection in the Amazon, and by including the element forest it was possible to find out its triangulation with the other elements and their implications for economic, social and economic factors. you set the mood.

Revolutionizing aquatic eco-environmental monitoring: Utilizing the RPA-Cas-FQ detection platform for zooplankton

The integration of recombinase polymerase amplification (RPA) with CRISPR/Cas technology has revolutionized molecular diagnostics and pathogen detection due to its unparalleled sensitivity and trans-cleavage ability. However, its potential in the ecological and environmental monitoring scenarios for aquatic ecosystems remains largely unexplored, particularly in accurate qualitative/quantitative detection, and its actual performance in handling complex real environmental samples. Using zooplankton as a model, we have successfully optimized the RPA-CRISPR/Cas12a fluorescence detection platform (RPA-Cas-FQ), providing several crucial “technical tips”. Our findings indicate the sensitivity of CRISPR/Cas12a alone is 5 × 109 copies/reaction, which can be dramatically increased to 5 copies/reaction when combined with RPA. The optimized RPA-Cas-FQ enables reliable qualitative and semi-quantitative detection within 50 min, and exhibits a good linear relationship between fluorescence intensity and DNA concentration (R2 = 0.956–0.974***). Additionally, we developed a rapid and straightforward identification procedure for single zooplankton by incorporating heat-lysis and DNA-barcode techniques. We evaluated the platform's effectiveness using real environmental DNA (eDNA) samples from the Three Gorges Reservoir, confirming its practicality. The eDNA-RPA-Cas-FQ demonstrated strong consistency (Kappa = 0.43***) with eDNA-Metabarcoding in detecting species presence/absence in the reservoir. Furthermore, the two semi-quantitative eDNA technologies showed a strong positive correlation (R2 = 0.58–0.87***). This platform also has the potential to monitor environmental pollutants by selecting appropriate indicator species. The novel insights and methodologies presented in this study represent a significant advancement in meeting the complex needs of aquatic ecosystem protection and monitoring.

Analysis of dissolved oxygen influencing factors and concentration prediction using input variable selection technique: A hybrid machine learning approach

Accurate quantification of dissolved oxygen (DO) is critically important for the protection and management of aquatic ecosystems. Successful applications have utilized mechanistic and data-driven models to simulate DO content in aquatic ecosystems. However, mechanistic models present challenges due to their complex and difficult-to-solve conditions, making them less portable. Additionally, data-driven model predictions are hindered by the challenge of numerous input variables, impacting both the running speed and prediction performance of the model. To address these challenges, water quality data and meteorological data of the Tanjiang River were obtained. The maximum information coefficient (MIC) input variable selection technique was employed to identify primary environmental factors influencing DO changes. Furthermore, coupled with support vector regression (SVR), two models (SVR and MIC-SVR) were employed to estimate the DO concentration of the Tanjiang River, and the optimal model was established. The results indicated a shift in the primary pollution factor from ammonia nitrogen to total phosphorus after recent treatment in the Tanjiang River. In comparison with the SVR model, the root mean square error (RMSE) of the MIC-SVR model was reduced by 4.46%, and the Nash-efficiency coefficient (NSE) was improved by 45.85%. In addition, study of kernel function selection revealed that considering as many kernel functions as possible is necessary for improving the performance of the SVR model. Conclusively, the proposed MIC-SVR model serves as an effective tool to analyze the relationship between DO and environmental factors, identifying the primary causes of low DO, and accurately predict the DO concentration in the Tanjiang River (especially in its middle and lower reaches), thus providing a reference for governmental decision-making on water environmental protection and water resource management.

Effects of ZnWO4 nanoparticles on growth, photosynthesis, and biochemical parameters of the green microalga Raphidocelis subcapitata

Nanoparticles have applications in many sectors in the society. ZnWO4 nanoparticles (ZnWO4-NPs) have potential in the fabrication of sensors, lasers, and batteries, and in environmental remediation. Thus, these NPs may reach aquatic ecosystems. However, we still do not know their effects on aquatic biota and, to our knowledge, this is the first study that evaluates the toxicity of ZnWO4-NPs in a eukaryotic organism. We evaluated the toxicity of ZnWO4-NPs on the green microalga Raphidocelis subcapitata for 96 h, in terms of growth, cell parameters, photosynthesis, and biochemical analysis. Results show that most of Zn was presented in its particulate form, with low amounts of Zn2+, resulting in toxicity at higher levels. The growth was affected from 8.4 mg L−1, with 96h–IC50 of 23.34 mg L−1. The chlorophyll a (Chl a) content increased at 30.2 mg L−1, while the fluorescence of Chl a (FL3-H) decreased at 15.2 mg L−1. We observed increased ROS levels at 44.4 mg L−1. Regarding photosynthesis, the NPs affected the oxygen evolving complex (OEC) and the efficiency of the photosystem II at 22.9 mg L−1. At 44.4 mg L−1 the qP decreased, indicating closure of reaction centers, probably affecting carbon assimilation, which explains the decay of carbohydrates. There was a decrease of qN (non-regulated energy dissipation, not used in photosynthesis), NPQ (regulated energy dissipation) and Y(NPQ) (regulated energy dissipation via heat), indicating damage to the photoprotection system; and an increase in Y(NO), which is the non-regulated energy dissipation via heat and fluorescence. The results showed that ZnWO4-NPs can affect the growth and physiological and biochemical parameters of the chlorophycean R. subcapitata. Microalgae are the base of aquatic food chains, the toxicity of emerging contaminants on microalgae can affect entire ecosystems. Therefore, our study can provide some help for better protection of aquatic ecosystems.

Combined effects of spinetoram and Microcystis aeruginosa on Daphnia pulex offspring: Maternal effects and multigenerational implications

The increasing occurrence of harmful algal blooms (HABs) in freshwater ecosystems detrimentally affect global water environments. Zooplankton's role in controlling HABs is hindered by contaminant exposure, necessitating research into combined stressors' ecological impacts. The response of Daphnia, a freshwater keystone species, to environmental stressors can be influenced by its maternal effects. Here, we investigated the combined effects of the world-widely used insecticide spinetoram and non-toxic HABs species Microcystis aeruginosa on the life-history traits of D. pulex offspring produced from different maternal food conditions. Four maternal groups were established, with each group receiving a specific blend of C. vulgaris (Ch) and M. aeruginosa (Ma) in varying proportions: A (100% Ch), B (90% Ch + 10% Ma), C (80% Ch + 20% Ma), and D (70% Ch + 30% Ma). The offspring from the third brood were gathered, and a 21-day experiment was carried out, involving various feeding groups (AA, AD, BA, BB, CA, CC, DA, and DD). Results demonstrated that grazing on M. aeruginosa by D. pulex induced maternal effects on their offspring, with the continuous exposure group showing an enhanced tolerance to M. aeruginosa. This study also unveiled that spinetoram could interfere with the molting of D. pulex, leading to developmental retardation. The Recovery Group exhibited an intriguing phenomenon: under the influence of both concentrations of the pesticide spinetoram (0.18, 0.35 μg L−1), D. pulex produced more offspring. This might be due to a combined strategy of allocating more energy towards reproduction in response to low-quality food and a potential hormetic effect from low concentrations of spinetoram. Assessing the interplay of combined stressors across multiple generations, encompassing harmful algal blooms (HABs) and environmental pollutants, is essential for predicting population responses to evolving environmental conditions. This understanding is vital for the protection and management of aquatic environments and ecosystems.

Use of singular spectral analysis to reconstruct average monthly flow time series with complex behavior

Time series analysis is a useful tool for many practical water resource management applications, such as planning and anticipating conflict around water use. These analyses are also necessary for the use, design and operation of hydrotechnical works and for the protection of aquatic ecosystems. Basically, his review focuses on classic models such as Box and Jenkins. However, restrictive assumptions about data and residuals make its use difficult. As an alternative, non-parametric approaches are interesting due to their application versatility. One of the techniques that has been widely used in the analysis of flow time series is Singular Spectral Analysis (SSA). However, its application is concentrated as a pre-processor or in hybrid approaches and, because of this, many studies focus only on the model to be improved, leaving gaps in the process understanding that underlie the SSA. Within this context, and because of this, the objective of this study is to present the SSA technique in detail, through an application to a time series of monthly average flows with complex behavior (Jucu River, located in Southeast Brazil), in order to overcome gaps associated to a rigorous understanding of the procedures that make up the SSA. The Sequential SSA technique was used to decompose signal and noise components. The reconstructed series preserved the dynamics of the observed series, suggesting a strong influence of the signal component (trend and seasonality) on its behavior. It’s expected that the technique can be used with greater fluidity by specialists and contribute to the management of water resources.
 Keywords: decomposition, reconstruction, singular spectrum analysis.

The impact of soil erosion on environments: A case study of the Oued Beht Watershed (Morocco)

Soil erosion poses a significant environmental challenge in the Oued Beht watershed, Morocco, impacting local ecosystems and water quality. This study investigates the causes and effects of soil erosion in this region, utilizing Geographic Information System (GIS) tools and field techniques to analyze land use changes, agricultural practices, soil properties, and precipitation patterns. The findings establish a clear link between soil degradation and declining water quality in nearby aquatic environments. Major contributors to soil erosion include intensive agriculture, climate change, deforestation, vegetation degradation, and steep terrain. To predict future erosion rates, models were used, emphasizing the need for proactive management strategies. To address these issues, the study suggests implementing sustainable agricultural practices and soil conservation measures like agroforestry, vegetative buffer strips, and slope management. These measures can effectively reduce soil erosion and its adverse effects on water quality. The study underscores the importance of integrated management approaches to preserve biodiversity and soil fertility in the region. The findings provide crucial information for policymakers to adopt sustainable land conservation and management policies, ensuring the protection of aquatic ecosystems and environmental sustainability in the Oued Beht watershed.

Indole-3-acetic acid improves periphyton's resistance to ultraviolet-B: From physiological-biochemical properties and bacteria community to livestock-polluted water purification

Livestock-polluted water is a pressing water environmental issue in plateau pastoral regions, necessitating the adoption of eco-friendly solutions. Despite periphyton being a promising alternative, its efficacy is limited by the prevalence of intense ultraviolet radiation, particularly ultraviolet-B (UVB), in these regions. Therefore, this study employs molecular tools and small-scale trials to explore the crucial role of indole-3-acetic acid (IAA) in modulating periphyton characteristics and mediating nutrient removal from livestock-polluted water under UVB exposure. The results revealed that IAA augments periphyton's resilience to UVB stress through several pathways, including increasing periphyton's biomass, producing more extracellular polymeric substances (EPS), and enhancing antioxidant enzyme activities and photosynthetic activity of periphyton. Moreover, IAA addition increased periphyton's bacterial diversity, reshaped bacterial community structure, enhanced community stability, and elevated the R2 value of neutral processes in bacterial assembly from 0.257 to 0.651 under UVB. Practically, an IAA concentration of 50 mg/L was recommended. Small-scale trials confirmed the effectiveness of IAA in assisting UVB-stressed periphyton to remove nitrogen and phosphorus from livestock-polluted water, without the risk of nitrogen accumulation. These findings offer valuable insights into the protection of aquatic ecosystems in plateau pastoral regions based on periphyton property in an eco-friendly manner.

A spatiotemporal optimization method for nutrient control in lake watersheds

Developing an efficient strategy for managing nutrients in less-developed lake watersheds that can balance the need for socioeconomic progress with the protection of aquatic ecosystems has become an urgent research subject for achieving sustainable development. This paper improves the optimization method for environmental and economic management of lake watersheds proposed in our previous research. A spatiotemporal optimization method based on a coupling model consisting of the Soil and Water Assessment Tool, system dynamics model, and objective programming model was applied to an agricultural non-point source (ANPS) pollution control program and a rural sewage treatment program at the Yilong Lake watershed as a case study. A simulation evaluation showed that the efficiency of the previous scheme was significantly improved after conducting spatiotemporal optimization. This scheme was dynamic and distributed, demonstrating an annual and high-resolution control program that can provide a basis for the precise management of ANPS. Although it still requires improvement, a framework for coupling simulation and two-step optimization was achieved in this study.

Nature reserves (zapovedniks) in the Volga catchment: protection, research and management

AbstractIn the Russian Federation, the protection category “Zapovednik” represents a strictly protected area, where the access is restricted and the aim is to keep the area “forever wild”. We provide an overview about the organization of these nature reserves and highlight their contribution to fundamental research. Aquatic ecosystems in zapovedniks provide pristine sites of great importance for long-term monitoring and research, which fosters process understanding regarding interannual variability and development of aquatic coenosis. We present a long term monitoring and research project about abiotic and biotic parameters in the Central Forest State Nature Biosphere Reserve. Examples from the Privolzhskaya Lesostep Nature Reserve include monitoring of invasive fish as well as analyses about the influence of beavers on fish. The Astrakhan Biosphere Nature Reserve in the Volga delta is a hotspot for fish biodiversity; thus, there the state nature reserve security service plays an important role to avoid poaching. Our case studies from the Volga Basin exemplify the structure and function of nature reserves and highlight their contribution to research, protection and management of aquatic ecosystems. Long-term datasets from the zapovedniks can (i) improve process understanding, (ii) ensure protection of aquatic systems and sustainable water management and (iii) support knowledge-based decisions.

Projected flow regimes and biodiversity changes under climate change in the planning western route source areas of the South-to-North Water Diversion Project

Scientific evaluation of the eco-hydrological regimes is of great significance for water resource management and aquatic ecosystem protection. The paper took the western route source areas (WRSA) of the South-to-North Water Diversion Project (SNWDP) as the research region. In order to quantify climate-induced eco-hydrological effects, a general framework was proposed to predict changes in flow regimes and fluvial biodiversity under climate change: The coupling of Global Climate Models (GCMs) and the Distributed Time Variant Gain Model (DTVGM) was used to simulate discharge under different climate conditions. Based on Indicators of Hydrologic Alteration (IHA), changes in eco-hydrological regimes were evaluated by using the Range of Variability Approach (RVA), assessment of overall hydrological change degree (D0), and Shannon index (SI). Changes in discharge, flow regimes, and fluvial biodiversity of WRSA were analyzed during the projected period (2041–2100) compared to the base period (1960–2014). According to the projections, under four SSPs-RCPs scenarios, the future discharge of WRSA increases significantly compared to the base period. D0 of WRSA is moderately or severely changed, and hydrological changes are mainly reflected in high flows such as monthly median flows during flood season, maximum flows, and high pulse duration. While flow regimes are disturbed, SI values of WRSA keep rising and the biodiversity is improved. The increase of discharge and SI becomes progressively greater with elevated radiation intensity, and the quantity of severely altered indicators of IHA increases. In conclusion, future hydrological alterations in SNWDP are expected to further intensify with higher levels of climate change, and these changes are generally conducive to the improvement of fish biodiversity.

Occurrence and environmental risk assessment of 22 pesticides in Brazilian freshwaters

Pesticide contamination in water resources is a global threat. Although usually found at low concentrations, pesticides raise considerable toxicological concerns, mainly when mixtures are considered. The occurrence of 22 pesticides (2,4 D, alachlor, aldicarb, aldrin, atrazine, carbendazim, carbofuran, chlordane, chlorpyrifos, DDT, diuron, glyphosate, lindane, mancozeb, methamidophos, metolachlor, molinate, profenofos, simazine, tebuconazole, terbufos, and trifluralin) was investigated, through consolidated database information, in surface freshwaters of Brazil. Moreover, scenarios of environmental risk assessment considering isolated compounds and mixtures were performed, as well as a meta-analytic approach for toxicity purposes. Pesticides in freshwater have been reported from 719 cities (12.9% of Brazilian cities), where 179 (3.2%) showed pesticide occurrence above the limit of detection or quantification. Considering cities with more than five quantified, 16 cities were prone to environmental risks considering individual risks. However, the number increased to 117 cities when the pesticide mixture was considered. The mixture risk was driven by atrazine, chlorpyrifos, and DDT. The national maximum acceptable concentrations (MAC) for nearly all pesticides are higher than the predicted no-effect concentration (PNEC) for the species evaluated, except aldrin. Our results show the need to consider mixtures in the environmental risk assessment to avoid underestimation and review MAC to protect aquatic ecosystems. The results presented here may guide the revision of the national environmental legislation to ensure the protection of Brazilian aquatic ecosystems.

Documenting the impacts of increasing salinity in freshwater and coastal ecosystems: Introduction to the special issue

Documenting the impacts of increasing salinity in freshwater and coastal ecosystems: Introduction to the special issue

Comprehensive assessment of the degree of contamination in surface water channels

The problems of clean water and the protection of aquatic ecosystems are becoming more acute, constantly getting worse and reaching such levels of pollution when the use of water for various purposes is severely limited or water can be harmful to humans. The article is devoted to the problems of pollution of water resources with harmful chemicals that affect human health. The analysis of a comprehensive assessment of the degree of contamination of surface waters is carried out, cases of high and extremely high pollution of surface waters on the territory of the Kurgan region are considered, ways of solving these problems are proposed.

Determination of Perfluorooctanoic Acid and Perfluorooctane Sulfonate Water Quality Criteria for Ecosystem Protection of Laguna Lake, Philippines

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are organic chemicals which pose concerns in the environment due to their persistence and bioaccumulative properties. This study used Assessment Factors and Species Sensitivities Distributions to derive specific thresholds to protect the ecosystem in the Laguna Lake, Philippines from risks posed by the toxicity of PFOS and PFOA using available ecotoxicity data for local species. For Assessment Factor method, the U.S. Environmental Protection Agency guideline for the narrative Tier II criteria was suitable based on the available toxicity data with calculated maximum concentration threshold for PFOS and PFOA of 0.51 and 0.75 mg L-1, respectively, and continuous maximum concentration values of 0.06 and 0.08 mg L-1, respectively. For the methods using Species Sensitivity Distribution (SSD), PFOS and PFOA thresholds extrapolated using factors for small datasets were 0.046 and 0.088 mg L-1, respectively. Lastly, PFOS and PFOA Hazardous Concentration (HC5) extrapolated from the weighted average SSD model estimates were 0.061 and 0.078 mg L-1, respectively. The results can serve as the first regulatory and risk assessment basis for aquatic ecosystem protection against risks posed by emerging contaminants in the lake.

Heterogeneity of nitrate reduction indicators across a tile drained agricultural catchment in East Jutland, Denmark

Detailed knowledge of the nitrate (NO3−) attenuation capacity of different landscapes is essential to support current aspirations of locally differentiated fertilizer nitrogen (N) regulation for protection of aquatic ecosystems. In this context, we studied the spatial heterogeneity of NO3−, ammonium (NH4+), and total N concentrations in pore water collected in an artificially drained sub-catchment and complemented this with measurements of apparent electrical conductivity (ECa), potential denitrification rates, and basic soil physico-chemical properties. Piezometer nests were installed in transects to represent a range of ECa and slopes in the sub-catchment and were then categorized according to predetermined classifications to delineate the different redox environments. Water samples were collected (February to August 2017) from piezometers that were installed in nests with screen depths at 25–75 cm, 85–115 cm and 125–165 cm. For transects with an average ECa higher than 20 mS m−1, NO3− concentrations were <5 mg N L−1 at the depth slightly above the drainage depth, whereas transects with an average ECa of <20 mS m−1 had NO3− concentrations ranging from 0.2 to 15 mg N L−1. Transects with ECa higher than 20 mS m−1 had the highest average clay content and estimated water contents and, possibly, higher macropore connectivity across the soil profile, which could enhance NO3− transport and the potential for development of anaerobic microsites facilitating microbial denitrification. Potential denitrification rates correlated with the presence of amorphous and poorly crystalline iron (Fe) oxides, yet the results were inconclusive regarding the possible role of Fe(II) mediated NO3− reduction. By categorizing the piezometer transects according to their average ECa values, patterns of N concentrations were found that reflected differences in nitrate attenuation capacity, thereby supporting the further pursuit of ECa as a simple and operational tool for mapping the variability in nitrate reduction patterns in the unsaturated zone on a sub-catchment scale.

Effects of aquatic heavy metal intoxication on the level of hematocrit and hemoglobin in fishes: A review

Environmental pollution caused due to the presence of heavy metals has become a great concern as it has an adverse effect on almost all types of ecosystem. In this sense, these pollutants have a tendency to pollute the aquatic ecosystem, thus badly affecting the health of aquatic organisms. As a result, toxicological studies believe them to be the most harmful pollutants in the aquatic environment. Among all the aquatic organisms, fish—being a chief organism in this system—become the easiest victim of these pollutants. Heavy metals enter fish bodies through the alimentary system by consumption of polluted food, or through the gills, and skin. They are finally delivered by the bloodstream to the organs and tissues where they accumulate after absorption. Ultimately, in this way heavy metals make their way into humans through the food chain. The fluctuations in the hematological values may serve as an initial indicator of the toxicant’s impact on fish health. It has been observed that when pollutants impact the quality of the aquatic medium, the first consequence is apparent in the form of physiological changes in fish, which are reflected in one or more hematological parameters, such as hemoglobin, hematocrit, red blood cell count, white blood cell count, etc. As a result of these alterations, fish become weak, anemic, and more susceptible to diseases. Over the past several decades, a vast number of studies have been reported on the qualitative and quantitative variations in hematological parameters due to the presence of heavy metal intoxication. Heavy metal contamination of water resources not only degrades the water quality but also negatively impacts the quality of food in the form of fish proteins. Therefore, this article sheds light on the effects of heavy metals on hemoglobin and hematocrit of fish hematology and calls for more attention to the protection and preservation of aquatic ecosystems, particularly those contaminated with heavy metals.