Substances In Aquatic Ecosystems Research Articles

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

Humic compounds in marine ecosystems - Ecological importance in transitional Mediterranean zones

By using the general term ‘humic substances’ (HS), a vast category is implied of heterogeneous organic compounds that are naturally occurred, formed under certain circumstances, bearing yellow to black colour. There are distinguishable fractions of the (HS) categorized e.g. according to hydrophilicity. Humic acids (HA), comprise the soluble fraction of (HS) at high pH values whereas fulvic acids (FA) represent the soluble fraction of (HS) under all pH conditions. The humin represents the unclassified, non-soluble fraction of organic material. (HS) are separating into two well distinctive categories i.e. allochthonous & autochthonous indicating a different origin. (HS) affect bioavailability of transition metal ions including Fe, Mn, Cu, and Zn due to (HS) chelating properties and high affinity towards those metals. (ΗΑ) stimulate biodegradation and favors removal of various pollutants serving as bioremediation agents. Organic compounds leached from plastic debris into the aquatic phase, become part of the marine dissolved organic carbon (DOC) pool. Humic part characteristics are tightly bound to the anthropogenic impacts stressed over the shoreline and contribute to diagenetic processing of the marine seabed. The scope of the present essay was to outline the multi-functionality of humic substances in aquatic ecosystems with the given emphasis on the Eastern Mediterranean region.

A worldwide evaluation of trophic magnification of per- and polyfluoroalkyl substances in aquatic ecosystems.

A review of the published literature on the trophic magnification factor (TMF) for per- and polyfluoroalkyl substances (PFAS) was conducted to assess how biomagnification varies across aquatic systems worldwide. Although the TMF has been recognized as the most reliable tool for assessing the biomagnification of organic contaminants, peer-reviewed studies reporting TMFs for PFAS are few and with limited geographical distribution. We found 25 published studies of the biomagnification of 35 specific PFAS, for which the TMF was generated through linear regression of individual log-PFAS concentration and the δ15 N-based trophic position of each organism in the food webs. Studies were concentrated mainly in China, North America, and Europe, and the most investigated compound was perfluorooctane sulfonate (PFOS), which was frequently shown to be biomagnified in the food web (TMFs ranging from 0.8 to 20). Other long-chain carboxylates displayed substantial variation in trophic magnification. Observed differences in the TMF were associated with length of the food web, geographic location, sampling methodologies, tissue analyzed, and distance from known direct PFAS inputs. In addition to biomagnification of legacy PFAS, precursor substances were observed to bioaccumulate in the food web, which suggests they may biotransform to more persistent PFAS compounds in upper trophic levels. This review discusses the variability of environmental characteristics driving PFAS biomagnification in natural ecosystems and highlights the different approaches used by each study, which can make comparisons among studies challenging. Suggestions on how to standardize TMFs for PFAS are also provided in this review. Integr Environ Assess Manag 2022;18:1500-1512. © 2022 SETAC.

Review of the biomonitoring of persistent, bioaccumulative, and toxic substances in aquatic ecosystems of Mexico: 2001-2016

Mexico is responsible for the protection and management of a large number and variety of aquatic bodies of national and international importance. Environmental pollution by so-called persistent and bioaccumulative toxic substances (PBTS) poses significant risks for all of the world's aquatic ecosystems, especially in countries with emerging economies, where environmental regulations are often poorly implemented. In Mexico, the development of industrial projects and the deficient application of environmental regulations, together with the rapid increase in population and the inefficient disposal of urban waste, have generated a severe problem of water pollution in the country. National environmental protection programs have not included the monitoring of PBTS, even though researchers have been monitoring the main aquatic ecosystems of the country for nearly three decades, generating valuable information that could help improve the protection and exploitation of these ecosystems. The present work reviewed a large portion of the available literature (~150 articles) on aquatic biomonitoring of the main PBTS (Hg, Cd, Pb, POCs, and PCBs) in Mexico. This work aims to collect, synthesize, and facilitate the management and interpretation of the reported data to improve the country's aquatic ecosystems' protection and management.

A Multi-Function Sensor for Eddy Correlation Measurements of Benthic Flux.

Eddy Correlation (EC) is a technique that can be used to measure transport of substances in aquatic ecosystems between bottom sediments and the overlying water (i.e. benthic fluxes). Based on high-speed, simultaneous, and co-located velocity and concentration measurements, EC has been successfully used in a variety of freshwater and marine settings to determine benthic fluxes of dissolved oxygen. Application to a larger range of compounds is limited, however, by the lack of suitable chemical sensors. Here, we describe FACT, a novel, high-speed, multi-function sensor created to expand the range of benthic fluxes that can be measured with EC. An optical fiber spectrofluorometer with a proximally located conductivity cell and thermistor, FACT enables benthic flux measurements of fluorescing compounds, such as fluorescent dissolved organic matter, as well as of heat and salinity which can be used as tracers for submarine groundwater discharge. The high bandwidth and open-beam geometry of the fluorescence sensor are particularly beneficial for EC measurements. FACT was integrated with a velocity sensor into a full EC system capable of simultaneous benthic flux measurements of fluorescing compounds, heat, and salinity. Tested in a laboratory tank, fluxes measured by all three sensors were found to track each other as well as compare favorably with expected values. Furthermore, the ability to measure fluxes of multiple substances both extends the applicability of EC to a wider range of natural sites, and can provide insight into issues of sensing volume and time responses as they affect the application of EC to natural waters.

Phytoplankton and Its Role in Accumulation of Microelements in Bottom Deposits of Azov Sea.

The importance of phytoplankton is high in transformation of substances in aquatic ecosystems and in formation of suspension's material structure. Its main functions are consumption of the dissolved biogenic components and chemical elements and their conversion to a firm phase. The article is devoted to the bioaccumulation of microelements by phytoplankton in the ecosystem of the Azov Sea. The fact that the algal biomass during the periods of blooming in the sea reaches 1,400 g/l makes this study especially urgent. The authors define the rates of biogeochemical cycle and the intensity of chemical elements' consumption and also investigate the role of phytoplankton in the formation chemical peculiarities of bottom deposits and its involvement in sedimentogenesis in the Azov Sea. The cause of the reduced trace element content in bottom deposits relatively to suspended material is established. It is noted that the amount of some elements annually consumed by algae of the Azov Sea is up to 75% from their maximum delivery by terrigenous material.

In search of a comprehensible set of endpoints for the routine monitoring of neurotoxicity in vertebrates: sensory perception and nerve transmission in zebrafish (Danio rerio) embryos.

In order to develop a test battery based on a variety of neurological systems in fish, three sensory systems (vision, olfaction, and lateral line) as well as nerve transmission (acetylcholine esterase) were analyzed in zebrafish (Danio rerio) embryos with respect to their suitability as a model for the screening of neurotoxic trace substances in aquatic ecosystems. As a selection of known or putative neurotoxic compounds, amidotrizoic acid, caffeine, cypermethrin, dichlorvos, 2,4-dinitrotoluene, 2,4-dichlorophenol, 4-nonylphenol, perfluorooctanoic acid, and perfluorooctane sulfonic acid were tested in the fish embryo test (OECD test guideline 236) to determine EC10 values, which were then used as maximum test concentration in subsequent neurotoxicity tests. Whereas inhibition of acetylcholinesterase was investigated biochemically both in vivo and in vitro (ex vivo), the sensory organs were studied in vivo by means of fluorescence microscopy and histopathology in 72- or 96-h-old zebrafish embryos, which are not regarded as protected developmental stages in Europe and thus - at least de jure- represent alternative test methods. Various steps of optimization allowed this neurotoxicity battery to identify neurotoxic potentials for five out of the nine compounds: Cypermethrin and dichlorvos could be shown to specifically modulate acetylcholinesterase activity; dichlorvos, 2,4-dichlorophenol, 4-nonylphenol, and perfluorooctane sulfonic acid led to a degeneration of neuromasts, whereas both vision and olfaction proved quite resistant to concentrations ≤ EC10 of all of the model neurotoxicants tested. Comparison of neurotoxic effects on acetylcholinesterase activity following in vivo and in vitro (ex vivo) exposure to cypermethrin provided hints to a specific enzyme-modulating activity of pyrethroid compounds. Enhancement of the neuromast assay by applying a simultaneous double-staining procedure and implementing a 4-scale scoring system (Stengel et al. 2017) led to reduced variability of results and better statistical resolution and allowed to differentiate location-dependent effects in single neuromasts. Since acetylcholinesterase inhibition and neuromast degeneration can be analyzed in 72- and 96-h-old zebrafish embryos exposed to neurotoxicants according to the standard protocol of the fish embryo toxicity test (OECD TG 236), the fish embryo toxicity test can be enhanced to serve as a sensitive neurotoxicity screening test in non-protected stages of vertebrates.

Genotoxicity of gemfibrozil in the gilthead seabream (Sparus aurata)

Widespread use of pharmaceuticals and suboptimal wastewater treatment have led to increased levels of these substances in aquatic ecosystems. Lipid-lowering drugs such as gemfibrozil, which are among the most abundant human pharmaceuticals in the environment, may have deleterious effects on aquatic organisms. We examined the genotoxicity of gemfibrozil in a fish species, the gilthead seabream (Sparus aurata), which is commercially important in southern Europe. Following 96-h waterborne exposure, molecular (erythrocyte DNA strand breaks) and cytogenetic (micronuclei and other nuclear abnormalities in cells) endpoints were measured. Gemfibrozil was positive in both endpoints, at environmentally relevant concentrations, a result that raises concerns about the potential genotoxic effects of the drug in recipient waters.

Critical analysis of molluscicide application in schistosomiasis control programs in Brazil.

In Brazil, Biomphalaria glabrata, B. tenagophila, and B. straminea are naturally infected by the trematode Schistosoma mansoni, the causative agent of schistosomiasis. Despite decades of governmental efforts through official control programs, schistosomiasis remains an important public health problem in the country: thousands of people are infected with the trematode each year and millions live in endemic areas. The World Health Organization recommends using a combination of molluscicide (niclosamide) and mass chemotherapy to control the transmission of schistosomiasis, with this treatment successfully reducing the morbidity of the disease. In the past, niclosamide has been used in official schistosomiasis control programs in Brazil. However, as B. glabrata recolonizes even after molluscicide application, the use of molluscicides has gradually decreased in the country until they were discontinued in 2002, mainly due to the rising global pressure to preserve the environment and the difficulties of obtaining licenses from the Brazilian Ministry of Environment to use toxic substances in aquatic ecosystems. Therefore, the discovery of new molluscicides, which could be more selective to Biomphalaria species and less harmful to the aquatic ecosystem, is necessary. In addition, political efforts to sensitize funders to provide grants for this field of research are required. In this context, this article aims to make a critical analysis of molluscicide application in schistosomiasis control programs in Brazil.Electronic supplementary materialThe online version of this article (doi:10.1186/s40249-016-0153-6) contains supplementary material, which is available to authorized users.

Toxic Effect of Benzene, Toluene and Formaldehyde to Response Behavior of Nematode (Caenorhabditis elegans) using Image Processing System

Toxic Response behavior of nematode by exposure toxic chemicals is assessed using automatic recognition of line movement through image processing system under the microscope. The nematode Caenorhabditis elegans was exposed in different toxic chemicals to determine the toxic response. Toxicity of formaldehyde, benzene and toluene might affect on the movement behavior of nematodes. Toxic response behavior of nematode in three toxic chemicals have found to be similar. This study is identified some sequential line-movements of nematode that could be used as an alternative tool for the real-time monitoring of toxic substances in aquatic ecosystems in the future.

CURRENT SITUATION OF WATER POLLUTION AND ITS EFFECT ON AQUATIC LIFE IN EGYPT

Water is a multi-dimensional issue and a prerequisite for achieving human security, from the individual to the international level. The Nile River has long been a crucial component of both the identity and the vitality of Egypt. Egypt faces a rapidly increasing deterioration of its surface and groundwater due to increasing discharges of heavily polluted domestic and industrial effluents into its waterways. Excessive use of pesticides and fertilizers in agriculture also causes water pollution problems. Many disasters in Egypt were happening and leading to water pollution. Toxicity of fishes in Egypt occurs due to water pollution from chemical plants and sewage pipes. The water quality assessment is very important for implementation of the monitoring and remediation programs to minimize the risk promoted by hazardous substances in aquatic ecosystems. Evaluation of the degree of contamination of aquatic environments must take in account its chemical characteristics which has potential toxic effects and allows an integrated evaluation of its effects on populations of the aquatic system. During the last few decades, great attention has been paid to the possible dangers of heavy metal poisoning in human due to the consumption of contaminated fish. Industrial and agricultural discharges such as coal and oil combustion, phosphate fertilizers, plastics and pesticides are considered the major sources of heavy metal pollutants of water.

Decision support systems for the management of hazardous materials in aquatic ecosystems

Many aquatic ecosystems suffer from anthropogenic disturbances, including the introduction of damaging levels of toxic substances. The effects of disturbances include complex relations with various components involved in the systems, and can include physical, chemical, and hydrological disruption depending of the contaminant. Decision Support Systems (DSSs) are developed to help decision makers to deal with complex management crises, through the systematic structuring and evaluation of decisions, and through providing easy-to-use and integrated tools for information elaboration and display. We reviewed various DSSs developed for toxic substances in aquatic ecosystems, and suggested a conceptual framework which is best suited to the management of such issues within Korea. It may assist stakeholders with their decision making process, and in the achievement of a consensus on water management solutions.

Occurrence of widely used organic UV filters in lake and river sediments

Environmental contextPersonal care products containing organic chemicals to filter the sun’s UV rays are produced and used on a broad scale worldwide. Consequently, these organic UV filters are now widespread in the environment. We investigate the occurrence of seven common organic UV filters in river and lake sediments thereby providing valuable data for the future environmental risk assessment of these chemicals to the benthic community of freshwater ecosystems. AbstractPersonal care products (PCPs) are produced and used in huge amounts. These formulations are permanently introduced into the aquatic environment during regular use, mainly through municipal sewage treatment plants. Although there is increasing concern about PCP residues in the aquatic environment, little is known about the extent and level of contamination. The occurrence and concentrations of the seven most frequently used ultraviolet (UV) filters in river and lake sediments have been investigated over a 6-month period by gas chromatography–mass spectrometry: benzophenone-3 (BP-3), 3-benzyliden camphor (3-BC), butyl-methoxydibenzoylmethane (B-MDM), ethylhexyl dimethyl p-aminobenzoic acid (ED-PABA), ethylhexyl-methoxycinnamate (EHMC), 3′-(4′-methylbenzyliden)camphor (4-MBC) and octocrylene (OCR). B-MDM, EHMC and OCR were identified as major contaminants. They were present in every sediment sample with maximum concentrations of 62.2, 6.8 and 642 µg kg–1. 3-BC and ED-PABA could not be detected in any sediment sample. The temporal distribution profile and concentrations of UV filters differed between lakes and rivers. Whereas concentrations of all UV filters in river sediments were low and constant over time, lake sediments exhibited high UV-filter levels during summer and concentrations dropped in autumn. These findings support risk assessment activities and contribute to a better understanding of the magnitude of contamination with organic UV-filter substances in aquatic ecosystems.

Lethal effects of abamectin on the aquatic organisms Daphnia similis, Chironomus xanthus and Danio rerio

Abamectin is used as an acaricide and insecticide for fruits, vegetables and ornamental plants, as well as a parasiticide for animals. One of the major problems of applying pesticides to crops is the likelihood of contaminating aquatic ecosystems by drift or runoff. Therefore, toxicity tests in the laboratory are important tools to predict the effects of chemical substances in aquatic ecosystems. The aim of this study was to assess the potential hazards of abamectin to the freshwater biota and consequently the possible losses of ecological services in contaminated water bodies. For this purpose, we identified the toxicity of abamectin on daphnids, insects and fish. Abamectin was highly toxic, with an EC50 48h for Daphnia similis of 5.1ngL−1, LC50 96h for Chironomus xanthus of 2.67μgL−1 and LC50 48h for Danio rerio of 33μgL−1.

Evaluation of surface water quality using an ecotoxicological approach: a case study of the Alqueva Reservoir (Portugal)

Background, aim, and scope Freshwater reservoirs can be impacted by several hazardous substances through inputs from agricultural activity, sewage discharges, and groundwater leaching and runoff. The water quality assessment is very important for implementation of the monitoring and remediation programs to minimize the risk promoted by hazardous substances in aquatic ecosystems. Evaluation of the degree of contamination of aquatic environments must not take in account only its chemical characterization but it must be complemented with biological assays, which determine potential toxic effects and allows an integrated evaluation of its effects in populations and aquatic ecosystem communities. The application of this type of strategy has clear advantages allowing a general evaluation of the effects from all the water components, including those due to unknown substances and synergic, antagonistic, or additive effects. There are only a few studies that reported ecotoxicological acute end points, for the assessment of surface water quality, and the relationship among toxicity results and the anthropogenic pollution sources and the seasonal period. The aim of this study was to assess the ecotoxicological characterization of the surface water from Alqueva reservoir (South of Portugal) and to evaluate the influence of anthropogenic sources of pollution and their seasonal variation in its toxicity. The construction of Alqueva reservoir was recently finished (2002) and, to our knowledge, an ecotoxicological assessment of its surface water has not been performed. Because of that, no information is available on the possible impact of pollutants on the biota. The surface water toxicity was assessed using acute and chronic bioassays. The results are to be used for developing a monitoring program, including biological methods.

Constraints in the construction and/or selection of kinetic box models for the uptake of radionuclides and heavy metals by suspended particulate matter

The uptake of radionuclides and heavy metals by suspended particulate matter (SPM) features characteristic times, which actually affect the transport, bioavailability and the final fate of such substances in aquatic ecosystems. Box models represent a useful approach to study this process. Based upon constant reaction rates, they are developed and calibrated from batch experiments. Considerable discrepancy is found in the structure of the proposed multi-reaction models, while traditional experiments cannot account for the intimate detail of the uptake mechanisms. This paper demonstrates that apparently different models are, nevertheless, mathematically equivalent, thereby questioning the physical meaning of transfer coefficients. The mathematical demonstration is a straightforward consequence of the methodology in general use. The equivalence is preserved, for closed and open systems, even if modifications are made to parameters which affect the bioavailability of those pollutants in aquatic environments: SPM concentrations, specific surface area and concentration of competitive ions. Furthermore, the possibilities for further research are discussed since this equivalence can be broken by changes in temperature.

The Analysis of the Seasonal, Spatial, and Compositional Distribution of Humic Substances in a Subtropical Shallow Lake

AbstractThe spatial and temporal distribution of humic substances in aquatic ecosystems can have important effects on ecosystem productivity, negatively impacting primary productivity while positively impacting secondary productivity. In the present investigation, a large shallow lake ecosystem was studied to determine the spatial and seasonal variation of the composition and concentration of humic substances. Concentrations of total dissolved organic matter, humic acid, and fulvic acid were found to display significant spatial distributions (1.3…13.5 mg/L, DOM; 0.1…5.4 mg/L, HA). The distribution is described by using mapping techniques and the analysis of the spatial distribution of the lake. An analysis of the seasonal variations also indicated the dependence of the occurrence of these compounds on meteorological and hydrological conditions.To identify the potential sources of these organic materials, an analysis was made of the ratio of humic and fulvic acid fractions and total DOM. It was found that areas of high DOM concentration coincided with the areas of highest HA percentage of total DOM. Furthermore using the ratio of the normalised concentrations of HA, FA, and residual DOM (< 5000 g/mol) it was found that areas dominated by each are spatially distinct. This confirms the hypothesis that in these shallow lakes, photodegradation and bacterioplankton activity will create a residence time dependent zonation of each component of the total DOM.

On the modelling of the particulate and dissolved fractions of substances in aquatic ecosystems — sedimentological and ecological interactions

In building mass–balance models for different substances in aquatic ecosystems, it is important to differentiate between the dissolved and the particulate phases. This is of fundamental importance both for the predictive power of mass–balance models and for predictions of ecosystem effects. The partition coefficient, K d, defined as the ratio between the particulate and the dissolved concentrations, is often used to get a mathematical representation of the distribution of a substance. In chemical contexts, where the equilibrium between the concentration in dissolved and particulate forms is studied, the K d-concept is important and justifiable to use. K d, however, is not a constant but a variable that depends on the biological, physical and chemical conditions in the water. K d varies both within and among aquatic ecosystems. In this paper, we demonstrate that the K d-concept is problematic for interpretation of field data, and should be used with great caution in dynamic mass–balance models. We show that it would be more appropriate in modelling contexts to use the particulate fraction, PF, defined as the ratio of particulate bound concentration to the total concentration. PF is a target variable in dynamic models since it directly, and not indirectly as K d, describes and distributes the mass flows of substances. Two more arguments support the usage of PF. First, it is very difficult to get reliable data on lake characteristic K d-values since, by definition, K d includes SPM (suspended particulate matter), which has a large inherent within-system variability. We demonstrate that PF generally shows a lower within-system variability than K d. Second, the formulation of K d as a ratio may lead to statistical inferences, with spurious correlations that explain part of the relationship between K d and environmental variables. This is a mathematical inevitability, which is generally disregarded in K d-models. One way to overcome these problems is to use PF and not K d, when relationships with environmental variables are studied and modelled.

Estimating ecotoxicological risk and impact using indigenous aquatic microbial communities

Emphasis has increased on accuracy in predicting the effect that anthropogenic stress has on natural ecosystems. Although toxicity tests low in environmental realism, such as standardized single species procedures, have been useful in providing a certain degree of protection to human health and the environment, the accuracy of such tests for predicting the effects of anthropogenic activities on complex ecosystems is questionable. The use of indigenous communities of microorganisms to assess the hazard of toxicants in aquatic ecosystems has many advantages. Theoretical and practical aspects of microbial community tests are discussed, particularly in related to widely cited problems in the use of multispecies test systems for predicting hazard. Further standardization of testing protocols using microbial colonization dynamics is advocated on the basis of previous studies, which have shown these parameters to be useful in assessing risk and impact of hazardous substances in aquatic ecosystems.

The role of volatilization in removing polycyclic aromatic hydrocarbons from aquatic environments

The movement of organic contaminants from water to the atmosphere can be important in reducing concentrations of foreign substances in aquatic ecosystems (HILL et al. 1976, DILLING 1977, MACKAY and LEINONEN 1975). Polycyclic aromatic hydrocarbons (PAH), a class of chemical produced in the combustion and pyrolysis of organic fuels, possess properties which suggest that their volatility in solution may be significant (MACKAY and WOLKOFF 1973). Since many PAH are potent carcinogens, a knowledge of their persistence, transport, and fate in aquatic environments is critical. The objective of this paper is to determine the relative volatility of two to five ring PAH structures in water, and estimate the importance of the volatilization process in removing PAH from aquatic environments. The theoretical basis for describing the transfer of vola: tile substances across an air-water interface has been succinctc}y detailed (LISS 1973, LISS and SLATER 1974). The rate of the process under a given set of conditions is described as a simple first order exponential decay with rate constant KL/depth. K L, the overall mass transfer coefficient, has units of distance time (such as cm/hr) and three components: kg, k I and H, related by the expression