Contamination Of Aquatic Ecosystems Research Articles

Future water quality monitoring: improving the balance between exposure and toxicity assessments of real-world pollutant mixtures

Environmental water quality monitoring aims to provide the data required for safeguarding the environment against adverse biological effects from multiple chemical contamination arising from anthropogenic diffuse emissions and point sources. Here, we integrate the experience of the international EU-funded project SOLUTIONS to shift the focus of water monitoring from a few legacy chemicals to complex chemical mixtures, and to identify relevant drivers of toxic effects. Monitoring serves a range of purposes, from control of chemical and ecological status compliance to safeguarding specific water uses, such as drinking water abstraction. Various water sampling techniques, chemical target, suspect and non-target analyses as well as an array of in vitro, in vivo and in situ bioanalytical methods were advanced to improve monitoring of water contamination. Major improvements for broader applicability include tailored sampling techniques, screening and identification techniques for a broader and more diverse set of chemicals, higher detection sensitivity, standardized protocols for chemical, toxicological, and ecological assessments combined with systematic evidence evaluation techniques. No single method or combination of methods is able to meet all divergent monitoring purposes. Current monitoring approaches tend to emphasize either targeted exposure or effect detection. Here, we argue that, irrespective of the specific purpose, assessment of monitoring results would benefit substantially from obtaining and linking information on the occurrence of both chemicals and potentially adverse biological effects. In this paper, we specify the information required to: (1) identify relevant contaminants, (2) assess the impact of contamination in aquatic ecosystems, or (3) quantify cause–effect relationships between contaminants and adverse effects. Specific strategies to link chemical and bioanalytical information are outlined for each of these distinct goals. These strategies have been developed and explored using case studies in the Danube and Rhine river basins as well as for rivers of the Iberian Peninsula. Current water quality assessment suffers from biases resulting from differences in approaches and associated uncertainty analyses. While exposure approaches tend to ignore data gaps (i.e., missing contaminants), effect-based approaches penalize data gaps with increased uncertainty factors. This integrated work suggests systematic ways to deal with mixture exposures and combined effects in a more balanced way, and thus provides guidance for future tailored environmental monitoring.

2,4-Dichlorophenoxyacetic acid herbicide effects on zebrafish larvae: development, neurotransmission and behavior as sensitive endpoints.

Assessment of pesticides toxicity using zebrafish early life stages is relevant for aquatic systems safety. This study aimed to evaluate the short-term effects of 2,4-dichlorophenoxyacetic acid (2,4-D) on zebrafish (Danio rerio) embryos from 3h post fertilization to 96hpf. A set of 2,4-D concentrations ranging from 0.32 to 80mg/L were tested and median lethal concentration (LC50) at 96-h was calculated as 2.86mg/L. A sub-teratogenic concentrations range from 0.02 to 0.8mg/L was then used to assess effects at ontogenic, biochemical, and behavioral levels. The main developmental defects were tail deformities and pericardial edema at concentrations equal or above 0.32mg/L. Cholinesterase activity (at 96hpf) and larvae swimming behavior (at 120hpf) were affected even at the lowest tested dose (0.02mg/L). The behavior analysis was a sensitive endpoint, with a decrease in the swimming distance of exposed larvae during light period. The effect of 2,4-D in ChE was translated by an inhibition of the enzyme activity in all treated groups. These findings demonstrate that 2,4-D can alter the cholinergic system by affecting ChE activity which may be involved in the locomotion reduction of exposed larvae and emphasize the potential of neurotransmission and behavioral endpoints as early warning signs of herbicides contamination in aquatic ecosystems.

Applying AQUATOX for the ecological risk assessment coastal of Black Sea at small industries around Samsun, Turkey

The Black Sea receives uncontrolled and irregular fresh water for the production of thermal and hydro energy and the use of coastal areas. Transportation, untreated domestic, industrial and agricultural wastes, fall out into rivers or directly into the sea. In order to discuss and assess further pollution loads and possible management techniques for the coastal pollution problems of Black Sea, different mathematical modeling techniques can be used. Mathematical models are also useful tools to save time and money, as well as to help solve ecological problems more easily and to select an appropriate management alternative for sustainable management. AQUATOX is one of the affinity models for aquatic ecosystems. AQUATOX seeks to determine the fate of various pollutants, such as nutrients and organic chemicals, and their impact on the ecosystem, including fish, invertebrates and aquatic plants. In this study, samples collected from five different points in the organized industrial zone in Samsun province in August and December 2017. pH, conductivity, dissolved oxygen, chemical oxygen demand, total organic carbon, total-N, total-P were carried out in water samples. The model was run for dissolved oxygen, total phosphorus and total nitrogen from the measured parameters, and the results were evaluated by adding to program inputs. The model was run to determine the contribution of contamination in aquatic ecosystems to the assessment of ecological risk. The models are thought to be an essential structure for ecosystems to determine their ecological protection levels.

Environmental causes and reproductive correlates of mercury contamination in European pond turtles (Emys orbicularis)

Assessing Hg contamination in aquatic ecosystems is difficult because wetlands are part of large and complex networks, and potential sources of Hg contamination are highly diverse. To investigate environmental determinants of Hg contamination, we studied one of the largest continental French wetlands structured as a dense network of artificial ponds. Such context allows to investigate the influence of pond characteristics on Hg contamination in an area relatively disconnected from direct sources of pollution. We relied on a bioindicator organism, the European pond turtle (Emys orbicularis) to assess Hg contamination in a relatively large number of sites (N > 255 turtles from 15 ponds sampled in 2016 and 2017). Non-invasive sampling in the claws of turtles show that Hg concentrations were not related to their sex or size, but we found an effect of age (1.62 ± 0.20 in juveniles and 2.21 ± 0.06 µg g−1 dw in adults), suggesting that turtles do bioaccumulate Hg through their life. Turtle Hg was different between ponds, and we found that pond age and pond usage (draining events linked to pond maintenance) were the main environmental determinants of Hg concentrations in turtles. Finally, and more importantly, our dataset allowed us to highlight potential negative effect of Hg concentrations on the proportion of reproductive females, suggesting an influence of Hg on reproductive mechanisms in this species. This result indicates that Hg contamination, even in absence of direct and strong sources of pollution, may have a critical impact on reproduction and thus the persistence of a long-lived vertebrate.

Inducible pesticide tolerance in Daphnia pulex influenced by resource availability.

Pesticides are a ubiquitous contaminant in aquatic ecosystems. Despite the relative sensitivity of aquatic species to pesticides, growing evidence suggests that populations can respond to pesticides by evolving higher baseline tolerance or inducing a higher tolerance via phenotypic plasticity. While both mechanisms can allow organisms to persist when faced with pesticides, resource allocation theory suggests that tolerance may be related to resource acquisition by the organism. Using Daphnia pulex, we investigated how algal resource availability influenced the baseline and inducible tolerance of D. pulex to a carbamate insecticide, carbaryl. Individuals reared in high resource environments had a higher baseline carbaryl tolerance compared to those reared in low resource environments. However, D. pulex from low resource treatments exposed to sublethal concentrations of carbaryl early in development induced increased tolerance to a lethal concentration of carbaryl later in life. Only individuals reared in the low resource environment induced carbaryl tolerance. Collectively, this highlights the importance of considering resource availability in our understanding of pesticide tolerance.

Bioaccumulation of heavy metals in common reed (Phragmites australis) growing spontaneously on highly contaminated mine tailing ponds in Serbia and potential use of this species in phytoremediation

Heavy metal contamination of aquatic ecosystems directly threatens the health, production and biodiversity of aquatic and surrounding terrestrial ecosystems, and it represents a serious global problem. Metal extraction during ore processing produces large amounts of wastes that remain in tailings at the mining site. Fine waste particles represent a long-term source of potentially toxic metals that can be released into the ground and surface water as a result of their progressive chemical weathering. Aquatic macrophythes have a major role in absorption and accumulation of heavy metals and thereby in natural water purification. The presence of naturally growing plants on mine tailing ponds indicates their tolerance of heavy metal pollution and suggests a possible role for them in phytoremediation. In the present study, we analysed the concentrations of heavy metals (Fe, Mn, Ni, Zn, Pb, Cd, Co, Cu) in Phragmites australis plants growing spontaneously in shallow water of several mine tailing ponds. The aims of the study were to define chemical properties of the mine spoils, determine the concentrations of heavy metals in different plant organs and assess the phytoremediation potential of common reed. The investigated sediments were notably rich in both total and available forms of Fe, Pb, Zn and Cu, with their upper concentrations close to phytotoxic levels. The greatest amounts of almost all of the investigated metals in plants from all three mine tailing ponds were found in the roots, with their concentrations positively correlated with the amounts of their available forms in the corresponding sediment. The far higher metal concentrations in the roots in comparison with other plant organs clearly indicate that the metals were strongly sequestrated within root cortical tissues and were not transferred across the endodermis. Taken altogether, the presence of the greatest amounts of metals in roots, high bioaccumulation factor and low translocation factor show that P. australis is an excluder plant species with a good phytostabilisation potential. As such, it might be efficiently used in rhizofiltration of wastewaters.

Identification and quantification of macro- and microplastics on an agricultural farmland

Microplastic contamination of aquatic ecosystems is a high priority research topic, whereas the issue on terrestrial ecosystems has been widely neglected. At the same time, terrestrial ecosystems under human influence, such as agroecosystems, are likely to be contaminated by plastic debris. However, the extent of this contamination has not been determined at present. Via Fourier transform infrared (FTIR) analysis, we quantified for the first time the macro- and microplastic contamination on an agricultural farmland in southeast Germany. We found 206 macroplastic pieces per hectare and 0.34 ± 0.36 microplastic particles per kilogram dry weight of soil. In general, polyethylene was the most common polymer type, followed by polystyrene and polypropylene. Films and fragments were the dominating categories found for microplastics, whereas predominantly films were found for macroplastics. Since we intentionally chose a study site where microplastic-containing fertilizers and agricultural plastic applications were never used, our findings report on plastic contamination on a site which only receives conventional agricultural treatment. However, the contamination is probably higher in areas where agricultural plastic applications, like greenhouses, mulch, or silage films, or plastic-containing fertilizers (sewage sludge, biowaste composts) are applied. Hence, further research on the extent of this contamination is needed with special regard to different cultivation practices.

Analytical Aspects of the Determination of the Total Concentration and Differentiation of Anthropogenic and Biogenic Hydrocarbons in Aquatic Ecosystems

Problems of determining the total concentration of anthropogenic and biogenic hydrocarbons in aquatic ecosystems are discussed. Hydrocarbons accumulating in water samples and bottom sediments are different in composition. Polycyclic aromatic hydrocarbons, resistant to degradation, are concentrated in bottom sediments; their amount in the aquatic environment is insignificant. It is shown that the level of oil pollution can be adequately assessed only taking into account the biogenic (natural) hydrocarbon background of water and bottom sediments of the investigated objects. A unified pattern for the analysis of water and bottom sediments for assessing the level of oil contamination of aquatic ecosystems taking into account the transformation of oil components and the origin of hydrocarbons of different genesis is proposed. A possibility of the differentiation of petroleum and biogenic hydrocarbons in aquatic ecosystems by the concentration of chlorophyll in them is substantiated.

Effect of phthalates on development, reproduction, fat metabolism and lifespan in Daphnia magna

Phthalates are used as plasticizers to increase durability, resistivity and flexibility of plastic materials. The commonly used phthalate, diethylhexyl phthalate (DEHP) is used in different plastic materials like food packaging, toys and medical devices. DEHP has been linked to different toxicities in humans as well as in animals, and as a consequence other phthalates, including dibutyl phthalate (DBP) and diethyl phthalate (DEP) are being introduced. The increased use of phthalates has resulted in contamination of aquatic ecosystem and it directly threatens the aquatic life. In this study, we analyzed the effects of three phthalates DEHP, DEP and DBP using freshwater organism Daphnia magna. Although, exposure of the three phthalates at 1 and 10 μM did not result any lethality and hatching delay, the chronic exposure for 14 days resulted in reduction of body length. There was enhanced fat accumulation on exposure to all the phthalates, as indicated by oil red O staining. qRT-PCR analysis of genes involved in fat metabolism suggests that the increase in fat content could be due to inhibition of absorption and catabolism of fatty acids. Reproduction analysis showed that DBP and DEP did not alter fecundity but surprisingly, DEHP at 1 μM increased reproduction by 1.5 fold compared to control group. Phthalates also showed negative effect on lifespan as DEP at 10 μM and DBP at both 1 and 10 μM significantly reduced the lifespan. Our data indicates that along with the banned phthalate DEHP, the other substitute phthalates DEP and DBP could also have detrimental effect on aquatic organisms.

Low-density polyethylene microplastics as a source and carriers of agrochemicals to soil and earthworms

Environmental contextMicroplastics, long recognised as contaminants in aquatic ecosystems, are increasingly of environmental concern for terrestrial ecosystems. This study focuses on the potential of microplastics to act as carriers of agrochemicals and the subsequent effects on soil biota. The results indicate the need for further studies into how soil properties influence both the degradation of microplastics and their role as pollutant carriers. AbstractMicroplastics (MPs) are of environmental concern to marine ecosystems owing to the evidence of their presence in and adverse effects on organisms, but studies to address this problem on soils and its biota are scarce. Several questions can arise related to this major environmental problem and its impact on terrestrial ecosystems, mainly, whether MPs can transport contaminants (e.g. pesticides) to the soil matrix and if they can be a carrier of pesticides to soil biota. To contribute to the understanding of these issues, earthworms (Eisenia fetida) were exposed for 14 days to soil containing two different sized MPs (5mm and 0.25 µm–1mm) that were either previously sprayed or not with chlorpyrifos (CPF). Acetylcholinesterase (AChE) activity and thiobarbituric acid reactive substances (TBARS) were measured to track the exposure of the earthworms to MPs, both non-sprayed and sprayed with CPF. The behaviour of the earthworms in the test containers and the movement of MPs in the soil were assessed. The concentration of CPF in soil at the end of the experiment differed between the treatments with MPs of different sizes (17.9ngg−1 and 2442ngg−1 for large and small MPs, respectively). Despite the ability of the MPs to release CPF to the soil, the earthworms avoided the contaminated MPs at the highest contaminant level. At a lower concentration of CPF (large MPs), the earthworms avoided the MPs, but the contact time with contaminated soil was higher, as shown by the enhanced level of TBARs and AChE inhibition. However, no evidence of MPs uptake was recorded, thus it was not demonstrated that MPs can be carriers of pesticides to earthworms.

The environmental effects of microplastics on aquatic ecosystems

Contamination of aquatic ecosystems by plastics under 5 mm in size, which are classified as microplastics (MPs), is becoming increasingly serious, and research on the ecotoxicity of MPs is needed. In this study, we aimed to present solutions to the problem of MPs through a review of the current state of research on the definition of MPs, usage, leakage, toxicity, and domestic and overseas circulation of plastics. Long-term exposure to MPs results in ecotoxicity. MPs not only deliver chemical substances within organisms, but also act as mediators for chemicals or other contaminants in aquatic environments. Co-exposure to MPs and chemical contaminants has been reported to increase toxicity in several organisms.

Comparative toxicity of selected PAHs in rainbow trout hepatocytes: genotoxicity, oxidative stress and cytotoxicity

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants in aquatic ecosystems, which may have potentially toxic effects on organisms. In this study occurrence of DNA strand breaks, oxidative stress, and cytotoxicity were investigated in rainbow trout hepatocytes following in vitro exposure for 24 h to four PAHs (0.01–10 µM): naphthalene, fluoranthene, pyrene, and benzo[a]pyrene (B[a]P). The exposed hepatocytes were analyzed for DNA strand breaks using the comet assay and for antioxidant status by measuring intracellular glutathione (GSH) content using the fluorescent probe mBCl. The cytotoxicity of PAHs was assessed using the fluorescent probe CFDA-AM. The results showed that fluoranthene, pyrene, and B[a]P were genotoxic at all exposure concentrations, whereas naphthalene was genotoxic at concentrations ≥0.1 µM. All treatments reduced the intracellular concentrations of GSH for all four PAHs, except 10 µM of B[a]P, suggesting that some level of oxidative stress was present. The cytotoxic effect was observed for naphthalene at concentrations ≥0.1 µM and pyrene at all exposure concentrations, whereas fluoranthene and B[a]P were not cytotoxic at the tested concentrations. The study shows that low-molecular-weight PAHs may cause DNA strand breaks as high-molecular-weight PAHs do in fish tissue. In addition, two- to five-ring PAHs can induce oxidative stress and cytotoxicity.

Acute exposure to boron in Nile tilapia (Oreochromis niloticus): Median-lethal concentration (LC50), blood parameters, DNA fragmentation of blood and sperm cells

Recently, Boron (B) contamination of aquatic ecosystem has received considerable critical attention due to its toxic effects at high concentrations on plants as well as animals. Previous studies on toxic effects of B have not dealt with DNA damages in blood and sperm cells of Nile tilapia (Oreochromis niloticus), together with blood parameters. This study consisted of two successive experiments purposes to determine these findings, including the median-lethal concentration (LC50) of B for Nile tilapia. In the first one, at 96 h, LC50 of B for Nile tilapia was 141.42 mg L−1 B. In the second one, Nile tilapia were treated with five elevated B concentrations (1, 5, 25, 50 and 100 mg L−1 B) and hematological, serum biochemical parameters, and DNA damages of Nile tilapia in these treatments were determined comparing with the control after 14 days of exposure. Hematological parameters (red blood cell count, hematocrit, and hemoglobin) were similar to each other in all groups while serum biochemical parameters (glucose, total protein, cholesterol, alkaline phosphatase, glutamic oxaloacetic transaminase, and glutamic pyruvic transaminase) in B treatments, especially in 50 and 100 mg L−1 B groups, were found significantly higher (P < 0.05). DNA fragmentation was detected in all blood cells in ≥25 mg L−1 B treatments, while all sperm cells in 100 mg L−1 B treatments. These results demonstrated the harmful effects of B at high concentration (50 and 100 mg L−1 B) on the DNA integrity of blood and sperm cells, and also the serum biochemical parameters.

A combined experimental and modeling study to evaluate pH-dependent sorption of polar and non-polar compounds to polyethylene and polystyrene microplastics

BackgroundThe contamination of aquatic ecosystems with both anthropogenic pollutants and particles in particular (microscopic) plastic debris items is of emerging concern. Since plastic particles can accumulate contaminants and potentially facilitate their transport, it is important to properly investigate sorption mechanisms. This is especially required for a large variety of chemicals that can be charged under environmental conditions and for which interactions with particles may hence go beyond mere partitioning.ResultsIn this study, sorption experiments with two types of microplastic particles (polyethylene and polystyrene) and 19 different contaminants (pesticides, pharmaceuticals, and personal care products) were performed at three different pH values. We could show that sorption to plastic particles is stronger for hydrophobic compounds and that neutral species usually contribute more to the overall sorption. Bulk partitioning coefficients were in the same order of magnitude for polyethylene and polystyrene. Furthermore, our results confirm that partition coefficients for polar compounds can only be accurately determined if the solid-to-liquid ratio in batch experiments is more than 6–7 orders of magnitude higher than any plastic concentration detected in the environment. Consequently, only a minor fraction of pollutants in water bodies is associated with microplastics.ConclusionsAlthough neutral species primarily dominate the overall sorption, hydrophobic entities of ionic species cannot be neglected for some compounds. Notwithstanding, our results show that since microplastic concentrations as currently observed in the environment are very low, they are only a relevant sorbent for strongly hydrophobic but not for polar compounds.

THE CHANGES OF ENVIRONMENT AND AQUATIC ORGANISM BIODIVERSITY IN EAST COAST OF SIDOARJO DUE TO LAPINDO HOT MUD

Lapindo hot mud to overflow and flood the east coast of Sidoarjo for 9 years has causedchanges in environmental factors, particularly aquatic ecosystems environment. This has an impact onbiodiversity of aquatic ecosystems in the eastern coastal Sidoarjo. This study aims to determine the quality ofaquatic ecosystems on the east coast of Sidoarjo contaminated by Lapindo hot mud and the impact onbiodiversity of aquatic organism. Data taken from 5 station consists of wetlands ecosystems, river, brackishwater ponds, estuaries, and coastal covering area districts of Porong, Jabon, Tanggulangin, and Sidoarjo, EastJava, Indonesia. Determination of stations and substations did purposively based on distribution mapsLapindo hot mud. Data obtained in the form of physical and chemical parameters of waters, biodiversity ofaquatic organism analyzed descriptively and quantitatively, and compared as well as the quality standard.The results showed contamination of aquatic ecosystems by Lapindo hot mud has led to changesenvironment factors and declining biodiversity of the aquatic organism in the eastern coastal of Sidoarjo.

A comparison of factors affecting the small-scale distribution of mercury from artisanal small-scale gold mining in a Zimbabwean stream system

Artisanal small-scale gold mining (ASGM) operations use mercury liberally in the gold extraction process and account for approximately one quarter of the anthropogenic mercury consumption worldwide. ASGM activities are concentrated in many impoverished and poorly regulated countries such as Zimbabwe, resulting in a number of negative impacts to health and the environment. To examine levels of mercury contamination in one such geographic locality, sediment and tailing samples were collected in a heavily mined watershed in southern Zimbabwe from May–June 2015. Samples were collected from multiple points within the stream system, as well as from around six stamp mills and a single industrial mine in the watershed. GPS point location data were taken for mining operations and sampling sites to examine the spatial patterns of mercury concentration. Data were first analyzed using linear regression and development of a MARS model, followed by application of an ANCOVA model to assess the relationship among mercury concentrations and percent organic material, distance downstream, and distance from potential contamination source. Mercury concentrations within the study area ranged from 6 to 1541 μg/kg dw (mean 142 μg/kg dw). Analyses of mercury concentrations indicated a positive relationship with percent organic material but a negative relationship with distance downstream and distance from potential contamination source. Results from this study help elucidate the relationship between gold production and the spatial scale of mercury contamination in aquatic ecosystems in Africa. These data may lead to a better understanding of the relationship between mercury use and community health, which may aid both the local and global communities in regulating mercury contamination of the environment.

Effect of oxygen, nitrate and aluminum addition on methylmercury efflux from mine-impacted reservoir sediment

Extensive contamination of aquatic ecosystems with mercury (Hg) has led to a growing interest in developing in situ management strategies to repress Hg bioaccumulation in aquatic biota in reservoirs. This study used experimental chamber incubations to assess the impact of three potential treatments, oxygen addition, nitrate addition and aluminum addition, to reduce the flux of toxic methylmercury (MeHg) from profundal reservoir sediment. The study sites, Almaden Lake and Guadalupe Reservoir, are located downstream of the historic New Almaden mining district in Santa Clara Valley, California, USA. In the first experiment (experiment 1), replicate chambers from both sites were incubated sequentially under aerobic and anaerobic conditions. At both sites, mean anaerobic fluxes of MeHg were higher than aerobic fluxes (Almaden: 11.0 vs. −2.3 ng/m2·d; Guadalupe: 22.3 vs 5.5 ng/m2·d), and anaerobic MeHg fluxes correlated with rates of sediment sulfate uptake, highlighting the linkage between MeHg production and microbial sulfate reduction. Under aerobic conditions, sediment from Guadalupe Reservoir released Hg(II), iron and sulfate, suggesting the oxidative dissolution of Hg-bearing sulfide minerals. A follow-up study at Almaden Lake (experiment 2) found that mean MeHg fluxes under aerobic conditions (5 ng/m2·d) and anoxic (nitrate-rich) conditions (1.7 ng/m2·d) were lower than anaerobic conditions (174 ng/m2·d), but aluminum addition had little effect (105 ng/m2·d) on MeHg flux. In both anaerobic and aluminum treated chambers, MeHg flux turned negative during the second half of the incubation, suggesting that highly reduced, sulfidic conditions lowered net methylation, possibly by enhancing demethylation or repressing Hg(II) bioavailability for methylation.

Biotic disturbance mitigates effects of multiple stressors in a marine benthic community

AbstractPredicting how communities respond to multiple stressors is challenging because community dynamics, stressors, and animal–stressor interactions can vary with environmental conditions, including the intensity of natural disturbance. Nevertheless, environmental laws stipulate that we predict, measure, and mitigate the ecological effects of some human‐induced stressors in the environment, including chemical contaminants in aquatic ecosystems. We conducted an experiment in Antarctica to test how a marine soft‐sediment benthic community responded to multiple chemical contaminants and biotic disturbance by manipulating organic carbon enrichment, copper metal contamination, access by large epibenthic animals, and their interaction. Biotic disturbance caused mainly by large echinoderms was manipulated with exclusion cages and cage‐control treatments. Colonization patterns in sediment trays revealed that total infaunal abundance and arthropods decreased with toxic Cu (0, 100, and 500 ppm) and total organic carbon (TOC; 0%, 1%, and 2% by wt), as enrichment produced increasing levels of sediment hypoxia/anoxia. Annelids and echinoderms decreased with Cu but increased with TOC because many colonizing polychaete worms, seastars, and epifaunal sea urchins were deposit feeders. Bioturbation by echinoderms disturbed sediments, leading to a substantial decline in total infaunal abundance in uncontaminated sediments, but also an increase in the relative abundance in contaminated sediments, as bioturbation mitigated the effect of both chemical stressors. Biotic disturbance also caused substantial shifts in the species composition of the invertebrate assemblages and an overall increase in species diversity. Prior predictions about the response of benthic marine phyla to the separate and combined effects of Cu and carbon enrichment appear robust to variation in natural biotic disturbance.

Effects of wind-wave disturbances on adsorption and desorption of tetracycline and sulfadimidine in water-sediment systems.

Wind-wave disturbances frequently disperse sediment particles into overlying water, which facilitates the adsorption and desorption of contaminants in aquatic ecosystems. Tetracycline (TC) and sulfadimidine (SM2) are common antibiotics that are frequently found in aquatic environments. This study utilized microcosms, comprising sediment and water from Lake Taihu, China, to examine the adsorption and desorption of TC and SM2 under different wind-wave disturbances in a shallow lake environment. The adsorption experiments were conducted with three different concentrations (1, 5, 10mg/L) of TC and SM2 in the overlying water, and two different (background and strong) wind-wave conditions for 72h. Subsequently, four microcosms were employed in a 12-h desorption study. Analysis of adsorption progress showed that TC concentration in the overlying water decreased quickly, while SM2 remained almost constant. In the desorption experiments, SM2 released to the overlying water was an order of magnitude greater than TC. These results indicate that sediment particles strongly adsorb TC but weakly adsorb SM2. Compared to background conditions, the strong wind-wave conditions resulted in higher concentrations of TC and SM2 in sediment and facilitated their migration to deeper sediment during adsorption, correspondingly promoting greater release of TC and SM2 from sediment particles into the overlying water during desorption.

A case study and a meta-analysis of seasonal variation in fish mercury concentrations.

Mercury contamination in aquatic ecosystems is a concern due to health risks of consuming fish. Fish mercury concentrations are highly variable and influenced by a range of environmental factors. However, seasonal variation in mercury levels are typically overlooked when monitoring fish mercury concentrations, establishing consumption advisories, or creating accumulation models. Temporal variation in sampling could bias mercury concentration estimates of accumulation potential. Thus, the objectives of this study were to first evaluate seasonal variation of largemouth bass (Micropterus salmoides) axial muscle mercury concentration from two Iowa, USA impoundments. Second, we conducted a meta-analysis to evaluate if seasonal variation in mercury concentration is dependent upon mean mercury concentration, waterbody type, or fish trophic level or mean length. Largemouth bass were collected four times between May and October (24-36 fish per month) from Twelve Mile (2013) and Red Haw (2014) lakes. Largemouth bass axial muscle mercury concentrations were variable within and between lakes, ranging from undetectable ( < 0.05 mg/kg) to 0.54 mg/kg. Largemouth bass mercury concentrations were similar across months in Twelve Mile but varied temporally in Red Haw and were highest in July, intermediate in May and September, and lowest during October. Results of the meta-analysis suggest that seasonal variation in mercury concentrations is more likely to occur as mean mercury concentration of the population increases but is unrelated to waterbody type, trophic status, and fish size. Understanding seasonal variation in fish mercury concentrations will aid in the development of standardized sampling programs for long-term monitoring programs and fish consumption advisories.