Effects of simulated CO₂ escape from sediments on the development of midge Chironomus riparius

The sediment of a river having ''good ecological status" turned out to be toxic to midge Chironomus riparius larvae: Implication for environmental monitoring?

Globally, monitoring of the surface waters is largely limited to the physico-chemical analysis of water in rivers and lakes. Sediment state in the aquatic systems including sediment chemical content or the structure and diversity of benthic communities or ecotoxicological studies with natural sediments remains largely overlooked by the monitoring programs. Hence we assessed the potential toxicity of three riverine sediments on the life-cycle traits (emergence and reproduction) of midge Chironomus riparius via an ecotoxicological testing method over two generations (according to OECD test 233 guidelines). In addition, the riverine sediments were spiked with polyamide (nylon) microplastic particles (1 g kg-1) to analyze an additive effect of microplastic on the sediment toxicity. As model river systems, three rivers (Karchaghbyur, Gavaraget, Argichi) in the Lake Sevan basin (Armenia) were selected. Results of ecotoxicity testing were compared with the indices of water quality (derived from the physico-chemical analysis) and the indices of the ecological status of the rivers (derived from the analysis of benthic communities). The results of testing demonstrated an unexpectedly low emergence of midges after the first generation exposed to the sediment of the river having ''good ecological status'' - the Argichi. Sediments of the Karchaghbyur and Gavaraget rivers impeded the emergence and reproduction of midges after the second generation. An addition of polyamide particles to the sediments did not significantly affect the life-cycle traits of C. riparius indicating the primary effect of the sediments' condition. The discrepancy of biotesting result with that of the other two methods (which indicated ''average water quality'' and "good ecological status") underlies the importance of designing more comprehensive monitoring programs for better assessment and protection of aquatic systems and resources.

Contribution of sediment contamination to multi-stress in lowland waters

Water bodies in densely populated lowland areas are often impacted by multiple stressors. At these multi-stressed sites, it remains challenging to quantify the contribution of contaminated sediments. This study, therefore, aimed to elucidate the contribution of sediment contamination in 16 multi-stressed drainage ditches throughout the Netherlands. To this end an adjusted TRIAD framework was applied, where 1) contaminants and other variables in the sediment and the overlying water were measured, 2) whole-sediment laboratory bioassays were performed using larvae of the non-biting midge Chironomus riparius, and 3) the in situ benthic macroinvertebrate community composition was determined. It was hypothesized that the benthic macroinvertebrate community composition would respond to all jointly present stressors in both water and sediment, whereas the whole-sediment bioassays would only respond to the stressors present in the sediment. The benthic macroinvertebrate community composition was indeed related to multiple stressors in both water and sediment. Taxa richness was positively correlated with the presence of PO₄-P in the water, macrophyte cover and some pesticides. Evenness, the number of Trichoptera families and the SPEAR_pesticides were positively correlated to the C:P ratios in the sediment, whilst negative correlations were observed with various contaminants in both the water and sediment. The whole-sediment bioassays with C. riparius positively related to the nutrient content of the sediment, whereas no negative relations to the sediment-associated contaminants were observed, even though the lowered SPEAR_pesticides index indicated contaminant effects in the field. Therefore, it was concluded that sediment contamination was identified as one of the various stressors that potentially drove the benthic macroinvertebrate community composition in the multi-stressed drainage ditches, but that nutrients may have masked the adverse effects caused by low and diverse sediment contaminants on C. riparius in the bioassays.

A GIS-Based Spatiotemporal Impact Assessment of Droughts in the Hyper-Saline Urmia Lake Basin on the Hydro-Geochemical Quality of Nearby Aquifers

Urmia Lake is a hyper-saline lake in northwestern Iran that has been drying up since 2005. The main objective of this study was to evaluate the water quality in aquifers that are the main source of fresh water for the eastern plains Urmia Lake, which has been drying up due to intensive land use/cover changes and climate change. We evaluated hydro-geochemical data and factors contributing to aquifer pollution and quality variation for nine aquifers in the vicinity of Urmia Lake during the dry and wet seasons from 2000–2020. Our methodology was based on the analysis of 10 years of data from 356 deep and semi-deep wells using GIS spatial analysis, multivariate statistical analysis, and agglomerative hierarchical clustering. We developed a Water Quality Index (WQI) for spatiotemporal assessment of the status of the aquifers. In doing so, we highlighted the value of combining Principal Component Analysis (PCA), WQI, and GIS to determine the hydro-geochemical attributes of the aquifers. We found that the groundwater in central parts of the study area was unsuitable for potable supplies. Anthropogenic sources of contamination, such as chemical fertilizers, industrial waste, and untreated sewage water, might be the key factors causing excessive concentrations of contaminants affecting the water quality. The PCA results showed that over 80% of the total variance could be attributed to two principal factors for most aquifers and three principal factors for two of the aquifers. We employed GIS-based spatial analysis to map groundwater quality in the study area. Based on the WQI values, approximately 48% of groundwater samples were identified as poor to unsuitable for drinking purposes. Results of this study provide a better hydro-geochemical understanding of the multiple aquifers that require preventive action against groundwater damage. We conclude that the combined approach of using a multivariate statistical technique and spatial analysis is effective for determining the factors controlling groundwater quality.

The Butterfly Effect: Mild Soil Pollution with Heavy Metals Elicits Major Biological Consequences in Cobalt-Sensitized Broad Bean Model Plants

Among the heavy metals (HMs), only cobalt induces a polymorphic response in Vicia faba plants, manifesting as chlorophyll morphoses and a ‘break-through’ effect resulting in the elevated accumulation of other HMs, which makes Co-pretreated broad bean plants an attractive model for investigating soil pollution by HMs. In this study, Co-sensitized V. faba plants were used to evaluate the long-term effect of residual industrial pollution by examining biochemical (H₂O₂, ascorbic acid, malondialdehyde, free proline, flavonoid, polyphenols, chlorophylls, carotenoids, superoxide dismutase) and molecular (conserved DNA-derived polymorphism and transcript-derived polymorphic fragments) markers after long-term exposure. HM-polluted soil induced a significantly higher frequency of chlorophyll morphoses and lower levels of nonenzymatic antioxidants in Co-pretreated V. faba plants. Both molecular markers effectively differentiated plants from polluted and control soils into distinct clusters, showing that HMs in mildly polluted soil are capable of inducing changes in DNA coding regions. These findings illustrate that strong background abiotic stressors (pretreatment with Co) can aid investigations of mild stressors (slight levels of soil pollution) by complementing each other in antioxidant content reduction and induction of DNA changes.

Scenario-based analysis of the impacts of lake drying on food production in the Lake Urmia Basin of Northern Iran

In many parts of the world, lake drying is caused by water management failures, while the phenomenon is exacerbated by climate change. Lake Urmia in Northern Iran is drying up at such an alarming rate that it is considered to be a dying lake, which has dire consequences for the whole region. While salinization caused by a dying lake is well understood and known to influence the local and regional food production, other potential impacts by dying lakes are as yet unknown. The food production in the Urmia region is predominantly regional and relies on local water sources. To explore the current and projected impacts of the dying lake on food production, we investigated changes in the climatic conditions, land use, and land degradation for the period 1990–2020. We examined the environmental impacts of lake drought on food production using an integrated scenario-based geoinformation framework. The results show that the lake drought has significantly affected and reduced food production over the past three decades. Based on a combination of cellular automaton and Markov modeling, we project the food production for the next 30 years and predict it will reduce further. The results of this study emphasize the critical environmental impacts of the Urmia Lake drought on food production in the region. We hope that the results will encourage authorities and environmental planners to counteract these issues and take steps to support food production. As our proposed integrated geoinformation approach considers both the extensive impacts of global climate change and the factors associated with dying lakes, we consider it to be suitable to investigate the relationships between environmental degradation and scenario-based food production in other regions with dying lakes around the world.

Chironomus sancticaroli (Diptera, Chironomidae) as a Sensitive Tropical Test Species in Laboratory Bioassays Evaluating Metals (Copper and Cadmium) and Field Testing

Despite that chironomids are the most widely used benthic insect test species worldwide, little research has been conducted so far with tropical chironomid representatives. This study was designed to evaluate the indigenous midge Chironomus sancticaroli as a candidate test species for use in tropical toxicity assessments. To this end, laboratory water-only toxicity tests were conducted evaluating copper and cadmium. Obtained lethal concentration values were overall comparable or lower than those reported for other chironomids, including those most commonly used in temperate regions (C. riparius and C. dilutus). In addition, C. sancticaroli was deployed in situ in the Monjolinho River (São Paulo State, Brazil), and toxicity of sediment from this river was evaluated in the laboratory. Several field water and sediment quality parameters also were measured to enable correlating these with the effects observed in these toxicity tests. Field sediment toxicity to C. sancticaroli appeared to be related with sediment endosulfan concentrations, whereas effects noted in the in situ test were likely due to low pH values measured in river water. Chironomus sancticaroli appears to be a suitable candidate for inclusion as a test species in tropical toxicity evaluations in both the laboratory and the field.

Response of Tradescantia plants to oxidative stress induced by heavy metal pollution of soils from industrial areas

Numerous investigations have demonstrated that even soil in which concentrations of individual elements do not exceed permissible limits can cause harmful effects in living organisms. In the present study, polluted-soil-induced oxidative stress was evaluated using Tradescantia clone 4430, which is widely used for genotoxicity evaluations, employing biochemical (superoxide dismutase (SOD), contents of ascorbic acid (AA), carotenoids (Car), hydrogen peroxide (H₂O₂), chlorophyll (Chl) a/b ratio), and molecular (RAPD and differential display (DD-PCR)) markers after long-term exposure. The activity (staining intensity) of SOD isoforms in Tradescantia leaves was higher in plants grown in all heavy-metal-polluted test soils compared to the control. No direct link between the soil pollution category and the contents of AA, Car, Chl a/b in Tradescantia leaves was revealed, but the concentration of H₂O₂ was shown to be a sensitive biochemical indicator that may appropriately reflect the soil contamination level. Both short-term (treatment of cuttings with H₂O extracts of soil) and long-term (0.5 and 1.0 year) exposure increased MN frequencies, but the coincidence of the MN induction and the soil pollution level was observed only in some cases of long-term exposure. Soil (geno)toxin-induced polymorphism in the RAPD profile was determined with two primers in plants after long-term exposure to soils of an extremely hazard category. Transcript profiling of plants after long-term cultivation in test soils using DD-PCR showed that the majority of differentially expressed transcript-derived fragments (TDFs) were homologous to genes directly or indirectly participating in photosynthesis, the abiotic stress response, and signal transduction cascades.

Effects of CO2 enrichment on two microalgae species: A toxicity approach using consecutive generations

As a result of the increasing pressure provoked by anthropogenic activities, the world climate is changing and oceans health is in danger. One of the most important factors affecting the marine environment is the well-known process called ocean acidification. Also, there are other natural or anthropogenic processes that produce an enrichment of CO₂ in the marine environment (CO₂ leakages from Carbon Capture and Storage technologies (CCS), organic matter diagenesis, volcanic vents, etc). Most of the studies related to acidification of the marine environment by enrichment of CO₂ have been focused on short-term experiments. To evaluate the effects related to CO₂ enrichment, laboratory-scale experiments were performed using the marine microalgae Tetraselmis chuii and Phaeodactylum tricornutum. Three different pH values (two treatments - pH 7.4 and 6.0 - and a control - pH 8.0) were tested on the selected species across four consecutive generations. Seawater was collected and exposed to different scenarios of CO₂ enrichment by means of CO₂ injection. The results showed different effects depending on the species and the generation used. Effects on T. chuii were shown on cell density, chlorophyll-a and metabolic activity, however, a slight adaptation across generations was found in this last parameter. P. tricornutum was more sensitive to acidification conditions through generations, with practically total growth inhibition in the fourth one. The conclusions obtained in this work are useful to address the potential ecological risk related to acidification by enrichment of CO₂ on the marine ecosystem by using consecutive generations of microalgae.

Effects of a hypothetical escape of CO2 gas from subterranean storage sites on water flea Daphnia magna

The impacts of a hypothetical CO₂ gas leak from freshwater sediments on the survival and reproduction of freshwater flea Daphnia magna were analyzed. Another objective was to assess the performance of standard toxicity testing protocols for CO₂-induced acidification research in freshwaters. Four pH levels (7.5, 7.0, 6.5, and 6.0) and two sediments with different contamination level were tested. The results revealed that the D. magna are susceptible to a gradual but relatively rapid CO₂ enrichment of the water column causing a change from circumneutral to acidic conditions. Standard 48-h immobilization test with D. magna tended to underestimate the toxicity at CO₂-induced acidity condition. Dissolved aluminum may be implicated in the toxicity to the parental daphnids exposed. Metal outflux from sediments and behavior in elutriate have been discussed.

Metal release from contaminated coastal sediments under changing pH conditions: Implications for metal mobilization in acidified oceans

To investigate the impacts and processes of CO2-induced acidification on metal mobilization, laboratory-scale experiments were performed, simulating the scenarios where carbon dioxide was injected into sediment-seawater layers inside non-pressurized chambers. Coastal sediments were sampled from two sites with different contamination levels and subjected to pre-determined pH conditions. Sediment samples and overlying water were collected for metal analysis after 10-days. The results indicated that CO2-induced ocean acidification would provoke increased metal mobilization causing adverse side-effects on water quality. The mobility of metals from sediment to the overlying seawater was correlated with the reduction in pH. Results of sequential extractions of sediments illustrated that exchangeable metal forms were the dominant source of mobile metals. Collectively, our data revealed that high metal concentrations in overlying seawater released from contaminated sediments under acidic conditions may strengthen the existing contamination gradients in Maluan Bay and represent a potential risk to ecosystem health in coastal environments.