Biomonitoring of antioxidant and oxidative stress responses in Perinereis gualpensis (Polychaeta: Nereididae) in Chilean estuarine regions under different anthropogenic pressure

Spatio-temporal variability in macroinvertebrate community structure and ecological health status of a tropical dynamic river-estuarine system, India: An integrated approach of multivariate analysis

River-estuarine ecosystems are under severe anthropogenic threat due to resource exploitation, transportation, sewage/industrial discharges, and pollutants from surrounding areas. Monitoring the water quality and biological communities is essential for assessing ecosystem health and sustainability. Present study integrated the ecological community data along with water quality analysis to understand the impact of anthropogenic pressures on benthic macroinvertebrates. Samples were collected from 10 locations (comprising of both rural and urban areas) for Benthic macroinvertebrates, physico-chemical and microbiological parameters along the lower stretch of the Bhagirathi-Hooghly river-estuarine (BHE) system during the post-monsoon seasons of 2020, 2021, and 2022. During the entire study period, a total of 5730 individuals from 54 families in 19 orders of 3 phylum of macroinvertebrate were recorded. Among them Thiaridae (27.1%) and Chironomidae (22.8%) were found to be the most abundant families. Based on the water quality data Cluster analysis and nMDS indicated two distinct groups of locations: Group-I with rural settings and Group-II with urban settings. Alpha diversity metrics showed higher diversity (2.817) and evenness (0.744) in rural locations (Group-I) compared to urban locations (Group-II). The overall saprobic score of the macroinvebrate data revealed Group-I (5.09) to be in good condition, while Group-II (4.95) showed moderately polluted conditions. Redundancy analysis (RDA) highlighted the correlation of pollution-tolerant species (Chironomidae, Culicidae) with high organic loads i.e., biochemical oxygen demand (BOD), chemical oxygen demand (COD) in Group-II. In contrast, Group-I locations exhibited positive correlations with Dissolved Oxygen (DO) and supported less pollution-tolerant organisms (Coenagrionidae, Dytiscidae). The study emphasizes the importance of integrated analysis of ecological community data and water quality parameters to assess the health status of river-estuarine ecosystems.

Submarine Tailings in Chile—A Review

This review aims to understand the environmental impact that tailings produce on the land and marine ecosystem. Issues related to flora, fauna, and the environment are revised. In the first instance, the origin of the treatment and disposal of marine mining waste in Chile and other countries is studied. The importance of tailings’ valuable elements is analyzed through mineralogy, chemical composition, and oceanographic interactions. Several tailings’ treatments seek to recover valuable minerals and mitigate environmental impacts through leaching, bioleaching, and flotation methods. The analysis was complemented with the particular legislative framework for every country, highlighting those with formal regulations for the disposal of tailings in a marine environment. The available registry on flora and fauna affected by the discharge of toxic metals is explored. As a study case, the “Playa Verde” project is detailed, which recovers copper from marine tailings, and uses phytoremediation to neutralize toxic metals. Countries must regularize the disposal of marine tailings due to the significant impact on the marine ecosystem. The implementation of new technologies is necessary to recover valuable elements and reduce mining waste.

Testing biomarker feasibility: a case study of Laeonereis culveri (Nereididae, Annelida) exposed to sewage contamination in a subtropical estuary

The feasibility of biomarkers to accurately detect pollution in estuaries and coastal areas appears to be overestimated in the scientific literature, and is likely stemming from a bias towards publishing only positive results. Herein, we test the applicability of antioxidant capacity and lipid peroxidation to detect potential in situ sewage impacts on a subtropical estuary. We experimentally assessed variation in malondialdehyde (MDA, an indicator of lipid peroxidation) and total antioxidant capacity against peroxyl radicals (ACAP) through transplantations of the worm Laeonereis culveri from control to sewage-polluted areas. Variations in biomarkers were more related to natural environmental variability and small-scale heterogeneity among areas than to experimental exposure to sewage. Use of oxidative stress biomarkers is promising but further experimental work under real-life conditions is necessary to further validate and establish their accuracy and feasibility for practical purposes.

Assessment of oxidative stress and bioaccumulation of the metals Cu, Fe, Zn, Pb, Cd in the polychaete Perinereis gualpensis from estuaries of central Chile

The estuaries of the Aconcagua and Maipo Rivers of central Chile are receptors of residues that contain metals from anthropic activities including agriculture, mining and smelters, which have different levels in the two basins. This study postulates that the exposition to metals is different in the two estuaries and that their sediments contain bioavailable chemical agents that produce oxidative stress. The aim of the study was to evaluate the effect of estuarine sediments on the polychaete Perinereis gualpensis using oxidative stress biomarkers and to determine the metal concentrations in sediments and their accumulation in P. gualpensis. Sediments and organisms were collected in December 2015 and January 2016 in the estuaries. The Catapilco estuary was used as control, since its basin has little anthropic activity. The metal concentrations of Fe Cu, Pb, Zn and Cd were determined in tissues of the organisms and in sediments. The granulometry, conductivity, redox potential, pH and organic matter in sediments were determined, as well as catalase activity and lipid peroxidation. The results show that the concentrations of metals in sediments were higher in the estuary of the Aconcagua River: Cu: 48 ± 2μgg^-1; Fe: 154 ± 19mgg^-1, Pb: 20 ± 3μgg^-1 and Zn: 143 ± 20μgg^-1. In tissues, Pb and Fe were higher in the estuary of the Maipo River, while Cd was detected only in the Catapilco River mouth. Catalase activity was greater in the estuary of the Aconcagua River and lipid peroxidation in the estuary of the Catapilco River. Significant regressions were found between biomarkers of oxidative stress and metal concentrations in tissues of P. gualpensis. In conclusion, the sediments of the studied estuaries contain bioavailable chemical agents that provoke oxidative stress in P. gualpensis, which may be a risk for the benthic communities of these ecosystems. This species is proposed to monitor metals bioavailability and oxidative stress in estuarine sediments.

Multibiomarker responses in aquatic insect Belostoma elegans (Hemiptera) to organic pollution in freshwater system

The present study analyzes a battery of biomarkers in the water bug Belostoma elegans from a stream polluted with organic matter (OMS), and another one considered as reference site (RS) during spring-summer season (December to March). Biochemical parameters of glucidic, lipidic and oxidative metabolic pathways were analyzed in males and females of this insect. In general, no significant differences were observed in all biomarkers assayed between both sexes, except lactate concentration which was higher in males than in females (p < 0.0006) in the first three months. About carbohydrate metabolism parameters, only pyruvate-kinase showed significant differences between insects collected in both streams (p < 0.05) during December. However, the total lipid content, saturated fatty acid, and mainly triacylglycerol were higher in insects from RS compared to those from OMS (p < 0.002) in all sampled months. Levels of lipoperoxidation, protein oxidation, reduced glutathione and glutathione-S-transferase activity showed no differences between insects collected from both streams. Nevertheless, the significant increase observed in superoxide dismutase and catalase activities (p < 0.004) could be due to the elevated oxidative metabolism in insects from RS compared to those from OMS with lower dissolved oxygen. Regarding those responding parameters, males accounted for the differences between the two sites during the study period. In conclusion, our results support that lipidic energetic reserves and antioxidant enzyme activities in B. elegans could be used as biomarkers of environmental pollution by organic matter.

The effects of salinity changes on the Polychaete Diopatra neapolitana: Impacts on regenerative capacity and biochemical markers

Polychaetes have been identified by several authors as a group of marine invertebrates that respond rapidly to anthropogenic stressors. However, studies investigating alterations in Polychaetes affected by climate changes are scarce. Thus, the present study aimed to assess the impact of salinity changes (14, 21, 28, 35, 42g/L) on the physiological and biochemical performance of the Polychaete Diopatra neapolitana, evaluating the species regenerative ability and biochemical alterations. The results obtained demonstrated that organisms exposed to extreme salinity conditions (14, 21 and 42g/L) presented higher mortality rates, needed more days to completely regenerate the missing body region and also regenerated less chaetigers, when compared to organisms exposed to salinities 28 and 35g/L. The present study further demonstrated that D. neapolitana presented significantly lower glycogen and protein content at salinities 21 and 42g/L, which can be explained by higher energy expenditure in the physiological and biochemical processes. A marked impairment of the glutathione redox status was also recorded at salinities 21 and 42g/L. Increased antioxidant enzyme activities were observed at salinity 21g/L while LPO levels were increased at salinity 42g/L. Overall the present study demonstrated that the regenerative capacity of D. neapolitana can be used as a tool to assess environmental changes, namely salinity shifts. Moreover, stress related biomarkers revealed to be useful to evaluate the alterations in Polychaetes due to salinity changes. D. neapolitana revealed to be a good bioindicator to salinity alterations.

Physiological and biochemical responses of the Polychaete Diopatra neapolitana to organic matter enrichment

Several studies have demonstrated that organic matter enrichment may be associated to aquaculture, leading to impoverished benthic communities and species succession with loss of biodiversity, but very few studies have investigated biochemical and physiological alterations that species affected by aquaculture activities undergo. Thus, in the present study, the effects of the organic enrichment originating from an oyster culture were studied in the Polychaete Diopatra neapolitana, a species already shown to be sensitive to inorganic contamination. For this, physiological responses and biochemical alterations were evaluated. The results obtained revealed that individuals from highly organically enriched areas presented lower capacity to regenerate their body but higher glycogen and protein levels. Furthermore, with increasing organic matter D. neapolitana increased the lipid peroxidation (LPO), the oxidized glutathione content (GSSG) and Glutathione S-transferase activity (GSTs) content, and the activity of the antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD). This study evidenced that organic matter enrichment induced biochemical and physiological alterations in D. neapolitana. Thus, this species was shown to be a good sentinel species to monitor organic contamination.

Assessment of the effect of silicon on antioxidant enzymes in cotton plants by multivariate analysis

Silicon has been extensively researched in relation to the response of plants to biotic and abiotic stress, as an element triggering defense mechanisms which activate the antioxidant system. Furthermore, in some species, adding silicon to unstressed plants modifies the activity of certain antioxidant enzymes participating in detoxifying processes. Thus, in this study, we analyzed the activity of antioxidant enzymes in leaves and roots of unstressed cotton plants fertilized with silicon (Si). Cotton plants were grown in hydroponic culture and added with increasing doses of potassium silicate; then, the enzymatic activity of catalase (CAT), guaiacol peroxidase (GPOX), ascorbate peroxidase (APX), and lipid peroxidation were determined. Using multivariate analysis, we found that silicon altered the activity of GPOX, APX, and CAT in roots and leaves of unstressed cotton plants, whereas lipid peroxidation was not affected. The analysis of these four variables in concert showed a clear differentiation among Si treatments. We observed that enzymatic activities in leaves and roots changed as silicon concentration increased, to stabilize at 100 and 200 mg Si L(-1) treatments in leaves and roots, respectively. Those alterations would allow a new biochemical status that could be partially responsible for the beneficial effects of silicon. This study might contribute to adjust the silicon application doses for optimal fertilization, preventing potential toxic effects and unnecessary cost.

Antioxidant enzymes in the liver of Chelidonichthys obscurus from the Montenegrin coastline

The activities of antioxidant defence enzymes — total, manganese and copper zinc containing superoxide dismutase (Tot SOD, Mn SOD, CuZn SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR) and biotransformation phase II enzyme glutathione-S-transferase (GST) — in the liver of longfin gurnard (Chelidonichthys obscurus) from the Montenegrin coastline (Adriatic sea) were investigated. The specimens were collected in winter (February) and late spring (May) at two localities: Platamuni (PL, potentially unpolluted) and the Estuary of the River Bojana (EB, potentially polluted). The obtained results show that the activities of Mn SOD, CAT, GSH-Px and GST in winter were significantly lower at EB than at PL. In spring, the activities of CAT and GST were decreased, while GR activity was increased at EB in comparison to PL. The activities of Mn SOD and GST at PL were decreased and GSH-Px, GR and GST activities at EB were increased in spring compared to winter. Our work represents the first study of liver antioxidant enzymes of longfin gurnard from the Montenegrin coastline and reveals that locality, as a variable, has a greater influence on antioxidant enzymes and biotransformation phase II enzyme GST activities compared to season.

Biochemical and behavioral responses in the estuarine polychaete Perinereis gualpensis (Nereididae) after in situ exposure to polluted sediments

In situ translocation experiments are advantageous relative to traditional laboratory experiments, particularly for understanding the bioavailability of trace metals like mercury (Hg). Individuals of the polychaete Perinereis gualpensis were translocated from a reference site (Raqui estuary, Chile) to an estuarine site with significant sediment Hg concentrations (Lenga estuary: 1.78-9.89 mg/kg). Individuals were exposed in polluted and non-polluted sediments for 21 days and sampled every 7 days with cages deployed at three different depths. Tissue Hg concentrations were measured in conjunction with oxidative stress responses. Translocated polychaetes rapidly accumulated Hg. Glutathione S-transferase (GST) activities measured from posterior body regions were 2-fold higher than control activities after 21 days of exposure. Other antioxidant measures were idiosyncratic. Distinct burrowing behavior differences were observed; control polychaetes exhibited more homogenous vertical distributions, whereas in Lenga, worms tended to remain in upper layers. These studies demonstrate that under natural conditions, Hg is highly bioavailable to polychaetes affecting both biochemical and behavioral responses after relatively short-term exposure.

Biochemical responses and physiological status in the crab Hemigrapsus crenulatus (Crustacea, Varunidae) from high anthropogenically-impacted estuary (Lenga, south-central Chile)

Estuarine environmental assessment by sub-individual responses is important in order to understand contaminant effects and to find suitable estuarine biomonitor species. Our study aimed to analyze oxidative stress responses, including glutathione-S-transferase (GST) activity, total antioxidant capacity (ACAP) and lipid peroxidation levels (TBARS) in estuarine crabs Hemigrapsus crenulatus from a high anthropogenically-impacted estuary (Lenga) compared to low and non-polluted estuaries (Tubul and Raqui), in a seasonal scale (winter-summer), tissue specific (hepatopancreas and gills) and sex related responses. Results showed that hepatopancreas in male crabs better reflected inter-estuary differences. Morpho-condition traits as Cephalothorax hepatopancreas index (CHI) could be used as an indicator of physiological status of estuarine crabs. Discriminant analysis also showed that GST and TBARS levels in summer are more suitable endpoints for establishing differences between polluted and non-polluted sites. These results suggest the importance of seasonality, target tissue, sex and physiological status of brachyuran crabs for estuarine biomonitoring assessment.

Multibiomarker approach at different organization levels in the estuarine Perinereis gualpensis (Polychaeta; Nereididae) under chronic and acute pollution conditions

This work aimed to study biochemical biomarkers and population responses in the polychaete Perinereis gualpensis (Nereididae) from two Chilean estuaries, Lenga (36°45'S; 73°10'W) and Tubul-Raqui (37°14'S,73°26'W). Lenga estuary is characterized by high mercury and PAH levels as consequence of several historic incidental spills while Tubul is mainly impacted by intensive fish activity. Raqui estuary, with low anthropogenic impact was considered the reference site. Worms were collected in winter and summer periods and tissues were differentiated between anterior (first 40 segments) and posterior region (the rest of the body). Levels of the antioxidant glutathione (GSH), glutathione-S-transferase (GST) activity, total antioxidant capacity against peroxyl radicals (ACAP), lipid peroxidation (TBARS) levels, Na+, K+-ATPase activity (NKA) and metalothioneins (MTs) content were determined in each region. L3 (combined length of prostomiun+peristomiun+first segment) length, size, frequency, histograms and density of individuals were studied in all sites and seasons. Significant differences (p<0.05) were observed among sites for most of the biochemical responses (GSH, GCL, GST, ACAP and TBARS), showing variation between seasons and body regions. Population responses in the most polluted estuary (Lenga) showed differences in size, frequency, lengths and low densities compared with lower impacted sites, indicating the costs associated with tolerance in organisms chronically exposed to estuarine pollution.

Effects of azinphos methyl and carbaryl on Rhinella arenarum larvae esterases and antioxidant enzymes

Organophosphate (OP) and carbamate pesticides are anticholinesterasic agents also able to alter antioxidant defenses in different organisms. Amphibian larvae are naturally exposed to these pesticides in their aquatic environments located within agricultural areas. We studied the effect of the carbamate carbaryl (CB) and the OP azinphos methyl (AM), compounds extensively used in Northern Patagonian agricultural areas, on reduced glutathione (GSH) levels and the activities of esterases and antioxidant enzymes of the toad Rhinella arenarum larvae. Larvae were exposed 48 h to AM 3 and 6 mg/L or CB 10 and 20 mg/L. Cholinesterase and carboxylesterases were strongly inhibited by CB and AM. In insecticide-exposed larvae, carboxylesterases may serve as alternative targets protecting cholinesterase from inhibition. GSH-S-transferase (GST) activity was significantly increased by CB and AM. Superoxide dismutase activity increased in tadpoles exposed to 6 mg/L AM. Conversely, catalase (CAT) was significantly inhibited by both pesticides. GSH levels, GSH reductase and GSH peroxidase activities were not significantly affected by pesticide exposure. GST increase constitutes an important adaptive response to CB and AM exposure, as this enzyme has been related to pesticide tolerance in amphibian larvae. Besides, the ability to sustain GSH levels in spite of CAT inhibition indicates quite a good antioxidant response. In R. arenarum larvae, CAT and GST activities together with esterases could be used as biomarkers of CB and AM exposure.