Oxidative stress biomarkers in Senegal sole, Solea senegalensis, to assess the impact of heavy metal pollution in a Huelva estuary (SW Spain): seasonal and spatial variation

Short-term in situ Exposure of Guinean Tilapia and Blue Crab Near a Sawmill Wastes-impacted Coastal Ecosystem Reveal Significant Oxidative Stress Effects

Coastal ecosystems are characterized by various human activities with potential adverse impacts. This study aimed to evaluate the potential oxidative stress effects in representative aquatic biota deployed in situ at a sawmill wastes dump (test site) and reference site in a coastal ecosystem for a short term (28 days) period. PAHs and OCPs were analysed using GC-FID and GC-MS respectively in surface water and sediments. Oxidative stress indices (malondialdehyde, glutathione-s-transferase, reduced glutathione, catalase and superoxide dismutase) were evaluated following standard methods in Coptodon guineensis (Guinean Tilapia) and Callinectes amnicola (Blue crab) over a period of 28 days. Sum PAHs in the test site sediments, oxidative stress indices in C. guineensis liver and C. amnicola haemolymph after 28 days exposure were significantly higher (p < 0.0.5) compared to the reference site. The results showed the adverse impacts to biota of sawmill wastes which are continuously burnt at the test site with potential for long-term effects. Sustainable sawmill wastes management at the test site are recommended to sustain life below water (UNSDG 14).

Nickel sources affect soil biological properties but do not affect sorghum growth

Nickel (Ni) is an essential element, but it can be phytotoxic in high concentration, which may be caused by high availability in soil solution. The objective of this study was to evaluate the effect of sources and doses of Ni applied to a dystrophic Red Latosol cultivated with sorghum on i) the availability of the metal in the soil; ii) the impact on biological and biochemical properties of the soil; iii) the absorption and distribution in sorghum plants; and iv) crop productivity. The experiment was carried out within a completely randomized design with two nickel sources [nickel(II) nitrate, Ni(NO3)2 and nickel(III) oxide, Ni2O3], three doses (35, 70, and 140 mg Ni kg-1 soil), plus controls without Ni, with 3 replications. The concentrations of Ni in the soil, soil microbial biomass (SMB), basal soil respiration (BSR), metabolic quotient (qCO2), fluorescein diacetate (FDA) hydrolysis, and urease activity were determined. The concentrations of Ni in the leaf diagnostic and in the plant (shoot, root, and grains) were also measured. In the soil, the concentrations of available Ni remained between 0.21 and 54.01 mg Ni kg-1. Ni2O3 contributed very little to the increase in available Ni. SMB and the FDA hydrolysis were not affected by the Ni source or Ni dose, but BSR and qCO2 had significant increase with Ni application rates, suggesting the soil microorganisms faced stress. Soil urease activity was affected by Ni dose but not by Ni source. The dose of Ni as Ni(NO3)2 decreased the metal concentration in the plant, while that of Ni2O3 increased it. Nickel source did not affect dry mass production of the plants, but grain yield was affected in a dose-dependent manner when Ni2O3 was the source of Ni.

Combined evaluation of multi-biomarkers and metal bioaccumulations in two different fish species (Sparus aurata and Chelon labrosus) from İzmir Bay, Türkiye (Aegean Sea): Spatial, temporal and tissue-specific approaches

Biomarkers were investigated to assess the effects of metal accumulation in Sparus aurata and Chelon labrosus in the İzmir Bay. Fish were collected from the Inner and Outer Bays in November 2020 and May 2021. According to the metal and biomarker measurements found in the organs, it was observed that the levels were higher in the liver and gill tissues than in the muscle tissues. Significant differences between tissues were found for all metals and biomarkers. In addition, biochemical biomarkers were found to be significant predictors of metal bioaccumulation. Histological changes were observed in liver and gills in each species and location. Although the metal levels determined according to the health risk assessment were below the threshold limits, the As levels for the lifetime cancer risk were within the limits to be considered. In conclusion, this study will provide robust results for its related study area.

Multilevel assessment of chlorothalonil sediment toxicity to Latin American estuarine biota: Effects on biomarkers, reproduction and survival in different benthic organisms

Chlorothalonil is an organochlorine compound that has long been used in agriculture. In recent years, this compound has been used as an antifouling booster biocide and its presence has been reported in marine coastal environments, especially in navigational areas. Although sediment can be a sink for chlorothalonil due to high affinity to fine particulate matter, toxicity studies with non-target marine and/or estuarine organisms is focused on waterborne exposure only. This study aimed to determine sediment-borne ecotoxicological effects of chlorothalonil on different benthic organisms of the Latin American biota using a integrative multilevel approach. Marine/estuarine organisms were exposed to sediments spiked with chlorothalonil (from 0 to 10.0 μg g^-1) and effects at sub-individual (biochemical biomarkers in Anomalocardia flexuosa), individual (lethal effects to Tiburonella viscana and Artemia salina) and subpopulation levels (Nitokra sp. reproduction) were assessed. Increasing chlorothalonil concentrations in sediment caused increasing ecotoxicological effects in different levels of biological organisation, from biochemical to subpopulation levels. The highest exposure concentrations showed increased biomarkers of effects (lipid peroxidation and DNA damage in gills and/or digestive gland of A. flexuosa), lower fecundity and lower survival of the test organisms. GPx activity associated with LPO levels in the digestive gland suggested a response to the oxidant challenge provided by the biocide. At the lowest concentration (0.001 μg g^-1), chlorothalonil detoxification mechanisms and defense against its oxidising action, involving GSH and glutathione-dependent enzymes (GST and GPx) were induced. At intermediate concentrations, there was a tendency of decreasing GSH levels, probably due to conjugation with chlorothalonil, which also affected the activities of the glutathione-dependent enzymes. At the highest tested concentration (10.0 μg g^-1), chlorothalonil may have restimulated GSH synthesis in the gills of A. flexuosa, although the prooxidant activity has induced effects. This study contributes to assessing the environmental risk of chlorothalonil in sediment for non-target marine and estuarine organisms.

Snapshot of the pollution-driven metabolic and microbiota changes in Carassius gibelio from Bucharest leisure lakes

In the last decades, increased intakes of contaminants and the habitats' destruction have produced drastic changes in the aquatic ecosystems. The environmental contaminants can accumulate in aquatic organisms, leading to the disturbance of the antioxidant/prooxidant balance in fish. In this context, we evaluated the level of organic, inorganic and microbiological pollutants in four leisure lakes (Chitila, Floreasca, Tei and Vacaresti) from Bucharest, the largest city of Romania, in order to compare their effects on hepatopancreas and gills metabolism and antioxidant defense mechanisms in Carassius gibelio, the most known and widespread freshwater fish in this country. The lowest level of oxidative stress was recorded in the case of fish collected from the Vacaresti lake, a protected wetland area where aquatic organisms live in wild environmental conditions. In contrast, significant oxidative changes were observed in the hepatopancreas and gills of fish from the Chitila, Floreasca and Tei lakes, such as reduced glutathione S-transferase activity and glutathione level, and increased degree of lipid peroxidation, being correlated with elevated levels of pesticides (such as 2,4'-methoxychlor) and Escherichia coli load in these organs. Although different patterns of pollutants' accumulation were observed, no important interindividual variations in cytosine methylation degree were determined. In conclusion, the presence and concentrations of metals, pesticides and antibiotics varied with the analyzed tissue and sampling site, and were correlated with changes in the cellular redox homeostasis, but without significantly affecting the epigenetic mechanisms.

Field validated biomarker (ValidBIO) based assessment of impacts of various pollutants in water

The sensitivity of fish towards pollutants serves as an excellent tool for the analysis of water pollution. The effluents generated from various anthropogenic activities may contain heavy metals, pesticides, microplastics, and persistent organic pollutants (POPs) and ultimately find its way to aquatic environment. The enzymatic activities of fish collected from water bodies near major cities, oil spillage sites, agricultural land, and intensively industrialized areas have been reported to be significantly impacted in various field studies. These significant alterations in enzymatic activities act as a biomarker for monitoring purposes. The use of biomarkers not only helps in the identification of known and unknown pollutants and their detrimental health impacts, but also identifies the interaction between pollutants and organisms. The conventional method majorly used is physicochemical analysis, which is recognized as the backbone of the system for monitoring water quality. In physicochemical monitoring, major problems exist in assessing or predicting biological effects from chemical or physical data. Xenobiotic-induced enzymatic changes in fish may serve as an intuitive and efficient biomarker for determining contaminants in water bodies. Therefore, field validated biomarker (ValidBIO) approach needs to be integrated in water quality monitoring program for environmental health risk assessment of aquatic life impacted due to various point and non-point sources of water pollution.

Adverse Effects of Toxic Metal Pollution in Rivers on the Physiological Health of Fish

Toxic metal pollution influences the lives of diverse aquatic organisms and humans who consume contaminated aquatic products. However, its potential impacts on aquatic organism health and, thus, ecological health, have been neglected in many regions. This research was carried out to contribute to filling that knowledge gap. Three freshwater fish species in the Nhue−Day River basin, Vietnam, have been chosen to study the bioaccumulation of metals (Zn, Cu, Pb, and Cd) in the tissues (livers, kidneys, gills) and their effects on fish physiological health (changes in the oxidative-GST activity, and physiological biomarkers-energy reserves, respectively) from 2013 to 2017. The extensive results revealed significant spatial and temporal variations in metal concentrations in tissues of common carp (Cyprinus carpio), silver carp (Hypothalmic molitrix), and tilapia (Oreochromis niloticus), and well correlated to their concentration in the water (p < 0.05). Fish bioaccumulated metals in the following order: Zn > Cu > Pb > Cd, with more in the kidneys and livers (spring and summer) than in other tissues. Metal accumulation in O. niloticus and C. carpio was higher than in H. molitrix. Biomarker responses (except for glycogen variation) were also higher during warm seasons. Changes in metal levels in water and fish tissues caused variations in biomarkers in the respective fish tissues, particularly in the livers, as demonstrated by significant correlations of metal concentrations in water and fish tissues to biochemical and physiological responses (p < 0.05). The findings suggest that metal pollution in the river basin adversely impacts the physiological health of both wild and cultured fish. Seasonal shifts in the levels of metal accumulation and biomarkers could be connected to species-specific differences in physiology and the levels of metals in environments. This biomarker set is simple but effective in assessing the impact of metal pollution on fish health and, hence, the aquatic ecosystem. This is one of the first biomonitoring studies to assist in designing better water management strategies for the Nhue−Day River basin.

The impact of background γ-radiation on erythrocyte nuclear pathology, the serotonergic system, and cytochrome P-450 in hens (GALLUS GALLUS DOMESTICUS) from Azerbaijan

High levels of background γ-radiation exist in the suburbs of Baku, Azerbaijan. We examined the impact of radiation on erythrocyte nuclear pathologies, levels of cytochrome P-450, and serotonin-modulating anticonsolidation protein (SMAP) in the tissues of the hens from three settlements with different levels of background radiation. Higher levels of radiation resulted in increased nuclear pathologies, upregulation of tissue SMAP levels, and downregulation of cytochrome P-450. We also carried out controlled dosage studies on Wistar male rats, which showed significant upregulation of heat shock proteins with molecular mass 70 kDa (HSP70) in the bone marrow 3 and 5 h after SMAP intraperitoneal administration. Administration of SMAP to rats 3 h prior to γ-radiation exposure (8 Gy) provided significant protection to somatic cell nuclei. We conclude that SMAP can provide protection from the genotoxic effects of γ-radiation through upregulation of HSP70 or the transformation of chromatin into a condensed, more protective conformational state.

Biomarkers responses and polybrominated diphenyl ethers and their methoxylated analogs measured in Sparus aurata from the Lagoon of Bizerte, Tunisia

This study aimed to the examination of the levels and effects of organobromine compounds (polybrominated diphenyl ethers: PBDEs and methoxylated brominated diphenyl ethers: MeO-PBDEs), in Sparus aurata native to the Lagoon of Bizerte. For that, different biomarkers of exposure (somatic indices, superoxide dismutase, and catalase activities) and effect (malondialdehyde level, histopathologic alterations, and DNA damage) as well as pollutant levels were measured in specimens collected from this impacted ecosystem and the Mediterranean Sea as a reference site. Bizerte Lagoon PBDE fish levels were higher than the Mediterranean Sea, whereas MeO-PBDEs were higher in the reference site. Fish from Bizerte Lagoon presented a higher hepatosomatic index, lower catalase and superoxide dismutase activity, higher level of malondialdehyde, and higher percentage of DNA tail in comparison to fish from the reference area. The histological study of the liver indicated substantial lesions in fish from the polluted site. The results showed strong positive correlations between the concentrations of the PBDE or MeO-PBDE and the MDA and DNA tail % levels and negative correlations for the activities of enzymes of SOD and CAT. Consequently, these findings could suggest a potential link between exposure to these pollutants and the observed biomarker responses in the Bizerte Lagoon seabream. Taken together, these results highlight the importance of biomarker selection and the selected sentinel fish species as useful tools for biomonitoring of aquatic pollution.

Short-term exposure to pharmaceuticals negatively impacts marine flatfish species: Histological, biochemical and molecular clues for an integrated ecosystem risk assessment

The marine habitat and its biodiversity can be impacted by released pharmaceuticals. The short-term (7 days) effect of 3 commonly used drugs - warfarin, dexamethasone and imidazole - on Senegalese sole (Solea senegalensis) juveniles was investigated. Occurrence of hemorrhages, histopathological alterations, antioxidant status, activity of antioxidant enzymes and expression of genes involved in the xenobiotic response (pxr, abcb1 and cyp1a), were evaluated. The results showed a time and drug-dependent effect. Warfarin exposure induced hemorrhages, hepatocyte vacuolar degeneration, and altered the activity of glutathione peroxidase (GPx) and the expression of all the studied genes. Dexamethasone exposure increased liver glycogen content, altered antioxidant status, GPx and superoxide dismutase activities, as well as abcb1 and cyp1a expression. Imidazole induced hepatocyte vacuolar degeneration and ballooning, and altered the antioxidant status and expression of the tested genes. The present work anticipates a deeper impact of pharmaceuticals on the aquatic environment than previously reported, thus underlining the urgent need for an integrated risk assessment.

First long-term assessment of metals and associated ecological risk in subtidal sediments of a human-impacted SW Atlantic estuary

The main objective of this article was to profile the metal accumulation, sources, pollution levels and trends during 6 years in a SW Atlantic coastal system (Bahía Blanca estuary). Subtidal sediment samples were taken from six stations with different human impacts, and chemical element analyses were performed using ICP-OES. As a result, metals tended to increase in time and differences were observed between a site profoundly impacted by sewage waters and the rest of the sampling stations. Values range from background levels to those considered toxic for the marine biota, as in the case of Cd and Cu. Besides, the geochemical analyses exhibited low to moderate pollution with probable adverse biological effects. Finally, the physicochemical parameters of the water column like pH and DO significantly decreased in time in all stations and temperature correlated with some metals, indicating a potential interaction.

Impacts of wildfires in aquatic organisms: biomarker responses and erythrocyte nuclear abnormalities in Gambusia holbrooki exposed in situ

Wildfires are an environmental concern due to the loss of forest area and biodiversity, but also because their role as drivers of freshwater systems contamination by metals. In this context, the fish Gambusia holbrooki was used as a model, deployed for in situ exposure in watercourses standing within a recently burnt area and further assessment of toxic effects. The fish were exposed during 4 days at four different sites: one upstream and another downstream the burnt area and two within the burnt area. Biochemical biomarkers for oxidative stress and damage were assessed. The extent of lipoperoxidative damage was monitored by quantifying malondialdehyde and DNA damage evaluated through erythrocyte nuclear abnormalities observation. Chemical analysis revealed higher metal levels within the burnt area, and exposed fish consistently showed pro-oxidative responses therein, particularly an increase of gill glutathione peroxidase and glutathione reductase activity, the records doubling compared to samples from sites in the unburnt area; also the activity of glutathione-S-transferases comparatively increased (by 2-fold in the liver) in samples from the burnt area, and malondialdehyde was produced twice as much therein and in samples downstream the burnt area reflecting oxidative damage. Consistently, the frequency of erythrocyte nuclear abnormalities was higher at sites within and downstream the burnt area. This study supports the use of sensitive oxidative stress and genotoxicity biomarkers for an early detection of potentially noxious ecological effects of wildfires runoff.

Seasonal dynamics of manganese accumulation in European larch (Larix decidua Mill.), silver birch (Betula pendula Roth), and bilberry (Vaccinium myrtillus L.) over 10 years of monitoring

Leaves of European larch, silver birch, and bilberry were sampled 5-7 times per growing season in 2010-2019 in a locality near the city of Litvínov in the Krušné Hory Mts. (Ore Mts.) near the Czech/German border. The locality is characterised by a large amount of plant-available Mn because of acidic soils in the study area. All three investigated plants at the studied site acquired manganese concentrations close to the definition of hyperaccumulation (ca. 10,000 mg kg^-1). This paper presents the most detailed collection of plant material for the characterisation of seasonal dynamics of Mn concentrations in the foliage of the three studied plants under field conditions and compares this information with that in published studies. Time (day in the year or day in the growing season) and cumulative precipitation anomalies were major and minor variables, respectively, explaining Mn dynamics in leaves, while temperature and insolation anomalies were not significant. The three investigated species showed plant-specific Mn acquisition rates in the growing season and specific effects of precipitation. Seasonal dynamics must be considered if plant leaves are used for environmental monitoring.

Biological responses and toxicopathic effects elicited in Solea senegalensis juveniles by waterborne exposure to benzo[a]pyrene

Polycyclic aromatic hydrocarbons (PAHs) are priority contaminants in coastal and estuarine ecosystems under anthropogenic pressure. Although PAHs tend to accumulate in the sediment, toxicity for benthic flat fish such as soles may be caused by PAHs released from the sediment to the water column. Within this context, the present investigation aims at recognizing toxicopathic effects elicited after waterborne exposure to benzo[a]pyrene B[a]P, a model individual PAH compound, in juvenile Solea senegalensis. Sole juveniles were exposed to various concentrations of waterborne B[a]P for 3 and 7 days. Brain, liver, gills and gonad were the target tissues selected to determine biochemical and lysosomal biomarkers, and histopathology. Biological responses and toxicopathic effects were consistent with B[a]P concentration and exposure time. From day 3, hepatic catalase inhibition indicated potential oxidative effects of B[a]P. At day 7, contaminant exposure produced hepatic glutathione-S-transferase induction at low concentrations and inhibition at higher levels, evidencing a bell-shaped response. A clear gradient in lysosomal membrane destabilisation was observed in relation with B[a]P concentrations. Histopathological lesions were more frequent at day 7 and at higher contaminant levels. It seems that environmentally relevant waterborne concentrations of B[a]P (1000 ng/l) would suffice to cause toxicopathic effects on sole juveniles in relatively short exposure times. In agreement, the Integrative Biological Response index (IBR/n) indicated a dose-dependent decline in health condition upon exposure to B[a]P (IBR/n_HighB[a]P > IBR/n_MidB[a]P > IBR/n_LowB[a]P > IBR/n_DMSO > IBR/n_Control). Overall, changes in antioxidant enzymes activity, lysosomal biomarkers and gill and liver histopathology are responsive early-warning signs of health disturbance in sole juveniles exposed to waterborne PAHs.

Seasonal modulation of oxidative stress biomarkers in mangrove oyster (Crassostrea gasar) from an Amazon estuary

Estuaries are the final destination of many pollutants derived from anthropogenic activity. Therefore, it is difficult to find this kind of ecosystem in a pristine condition. In this context, biomonitoring studies that characterize the organism's conditions against the environment' s natural variation are essential for future impact analysis due to anthropic activity. The present study aims to characterize the natural modulation of biochemical biomarkers in oysters Crassostrea gasar. The research was conducted in Japerica Bay, an estuary region located in the Eastern Amazon (Pará, Brazil), which has remained in pristine condition for many years. The samplings were carried out throughout one year during the rainy-dry transition period (June/2013), dry period (September/2013), dry-rainy transition period (November / 2013), and rainy period (February / 2014) in the lower and upper estuary. The activity of glutathione-S-transferase (GST) and total antioxidant capacity (ACAP) were evaluated as biomarkers of exposure and lipid peroxidation (LPO) as an effect biomarker. In gills, GST decreased during the rainy season in both sites and increased during the salinity peak (dry-rainy transition period) for the upper estuary's organisms. In this organ, the lowest levels of LPO occurred during the dry season for both points. There was an induction of ACAP in muscle during the rainy-dry transition period compared to the dry and dry-rainy transition periods for the lower estuary's organisms, and there were no differences for GST suggesting low tissue sensitivity. There was an increase in LPO during the rainy season compared to the rainy-dry transition period for the lower estuaries animals. Biomarkers in gills suggest a metabolic challenge to the rainy season and stability during the dry season. The species shows high viability of use in biomonitoring programs. However, these seasonality-induced alterations in biomarkers responses must be taken into account to interpret the results.

Nutritional content of Totoaba macdonaldi (Gilbert, 1890), Antioxidants and lipid peroxidation in muscle

Background

Totoaba, Totoaba macdonaldi, is an endemic species of the Gulf of California, where wide variations in sea temperature throughout the year, surface salinities that gradually increase towards the north, and contamination by discharge of wastewater have been recorded. In addition to the challenges of reproduction and swimming, its characteristic biannual migration presents totoaba with changes in environmental factors that could affect oxidative stress indicators. The objective of this study was to assess spatial and seasonal changes in the oxidative stress indicators in muscle samples of totoaba.

Methods

Reactive oxygen species production, antioxidant enzyme activities and lipid peroxidation levels were quantified by spectrophotometry.

Results

Results suggest spatial-temporal variations of the oxidative stress indicators in muscle of totoaba that may be associated to a complex interaction between environmental and biological factors, including reproduction and nutrient availability. These results contribute to explain the appeal of totoaba as a marketable meat and suggest totoaba may provide antioxidant nutrients to consumers.

Biological responses and toxicopathic effects elicited in Solea senegalensis juveniles on exposure to contaminated sediments under laboratory conditions

Whole-sediment toxicity assays contribute to elucidating the intricate association between the presence of contaminants in sediments and their toxicopathic effects in benthic fish. In the present study, Solea senegalensis juveniles were exposed under laboratory conditions to contaminated whole-sediments for 7 and 28 days. Sediments were obtained from a low to moderately polluted estuary, a highly polluted harbour and from the mixture of both field-collected sediments. Biometry data were recorded. Liver, brain, gills, and gonads were dissected out and processed to determine markers of oxidative stress, neurotoxicity and lysosomal biomarkers, and histopathology. Analyses of sediment granulometry and chemical profiles indicated different degrees of toxicity and suggested a distinct release of pollutants from each sediment in relation with their physicochemical properties. Interestingly, biological responses were in agreement with contaminant levels reported in source sediments. The most distinct toxicopathic effects were detected upon exposure to the harbour's sediment and particularly on day 28. Overall, enhanced hepatic glutathione-S-transferase activity and lysosomal enlargement were detected in all experimental groups, demonstrating a toxic effect from all sediments whilst catalase inhibition, lysosomal membrane destabilisation, changes in lysosomal content and liver histopathology were most pronounced in soles exposed to the harbour's sediment. The Integrative Biomarker Response index (IBR/n) evidenced that exposure to the three sediments caused an impact of diverse magnitude in sole health (IBR/n_Harbour > IBR/n_Mixture > IBR/n_Estuary). The magnitude of biological responses essentially depended on the presence of contaminants in source sediments, which seemed to be altered by the conditions imposed by whole-sediment toxicity assays.

Changes in oxidative stress biomarkers in Sinonovacula constricta in response to toxic metal accumulation during growth in an aquaculture farm

Clam farming comprises an important part of China's economy. However, increasing pollution in the ocean caused by toxic metals has led to the bioaccumulation of toxic metals in marine animals, especially the bivalves such as clams, and the consequence of heavy metal-associated toxicity in these animals. Such toxicity can enhance the production of reactive oxygen species (ROS) within the tissues of the animals. In aquatic species, oxidative stress mechanisms have been studied by measuring the antioxidant and oxidative damage index in the tissues. The objectives of this study were to investigate the levels of different toxic metals and the extent of oxidative stress responses in the clam Sinonovacula constricta at different growth periods (from May to October) in an aquaculture farm in Wengyang, an important economic shellfish culture zone in Zhejiang Province, China. Water and sediment samples taken from the farm were subjected to Pb, Hg, Cd, Cr assays. Overall, the levels of these metals in the water and sediment could be considered as light pollution, though the levels of Hg in the water (0.266) and Cd in the sediment (0.813) could be considered as reaching moderate pollution. In addition, the levels of these metals, H₂O₂, MDA and GSH content, antioxidant enzyme (CAT, SOD, GPx) activities as well as the level of metallothioneins (MT) mRNA in the tissues of S. constricta were also analyzed. The levels of Pb, Hg, Cd, Cr increased with increasing culturing time, and a higher level of these metals was accumulated in the visceral mass than in the foot. The levels of MDA and GSH, as well as the level of SOD activity in the viscera and foot of S. constricta increased with increasing metal accumulation. However, CAT and GPX activities, H₂O₂ level and the expression of MT initially increased and then decreased. This suggested that S. constricta might have the ability to control oxidative damage by triggering antioxidant defense in coordination with the metal sequestering response. The results also implied that toxic metal pollution should be taken into account when selecting the site to be used as an aquaculture farm. In addition, the visceral mass should be considered to be a good tissue for measuring the level of metal pollutants.

Environmental behavior of and gastropod biomarker response to trace metals from a backwater area of Xian'nv lake

Combined with sediment pollutant analysis, the gastropod Cipangopaludina cahayensis was chosen as an indicator organism to evaluate the environmental behavior of trace metals and the aquatic ecological risk that they present in a backwater area of Xian'nv Lake. Based on hydrological characteristics, 24 sampling sites representing the main stream (MS), tributaries (TR), lake area (LA) and lake tributaries (LT) were collected. The results revealed that cadmium (Cd) was the main pollutant and that it significantly accumulated in sediments of the research area. Based on the pollutant concentrations, the degree of Cd pollution was ranked in the following order: LA > MS > TR > LT. Several intersections between the rivers and Xian'nv Lake, including LA1, LA7 and LA 10, were observed to have higher Cd deposition. There was a significant difference in the spatial distribution of pollutants, which resulted in a higher accumulation of trace metals in the backwater area and its tributary. The Cd content in the visceral sac of C. cahayensis was positively correlated with the concentration of heavy metals in the sediment. The response of multiple antioxidant biomarkers, including superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST), as well as the glutathione (GSH) content and the level of by-products of lipid peroxidation (TBARS), in C. cahayensis revealed a potential relationship to the environmental behavior of the pollutants. By combining the different biomarkers responses, the integrated biomarker response index (IBR) corresponded well with the pollution distribution characteristics in different areas.

Antioxidative Defense and Fertility Rate in the Assessment of Reprotoxicity Risk Posed by Global Warming

The objective of this review is to briefly summarize the recent progress in studies done on the assessment of reprotoxicity risk posed by global warming for the foundation of strategic tool in ecosystem-based adaptation. The selected animal data analysis that was used in this paper focuses on antioxidative markers and fertility rate estimated over the period 2000-2019. We followed a phylogenetic methodology in order to report data on a panel of selected organisms that show dangerous effects. The oxidative damage studies related to temperature fluctuation occurring in biosentinels of different invertebrate and vertebrate classes show a consistently maintained physiological defense. Furthermore, the results from homeothermic and poikilothermic species in our study highlight the influence of temperature rise on reprotoxicity.

Common snook juveniles, Centropomus undecimalis, as biomonitor organisms to evaluate cytogenotoxicity effects of surface estuarine water from Southern Brazil

Centropomus undecimalis fish inhabit the highly contaminated Santos-São Vicente Estuarine System (SESS) and could be a good biomonitor of contaminants. This study aimed to investigate the cytogenotoxic potential of superficial water from SESS using C. undecimalis as a biomonitoring model and to validate the use of farmed fish as controls. Using biochemical (DNA damage and Lipid Peroxidation - LPO), cellular (erythrocyte nuclear abnormality - ENA) and tissue (8-OHdG immunoexpression) biomarkers, our results showed fish from SEES had higher LPO concentration in gills and higher frequency of reniform, lobed and total ENA in erythrocytes when compared with control farmed fish. Thus, SESS surface water are cytogenotoxic for blood and gills cells of fishes. C. undecimalis has shown to be a good biomonitor model and farmed fish can be used as control only if livers were not the target organs of study since the dietary food from farmed fish causes steatosis.

Testing the impact of contaminated sediments from the southeast marine coast of Tunisia on biota: a multibiomarker approach using the flatfish Solea senegalensis

Coastal marine areas are highly vulnerable to the exposure to various types of stressors and impact of chemical pollution resulting from increasing anthropogenic activities, namely pollution by metals and polycyclic aromatic hydrocarbons (PAHs). To assess ecosystem quality and functions, biomarkers can provide information about the presence and adverse effects of pollutants. Accordingly, the present study was conducted to evaluate the chronic (28 days) biologic effects of putatively contaminated sediments from the Zarzis area, located in the south of the Gulf of Gabes on the Southern Tunisian coast, on the marine flatfish Solea senegalensis. Sediments were collected at three sampling sites, impacted by wastewater discharges, aquaculture activities, and industrial contamination, and then surveyed for metals (Cd, Cu, Cr, Hg, Zn, and Pb) and organic contaminants (polycyclic aromatic hydrocarbons). The quantified biomarkers involved the determination of oxidative stress, phase II metabolism, and the extent of lipid peroxidation (catalase, CAT; glutathione peroxidase activity: total and selenium-dependent, T-GPx and Se-GPx; activities of glutathione-S-transferases, GSTs; levels of lipid peroxidation, by means of the thiobarbituric acid reactive substances assay, TBARS) and neurotoxicity (activity of acetylcholinesterase, AChE). S. senegalensis exposed to potentially contaminated sediments, collected near the aquaculture facility, presented the highest values for the generality of biomarkers tested, and a significant inhibition of AChE activity. A few lesions have been also recorded in the gills and liver tissues of S. senegalensis following chronic exposure. However, the observed lesions in gills (e.g., epithelial lifting, lamellar fusion, gills hyperplasia and hypertrophy, and leukocyte infiltration) and liver (cytoplasmic vacuolation, enlargement of sinusoids, foci of necrosis, and eosinophilic bodies) were of minimal pathological importance and/or low prevalence that did not significantly affect the weighted histopathological indices. Finally, the biological responses evidenced by this flatfish can be potentially caused by metal and PAH pollution occurring in specific areas in the southeast of Tunisia. The type and extent of the observed biochemical alterations strongly suggest that the contaminated sediments from the surveyed areas could cause early adverse biological effects on exposed biota.

Multi-annual survey of health status disturbance in the Bilbao estuary (Bay of Biscay) based on sediment chemistry and juvenile sole (Solea spp.) histopathology

The Bilbao estuary (SE Bay of Biscay) is a recovering ecosystem whose sediments are still contaminated. They represent a potential risk for the biota including benthic and demersal species living in direct contact with the sediment. In this context, the present study aims to survey trends of the health status of the Bilbao estuary based on sediment chemistry and sole (Solea spp.) histopathology. Monitoring campaigns were carried out every autumn from 2011 to 2017 along the estuary. Contaminant levels were measured in sediments; liver, gills and gonads of juvenile fish were collected for histopathology. Overall, contaminant levels fluctuated throughout the years, with highest values recorded in the earlier years of the study period. Sole histopathology showed alterations of mild severity. Results permitted to assess the environmental health status of the Bilbao estuary during 7 years, although no clear temporal trend was detected. Longer-term monitoring programmes are necessary to confirm the ecosystem recovery.

Toxicity Assessment of Impacted Sediments from Southeast Coast of Tunisia Using a Biomarker Approach with the Polychaete Hediste diversicolor

Toxicity caused by exposure to pollutants from marine sediments is a consequence of the interaction between biota and xenobiotics most frequently released by anthropogenic activities. The present work intended to characterize the toxicity of natural sediments putatively impacted by distinct human activities, collected at several sites located in the south of the Gulf of Gabes, Zarzis area, Tunisia. The selected toxicity criteria were analysed following ecologically relevant test conditions. Organisms of the polychaete species Hediste diversicolor were chronically exposed (28 days) to the mentioned sediments. Toxicity endpoints were biomarkers involved in the toxic response to common anthropogenic chemicals, namely neurotoxic (acetylcholinesterase), anti-oxidant (catalase, glutathione peroxidase), metabolic (glutathione S-transferases) enzymatic activities, and oxidative damage (lipid peroxidation, TBARS assay). The chemical characterization of sediments showed that the samples collected from the site near an aquaculture facility were highly contaminated by heavy metals (Cd, Cu, Cr, Hg, Pb, and Zn) and polycyclic aromatic hydrocarbons (fluorene, phenanthrene, anthracene, fluoranthene and pyrene). H. diversicolor individuals exposed to the sediments from this specific site showed the highest values among all tested biomarkers, suggesting that these organisms were possibly under a pro-oxidative stress condition potentially promoted by anthropogenic pollution. Moreover, it was possible to conclude that individuals of the polychaete species H. diversicolor responded to the chronic exposure to potentially contaminated sediments from the southeast coast of Tunisia, eliciting adaptive responses of significant biological meaning.

Enteric nervous system analyses: New biomarkers for environmental quality assessment

The gastrointestinal tract (GIT) of fish is a target of contaminants since it can absorb these substances. We evaluated the morphophysiological alterations in the GIT of Sphoeroides testudineus collected in two estuaries presenting differences in their environmental quality (NIA and IA). The intestine was analyzed for histological and neuronal changes; liver and gills for biochemical markers; muscle tissues for neurotoxicity and peripheral blood for genotoxic damage. The results showed alterations in the GIT of the animals collected in the IA, such as muscle tunica and goblet cell density reduction, increased intraepithelial lymphocytes density and changes in neuronal density. Furthermore, changes were observed in MTs and LPO in the gills. Thus, we suggest that TGI is functioning as a barrier that responds to ingested contaminants, in order to reduce their absorption and translocation. Thus, alterations in morphophysiological and enteric neurons in S. testudineus can be used as biomarkers of environmental contamination.

Bioaccumulation, cytotoxicity and oxidative stress of the acute exposure selenium in Oreochromis mossambicus

Selenium (Se) is an essential trace-element that becomes toxic when present at high concentrations for aquatic organisms. The knowledge about the mechanism of Se toxicity in freshwater ecosystem is still poorly studied. Thus the aim of the present study was to assess the impact of environmentally relevant concentrations of Se toxicity: 5, 10, 25, 50 and 100 µg/L or water only (control) for periods of 96 hour (h) to test for Se accumulation (gill, liver and brain), its effects on enzymatic and non-enzymatic antioxidant defenses (gill and liver), oxidative stress effects on lipid, protein (gill and liver), DNA (liver) and inhibition of AchE (brain) activity were measured in Mozambique tilapia, Oreochromis mossambicus. Our result showed that Se accumulation was observed in the gill, liver and brain tissues of fish exposed to different concentrations and accumulation varied upon different tissues. Enzymatic (SOD, CAT, GPx and GST) and non-enzymatic (GSH and MT) antioxidant enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione-s-transferase (GST) were significantly increased after 96 h exposure of higher concentrations Se in the gill and liver tissue with the exception of GST activity was significantly inhibited in liver after 96 h exposure of higher concentrations of Se. In contrast, catalase (CAT) activities were inhibited for both tissues of Se exposure at 96 h. Reduced glutathione (GSH) and Metallothionein (MT) levels were increased in the gill and liver tissues after exposure to Se for 96 h. We also observed that Se affected antioxidant defense, increasing oxidative stress indicator of lipid peroxidation (LPO) and protein carbonyl (PCO) in gill and liver tissues of fish exposed to Se for 96 h at the concentration dependent manner. Increased DNA damage scores observed in liver tissue of fish exposed to Se for concentrations dependent manner, indicating potential of Se on fish. We also observed inhibition of acetylcholine esterase (AchE) activity in brain tissue of fish exposed to Se for higher concentrations. The changes in these parameters can be used as suitable biomarkers for monitoring the toxicity of Se in the aquatic environment.

Baseline levels of environmental genotoxicity and potential confounding factors using common sole (Solea solea) as sentinel organism

Micronuclei (MN) and nuclear buds (NB) frequency was assessed monthly over a one-year period in erythrocytes of common soles (Solea solea) from the Basque continental shelf, a minor disturbed area, in order to determine baseline levels and potential biotic and abiotic confounding factors within biomonitoring purposes. Both genotoxic parameters presented seasonal variations, although only NB frequency was positively correlated with environmental variables (i.e. water temperature and salinity). On the contrary, MN and NB were not affected by age and gender. Therefore, samples of combined age and gender can be used for biomonitoring genotoxic effects, although sampling period together with water temperature and salinity should be thoroughly considered for NB. Overall, these findings are the first attempt to establish baseline MN (0.10-0.78‰) and NB (0.13-0.82‰) frequencies in common sole from Basque marine waters, which are useful for upcoming data comparisons and integration within genotoxicity evaluation procedures of similar marine environments under biomonitoring scopes.

Significance of metallothioneins in differential cadmium accumulation kinetics between two marine fish species

Impacted marine environments lead to metal accumulation in edible marine fish, ultimately impairing human health. Nevertheless, metal accumulation is highly variable among marine fish species. In addition to ecological features, differences in bioaccumulation can be attributed to species-related physiological processes, which were investigated in two marine fish present in the Canary Current Large Marine Ecosystem (CCLME), where natural and anthropogenic metal exposure occurs. The European sea bass Dicentrarchus labrax and Senegalese sole Solea senegalensis were exposed for two months to two environmentally realistic dietary cadmium (Cd) doses before a depuration period. Organotropism (i.e., Cd repartition between organs) was studied in two storage compartments (the liver and muscle) and in an excretion vector (bile). To better understand the importance of physiological factors, the significance of hepatic metallothionein (MT) concentrations in accumulation and elimination kinetics in the two species was explored. Accumulation was faster in the sea bass muscle and liver, as inferred by earlier Cd increase and a higher accumulation rate. The elimination efficiency was also higher in the sea bass liver compared to sole, as highlighted by greater biliary excretion. In the liver, no induction of MT synthesis was attributed to metal exposure, challenging the relevance of using MT concentration as a biomarker of metal contamination. However, the basal MT pools were always greater in the liver of sea bass than in sole. This species-specific characteristic might have enhanced Cd biliary elimination and relocation to other organs such as muscle through the formation of more Cd/MT complexes. Thus, MT basal concentrations seem to play a key role in the variability observed in terms of metal concentrations in marine fish species.

Historical legacies of river pollution reconstructed from fish scales

Many rivers have been impacted by heavy metal pollution in the past but the long-term legacies on biodiversity are difficult to estimate. The River Ulla (NW Spain) was impacted by tailings from a copper mine during the 1970-1980s but absence of baseline values and lack of subsequent monitoring have prevented a full impact assessment. We used archived fish scales of Atlantic salmon to reconstruct levels of historical copper pollution and its effects on salmon fitness. Copper bioaccumulation significantly increased over baseline values during the operation of the mine, reaching sublethal levels for salmon survival. Juvenile growth and relative population abundance decreased during mining, but no such effects were observed in a neighbouring river unaffected by mining. Our results indicate that historical copper exposure has probably compromised the fitness of this Atlantic salmon population to the present day, and that fish scales are suitable biomarkers of past river pollution.

The levels of oxidative stress and antioxidant capacity in hibernating Nanorana parkeri

The effect of hibernation on oxidative stress and antioxidant defense was assessed in the frog Nanorana parkeri which inhabits the southern Tibetan Plateau. We compared the indices of oxidative stress (GSSG/GSH), the degree of oxidative damage (content of carbonyl proteins and lipid peroxide products) and the activities of antioxidant enzymes (SOD, CAT, GPx, GST and GR) in liver, brain, heart and muscle of N. parkeri sampled during summer and winter. Obtained results showed that hibernation induced a significant decrease in the level of GSH in heart, liver, and muscle, while the ratio of GSSG/GSH markedly increased in all tissues except for muscle. Regarding oxidative damage, significant increases in TBARS were observed in all tissues of N. parkeri in the midst of hibernation, and the lipid peroxides level also clearly elevated in these tissues except the liver. In liver and brain, the level of carbonyl proteins was significantly higher in winter relative to summer. Additionally, the activity of antioxidant enzymes obviously reduced in the liver of hibernating N. parkeri. The total antioxidant capacity was also significantly lower in all tissues during winter than summer. In conclusion, hibernation in N. parkeri induced oxidative stress which was supported by oxidative damage to lipids and proteins with suppression of antioxidant defense.

Biomarker responses of Cu-induced toxicity in European seabass Dicentrarchus labrax: Assessing oxidative stress and histopathological alterations

A comprehensive approach to chemical accumulation and biological effects of short-term Cu exposure in juveniles of European seabass (Dicentrarchus labrax) has been achieved. Fish were exposed to 0.01-10mgL^-1 nominal Cu concentrations for 24-96h. Metal concentrations in water and gills, liver, muscle and brain tissues were studied along with oxidative stress biomarkers (superoxide dismutase, catalase, glutathione peroxidase, lipid peroxidation). Induction of oxidative damage was observed in all the organs with differential antioxidant responses; gills appearing as the most sensitive from low environmentally water Cu concentrations as 0.01mgL^-1. Histopathological alterations were also observed in liver and gills, even without a significant Cu accumulation. The results show that the combination of oxidative stress parameters, particularly lipid peroxidation and glutathione peroxidase activities, and histopathological alterations provide a good model fish and reliable early biomarkers for monitoring Cu pollution in seawater and might call for the protection agencies to revise the Cu environmental standards.

The influence of heavy metals on toxicogenetic damage in a Brazilian tropical river

Anthropogenic activities in tropical rivers favor the eutrophication process, which causes increased concentration of heavy metals. The presence and bioaccumulation of metals are directly related to the presence of genotoxic damage in aquatic organisms. Thus, we evaluated the presence of heavy metals (Fe, Zn, Cr, Cu and Al) and performed toxicogenetic tests in surface (S) and bottom (B) of water samples of the Poti river (Piaui/Brazil). Cytotoxicity and genotoxicity tests were performed in Allium cepa, and micronucleus (MN) and comet assay were performed in Oreochromis niloticus. The chemical analysis showed concentrations above the limit for Cu, Cr, Fe and Al according to Brazilian laws, characterizing anthropogenic disturbance in this aquatic environment. Toxicogenetic analysis presented significant cytotoxic, mutagenic and genotoxic effects in different exposure times and water layers (S and B), especially alterations in mitotic spindle defects, MN formations, nuclear bud and DNA strand breaks. Correlations between Fe and cytotoxicity, and Al and mutagenicity were statistically significant and point out to the participation of heavy metals in genotoxic damage. Therefore, Poti river water samples presented toxicogenetic effects on all bioindicators analyzed, which are most likely related to heavy metals pollution.

Impairment of antioxidant mechanisms in Japanese Medaka (Oryzias latipes) by acute exposure to aluminum

Increasing aluminum (Al) concentrations in aquatic habitats as a result of anthropogenic acidification and industrialization is a global issue. Moreover, in extensive areas of the humid tropics and subtropics, high Al concentrations in freshwater are observed because of both naturally low pH and high Al concentrations in soil. Al increases production of reactive oxygen species and enhances oxidative damage in mammals. However, no studies have examined the effect of environmentally relevant concentrations of Al at low pH on oxidative stress in fish. This study assessed Al-induced effects on enzymatic and non-enzymatic antioxidants, lipid peroxidation, and on expression of oxidative stress-related genes at low pH using Japanese Medaka (Oryzias latipes). Larval fish were exposed to dissolved Al concentrations of 0, 1.7, 6.2 and 16.7μgL^-1 for 4days at pH5.3 in soft water. Al caused a significant reduction in activity of glutathione peroxidase at 6.2 and 16.7μgL^-1, and of glutathione reductase at 16.7μgL^-1 in whole body homogenates. No changes were observed in the expression of the glutathione peroxidase gene, and expression levels of the glutathione reductase gene were too low to be quantitated. Even though there was an overall decrease in the activity of catalase and in the concentration of glutathione, differences were not significant compared to the control. Changes in lipid peroxidation were not found. This study showed that exposure to environmentally relevant concentrations of Al at low pH impairs antioxidant defense mechanisms of Medaka.

Fluctuating asymmetry rather than oxidative stress in Bufo raddei can be an accurate indicator of environmental pollution induced by heavy metals

Oxidative stress (OS) and fluctuating asymmetry (FA) as risk markers for environmental stress are widely used to predict changes in the health and fitness of many animals exposed to pollutants. However, from the perspective of protecting declining amphibians, it remains to be verified which one would be a reliable indicator for amphibians exposed to long-term heavy metal pollution under natural conditions. In this study, the OS and FA of Bufo raddei exposed to natural heavy metal pollution were analyzed to determine which marker is more accurate for indicating heavy metal-induced stress. Three years of data were collected during the breeding season of B. raddei from Baiyin (BY), which has been mainly contaminated with Cu, Zn, Pb, and Cd compounds for a long period, and from Liujiaxia (LJX), which is a relatively unpolluted area. Unexpectedly, although significant accumulation of the four heavy metals was found in the kidney and liver of B. raddei from BY, the levels of superoxide dismutase, glutathione peroxidase, and malondialdehyde in these two organs were found to be irregular, with low repeatability in both BY and LJX. However, significant differences in the levels of FA were observed in B. raddei populations from these two areas over the past 3 years (P < 0.01). The degrees of FA in B. raddei populations from BY and LJX were assessed as degree 4 and 1, respectively. In short, this study suggested that FA was a more reliable and effective indicator than OS to monitor and predict long-term environmental stress on anuran amphibians.

Trace element and metal sequestration in vitellaria and sclerites, and reactive oxygen intermediates in a freshwater monogenean, Paradiplozoon ichthyoxanthon

Exposure to metals and other trace elements negatively affects infection dynamics of monogeneans, including diplozoids, but, physiological mechanisms linked to exposure have yet to be documented. In this study sequestration of trace elements and reactive oxygen intermediate production in the monogenean, Paradiplozoon ichthyoxanthon, was demonstrated. During dissection of host fish, Labeobarbus aeneus, the gills were excised and assessed for P. ichthyoxanthon, which were removed and frozen for fluorescence microscopy or fixed for transmission electron microscopy. Trace elements were sequestered in the vitellaria and sclerites in P. ichthyoxanthon, and the presence of reactive oxygen intermediates was observed predominantly in the tegument of the parasite. Trace elements and metals identified and ranked according to weight percentages (wt%) in the vitellaria were Cu > C > Au > O > Cr > Fe > Si while for the sclerites C > Cu > O > Au > Fe > Cr > Si were identified. For most element detected, readings were higher in the vitellaria than the sclerites, except for C and O which were higher in sclerites. Specifically for metals, all levels detected in the vitellaria were greater than in sclerites. Based on the proportion of trace elements present in the vitellaria and sclerites it appears that most trace elements including metals were sequestered in the vitellaria. The results of reactive oxygen intermediate production in the tegument of the parasite suggests either trace element accumulation takes place across the tegument or results from the action of the host's immune response on the parasite. The results serve as the first demonstration of trace element sequestration and reactive oxygen intermediates in a freshwater monogenean parasite.

Uranium (238U)-induced ROS and cell cycle perturbations, antioxidant responses and erythrocyte nuclear abnormalities in the freshwater iridescent shark fish Pangasius sutchi

The strategic plan of this study is to analyze any possible radiological impact on aquatic organisms from forthcoming uranium mining facilities around the Nagarjuna Sagar Dam in the future. The predominantly consumed and dominant fish species Pangasius sutchi, which is available year-round at Nagarjuna Sagar Dam, was selected for the study. To comprehend the outcome and to understand the mode of action of ²³⁸U, the fish species Pangasius sutchi was exposed to ¼ and ½ of the LC₅₀ doses of waterborne ²³⁸U in a static system in duplicate for 21 days. Blood and organs, including the gills, liver, brain and muscles, were collected at different time periods-0h, 24h, 48h, 72h, 96h, 7, days 14days and 21 days-using ICP-MS to determine the toxic effects of uranium and the accumulation of ²³⁸U concentrations. The bioaccumulation of ²³⁸U in P. sutchi tissues was dependent on exposure time and concentration. The accumulation of uranium was, in order of magnitude, measured as gills>liver>brain>tissue, with the highest accumulation in the gills. It was observed that exposure to ²³⁸U significantly reduced antioxidant enzymes such as superoxide dismutase, catalase, and lipid peroxidase. The analysis of DNA fragmentation by comet assay and cell viability by flow cytometry was performed at different time intervals. DNA histograms by flow cytometry analysis revealed an increase in the G2/M phase and the S phase. The long-term ²³⁸U exposure studies in fish showed increasing micronucleus frequencies in erythrocytes with greater exposure time. The higher the concentration of ²³⁸U is, the greater is the effect observed, suggesting a close relationship between accumulation and toxicity. A possible ROS-mediated ²³⁸U toxicity mechanism and antioxidant responses have been proposed.

A protocol for identifying suitable biomarkers to assess fish health: A systematic review

Background

Biomarkers have been used extensively to provide the connection between external levels of contaminant exposure, internal levels of tissue contamination, and early adverse effects in organisms.

Objectives

To present a three-step protocol for identifying suitable biomarkers to assess fish health in coastal and marine ecosystems, using Gladstone Harbour (Australia) as a case study.

Methods

Prior to applying our protocol, clear working definitions for biomarkers were developed to ensure consistency with the global literature on fish health assessment. First, contaminants of concern were identified based on the presence of point and diffuse sources of pollution and available monitoring data for the ecosystem of interest. Second, suitable fish species were identified using fisheries dependent and independent data, and prioritised based on potential pathways of exposure to the contaminants of concern. Finally, a systematic and critical literature review was conducted on the use of biomarkers to assess the health of fish exposed to the contaminants of concern.

Results/Discussion

We present clear working definitions for bioaccumulation markers, biomarkers of exposure, biomarkers of effect and biomarkers of susceptibility. Based on emission and concentration information, seven metals were identified as contaminants of concern for Gladstone Harbour. Twenty out of 232 fish species were abundant enough to be potentially suitable for biomarker studies; five of these were prioritised based on potential pathways of exposure and susceptibility to metals. The literature search on biomarkers yielded 5,035 articles, of which 151met the inclusion criteria. Based on our review, the most suitable biomarkers include bioaccumulation markers, biomarkers of exposure (CYP1A, EROD, SOD, LPOX, HSP, MT, DNA strand breaks, micronuclei, apoptosis), and biomarkers of effect (histopathology, TAG:ST).

Conclusion

Our protocol outlines a clear pathway to identify suitable biomarkers to assess fish health in coastal and marine ecosystems, which can be applied to biomarker studies in aquatic ecosystems around the world.

Developmental exposure to heavy metals alters visually-guided behaviors in zebrafish

This laboratory-based study determined the consequences of heavy metal exposure using zebrafish Danio rerio. Embryos were transiently exposed to environmentally-relevant concentrations of cadmium or nickel until 72 h postfertilization (hpf), then they were returned to system water and allowed to grow until 7, 9, and 11 days postfertilization (dpf), when they were examined morphologically and behaviorally. Morphological measures of notochord length, eye diameter, and inter-eye distance were not different across treatments; however, significant differences in optomotor responses were observed in treated larvae at all ages tested. These results suggest that initial developmental exposure to cadmium and nickel significantly impacts visually-guided larval behavior. The absence of significant differences in gross morphology suggests that the effects of these metals are subtle and may occur at the cellular level. By using this ecologically relevant model and pollutant type, this study has broad application and implications with regard to safe levels of contaminant in drinking water and freshwater ecosystems.

Insight into the heat resistance of fish via blood: Effects of heat stress on metabolism, oxidative stress and antioxidant response of olive flounder Paralichthys olivaceus and turbot Scophthalmus maximus

High temperature has direct confinement on fish survival and growth, especially under the background of global warming. Selection of fish line with heat resistance is an important means to address this problem. In the present study, we analyzed the difference in heat resistance between families of olive flounder Paralichthys olivaceus and turbot Scophthalmus maximus, two flatfish species occupying slightly different thermal niches. Then the chosen families were tested to determine their differential response to heat stress (ΔT = +8 °C and +12 °C) in blood, including anaerobic metabolism (lactate), oxidative stress (lipid peroxidation and protein carbonylation) and antioxidant enzymes. Results showed a difference in heat resistance between families of the two species. Among the chosen parameters, growth traits had a significant effect on contents of lactate and malondialdehyd (MDA), and activities of catalase (CAT) and glutathione S-transferase in flounder (P < 0.05), and on MDA content and CAT activity in turbot (P < 0.05). In comparison with heat-sensitive family of each species, levels of all studied parameters were lower and more stable in heat-resistant families after heat stress. What's more, heat resistance of fish significantly influenced contents of lactate and MDA and activity of CAT in flounder (P < 0.05), as well as contents of lactate, MDA and carbonyl and activity of superoxide dismutate (SOD) in turbot (P < 0.05). These results demonstrated that such physiological phenotypes as anaerobic metabolism, oxidative stress and antioxidant enzymes are good biomarkers of fish heat-resistance, being potentially valuable in fish breeding. However, these markers should be applied with more caution when there is a growth discrepancy between fish families.

Acclimation capacity of the three-spined stickleback (Gasterosteus aculeatus, L.) to a sudden biological stress following a polymetallic exposure

To get closer to the environmental reality, ecotoxicological studies should no longer consider the evaluation of a single pollutant, but rather combination of stress and their interaction. The aim of this study was to determine if responses of a fish to a sudden biological stress could be modified by a prior exposure to a chemical stress (a polymetallic contamination). For this purpose, in situ experiment was conducted in three ponds in the Haute-Vienne department (France). One pond was chosen for its high uranium concentration due to uranium mine tailings, and the two other ponds, which were not submitted to these tailings. Three-spined sticklebacks (Gasterosteus aculeatus) were caged in these ponds for 14 days. After this period, fish were submitted to a biological stress, exerted by lipopolysaccharides injection after anesthesia, and were sacrificed 4 days after these injections for multi-biomarkers analyses (leucocyte viability, phagocytic capacity and reactive oxygen species production, antioxidant peptide and enzymes, lipid peroxidation and DNA damage). The pond which received uranium mine tailings had higher metallic concentrations. Without biological stress, sticklebacks caged in this pond presented an oxidative stress, with increasing of reactive oxygen species levels, modification of some parts of the antioxidant system, and lipid peroxidation. Caging in the two most metal-contaminated ponds resulted in an increase of susceptibility of sticklebacks to the biological stress, preventing their phagocytic responses to lipopolysaccharides and modifying their glutathione contents and glutathione-S-transferase activity.

Biomarker responses in eelpouts from four coastal areas in Sweden, Denmark and Germany

To increase our understanding of possible chemical impacts on coastal fish populations in the Baltic Sea, Kattegat and Skagerrak, the viviparous eelpout (Zoarces viviparus) was used as sentinel species in two major sampling campaigns (spring and autumn) in 16 different coastal sites. Condition factor (CF), liver somatic index (LSI), gonad somatic index (GSI) were measured and the activity of the hepatic enzymes ethoxyresorufin-O-deethylase (EROD), glutathione reductase GR), glutathione S-transferase (GST), catalase (CAT) and muscular activity of acetylcholinesterase (AChE) were assessed. PAH metabolites in bile were also analyzed. The most notable finding in the data set was the low EROD activity in eelpouts collected at the relatively polluted region in Germany compared to the other regions, which could be due to an inhibition of the CYP1A-system or to adaptation to chronic exposure of pollutants in this area. Additionally, low AChE activity was noted in the German region in the autumn campaign and low AChE activity detected in the Danish region in the spring campaign. These differences suggest possible season-specific differences in the use and release of AChE-inhibiting chemicals in the Danish and German regions. Clustering of biomarkers on site level indicated a relationship between CF and GSI and suggested that sites with a high CF contained eelpout that put a larger effort into their larvae development. Clustering of the oxidative stress markers GR, GST and CAT on the individual level reflected a possible coordinated regulation of these enzymes. Overall, the results support the importance of taking into account general regional differences and seasonal variation in biomarker activity when monitoring and assessing the effects of pollution. Despite the expected seasonal variation for most of the measured endpoint, several markers (GSI, EROD and CF) vary similarly between all selected sites in both spring and autumn. This suggests that the differences between sites for these endpoints are independent of season.

In situ effects of metal contamination from former uranium mining sites on the health of the three-spined stickleback (Gasterosteus aculeatus, L.)

Human activities have led to increased levels of various pollutants including metals in aquatic ecosystems. Increase of metallic concentrations in aquatic environments represents a potential risk to exposed organisms, including fish. The aim of this study was to characterize the environmental risk to fish health linked to a polymetallic contamination from former uranium mines in France. This contamination is characterized by metals naturally present in the areas (manganese and iron), uranium, and metals (aluminum and barium) added to precipitate uranium and its decay products. Effects from mine releases in two contaminated ponds (Pontabrier for Haute-Vienne Department and Saint-Pierre for Cantal Department) were compared to those assessed at four other ponds outside the influence of mine tailings (two reference ponds/department). In this way, 360 adult three-spined sticklebacks (Gasterosteus aculeatus) were caged for 28 days in these six ponds before biomarker analyses (immune system, antioxidant system, biometry, histology, DNA integrity, etc.). Ponds receiving uranium mine tailings presented higher concentrations of uranium, manganese and aluminum, especially for the Haute-Vienne Department. This uranium contamination could explain the higher bioaccumulation of this metal in fish caged in Pontabrier and Saint-Pierre Ponds. In the same way, many fish biomarkers (antioxidant and immune systems, acetylcholinesterase activity and biometric parameters) were impacted by this environmental exposure to mine tailings. This study shows the interest of caging and the use of a multi-biomarker approach in the study of a complex metallic contamination.

Accumulation of heavy metals and antioxidant responses in Pinus sylvestris L. needles in polluted and non-polluted sites

The purpose of this study was to determine the concentrations of heavy metals (cadmium, iron, manganese, lead and zinc) in current-year, 1-year old and 2-year old needles of Pinus sylvestris L. Trees were from three heavily polluted (immediate vicinity of zinc smelter, iron smelter and power plant) and three relatively clean sites (nature reserve, ecologically clean site and unprotected natural forest community) in southern Poland. Analysis also concerned the antioxidant response and contents of protein, proline, total glutathione, non-protein thiols and activity of guaiacol peroxidase (GPX) in the needles. Generally, in pine needles from the polluted sites, the concentrations of the metals were higher and increased with the age of needles, and in most cases, antioxidant responses also were elevated. The highest levels of Cd, Pb and Zn were found in 2-year old pine needles collected near the polluted zinc smelter (respectively: 6.15, 256.49, 393.5 mg kg(-1)), Fe in 2-year old pine needles in the vicinity of the iron smelter (206.82 mg kg(-1)) and Mn in 2-year old needles at the ecologically clean site (180.32 mg kg(-1)). Positive correlations were found between Fe, Mn and Pb and the content of proteins and NPTs, between Cd and non-protein -SH groups, and between Zn and proline levels. The activity of GPX increased under the influence of Mn, while glutathione levels tended to decrease as Mn levels rose. The data obtained show that the levels of protein and non-protein -SH groups may be useful in biological monitoring, and that these ecophysiological parameters seem to be good evidence of elevated oxidative stress caused by heavy metals.

Use of Arius thalassinus fish in a pollution biomonitoring study, applying combined oxidative stress, hematology, biochemical and histopathological biomarkers: A baseline field study

The present field study aimed to determine the extent of pollution in the Red Sea coast of Yemen Republic using a battery of biomarkers in sea catfish, Arius thalassinus, originating from a reference site in comparison with a polluted site. We reported the concentration of heavy metals in some vital fish organs and their effects on the morphological, hematological, biochemical and oxidative stress biomarkers accompanied by the examination of histopathological alterations. The obtained results showed clear signs of stress in fish from a polluted site. Linear correlation analysis exhibited that the biomarkers response could be linked to the detected metals bioaccumulation. In addition, principal component analysis showed a clear separation of sampling sites in two different assemblages. Semi-quantitative analysis for the observed histopathological lesions revealed that gills were the most affected organs with signs of severe alterations. This field investigation provides a baseline data on pollution status in this region.

An Overview of Seasonal Changes in Oxidative Stress and Antioxidant Defence Parameters in Some Invertebrate and Vertebrate Species

Antioxidant defence system, a highly conserved biochemical mechanism, protects organisms from harmful effects of reactive oxygen species (ROS), a by-product of metabolism. Both invertebrates and vertebrates are unable to modify environmental physical factors such as photoperiod, temperature, salinity, humidity, oxygen content, and food availability as per their requirement. Therefore, they have evolved mechanisms to modulate their metabolic pathways to cope their physiology with changing environmental challenges for survival. Antioxidant defences are one of such biochemical mechanisms. At low concentration, ROS regulates several physiological processes, whereas at higher concentration they are toxic to organisms because they impair cellular functions by oxidizing biomolecules. Seasonal changes in antioxidant defences make species able to maintain their correct ROS titre to take various physiological functions such as hibernation, aestivation, migration, and reproduction against changing environmental physical parameters. In this paper, we have compiled information available in the literature on seasonal variation in antioxidant defence system in various species of invertebrates and vertebrates. The primary objective was to understand the relationship between varied biological phenomena seen in different animal species and conserved antioxidant defence system with respect to seasons.

The use of biotic and abiotic components of Red Sea coastal areas as indicators of ecosystem health

A biomonitoring study was conducted using some biotic (Pomadasys hasta and Lutjanus russellii fish) and abiotic (water and sediment) components of the Red Sea coast of Hodeida, Yemen Republic along two polluted sites (Al-Dawar beach and Urj village) in comparison to a reference site (Al-Nukhailah beach). The studied fish biomarkers included hepatosomatic index (HSI), condition factor (K), scaled mass index (SMI), catalase, glutathione-S-transferase (GST), malondialdehyde (MDA), total protein and albumin. In addition, metals (Fe, Cu, Zn, Pb and Cd) concentrations in water and sediment were measured and sediment pollution assessment was carried out using contamination factor (CF), geoaccumulation index (Igeo), pollution load index (PLI) and enrichment factor (EF). The studied metals concentration in water and sediment samples showed significant increase among the polluted sites in comparison to the reference site. Sediment pollution assessment generally confirmed that Urj village was the most contaminated site followed by Al-Dawar beach. Catalase, GST and MDA proved to be the most responsive biomarkers with increased values of GST and MDA at sites influenced by agricultural, urban and industrial activities while catalase, HSI, K, SMI, total protein and albumin showed the opposite trend. This study recommends monitoring of sediment Igeo and EF values as well as SMI, catalase, GST and MDA as sensitive indicators of different anthropogenic activities and their effects on aquatic ecosystems under complex and different gradients of metal pollution. In addition, P. hasta proved to be more sensitive towards the detected pollution condition.

Longevity of animals under reactive oxygen species stress and disease susceptibility due to global warming

The world is projected to experience an approximate doubling of atmospheric CO₂ concentration in the next decades. Rise in atmospheric CO₂ level as one of the most important reasons is expected to contribute to raise the mean global temperature 1.4 °C-5.8 °C by that time. A survey from 128 countries speculates that global warming is primarily due to increase in atmospheric CO₂ level that is produced mainly by anthropogenic activities. Exposure of animals to high environmental temperatures is mostly accompanied by unwanted acceleration of certain biochemical pathways in their cells. One of such examples is augmentation in generation of reactive oxygen species (ROS) and subsequent increase in oxidation of lipids, proteins and nucleic acids by ROS. Increase in oxidation of biomolecules leads to a state called as oxidative stress (OS). Finally, the increase in OS condition induces abnormality in physiology of animals under elevated temperature. Exposure of animals to rise in habitat temperature is found to boost the metabolism of animals and a very strong and positive correlation exists between metabolism and levels of ROS and OS. Continuous induction of OS is negatively correlated with survivability and longevity and positively correlated with ageing in animals. Thus, it can be predicted that continuous exposure of animals to acute or gradual rise in habitat temperature due to global warming may induce OS, reduced survivability and longevity in animals in general and poikilotherms in particular. A positive correlation between metabolism and temperature in general and altered O₂ consumption at elevated temperature in particular could also increase the risk of experiencing OS in homeotherms. Effects of global warming on longevity of animals through increased risk of protein misfolding and disease susceptibility due to OS as the cause or effects or both also cannot be ignored. Therefore, understanding the physiological impacts of global warming in relation to longevity of animals will become very crucial challenge to biologists of the present millennium.

Effects of low arsenic concentration exposure on freshwater fish in the presence of fluvial biofilms

Arsenic (As) is a highly toxic element and its carcinogenic effect on living organisms is well known. However, predicting real effects in the environment requires an ecological approach since toxicity is influenced by many environmental and biological factors. The purpose of this paper was to evaluate if environmentally-realistic arsenic exposure causes toxicity to fish. An experiment with four different treatments (control (C), biofilm (B), arsenic (+As) and biofilm with arsenic (B+As)) was conducted and each one included sediment to enhance environmental realism, allowing the testing of the interactive effects of biofilm and arsenic on the toxicity to fish. Average arsenic exposure to Eastern mosquitofish (Gambusia holbrooki) was 40.5 ± 7.5 μg/L for +As treatment and 34.4 ± 1.4 μg/L for B+As treatment for 56 days. Fish were affected directly and indirectly by this low arsenic concentration since exposure did not only affect fish but also the function of periphytic biofilms. Arsenic effects on the superoxide dismutase (SOD) and glutathione reductase (GR) activities in the liver of mosquitofish were ameliorated in the presence of biofilms at the beginning of exposure (day 9). Moreover, fish weight gaining was only affected in the treatment without biofilm. After longer exposure (56 days), effects of exposure were clearly seen. Fish showed a marked increase in the catalase (CAT) activity in the liver but the interactive influence of biofilms was not further observed since the arsenic-affected biofilm had lost its role in water purification. Our results highlight the interest and application of incorporating some of the complexity of natural systems in ecotoxicology and support the use of criterion continuous concentration (CCC) for arsenic lower than 150 μg/L and closer to the water quality criteria to protect aquatic life recommended by the Canadian government which is 5 μg As/L.