Oil spill in an amazon blackwater environment: Biochemical and physiological responses of local fish species

The accidental spill of petroleum asphalt cement (PAC) in São Raimundo (SR Harbor, located on the Rio Negro (Manaus, Amazonas, Brazil) was monitored through the analysis of polyciclic aromatic hydrocarbons (PAHs) in water and a set of biomarkers in fishes (exposure biomarkes: PAHs-type metabolites concentrations in bile; the activities of ethoxyresorufin-O-deethylase (EROD), glutathione-S-transferase (GST), catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) in liver. Effect biomarkers: lipid peroxidation concentration (LPO) in liver, acetylcholinesterase activity in brain, and genotoxic DNA damage in erythrocytes). Two fish species, Acarichthys heckelii and Satanoperca jurupari, were collected 10, 45, and 90 days after the PAC spill in São Raimundo. At the same time, fish were collected from the Tupé Sustainable Development Reserve (Tupé) which served as a reference area. The sampling periods were related to the rising waters of the natural flood pulse of the Rio Negro. Higher concentrations of PAHs in water were observed at 10 and 45 days and returned to the values of TP 90 days after the PAC spill, a period in which harbor waters rose about 0.2 m. Unlike the PAHs in water, biomarker responses in both fish species significantly increased following the PAC spill in SR. Hepatic ethoxyresorufin-O-deethylase (EROD), PAH-like metabolites in bile, and erythrocyte DNA damage increases, together with inhibition of acetylcholinesterase (AChE) activity in the brain were the most evident responses for both fish species. The calculated pyrolytic index showed mixed sources of PAHs (petrogenic and pyrolytic). The applied PCA-FA indicated important relationships between dissolved organic carbon (DOC) and PAHs concentrations in water, where DOC and PAHs concentrations contributed to biomarkers responses for both fish species in all collection periods.

The concentrations of polycyclic aromatic hydrocarbons in fish: A systematic review

This study was conducted on the concentrations of PAHs, including benzo[a]pyrene and the sum of four PAHs (benz[a]anthracene, chryseno, benzo[b]fluoranthene, and benzo[a]pyrene), in unsmoked fish tissues. The values were related to the time period, locality (country and region), living habits, eating habits, and types of environments of the fish species. The data obtained has been also compared with the limits established by the United States Environmental Protection Agency (U.S. EPA) and European Union (E.U.) legislation. The data were collected through a PRISMA systematic review (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) from 1982 to 2020. Only documents that presented the PAHs concentration values were selected. China, Nigeria, and Iran had the highest number of studies. The species Coptodon zillii, Siganus punctatus, and Liza abu were the most commonly used bioindicators. Fish inhabiting demersal and pelagic environments showed the highest concentrations of PAHs. The majority of PAH concentrations of the analyzed documents fell within permissible limits for human consumption, representing a total percentage of 79.49 % for benzo[a]pyrene and 82.86 % for the sum of the 4 PAHs. Although some studies identified concentrations of benzo[a]pyrene alone and benzo[a]pyrene, benz[a]anthracene, chryseno, benzo[b]fluoranthene above the legislation limits, in most of them, the concentrations reported in fish tissue were below the limits defined by European Legislation for human consumption.

Osmoregulatory responses in the neotropical fish species Astyanax lacustris, exposed to single and combined microplastics, polycyclic aromatic hydrocarbons, and their mixture

Microplastic (MP) pollution poses a significant environmental threat. These MPs can adsorb toxic compounds such as polycyclic aromatic hydrocarbons (PAH), which are highly lipophilic and carcinogenic. To assess the potential effects of virgin MP, PAH, and MP+PAH in association with osmoregulation and energetic substrate, we conducted experiments with the tetra cardinal Astyanax lacustris. The environmentally relevant concentration of MP (10 mg L-1) and 20 % of the LC50-96 h of crude oil for A. lacustris (2.28 µg L-1) were used during the 96-h exposure. Fish were exposed to virgin MP, PAH, MPC (MP loaded with PAH), PAH+MP (PAH and MP in association), and the control without (CT) and with handling (CH). After 96 h, blood was collected for osmoregulatory parameters (plasma osmolality; Na+, K+, Cl-, Mg2+; glycose and lactate); gills for osmoregulatory enzyme activities (Na+, K+ ATPase, H+ ATPase, and carbonic anhydrase); and white muscle samples were used to determine glycogen as an energetic substrate. The low molecular weight PAH was not detected in PAH-loaded MP (MPC) and PAH in combination with MP (PAH+MP). The PAH concentration of the MPC and PAH+MP was similar and low compared to other works. Virgin MP, PAH, MPC, and PAH+MP were able to cause muscle glycogen depletion. The activity of v-type H+ ATPase and plasma Na+ concentrations were lower in PAH with MP (MPC). However, the hydromineral balance (K+, Mg2+, Cl-, and osmolality) was not affected by any treatment. In this sense, we can conclude that the MPC caused osmoregulatory disturbances not seen in the MP associated with PAH (MP+PAH). However, this seems unrelated to the PAH leaking from the MPC or the PAH absorption to the virgin MP once the PAH concentrations from the MPC and PAH+MP were similar.

Emersion and recovery alter oxygen consumption, ammonia and urea excretion, and oxidative stress parameters, but not diffusive water exchange or transepithelial potential in the green crab (Carcinus maenas)

The green crab (C. maenas) is an "inshore" species affected by intertidal zonation patterns, facing periods of emersion during low tide, and submersion during high tide. During these periods of air and subsequent water exposure, these species can face physiological challenges. We examined changes in O2 consumption rate (MO2), ammonia (JAmmnet) and urea (JUreanet) excretion rates over sequential 14 h periods in seawater (32 ppt, control), in air, and during recovery in seawater after air exposure (13°C throughout). At the end of each exposure, the anterior (5th) and posterior (8th) gills, and the hepatopancreas were removed for measurements of oxidative stress parameters (TBARs and catalase in the gills and hepatopancreas, and protein carbonyls in the gills). MO2 remained unchanged during air exposure, but increased greatly (3.4-fold above control levels) during the recovery period. Ammonia and urea net fluxes (JAmmnet and JUreanet) were reduced by 98% during air exposure, but rebounded during recovery to >2-fold the control rates. Exchangeable water pools (VH2O), rate constants of diffusive water exchange (k), and unidirectional diffusive water flux rates (JH2O) (using tritiated water) and transepithelial potential (TEP) were also measured during control and recovery treatments, but exhibited no significant changes. Damage to proteins was not observed in either gill. However, lipid damage occurred in the anterior (respiratory) gill after the air exposure but not in the posterior (ionoregulatory) gill or hepatopancreas. Catalase activity also decreased significantly in recovery relative to levels during air exposure in both the anterior gill and hepatopancreas, but not in the posterior gill. The crabs did not modify water metabolism or permeability. We conclude that MO2 can be maintained during air exposure, it does not meet increased metabolic demand, and ammonia and urea-N excretion are impaired. As a result, all these parameters increase greatly during re-immersion recovery, and oxidative stress also occurs. Clearly, emersion is not without physiological costs.

Settleable atmospheric particulate matter harms a marine invertebrate: Integrating chemical and biological damage in a bivalve model

Some atmospheric pollutants may affect aquatic ecosystems after settling, generating contamination, bioaccumulation, and threats to aquatic species. Metallurgical processes result in the emission of settleable atmospheric particulate matter (SePM), including metals and metalloids, along with rare earth elements (REE) that are considered emerging contaminants. We report the 30-day exposure of brown mussels (Perna perna) to SePM collected in a metallurgical area of southeast Brazil close to estuarine ecosystems, followed by a 30-day clearance period, to evaluate the toxic potential of SePM to this model mollusk. The bioaccumulation of 28 elements identified in SePM and the sublethal effects were evaluated. REEs were found in SePM (Ce, Y, and La). Significant bioaccumulation of eight metals (Fe, Ni, Cu, Zn, Rb, Sr, Cd, and Ba) was found in the bivalves and correlates with the cytotoxicity and genotoxicity, showing a dose-dependent mode and suggesting a pre-pathological condition that could lead to ecological disturbances over time. Conversely, the unchanged lipid-peroxidation level after SePM exposure could indicate the effectiveness of the antioxidant system in protecting gills and digestive glands. The clearance period was not enough to successfully reverse the negative effects observed. So far, the current results enhance the comprehension of the negative role of SePM on metal bioaccumulation and metal-induced toxicity to aquatic biota. Thus, this report adds innovative findings on the role of SePM in aquatic pollution in coastal areas affected by atmospheric pollution, which should be relevant for future public policies to verify and control the environmental pollution.

Response of Oreochromis niloticus (Teleostei: Cichlidae) exposed to a guanitoxin-producing cyanobacterial strain using multiple biomarkers

Changes in environmental conditions in aquatic ecosystems caused by anthropic actions can modify the composition of primary producers, promoting the excessive proliferation of cyanobacteria. These organisms can form cyanobacterial blooms, which directly affect aquatic life. The present study investigated the mutagenicity of the cyanobacterium Sphaerospermopsis torques-reginae (strain ITEP-024), guanitoxin-producing (natural organophosphate), and sublethal effects on fish in relevant environment concentrations. For this, the Ames test (Salmonella/microsome) was performed as a mutagenic assay for extracts of the ITEP-024 strain. Specimens of Oreochromis niloticus (Teleostei: Cichlidae) were subjected to acute 96 h exposure to different concentrations of aqueous extract of the strain: C = control group; T1 = 31.25 mg/L; T2 = 62.5 mg/L; T3 = 125 mg/L; and T4 = 250 mg/L. Genotoxic, biochemical, osmoregulatory, and physiologic biomarkers were analyzed. Our results showed that the cyanobacterium had a weak mutagenic response for the TA102 strain of Salmonella with and without metabolic activation by S9. Strains TA98 and TA100 were not affected. Fish from treatments T3 and T4 showed changes in oxidative stress (CAT, SOD, and GST enzymes), inhibition of the enzyme acetylcholinesterase activity, micronucleus formation, and osmoregulatory disorders. No guanitoxin accumulation was detected in the different tissues of O. niloticus by LC-MS/MS. Our results showed unprecedented mutagenicity data of the guanitoxin-producing cyanobacteria by the Ames test and biochemical, osmoregulatory, and genotoxic disorders in fish, providing efficient aquatic contamination biomarkers. Despite the great concern related to the presence of guanitoxin in blooms in freshwater ecosystems, its concentration is not yet regulated, and thus there is no monitoring agenda in current legislation.

Contamination gradient affects differently carbonic anhydrase activity of mollusks depending on their feeding habits

Aquatic organisms that inhabit coastal areas are often exposed to several contaminants. It is known that the bioaccumulation of contaminants can be amplified according to the species feeding habits and contaminant properties. As a consequence, species can experience different effects to contaminant exposure even if they inhabit the same area. The present study aimed to investigate the activities of carbonic anhydrase (CA), Ca²⁺-ATPase, and Mg²⁺-ATPase in different tissues (soft tissue, mantle, and gill) of three mollusk species (Lottia subrugosa, Stramonita brasiliensis, and Crassostrea brasiliana) with different feeding habits (herbivore, carnivore, and filter-feeder, respectively) which were sampled within a known contamination gradient at Santos Estuarine System (Southeastern Brazil). From the three enzymes tested, only CA was affected by the presence of contaminants within the contamination gradient evaluated. In general, the CA activity from the three species were lower in contaminated sites when compared to the reference site. The contrasting CA activity response observed in S. brasiliensis compared to L. subrugosa and C. brasiliana could be related to the tissue-specificity of this enzyme activity and species feeding habits (filter-feeders can accumulate more contaminants than herbivores and even carnivores). Results indicated that C. brasiliana mantle is the most suitable tissue for the use of CA analysis as a biomarker.

Physicochemical properties of the dissolved organic carbon can lead to different physiological responses of zebrafish (Danio rerio) under neutral and acidic conditions

Previous studies have suggested that the capacity of natural dissolved organic carbon (DOC) molecules to interact with biological membranes is associated with their aromaticity (SAC₃₄₀ ); origin (allochthonous versus autochthonous, FI); molecular weight (Abs_254/365 ); and relative fluorescence of DOC moieties (PARAFAC analysis). These interactions may be especially important when fish are challenged by acidic waters, which are known to inhibit the active uptake of Na⁺ and Cl^- , while stimulating diffusive ion losses in freshwater fishes. Therefore, zebrafish were acclimated (7 days, pH 7.0) to five natural DOC sources (10 mg C/L), two from the Amazon Basin and three from Canada, together with a "no-added DOC" control. After the acclimation, fish were challenged by exposure to acidic water (pH 4.0) for 3 h. Osmoregulatory parameters were measured at pH 7.0 and 4.0. Acclimation to the five DOC sources did not disturb Na⁺ , Cl^- and ammonia net fluxes, but resulted in differential elevations in Na⁺ , K⁺ ATPase and v-type H⁺ ATPase activities in fish at pH 7.0. However, after transfer to pH.4.0, the control fish exhibited rapid increases in both enzymes. In contrast the DOC- acclimated animals exhibited unchanged (Na⁺ , K⁺ ATPase) or differentially increased (v-type H⁺ ATPase) activities. Na⁺ , Cl^- and ammonia net fluxes remained unchanged in the control fish, but were differentially elevated in most of the DOC treatments at pH 4.0, relative to the same DOC treatments at pH 7.0. Correlations between the osmoregulatory data the DOCs properties highlight that the DOC properties drive different effects on gill physiology.

Shell form and enzymatic alterations in Lottia subrugosa (Gastropoda, Lotiidae) transplanted to a contaminated site

Studies have shown that shell morphology and enzymatic activities in mollusks are affected by contaminants exposure. However, the correlation between enzymatic activities and the biomineralization process are not fully understood. The present study used a transplant bioassay and field sampling to evaluate shell measurements and the activities of carbonic anhydrase, Ca²⁺-ATPase, and Mg²⁺-ATPase in Lottia subrugosa sampled in Brazilian sites under different contamination levels. Results showed that, in general, shells from the reference site (Palmas) were more rounded than the ones from the contaminated site (Balsa). Effects in enzymatic activities in specimens from transplant bioassay were attributed to the known high contaminant levels present at Balsa. While the lack of enzymatic activity alterations during field sampling was attributed to physiological adaptation to contaminants exposure. Enzymatic activities were not correlated to shell biometric parameters in field sampling, indicating that these enzymes were not related to shell alterations detected in the present study.

Effects of water-accommodated fraction of diesel fuel on seahorse (Hippocampus reidi) biomarkers

The present work aimed to investigate the effects of acute (12, 24, 48 and 96 h) and subchronic (168 and 336 h) exposure of seahorse, Hippocampus reidi to water-accommodated fraction (WAF) of diesel fuel on biotransformation parameters, antioxidant defenses and DNA integrity. In addition, a recovery experiment was performed, where the organisms remained in absence of the contaminant for 336 h, after WAF exposure for 168 h (totaling 504 h). At the end of each experimental protocol, the concentration of pyrene-, benzo(a)pyrene- and naphthalene-type metabolites in bile, hepatic activity of glutathione-S-transferase (GST), superoxide dismutase (SOD), and catalase (CAT), as well as lipid peroxidation (LPO) levels in hepatocytes, were analyzed, in addition to the DNA damage and the micronucleus (MN) test in the peripheral blood. It was observed that both acute and subchronic WAF exposure affected the investigated parameters in different ways. In general, the exposed groups presented higher mean values for the investigated parameters if compared with their respective controls. After the recovery experiment, the mean values of PAH metabolites, LPO, DNA damage and MN frequency were significantly lower than those of animals exposed for 168 h, indicating that the recovery period was appropriately long for the evaluated biomarkers return to the control levels. The results indicated that the selected H. reidi biomarkers proved to be adequate and complementary tools in determining the first impacts of acute and subchronic exposure caused by WAF of diesel fuel in fish, as well as their recovery in clean water.

Does dissolved organic carbon from Amazon black water (Brazil) help a native species, the tambaqui Colossoma macropomum to maintain ionic homeostasis in acidic water?

To assess how the quality and properties of the natural dissolved organic carbon (DOC) could drive different effects on gill physiology, we analysed the ionoregulatory responses of a native Amazonian fish species, the tambaqui Colossoma macropomum, to the presence of dissolved organic carbon (DOC; 10 mg l^-1 ) at both pH 7.0 and pH 4.0 in ion-poor water. The DOC was isolated from black water from São Gabriel da Cachoeira (SGC) in the upper Rio Negro of the Amazon (Brazil) that earlier been shown to protect a non-native species, zebrafish Danio rerio against low pH under similar conditions. Transepithelial potential (TEP), net flux rates of Na⁺ , Cl^- and ammonia and their concentrations in plasma and Na⁺ , K⁺ ATPase; v-type H⁺ ATPase and carbonic anhydrase activities in gills were measured. The presence of DOC had negligible effects at pH 7.0 apart from lowering the TEP, but it prevented the depolarization of TEP that occurred at pH 4.0 in the absence of DOC. However, contrary to our initial hypothesis, SGC DOC was not protective against the effects of low pH. Colossoma macropomum exposed to SGC DOC at pH 4.0 experienced greater net Na⁺ and Cl^- losses, decreases of Na⁺ and Cl^- concentrations in plasma and elevated plasma ammonia levels and excretion rates, relative to those exposed in the absence of DOC. Species-specific differences and changes in DOC properties during storage are discussed as possible factors influencing the effectiveness of SGC DOC in ameliorating the effects of the acid exposure.

Does hypoxia or different rates of re-oxygenation after hypoxia induce an oxidative stress response in Cyphocharax abramoides (Kner 1858), a Characid fish of the Rio Negro?

We examined whether oxidative damage and antioxidant responses are more likely to occur during hypoxia or re-oxygenation in hypoxia-tolerant fish, and whether there is an influence of the rate of re-oxygenation. An hypoxia/re-oxygenation experiment using wild-caught Cyphocharax abramoides (Rio Negro, Brazil), was designed to answer these questions. Lipid peroxidation (MDA), a measure of oxidative damage, and antioxidant activities (superoxide dismutase (SOD), glutathione peroxidase (GPx), antioxidant capacity against peroxyl radicals (ACAP)), were measured in brain, gill and liver tissues after normoxia, 3-h hypoxia (2.7 kPa), and 3-h hypoxia followed by 1-h or 3-h re-oxygenation, implemented either immediately or slowly (3.0 kPa·h^-1). Critical oxygen tension of routine oxygen consumption rate (Pcrit) (4.1 kPa) and the P_O2 at loss of equilibrium (LOE) (1.7 kPa) were determined to set the experimental hypoxia exposure. The Regulation Index, a measure of oxyregulation with declining P_O2, was 0.32. Oxidative damage occurred during hypoxia: no additional damage was observed during re-oxygenation. Tissues responded differentially. GPx and MDA rose in the brain and gills, and SOD (and likely GPx) in the liver during hypoxia. Antioxidants increased further at LOE. Rate of oxygen increase during re-oxygenation did not affect antioxidant responses. In brain and gills, GPx and MDA decreased or recovered after 1-h re-oxygenation. In liver, SOD remained high and GPx increased. In summary, C. abramoides incurred oxidative damage during hypoxic exposure with no additional damage inflicted during re-oxygenation: the rate of re-oxygenation was inconsequential. Literature data support conclusion of greater damage during hypoxia than during re-oxygenation in hypoxia-tolerant fish.

Biomarker responses and PAH ratios in fish inhabiting an estuarine urban waterway

Many cities worldwide are established adjacent to estuaries and their catchments resulting in estuarine contamination due to intense anthropogenic activities. The aim of this study was to evaluate if fish living in an estuarine urban waterway were affected by contamination, via the measurement of a suite of biomarkers of fish health. Black bream (Acanthopagrus butcheri) were sampled in a small urban embayment and a suite of biomarkers of fish health measured. These were condition factor (CF), liver somatic index (LSI), gonadosomatic index (GSI), hepatic EROD activity, polycyclic aromatic hydrocarbon (PAH) biliary metabolites, serum sorbitol dehydrogenase (s-SDH) and branchial enzymes cytochrome C oxidase (CCO), and lactate dehydrogenase (LDH) activities. The biomarkers of exposure EROD activity, and pyrene- and B(a)P-type biliary metabolites confirmed current or recent exposure of the fish and that fish were metabolizing contaminants. Relative to a reference site, LSI was higher in fish collected in the urban inlet as was the metabolic enzyme LDH activity. CF, GSI, s-SDH, CCO, and naphthalene-type metabolites were at similar levels in the urban inlet relative to the reference site. PAH biliary metabolite ratios of high-molecular-weight to low-molecular-weight suggest that fish from the urban inlet were exposed to pyrogenic PAHs, likely from legacy contamination and road runoff entering the embayment. Similarly, the sediment PAH ratios and the freshness indices suggested legacy contamination of a pyrogenic source, likely originating from the adjacent historic gasworks site and a degree of contamination of petrogenic nature entering the inlet via storm water discharge. Biomarkers of exposure and effect confirmed that black bream collected in the Claisebrook Cove inlet, Western Australia, are currently exposed to contamination and are experiencing metabolic perturbations not observed in fish collected at a nearby reference site.

Influence of the natural Rio Negro water on the toxicological effects of a crude oil and its chemical dispersion to the Amazonian fish Colossoma macropomum

The increment in crude oil exploitation over the last decades has considerably increased the risk of polycyclic aromatic hydrocarbon (PAH) contamination to Amazonian aquatic environments, especially for the black water environments such as the Rio Negro. The present work was designed to evaluate the acute toxicity of the Urucu crude oil (CO), the chemically dispersed Urucu crude oil (CO + D), and the dispersant alone (D) to the Amazonian fish Colossoma macropomum. Acute toxicity tests were performed, using a more realistic approach, where fish were acclimated to both groundwater (GW), used as internal control, and natural Rio Negro water (RNW) and exposed to CO, CO + D and D. Then, biomarkers such as ethoxyresorufin-O-deethylase (EROD), superoxide dismutase (SOD), lipid peroxidation (LPO), serum sorbitol dehydrogenase (s-SDH) in liver, DNA damage in blood cells, and the presence of the benzo[a]pyrene-type, pyrene-type, and naphthalene-type metabolites in fish bile were assessed. Fish exposed to CO and CO + D, at both water types tested, presented increased biomarker responses and higher PAH-type metabolites in the bile. However, fish exposed to these treatments after the acclimation to RNW increased the levels of LPO, s-SDH (hepatotoxicity), DNA damage in blood cells (genotoxicity), and benzo[a]pyrene-type metabolites when compared to fish in GW. Our data suggests that some physicochemical properties of Rio Negro water (i.e., presence of natural organic matter (NOM)) might cause mild chemical stress responses in fish, which can make it more susceptible to oxidative stress following exposure to crude oil, particularly to those chemically dispersed.

The transition from water-breathing to air-breathing is associated with a shift in ion uptake from gills to gut: a study of two closely related erythrinid teleosts, Hoplerythrinus unitaeniatus and Hoplias malabaricus

The evolutionary transition from water-breathing to air-breathing involved not only a change in function of the organs of respiratory gas exchange and N-waste excretion, but also in the organs of ion uptake from the environment. A combination of in vivo and in vitro techniques was used to look at the relative importance of the gills versus the gut in Na(+), Cl(-), and K(+) balance in two closely related erythrinid species: a facultative air-breather, the jeju (Hoplerythrinus unitaeniatus) and an obligate water-breather, the traira (Hoplias malabaricus). The jeju has a well-vascularized physostomous swimbladder, while that in the traira is poorly vascularized, but the gills are much larger. Both species are native to the Amazon and are common in the ion-poor, acidic blackwaters of the Rio Negro. Under fasting conditions, the traira was able to maintain positive net Na(+) and Cl(-) balance in this water, and only slightly negative net K(+) balance. However, the jeju was in negative net balance for all three ions and had lower plasma Na(+) and Cl(-) concentrations, despite exhibiting higher branchial Na(+), K(+)ATPase and v-type H(+)ATPase activities. In the intestine, activities of these same enzymes were also higher in the jeju, and in vitro measurements of net area-specific rates of Na(+), Cl(-), and K(+) absorption, as well as the overall intestinal absorption capacities for these three ions, were far greater than in the traira. When acutely exposed to disturbances in water O2 levels (severe hypoxia ~15% or hyperoxia ~420% saturation), gill ionoregulation was greatly perturbed in the traira but less affected in the jeju, which could "escape" the stressor by voluntarily air-breathing. We suggest that a shift of ionoregulatory capacity from the gills to the gut may have occurred in the evolutionary transition to air-breathing in jeju, and in consequence branchial ionoregulation, while less powerful, is also less impacted by variations in water O2 levels.

Roundup® exposure promotes gills and liver impairments, DNA damage and inhibition of brain cholinergic activity in the Amazon teleost fish Colossoma macropomum

Roundup Original® (RD) is a glyphosate-based herbicide used to control weeds in agriculture. Contamination of Amazon waters has increased as a consequence of anthropogenic pressure, including the use of herbicides as RD. The central goal of this study was to evaluate the toxic effects of RD on juveniles of tambaqui (Colossoma macropomum). Our findings show that biomarkers in tambaqui are organ specific and dependent on RD concentration. Alterations in gills structural and respiratory epithelium were followed by changes in hematological parameters such as concentration of hemoglobin, particularly in fish exposed to the higher concentration tested (75% of RD LC50 96 h). In addition, both RD concentrations affected the biotransformation process in gills of tambaqui negatively. Instead, liver responses suggest that a production of reactive oxygen species (ROS) occurred in fish exposed to RD, particularly in the animals exposed to 75% RD, as seen by imbalances in biotransformation and antioxidant systems. The increased DNA damage observed in red blood cells of tambaqui exposed to RD is in agreement with this hypothesis. Finally, both tested sub-lethal concentrations of RD markedly inhibited the cholinesterase activity in fish brain. Thus, we can suggest that RD is potentially toxic to tambaqui and possibly to other tropical fish species.

The impact of organochlorines and metals on wild fish living in a tropical hydroelectric reservoir: bioaccumulation and histopathological biomarkers

This study evaluates the contaminants in water and their bioaccumulation in the gills and liver of two ecologically distinct fish species, Astyanax fasciatus and Pimelodus maculatus, living in the reservoir of the Furnas hydroelectric power station located in Minas Gerais in the southeastern Brazil. The histological alterations in these organs are also examined. Water and fish were collected in June and December from five sites (site 1: FU10, site 2: FU20, site 3: FU30, site 4: FU40 and site 5: FU50) in the reservoir, and agrochemicals and metals selected based on their use in the field crops surrounding the reservoir were analyzed in the water and in the fish gills and livers. The concentrations of the organochlorines aldrin/dieldrin, endosulfan and heptachlor/heptachlor epoxide as well as the metals copper, chromium, iron and zinc in the gills and livers of both fish species were higher in June than in December; the liver accumulated higher concentrations of contaminants than the gills. The organochlorine metolachlor was detected only in the liver. The histological pattern of changes was similar in both species with regard to contaminant accumulation in the gills and liver. Fish from FU10, the least contaminated site, exhibited normal gill structure and moderate to heavy liver damage. Fish collected at FU20 to FU50, which were contaminated with organochlorines and metals, showed slight to moderate gill damage in June and irreparable liver damage in the livers in June and December. The histological changes in the gills and liver were suitable to distinguishing contaminated field sites and are therefore useful biomarkers for environmental contamination representing a biological end-point of exposure.

Integrated use of antioxidant enzymes and oxidative damage in two fish species to assess pollution in man-made hydroelectric reservoirs

This study investigated the relationship between contaminant body burden and the oxidative stress status of the gills and livers of two wild fish species in the Furnas Hydroelectric Power Station (HPS) reservoir (Minas Gerais, Brazil). Gills and livers presented similar pathways of metals and organochlorine bioaccumulation. During June, organochlorines were associated with lipid peroxidation (LPO), indicating oxidative stress due to the inhibition of the antioxidant enzymes superoxide dismutase and glutathione peroxidase. In the most polluted areas, metal concentrations in the liver were associated with metallothionein. During December, contaminants in the gills and liver were associated with catalase activity and LPO. Aldrin/dieldrin was the contaminant most associated with oxidative damage in the livers of both species. This integrated approach shed light on the relationship between adverse biological effects and bioaccumulation of contaminants inputted by intensive agricultural practices and proved to be a suitable tool for assessing the environmental quality of man-made reservoirs.

Organochlorines and metals induce changes in the mitochondria-rich cells of fish gills: an integrative field study involving chemical, biochemical and morphological analyses

Through integrating chemical, biochemical and morphological analyses, this study investigated the effects of multiple pollutants on the gill mitochondria-rich cells (MRCs) in two fish species, Astyanax fasciatus and Pimelodus maculatus, collected from five sites (FU10, FU20, FU30, FU40 and FU50) in the Furnas Hydroelectric Power Station reservoir. Water analyses revealed aluminum, iron and zinc as well as organochlorine (aldrin/dieldrin, endosulfan, heptachlor/heptachlor epoxide and metolachlor) contamination at all of the sites, with the exception of FU10. Copper, chrome, iron and zinc were detected in the gills of both species, and aldrin/dieldrin, endosulfan and heptachlor/heptachlor epoxide were detected in the gills of fish from all of the sites, with the exception of FU10. Fish collected at FU20, FU30 and FU50 exhibited numerous alterations in the surface architecture of their pavement cells and MRCs. The surface MRC density and MRC fractional area were lower in fish from FU20, FU30, FU40 and FU50 than in those from the reference site (FU10) in the winter, and some variability between the sites was observed in the summer. The organochlorine contamination at FU20 and FU50 was associated with variable changes in the MRCs and inhibition of Na(+)/K(+)-ATPase (NKA) activity, especially in P. maculatus. At FU30, the alterations in the MRCs were associated with the contaminants present, especially metals. A multivariate analysis demonstrated a positive association between the biological responses of both species and environmental contamination, indicating that under realistic conditions, a mixture of organochlorines and metals affected the MRCs by inhibiting NKA activity and inducing morphological changes, which may cause an ionic imbalance.

Using condition factor and blood variable biomarkers in fish to assess water quality

The condition factor and blood variables, including erythrocyte lipid peroxidation (LPO) and the activity of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), in two ecologically distinct fish species (Astyanax fasciatus and Pimelodus maculatus) were evaluated at five sites in the Furnas Hydroelectric Power Station reservoir (Brazil) to assess water quality. Aldrin/dieldrin, endosulfan, heptachlor epoxide, and metolachlor were detected at different concentrations in four of the sites. Condition factor was not directly affected by such contaminants. A negative correlation between hematocrit and heptachlor was detected in P. maculatus. Positive correlations between red blood cells and heptachlor as well as an interactive effect of metolachlor and aldrin/dieldrin were detected in A. fasciatus. The erythrocytes of both species collected from the contaminated sites showed high levels of LPO, an increase in SOD and GPx activities and a decrease in CAT activity. Although the leukocyte number and the differential percentage of leukocytes varied among the sites, the hematological variables, the LPO levels, and the antioxidant enzyme activities could be used to assess water quality, regardless of the differences in the responses of the fish species.