Biomarkers of exposure and effect in the armoured catfish Hoplosternum littorale during a rice production cycle

High toxicity of agro-industrial wastewater on aquatic fauna of a South American stream: Mortality of aquatic turtles and amphibian tadpoles as bioindicators of environmental health

The aim of this study was to characterize an aquatic system of Santa Fe province (Argentina) receiving wastewater from agro-industrial activities (mainly dairy) by in situ assessment (fauna mortality, physicochemical, microbiological, and pesticide residues measurement), and ecotoxicity bioassays on amphibian tadpoles. Water and sediment samples were obtained from the Los Troncos Stream (LTS), previous to the confluence with the "San Carlos" drainage channel (SCC), and from the SCC. Biological parameters (mortality and sublethal biomarkers) were used to evaluate ecotoxicity during 10-day exposure of Rhinella arenarum tadpoles to LTS and SCC samples. Nine pesticides were detected in both LTS and SCC. Chemical and biochemical oxygen demand, ammonia, and coliform count recorded in SCC greatly exceeded limits for aquatic life protection. At SCC and LTS after the confluence with SCC, numerous dying and dead aquatic turtles (Phrynops hilarii) were recorded. In the ecotoxicity assessment, no mortality of tadpoles was observed in LTS treatment, whereas total mortality (100%) was observed in SCC treatments in dilution higher than 50% of water and sediment. For SCC, median lethal concentration and the 95% confidence limits was 18.30% (14.71-22.77) at 24 h; lowest-observed and no-observed effect concentrations were 12.5% and 6.25%, respectively. Oxidative stress and neurotoxicity were observed in tadpoles exposed to 25% SCC dilution treatment. In addition, there was a large genotoxic effect (micronuclei test) in all sublethal SCC dilution treatments (6.25%, 12.5%, and 25%). These results alert about the high environmental quality deterioration and high ecotoxicity for aquatic fauna of aquatic ecosystems affected by agro-industrial wastewater. PRACTITIONER POINTS: Great mortality of turtles was observed in a basin with a high load of agro-industrial wastewater. San Carlos Channel (SCC), where effluents are spilled, is environmentally deteriorated. The water-sediment matrix of SCC caused 100% lethality in tadpoles. SCC dilutions caused neurotoxicity, oxidative stress, and genotoxicity on tadpoles.

Pesticide concentrations in a threatened freshwater turtle (Emys orbicularis): Seasonal and annual variation in the Camargue wetland, France

Wetlands are among the most threatened ecosystems on the planet and pollution is a major factor causing the decline of wetland biodiversity. Despite the increasing use of pesticides, their fate and effects on freshwater reptiles remain largely unknown. We studied the European pond turtle (Emys orbicularis), a long-lived species at risk with a high exposure potential to pesticides. Between 2018 and 2020, we measured 29 pesticides and metabolites in 408 blood samples of turtles from two populations in the Camargue wetland (France). We were able to quantify 24 compounds and at least one pesticide or one degradation product in 62.5% of samples. Pesticide occurrences and concentrations were low, except for a herbicide widely used in rice cultivation and locally detected in water: bentazone that reached high blood concentrations in E. orbicularis. The occurrence and the concentration of pesticides in E. orbicularis blood depended mainly on the site and the sampling date in relation to pesticide application. Individual characteristics (sex, age, body condition) did not explain the occurrence or the concentration of pesticides found in turtle blood. Assessing the exposure of aquatic wildlife to a cocktail of currently-used pesticides is a first and crucial step before studying their effects at the individual and population levels.

Effects of glyphosate exposure on gut-liver axis: Metabolomic and mechanistic analysis in grass carp (Ctenopharyngodon idellus)

Glyphosate, one of the most widely used herbicide worldwide, is potentially harmful to non-target aquatic organisms. However, the environmental health risks regarding impacts on metabolism homeostasis and underlying mechanisms remain unclear. Here we investigated bioaccumulation, metabolism disorders and mechanisms in grass carp after exposure to glyphosate. Higher accumulation of glyphosate and its major metabolite, aminomethylphosphonic acid, in the gut was detected. Intestinal inflammation, barrier damage and hepatic steatosis were caused by glyphosate exposure. Lipid metabolism disorder was confirmed by the decreased triglyceride, increased total cholesterol and lipoproteins in serum and decreased visceral fat. Metabolomics analysis found that glyphosate exposure significantly inhibited bile acids biosynthesis in liver with decreased total bile acids content, which was further supported by significant downregulations of cyp27a1, cyp8b1 and fxr. Moreover, the dysbiosis of gut microbiota contributed to the inflammation in liver and gut by increasing lipopolysaccharide, as well as to the declined bile acids circulation by reducing secondary bile acids. These results indicated that exposure to environmental levels of glyphosate generated higher bioaccumulation in gut, where evoked enterohepatic injury, intestinal microbiota dysbiosis and disturbed homeostasis of bile acids metabolism; then the functional dysregulation of the gut-liver axis possibly resulted in ultimate lipid metabolism disorder. These findings highlight the metabolism health risks of glyphosate exposure to fish in aquatic environment.

Cocktails of pesticide residues in Prochilodus lineatus fish of the Salado River (South America): First record of high concentrations of polar herbicides

Muscle and viscera (gills-liver) of the fish Prochilodus lineatus were obtained from four sites of lower course of Salado river and one site at Santa Fe river near to its confluence with Salado river from Santa Fe (Argentina) between December 2021 and February 2022. Sediment samples were also obtained from the same sites. All samples were analyzed for pesticide residues following the QuEChERS method to quantify 136 compounds by UHPLC-ESI-MS/MS and GC-EI-MS/MS. Overall, muscle fish tissue showed very high concentrations (maximum concentrations detected) of the insecticide cypermethrin (204 μg/kg), polar herbicides (glyphosate; 187 μg/kg and its degradation product (aminomethylphosphonic acid) AMPA; 3116 μg/kg, and glufosinate-ammonium; 677 μg/kg), and the fungicide pyraclostrobin (50 μg/kg). In viscera samples, high values of cypermethrin (506 μg/kg), chlorpyrifos (78 μg/kg), and lambdacyhalothrin (73 μg/kg) were the main pesticides found. Mean residues concentrations detected among sites were not significantly different neither in muscle nor viscera of P. lineatus in most of the cases. Exceptionally, the southernmost studied site of the Lower Salado river showed significant differences in concentration of residues found in muscle, due to high concentrations of glyphosate and glufosinate-amonium (KW = 11.879 and KW = 13.013, respectively, P < 0.05). Other norther Lower Salado river site showed significant higher AMPA concentration in fish viscera than in the rest of the studied sites (KW = 12.86 P < 0.05). Some sediment samples showed low levels of herbicides such as glyphosate (24 μg/kg) and fungicides. However, the world highest levels of polar herbicides were recorded in fish muscle. The results of this study highlight the need for periodic monitoring due to the high concentration of pesticides and its potential risk in a very important commercial freshwater fish from Argentina, which is consumed locally and exported to other countries for human consumption.

Adverse effects of herbicides in freshwater Neotropical fish: A review

Although herbicides have been developed to act on the physiological processes of plants, they are responsible for causing deleterious effects on animals. These chemical compounds are widely used throughout the world, but especially in countries that export agricultural products such as Central and South America, their use has increased in recent years. Aquatic environments are natural reservoirs of herbicides, which after being applied on crops, run off through the soil reaching rivers, lakes, and oceans. Fish are among the many organisms affected by the contamination of aquatic environments caused by herbicides. These animals play an important ecological role and are a major source of food for humans. However, few studies address the effects of herbicides on fish in this region. Thus, in the present review we discuss the morphophysiological and molecular consequences of herbicide exposure in Neotropical fish systems as well as how the environmental and land use characteristics in this region can influence the toxicity of these pollutants. A toxicity pathway framework was developed summarizing the mechanisms by which herbicides act and endpoints that need to be further investigated.

Neuro-hepatopathological changes in juvenile Oreochromis niloticus exposed to sublethal concentrations of commercial herbicides

The current study estimates the impact of different common herbicides on antioxidant defenses and histological structure of liver and spinal cord of juvenile tilapia. Eighty-four fish were divided into seven groups: group 1 fish acted as controls and the remaining fish were exposed to sublethal concentrations of acetochlor, bispyribac-sodium, bentazon, bensulfuron-methyl, halosulfuron-methyl, or quinclorac at sublethal concentrations 2.625, 0.800, 36.00, 2.50, 1.275, and 11.250 mg/l, respectively, for 96 h. Antioxidant parameters changed in response to some test herbicides and the greatest effects were caused by exposure to acetochlor and quinelorac for all antioxidant measurements. Prominent histological changes in liver tissue included loss of liver architecture and the appearance of fatty liver cells, necrotic areas, foci of leukocytic infiltration and many apoptotic cells. The most obvious changes in the spinal cord in all treated fish were degradation of myelinated white matter fibers with the emergence of empty spaces, large aggregation of pyknotic neuroglial nuclei, and damaged areas in the dorsal horn of gray matter. Collectively, the harmful effect of tested herbicides on antioxidant capacity and significant alterations in histological structures of liver and spinal cord of Oreochromis niloticus.

Glyphosate and glufosinate-ammonium in aquaculture ponds and aquatic products: Occurrence and health risk assessment

As the two most commonly used organophosphorus herbicides, glyphosate (Gly) and glufosinate-ammonium (Glu) have unique properties for weed control and algae removal in aquaculture. However, the occurrences and health risks of Gly and Glu in aquaculture ponds are rare known. This study aimed to investigate the occurrences of Gly, AMPA (primary metabolity of Gly) and Glu in surface water, sediment and aquatic products from the grass carp (ctenopharyngodon idella), crayfish (procambarus clarkii) and crab (eriocheir sinensis) ponds around Lake Honghu, the largest freshwater lake in Hubei province, China where aquaculture has become the local pillar industry. Three age groups (children, young adults, middle-aged and elderly) exposure to these compounds through edible aquatic products (muscle) consumption were also assessed by target hazard quotient (THQ) method. The results indicated that Gly, AMPA and Glu were widely occurred in surface water, sediment and organisms in the fish, crayfish and crab ponds. AMPA was more likely to accumulate in the intestine of aquatic products than Gly and Glu. According to the total THQ value (1.04＞1), muscle consumption of grass carp may pose potential risk to children.