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Substances derived from anthropogenic activities induce changes in the physical and chemical characteristics of the aquatic environment. Physicochemical and biological studies are necessary to understand how changes in landscape affect the health of the aquatic environment. The main goal of this study was to evaluate how the landscape at different spatial scales affects (1) water quality and (2) the health status of Heptapterus mustelinus, based on several biomarkers. During the dry season, individuals were caught in three sites with different degrees of anthropogenic activity. The quality of the terrestrial environment was assessed using the Riparian Quality and Land Use Indices. The water quality condition was evaluated using a water quality index, and pesticides and pharmaceuticals were measured in water. The following biomarkers were analyzed in the fish: general health status (Condition Factor, Hepatosomatic index and energetic costs), enzymatic activity (GST, CAT, AchE), carbonyl content in proteins and histopathological responses in liver and gills. The most impacted sites by the presence of pesticides showed more alterations in the surrounding landscape; specially, changes in the riparian area. In this area, biomarkers denoted more damage than in sites with protected riparian zone. Conservation status of riparian ecosystems is crucial in the determination of rivers ecological quality. Our results demonstrate the importance of monitoring the environmental quality through an integrated analysis, using native fish to understand the effects of human activities on the biota.

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The objective of this work was to evaluate the health status of an economic and ecologically important fish species from Mar Chiquita Lake, a RAMSAR site located in Cordoba, Argentina, relative to the levels of selected persistent organic pollutants (POPs) in lake water and fish tissues. Odontesthes bonariensis was used as a model species, and its health was estimated by means of histological indices in gills and liver. Sampling was performed according to rainy and dry seasons (i.e. dry, rainy and post-rainy). Gill and liver histopathology were evaluated by semi-quantitative indices and morphometric analysis. Although epithelial lifting in gills and lipid degeneration in liver were frequently registered, they are considered as reversible if environmental conditions improve. During rainy and post-rainy seasons fish presented significantly higher scores of liver and total indices. These higher index scores were correlated with increased levels of POPs in gill and liver tissue. Therefore, preventive measures are needed to mitigate the entry of these compounds into the lake.

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Endocrine disruption on aquatic wildlife is being increasingly reported, and the changes in gene aromatase expression are used as indicators. However, natural fluctuations in brain and gonadal aromatase expression and physiological indexes have not been previously measured in a fish species (Jenynsia multidentata) throughout a complete reproductive cycle, nor the biological effects of anthropogenic inputs on these responses. Accordingly, males were monthly collected over a year in both, a reference and a contaminated site. Physicochemical analyses of water samples were done and reflected a strong anthropogenic impact. Brain aromatase fluctuates along the reproductive cycle of this species and, noticeably, the increase of brain gene expression begins with a 1 month delay in the contaminated site. This mismatch is also evidenced for testes weight. Hepatosomatic index also revealed adverse effects in the polluted site. In turn, the alterations observed in biological responses could be affecting the reproduction of this fish species.

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There is a growing interest in evaluating the presence of pharmaceutical residues and their metabolites in aquatic biota. In this study, twenty pharmaceuticals, including carbamazepine (CBZ) and two metabolites, were analyzed in homogenates of two fish species (Gambusia affinis and Jenynsia multidentata) captured in polluted areas of the Suquía River (Córdoba, Argentina). The twenty target pharmaceuticals were found in G. affinis, while only fifteen were detected in J. multidentata. We observed a noticeable difference in the accumulation pattern of both fish species, suggesting different pathways for the bioaccumulation of polar pharmaceuticals in each fish. In order to investigate uptake and tissue distribution of pharmaceuticals, a detailed study was performed under controlled laboratory conditions in J. multidentata, exposed to CBZ. CBZ and two of its metabolites (carbamazepine-10,11-epoxide - CBZ-EP and 2-hydroxycarbamazepine - 2-OH-CBZ) were monitored in five organs of fish under laboratory exposure. To our knowledge, this is the first report on the presence of CBZ and its metabolite 2-OH-CBZ in gills, intestine, liver, brain and muscle of fish, while the metabolite carbamazepine-10,11-epoxide (CBZ-EP) was detected in gills and muscle. A ratio CBZ-EP/CBZ close to 0.1 suggests that gills and muscle of J. multidentata could metabolize CBZ through the CBZ-EP pathway. Our results reinforce the need of analyzing multiple species to account for the environmental impact of pollutants, negating the simplification of a single, "representative model" during ecotoxicological biomonitoring. To our knowledge, the biotransformation of CBZ to its metabolites (CBZ-EP, 2-OH-CBZ) in fish, under controlled laboratory in vivo exposures, is reported for the first time.

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RAMSAR sites are determined by specific characteristics of the environment in terms of ecological productivity as well services for human development, but they are also one of the most threatened ecosystems. Thus, the objective of this work was to evaluate the dynamic of Persistent Organic Pollutants (POPs) in different biotic and abiotic matrixes of the RAMSAR site (wetlands with international importance), Mar Chiquita Lake. Sampling was performed according to land use (agricultural, urban, and industrial) at two stations: Laguna del Plata and Campo Mare. POPs were analyzed in superficial water (Sw), suspended particulate material (SPM), bottom sediment (Bs) and fish tissues (Odontesthes bonariensis). Organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) were analyzed by GC-ECD. HCHs, Endosulfans, DDTs, PCBs and PBDEs were found in all matrixes at both stations. The high persistence and transport processes are responsible for the occurrence of HCHs, DDTs and PCBs in Bs, SPM and fish tissues, even many years after their prohibition. PBDEs showed lower levels according to the scarcity of punctual sources in the area. Endosulfan showed variable amounts in agreement with application periods since this pesticide was used until a few years ago in this area. Finally, PCB levels overpassed the acceptable daily intake for human consumption being a risk for human health Thus, the present report confirms the occurrence of POPs in Mar Chiquita lake, alerting on the contribution of agricultural and urban pollutants in a RAMSAR site. Current results also raise concerns on biomagnification processes through the food web.

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The synthetic estrogen 17α-ethynylestradiol (EE2) has been increasingly detected in sewage effluents in the last two decades. The aim of the present study was determined if EE2 exposure adversely affected reproduction in internally fertilizing fish species Jenynsia multidentata. Sexual behavior, brain and gonadal aromatase expression as well as sperm quality were evaluated. The brain aromatase expression, reproductive behavior, spermatozoa viability and gonadosomatic index were sensitive biomarkers of EE2 effects on this species. The condition factor, hepatosomatic index, gonadal aromatase expression, sperm count and sperm velocities were unaltered after EE2 exposure. The present work highlights the importance of using a combination of several biomarkers to study the effects of estrogenic compounds, especially when trying to link these results to potential population-level effects.

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The study reports the accumulation, distribution and metabolism of technical endosulfan in Jenynsia multidentata. Adult females were exposed to acute sublethal concentrations (0.072, 0.288 and 1.4 µg L⁻¹). After 24 h, fish were sacrificed and gills, liver, brain, intestine and muscle were removed. Results show that both isomers of technical-grade endosulfan (α- and ß-) are accumulated in fish tissues and biotransformation to endosulfan sulfate occurs at all concentrations tested. Significantly differences in endosulfan accumulation were only found at 1.4 µg L⁻¹ but not between the lowest concentrations. However a similar distribution pattern was observed at all exposure levels where liver, intestine and brain had the highest levels of α-, ß-endosulfan and endosulfan sulfate. Moreover, liver and brain showed the highest endosulfan sulfate:α-endosulfan ratios due to high biotransfomation capacity. J. multidentata demonstrated to be a sensitive species under exposure to technical endosulfan and, therefore, could be used to assess aquatic pollution.

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We assessed changes in spontaneous swimming activity and acetylcholinesterase (AchE) activity of Jenynsia multidentata exposed to Endosulfan (EDS). Females of J. multidentata were exposed to 0.072 and 1.4 microg L(-1) EDS. Average speed and movement percentage were recorded during 48 h. We also exposed females to EDS at five concentrations between 0.072 and 1.4 microg L(-1) during 24 h, and measured the AchE activity in brain and muscle. At 0.072 microg L(-1) EDS swimming motility decreased relative to the control group after 45 h, while at 1.4 microg L(-1) EDS swimming motility decreased after 24 h. AchE activity significantly decreased in muscle when J. multidentata were exposed to EDS above 0.072 microg L(-1), while no significant changes were observed in brain. Thus, changes in swimming activity and AchE activity in muscle are good biomarkers of exposure to EDS in J. multidentata.

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We evaluate antioxidant responses of Jenynsia multidentata experimentally exposed to sublethal concentrations of endosulfan (EDS). The main goal was to determine differences in the response between different organs to assess which one was more severely affected. Thus, we exposed females of J. multidentata to EDS during 24h, measuring the activity of GST, GR, GPx, CAT and LPO in brain, gills, liver, intestine and muscle of both exposed fish and controls. GST activity was inhibited in gills, liver, intestine and muscle of exposed fish but was induced in brain. GR and GPx activities were increased in brain and gills at 0.014 and 0.288 microg L(-1), respectively. GPx activity was inhibited in liver and muscle at all studied concentrations whereas inhibition was observed in the intestine above 0.288 microg L(-1). Exposure to 1.4 microg L(-1) EDS caused CAT inhibition and increase of LPO levels in liver. LPO was also increased in brain at almost all concentrations tested. We find that the brain was the most sensitive organ to oxidative damage. Thus, J. multidentata could be used as a suitable bioindicator of exposure to EDS measuring activities of antioxidant enzymes in brain and liver as biomarkers.

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We analyzed the variation of fish species richness and trophic structure along an upstream-downstream gradient and identified the factors associated with the pattern observed. The fish community composition varied along a headwater-downstream gradient. Species richness and trophic structure decreased significantly with increasing altitude and increased with stream order and distance from source. Headwater communities showed a simple structure. Oncorhynchus mykiss was the only fish captured or noticeably dominant at high altitudes. Thus, headwater can be classified as "trout zones". From these zones to downstream areas fish communities changed because of the addition of other fish species. This phenomenon probably occurs because of an increase in habitat diversity

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We analyzed the variation of fish species richness and trophic structure along an upstream-downstream gradient and identified the factors associated with the pattern observed. The fish community composition varied along a headwater-downstream gradient. Species richness and trophic structure decreased significantly with increasing altitude and increased with stream order and distance from source. Headwater communities showed a simple structure. Oncorhynchus mykiss was the only fish captured or noticeably dominant at high altitudes. Thus, headwater can be classified as "trout zones". From these zones to downstream areas fish communities changed because of the addition of other fish species. This phenomenon probably occurs because of an increase in habitat diversity.

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