ABSTRACT
The objectives of this study were to evaluate the ecophysiological state of the biota using a set of biomarkers in the upper-middle Luján River. To this aim, we collected adult Cnesterodon decemmaculatus fish, biofilm and water at three sampling sites in the upper-middle Luján River (S1: rural area, S2: Luján City and S3: urban area after passing Lujan City). For each site we determined physicochemical variables, heavy metal concentration in water, 19 biomarkers in fish (morphometric, histological, genotoxic, oxidative stress, metabolic and neurotoxic) and six biomarkers in biofilm (oxidative stress and extracellular enzyme). Additionally, we compared the responses of fish and biofilm with those of laboratory controls obtained from outdoor cultures. Our results indicated increased heavy metal concentration at all sites, mainly As and Cd, and decreased dissolved oxygen at S1 and S3. In fish, genotoxic biomarkers showed significant differences with respect to the control. The comet assay indicated damage in fish at the urbanized sites (S2 and S3) and an increased frequency of erythrocytes with nuclear aberrations at all sites. The CEA index (cellular energy allocation), calculated from the metabolic biomarkers and lipid concentration were significantly increased at S1. The gill damage evaluated histologically and with three indices indicated severe damage at all sites. Gills showed thickened primary and secondary lamellae and fusion of filaments at all sites, but a significant increase in mucous cells was only found at S1 and S3. Biofilm showed increased values of extracellular enzymes (ß-glucosidase and alkaline phosphatase, lipid peroxidation and oxidative stress enzymes (i.e., catalase) at S3. These results are novel in that they incorporated laboratory controls allowing for comparisons with fish and biofilm from the field. They provided information on the status of a fish population and biofilm community, indicating the negative effect of river water deterioration on the tested organisms. Moreover, results showed what biomarkers were most sensitive for each biological sample.
ABSTRACT
In the field of aquatic ecotoxicology, indexes obtained from a battery of biomarkers have proved to be a useful tool for assessing quantifiable and integrated health responses of organisms exposed to pollutants. The objective of this work was to evaluate the effects of exposure to the Reconquista River water (RR) on adults of Cnesterodon decemmaculatus using different integrated indexes. We conducted a 12-d laboratory assay involving the exposure of fish to RR, a negative control (moderately hard water - MHW medium), and a positive control (for genotoxicity with MHWâ¯+â¯Cyclophosphamide, CP). There were measured metabolic (food intake and specific assimilation, specific metabolic rate, oxygen extraction efficiency, ammonia excretion, and ammonia quotient), genotoxic (comet assay, micronucleus test, and nuclear abnormalities), morphological variables (total length, body and liver weight) and biochemical variables (Electron Transport System - ETS, Acetylcholinesterase activity - AChE, Catalase - CAT, Glutathione-S-transferase - GST, Glutathione content - GSH and tissue proteins). These variables were grouped into different indexes: morphological (Condition Factor - K and Liver Somatic Index-LSI), metabolic (Scope for Growth-SFG), genetic damage (GDI) and integrated biomarker response - IBR (AChE brain, CAT, GST and GSH liver, GSH gills, ETS muscle) indexes. Results indicated that RR water induced metabolic, biochemical and genetic damages. The SFG, GDI and IBR were suitable to assess the effects of exposure to an environmental sample in an integrated approach, reducing uncertainty due to inherent biomarker variability. These indexes have emerged as promising tools for environmental monitoring studies.
