An integrated approach to assess water quality and environmental contamination in the fluvial-lagoon system of the Palizada River, Mexico

Abstract

Water quality and the contamination in relation to land use in the fluvial-lagoon system of the Palizada River (FLSPR; State of Campeche, Mexico) was investigated using an integrated approach including 21-d in situ bioassays with the native mosquito fish Gambusia yucatana, determination of cholinesterase (ChE) activity in wild populations of this species, and water-quality variables. The present study was performed over 19 months at three sites with different types of anthropogenic impact. Significant differences in a water-quality index for aquatic life (WQI) were found among sites. Fish mortality was significantly and negatively correlated with WQI, dissolved oxygen, and sulfates. High survival rates (>= 80%) were found in preliminary exposures and in some of the bioassays performed at all sites. Therefore, test chambers and the cabinet seemed to be suitable for use in toxicity bioassays with G. yucatana. The in situ bioassay was able to discriminate levels of water contamination in both time and space, indicating that it is suitable for use in conditions similar to those found in the FLSPR. In the biomonitoring study, a ChE inhibition of greater than 20% in wild fish was found in some periods of the year at all sampling sites. This indicates the presence of anticholinesterase agents in the water. Fish from two of the sites had a ChE inhibition of greater than 40% in some sampling months, suggesting that deleterious effects already may have been induced in fish. Furthermore, at these sites, the pattern of ChE inhibition was in good agreement with the probable runoff of pesticides from agricultural fields.