Environmental quality of the La Polvora urban lagoon in the Grijalva river watershed

Water quality and the diversity of epibenthic macrofauna and fish was analyzed in La Pólvora urban lagoon during low water season. The potential of hydrogen, total suspended solids, dissolved oxygen, biochemical oxygen demand, nitrates and total phosphorus met current Mexican norms for secondary contact recreational use. Nevertheless, values for fecal coliforms exceeded the norms and represented a health risk, although the water quality was classified as good according to the Water Quality Index. The doubling of total phosphorus recorded 15 years earlier in La Pólvora lagoon helps to explain the current hyper-eutrophic state. The diversity of epibenthic macrofauna and fish was lower than other limnetic ecosystems in the region due to the small number of species of mollusks and fish collected as well as the absence of aquatic insects and macrocrustaceans and fish belonging to the Poecillidae family. This lagoon is shown to be undergoing environmental degradation, as indicated by its hyper-eutrophic state, high values for fecal coliforms, low values for diversity of epibenthic macrofauna and fish, the percentage of exotic species and low values for the conditional factor of 11 fish species. These findings suggest the need to review the management program and its operations in this ecosystem