Micronucleus test in fishes as indicators of environmental quality in subestuaries of the Río de la Plata (Uruguay)

• We used Micronuclei test to evaluate genetic damage in estuarine fishes.
• We provide knowledge about the health status of fishes and water quality levels.
• Odontesthes argentinensis was the species with more susceptibility.
• Pando sub-estuary exhibited the highest levels of micronuclei in fishes.

Genotoxic agents may exert damage that may be active through following generations. Micronuclei are cytoplasmic chromatin masses outside the main cell nucleus, indicators of chromosomal damage. This study applied micronuclei test to evaluate genetic damage of fish in three breeding and nursery areas of commercially important fishes exposed to differing degrees of anthropogenic impact: Pando, Solís Chico and Solís Grande sub-estuaries. The micronuclei test revealed differences in the presence and concentrations of genotoxic components in these sub-estuaries. Fish in the urban and industrialized Pando sub-estuary presented the highest percentages of micronuclei. The absence of seasonal changes in micronuclei in Pando fish could be explained by physical characteristics of the sub-estuary and by regional weather conditions. Odontesthes argentinensis (Valenciennes, 1835) was the species most susceptible to genotoxic components. It is recommended the use of a battery of biomarkers to better explain the health of organisms in that important nursery area.