Biological Effects of Chemical Pollution in Feral Fish and Shellfish Populations from Ebro River: From Molecular to Individual Level Responses

A multilevel approach, from whole animal to molecular level, was applied to the study of the biological impact of chemical pollution in fish and shellfish populations from the rivers Vero, Cinca, and from the Flix reservoir in the Ebro River. The analysis provided a general picture of the health status of the rivers and quantified the physiological effects of different pollutants originating in existing chemical plants discharging in the area. The data show that fish acclimated to very high concentrations of some toxicants, like mercury, whereas organochlorinated compounds (OCs) and poly bromo diphenyl ethers apparently induce permanent negative effects, including oxidative stress, poor condition and fertility, DNA damage, and liver and kidney histological anomalies. Toxic determinants appeared different for vertebrates and invertebrates and suggest that a key difference between both animal groups may be the presence of activable aryl hydrocarbon receptor (AhR), which only occurs in deuterostomata (Chordates, Echynoderma and alikes). The adverse biological effects were recorded up to 30–35 km downstream the different sources, and their distribution differed for OCs and for Hg. Intensive local agricultural practices, rather than pollution from the Ebro’s chemical plants, seem to account for adverse biological effects observed in the Ebro Delta.