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Transitional water ecosystems, like brackish coastal lagoons, provide important services but are subjected to several anthropogenic impacts that can initially lead to biodiversity modifications and then to critical alterations of ecosystem processes. Assessment and monitoring of the health status of these ecosystems is extremely important. This study reports the case study of “Capo Peloro” lakes (southern Italy), where ecotoxicological biomarkers in the key fish species Atherina boyeri have been used to reveal potential contamination in a transitional water ecosystem. The goal was to detect changes that occurred after the summer season, when the surrounding human population significantly increases, with the consequent enhancement of anthropic pressures. Lake Trasimeno, a reference protected site, was also selected. This study is the follow-up of a previous one carried out in the same environment reporting biomarkers employed on the copepod species Paracartia latisetosa, on which Atherina boyeri feeds. The main aim of the present study was to test the responses given by the same type of contamination in a planktivorous fish species, which occupies a higher trophic level. Several biochemical and genotoxic biomarkers were evaluated: Acetylcholinesterase (AChE), Benzo(a)pyrene-monooxygenase (BPMO), Polycyclic Aromatic Hydrocarbons (PAH) metabolites in bile, Erythrocytic Nuclear Abnormalities (ENA) assay. This study confirms the contamination already shown in P. latisetosa from pesticides and carbamates, and/or polycyclic and polyhalogenated aromatic hydrocarbons, heavy metals, surfactants in both “Capo Peloro” lakes. A higher concentration of contaminants was demonstrated in early autumn with respect to the summer season, due to enhanced anthropogenic activities around and on the lakes. This study highlights that, although “Capo Peloro” lakes and Lake Trasimeno are protected areas, they are affected by environmental degradation. This study also confirms the benefits gained with a biomarker approach in monitoring transitional water ecosystems.

Transitional water ecosystems can be exposed to high levels of anthropic pressure. The main aim of this study was to present the ‘Capo Peloro’ lakes (southern Italy) case study, which highlights the advantageous use of ecotoxicological biomarkers in key copepod species, to reveal potential contamination in transitional water ecosystems. The focus was on changes that occur after the summer season, as during the summer, the surrounding human population increases significantly, with the consequent enhancement of anthropic pressures. Biomarkers were defined to monitor the zooplankton copepods Paracartia latisetosa, Acartia tonsa and Oithona brevicornis. Acetylcholinesterase, lipid peroxidation, and benzo(a)pyrene-monooxygenase activities were determined. P. latisetosa, A. tonsa and O. brevicornis show linear increases in their acetylcholinesterase activities with increasing concentrations in sample homogenates, which defines their high metabolic rates, and thus the suitability of these species as bioindicators. Biochemical alterations in these species induce changes in their biological attributes that can also lead to their disappearance, with a cascade of consequences for the higher trophic levels in the food chain. These data indicate that for the two lakes of Capo Peloro there is contamination by pesticides, carbamates and polycyclic and polyhalogenated aromatic hydrocarbons. This occurs mainly at the end of the summer season, and only affects the species of the low trophic levels. This case study shows the benefits provided by this biomarker approach as applied to zooplankton species, to monitor transitional water ecosystems and to estimate their toxicological risk, and thus to provide an early warning signal for loss of ecosystem integrity.