Ecotoxicology Impacts on Aquatic Vertebrates

Abstract

Freshwater and marine aquatic vertebrates are among the most toxicologically exposed animal groups globally,
inhabiting receiving water bodies that concentrate agricultural pesticides, pharmaceutical compounds, heavy metals, and
endocrine-disrupting chemicals (EDCs) discharged from urban, industrial, and agricultural sources. This study
characterised the ecotoxicological impacts of four priority pollutant classes — glyphosate-based herbicides, synthetic
estrogens (17α-ethinylestradiol; EE2), cadmium (Cd), and polychlorinated biphenyls (PCBs) — on four aquatic vertebrate
species representing key trophic levels: European eel (Anguilla anguilla; apex consumer), brown trout (Salmo trutta;
mesopredator), European perch (Perca fluviatilis; omnivore), and common frog (Rana temporaria; amphibian) across 48
river and lake sites in Italy, Austria, and Sweden spanning a pollution gradient. Tissue concentrations of each pollutant
class were quantified by LC-MS/MS and ICP-MS (n = 284 individuals per species). Biomarkers of toxicological effect
were measured: vitellogenin (VTG) for EDC exposure, acetylcholinesterase (AChE) activity for pesticide neurotoxicity,
metallothionein (MT) induction for heavy metal stress, and histopathological liver and gonad scoring. Vitellogenin was
detected in male fish at 38 of 48 sites (79.2%), with mean VTG concentrations in male S. trutta positively correlated with
upstream EE2 discharge load (r(S) = +0.84, p < 0.001). AChE activity was reduced by a mean of 42.4 ± 8.4% in fish from
glyphosate-impacted sites relative to reference sites (t = 8.42, p < 0.001). R. temporaria showed the highest
bioaccumulation factor for Cd (BAF = 48.4 ± 12.4) and the highest liver histopathological score at multi-pollutant sites
(mean score 3.2 ± 0.4 vs. reference 0.8 ± 0.2). Pollution Sensitivity Index (PSI), combining tissue concentrations and
biomarker responses, was significantly correlated with distance from municipal wastewater treatment plant outfalls (r(S) =
-0.78, p < 0.001) and predicted independently of chemical monitoring data. These results provide biomarker-based
evidence for widespread EDC, neurotoxic, and heavy metal impacts on aquatic vertebrates across Italian, Austrian, and
Swedish freshwater systems and support incorporation of vertebrate biomarkers into EU Water Framework Directive
biological quality element assessment protocols.