Trophic Magnification of Legacy (PCB, DDT and Hg) and Emerging Pollutants (PFAS) in the Fish Community of a Small Protected Southern Alpine Lake (Lake Mergozzo, Northern Italy)

Michela Mazzoni,Pietro Volta,Roberta Bettinetti,Sara Valsecchi,Katrine Borgå,Roberta Piscia,Stefano Polesello,Davide Cicala,Claudia Ferrario

doi:10.3390/w12061591

Abstract

The biomagnification of mercury, polychlorobiphenyls (PCBs), dichlorodiphenyltrichloroethane and its metabolites (DDTs) and perfluoroalkyl acids substances (PFASs) was evaluated in the trophic web of Lake Mergozzo, a small and deep Italian subalpine lake, which has been chosen because it is a protected environment, and discharges into the lake are mostly avoided. Carbon source and relative trophic levels were calculated by using 13C and 15N stable isotopes, respectively, and trophic magnification factors (TMFs) were derived. Zooplankton and thirteen species of fish were collected and analyzed, and the results showed the elevated level of biota contamination from both legacy and emerging pollutants, even if direct discharges were avoided. Concentrations in biota, expressed as sums of compounds, ranged from 0.4 to 60 µg kg−1 wet weight (ww) for PFASs, from 16 to 1.3 104 µg kg−1 lipid content (lw) for DDTs, from 17 to 1.5 104 µg kg−1 lw for PCBs and from 20.0 to 501 µg kg−1 ww for mercury (Hg). TMFs of this deep, cold lake, with a prevalent pelagic trophic chain, were high and clearly indicated fish biomagnification, except for PFAS. The biomagnification capability of PFAS in a fish-only food web was discussed by using the biomagnification of Hg as a benchmark for assessing their bioaccumulation potential.

Highlights

Bioaccumulation is the process that leads to a higher chemical concentration in an organism due to the uptake by all exposure routes, including dietary and dermal absorption and transport across respiratory surfaces [1]
The biomagnification capability of perfluoroalkyl acids substances (PFASs) in a fish-only food web was discussed by using the biomagnification of Hg as a benchmark for assessing their bioaccumulation potential
DDTs and PCBs concentrations were normalized to the lipid content, while PFASs and Hg are reported as wet weight concentrations, as requested by EU regulations, and a brief summary is given below

Summary

Introduction

Bioaccumulation is the process that leads to a higher chemical concentration in an organism due to the uptake by all exposure routes, including dietary and dermal absorption and transport across respiratory surfaces [1]. Among the different metrics to evaluate bioaccumulation, the trophic magnification factor (TMF) can be useful when diet is the major route of exposure [2,3]. Stable nitrogen and carbon isotope values provide reliable calculations of organism trophic levels. The change in δ15 N or δ 13 C values from prey to predator, called trophic fractionation, provide useful information: nitrogen is more enriched in consumers’ tissues than in prey and is used to calculate the trophic positions, whereas carbon has very small variations in the same trophic web and is typically used to discriminate among the sources of dietary carbon [7,8]

Methods

Results

Conclusion