Assessing bioaccumulation of chemicals in lacustrine food webs

In Italy, subalpine lakes provide fundamental ecosystem services; they support commercial and recreational fishing activities, they are important tourist destinations and they are intensively exploited for water supply in agriculture, industry and for drinking purposes. In aquatic environment, DDTs and PCBs, perfluoroalkyl substances (PFASs) and mercury are ubiquitous contaminants, persistent and bioaccumulative. The main aim of this Ph.D. study is to highlight the dynamics of redistribution of these selected chemicals with different physico-chemical properties in trophic webs of four major Italian southern alpine deep lakes (Lake Maggiore, Lake Como, Lake Iseo, Lake Garda) and a smaller one (Lake Mergozzo). Specifically, stable isotope analysis of carbon and nitrogen and trophic magnification factor were used, respectively, for the description of the trophic interactions to elucidate chemicals behaviour in biota and to model the biomagnification in food web. In conclusion, notwithstanding the normative restrictions, DDTs, PCBs, PFOS and Hg still reached quantifiable concentrations in biota of the studied lakes. The analysis of trophic webs revealed that feeding relationships are not fixed and stable over time but they are probably ruled by the availability of resources. DDTs, PCBs and Hg biomagnify, as described in literature, confirming that sampling and analysis were correct; on the contrary, biomagnification for PFOS was not well characterised and further studies should be carried out. Future researches should fill the gap of knowledge of contamination in Lake Garda and Lake Iseo that were not deeply investigated due to time schedules