Contamination (DDT, PCB and Hg), density and biomass of zooplankton in Lake Maggiore (Italy).

Lake Maggiore is a southern subalpine lake located across the border between Italy and Switzerland. It is well studied since 1972 thanks to a monitoring program funded by the International Commission for the Protection of Italian-Swiss Waters (CIPAIS; https://www.cipais.org/web/). This program comprises the analysis of trace elements and persistent organic pollutants (POPs) in sediments of the lake and of the main tributaries and in different bioindicators: zooplankton, lake molluscs, riverine benthic invertebrates, and fish. This lake is characterized by legacy DDT and mercury contamination deriving from industrial activities. However, several different anthropogenic pressures act as potential sources of contamination. The program was extended to POPs analysis in fish and in sediment cores after the discovery of fresh DDT discharge into the lake and later to a wide range of contaminants in different matrices like zooplankton organisms, which are directly preyed by fish. The present dataset (on excel file) consists of contaminant concentrations in 50 samples of zooplankton belonging to the size fractions ≥450 μm and ≥850 μm collected seasonally in the central part of Lake Maggiore between 2022 and 2024. The analyses comprised: - Dichlorodiphenyltrichloroethane (DDT): 6 congeners and isomers (o,p' DDD, p,p' DDD, o,p' DDE, p,p' DDE, o,p' DDT and p,p' DDT) and total DDT; - Polychlorinated biphenyls (PCBs): 14 congeners (PCB-18, -28+31, -44, -52, -101, -118, -138, -149, -153, -170, -180, -194, -209), and sumPCB14; - Polycyclic musk fragrances (PMFs): ADBI (Celestolide), AHDI (Phantolide), HHCB (Galaxolide), AHTN (Tonalide), HHCB-L (Galaxolidone), and sumPMFs; - total mercury (THg) and methylmercury (MeHg). Data of concentration of isomers and congeners of DDT, PCBs and of analysed PMFs, allow us to clarify better the age and origin of these contaminants. In addition, we report the lipid content of zooplankton samples and we provide the Standing Stock Density (SSD; ind m−3) and Standing Stock Biomass (SSB; µg m−3) of pelagic crustacean plankton organisms belonging to the already mentioned size fraction. The dataset allows for detecting changes in the concentration over the three-year period and intra-year, thus providing evidence for the seasonal and the plurennial variations in the presence of these pollutants in the lake. They also provide a basis for further studies aimed at modelling paths and the fate of analysed pollutants, for which the amount of toxicants stocked in the zooplankton compartment linked to fish is a crucial estimate. This research was funded by the International Commission for the Protection of Italian-Swiss Waters (CIPAIS), monitoring program 2022-2024 (https://www.cipais.org/web/).