Diatom composition and Functional Groups in Lake Maggiore through 20 years of monitoring data

Lake Maggiore is a deep oligotrophic subalpine lake in Northern Italy which underwent a stage of eutrophication from the 1960s to the mid 1980s. During the recent period, climate-driven events became more prominent, overlapping with the long-term oligotrophication pattern. Recent studies showed that shifts in diatoms assemblages indicate changes in climate and trophic changes. So herein, we used phytoplankton monthly and fortnightly data for the period 1999- 2019 collected within the research program funded by the International Commission for the Protection of Swiss-Italian Waters (CIPAIS). The taxa recorded were grouped in Functional Groups (FG) according to Reynolds and species were selected as those that contributed at least 5% of the mean phytoplankton biomass. We report the results of FG application of variations in diatom community structure and diversity as a possible response to long-term change in nutrient and climate conditions in Lake Maggiore over the last 20 years. Our results suggest that, beside the trophic status, climate warming can alter the structure of the diatom community, thus increasing awareness towards the functional properties of the species involved.