The recent reduction of the presence of the alga Planktothrix rubescens in Lake Ledro is the result of effective interventions aimed at reducing phosphorus, implemented by the Provincial Agency for Environmental Protection (APPA) and other entities since 2014. According to collected data, as of November 2023, the alga has shown an 81% decrease in biovolume compared to the average values of the last nine years, dropping from 1,352 mm³/m³ to just 252 mm³/m³. This positive change is attributed to measures taken to limit nutrient inputs into the lake, thereby improving water quality.
The phenomenon of Planktothrix rubescens blooms, reported since the 1970s and responsible for significant ecological alterations, has prompted local authorities to initiate in-depth studies and experiments to address the sources of phosphorus in the watershed. Interventions at the wastewater treatment plant in Pieve di Ledro and the management of livestock waste on pastures have been central to this process. Currently, total phosphorus levels in the lake range between 12 and 13 mg/L, approaching the desired target of below 10 mg/L to ensure a healthy and sustainable aquatic environment.
