Lake warmer by 1.5 degrees Alien species on the rise

28 April 2026

 

Water temperatures in the lake are rising, and the effects are being felt by living organisms. Increasingly frequent algal blooms are being observed, along with the acclimatization of alien species and the decline of endemic species such as the carpione. In addition, the presence of emerging contaminants such as microplastics and PFAS—also found in the lake—should not be underestimated, as they indicate environmental pollution in the area.
 

These are some of the findings presented in the report on “Lake health and the impact of plastic pollution on aquatic ecosystems,” delivered by Dr. Luca Bonacina, researcher at the Hydrobiology Unit of the Edmund Mach Foundation in San Michele all’Adige, during the conference “Let’s protect the environment to save ourselves.” The conference was organized with the patronage of the municipality, the Marie Curie Institute of Garda, led by Anastasia Zanoncelli, and the Plastic Free ODV association, with provincial representative and deputy regional coordinator Giovanna Leardini.
 

Bonacina illustrated several activities carried out by the research institute, including “monitoring water quality and studying living organisms, particularly plankton.” Among the most significant findings is that over the past 30 years, surface water temperatures have increased from 7.75 to 9.25 degrees—an increase of one and a half degrees—a phenomenon observed globally in lakes due to climate change. This has several implications: “Among them,” he explained, “the proliferation of certain cyanobacteria, which can be potentially toxic but are constantly monitored. In Lake Garda, this occurs only sporadically, mainly at the end of summer, under conditions of particularly warm and still waters, such as in bays rather than in open lake areas.”
 

Rising temperatures also favor thermophilic species such as the American crayfish (Faxonius limosus), an invasive alien species among more than 45 recorded in the lake. At the same time, endemic species adapted to colder waters, such as the carpione, are suffering and are at risk of conservation, also due to past overfishing and the arrival of alien species.
 

One of the most recent species to invade the lake is Dreissena bugensis. “It is a bivalve mollusk originating from Eastern Europe that has progressively colonized water bodies in Central Europe. Since 2022 it has been found in Lake Garda, making it the first Italian lake invaded by this organism. Over the past two years, bugensis has spread throughout the basin, partially replacing Dreissena polymorpha, another alien mollusk that settled in the lake in the 1970s.”
 

Emerging contaminants

Bonacina also addressed “emerging contaminants.” “Based on scientific literature from other research institutes, we find that these include microplastics—plastics smaller than 5 millimeters. Those present in the lake may originate from the fragmentation of larger plastic items (such as packaging or objects), from soil runoff, or from direct discharges. The average concentration found in Lake Garda waters, according to one of the first studies published in 2018, is 25,000 particles per square kilometer, slightly lower than that recorded in Lakes Iseo and Maggiore.”
 

Finally, Bonacina mentioned another category of emerging pollutants, PFAS: “A study published in 2019 detected one of these compounds, PFOS (perfluorooctane sulfonic acid), in the fish species Alosa agone, with an average concentration of 4.8 nanograms per gram of sample. These values, similar to those found in other lakes such as Iseo or Como, although relatively low, are indicative of background anthropogenic contamination typical of highly industrialized areas.”