## 2 Materials and Method  
### Study Area  
Lake Garda is the largest Italian lake, with a surface of 368 km\({}^{2}\), and is located in the continental bioregion of Europe. It is characterized by a maximum depth of 350 m and a volume of 49 km\({}^{3}\). Lake Garda contains 30% of Italy's whole natural and artificial lake water resources and represents an essential strategic water supply for agriculture, industry, energy, fishing, and drinking [42]. This oligotrophic lake [43] of glacial origin is located at an altitude of 65 m a.s.l. and counts a total of 25 tributaries, including the main inflow River Sarca located at the northern edge of the lake. The only emissary of Lake Garda is the River Mincio in the southeast of the lake, with average discharge in the winter season of 25 m\({}^{3}\) s\({}^{-1}\), while removal for irrigation ranges between 40 and 80 m\({}^{3}\) s\({}^{-1}\)[44]. The hydrometric level of the lake is influenced by the regulation of its flow at Salionze dam.  
The catchment of Lake Garda is composed of 60% sedimentary rocks, while the remaining 40% is equally distributed between crystalline rocks and secondarily deposited glacial and fluvial sediments [45]. In addition, the catchment is relatively small compared to the surface area of the lake (6:1). This characteristic, combined with low annual precipitation, has led to a long theoretical water renewal time (27 years) [46]. Moreover, Lake Garda is characterized by long periods of incomplete vertical winter water circulation, which are interrupted by full mixing of the water column after the occurrence of harsh winters [47]; consequently, Lake Garda can be defined as warm monomotic and oligomatic.  
Regarding the physical-chemical characteristics, the average value of Secchi disk changes considerably on a seasonal basis: in summer it can vary between 4-5 m, while in winter reaches up to 16 m [48]. Furthermore, the detectable concentration of total phosphorus in the epilimnion is below or around 10 \(\mu\)g L\({}^{-1}\), while the average chlorophyll-a (Chl-a) concentration is about 3 mg m\({}^{-3}\)[48]. Lastly, according to [PERSON] et al. (2003) [49], the suspended particulate matter (SPM) concentration spans a winter-summer range between 0.1 and 5.5 g m\({}^{-3}\) (average value 2.5 g m\({}^{-3}\)).  
With respect to morphology, Lake Garda can be divided into two different portions, separated by an underwater ridge connecting Punta San Vigilio with the Sirmione Peninsula, our study area (Figure 1): the largest part is located to the west and is characterized by a greater maximum depth (350 m), while the east part is much less extensive (representing less than 7% of the total volume of the lake) and is characterized by shallower waters (maximum depth of 80 m).  
Sirmione Peninsula is one of the most popular tourist destinations in the Lake Garda region (with more than a million tourists per year), with attractions such as the ruins of Roman villas and the Scaligeri castle, as well as hot springs and spa facilities. This area extends for about 4 km into the lake and its shores are characterized by moderate slopes inhabited by diverse species of macrophytes [6]. Less urbanized shores are characterized by reedbeds dominated by _Plragmites australis_ (Cav.) Trin. [PERSON], while submerged aquatic vegetation are dominated by several _Chara_ species (_Chara globularis_ [PERSON] 1799, _C. polyacantha_ [PERSON] in [PERSON], [PERSON] 1859, _C. tomentosa_ [PERSON] 1753), _Valliseria spiralis_ [PERSON], _Lagrosiphon major_ (Ridl.) [PERSON], and a few taxa of the _Potamogeton_ genus [6,50].