## 1 Introduction  
The issue of the dynamics of primary producers of lake ecosystems is acquiring more and more relevance because of increasingly marked effects of climate change on the functioning of these systems [1, 2]. Indeed, the progressive reduction in the availability of water resources sharpens conflicting interests on the water uses, imposing increasingly robust assessments of macroclimatic, biological, and human drivers of lacustrine biota and functions [3]. In this regard, the capability to assess and predict the dynamics of lacustrine primary producers, especially macrophytes, represents a key knowledge to offer effective solutions and adaptations to external pressures [4; 5]. In the last decade, some studies have started to quantify the dynamics of lacustrine macrophytes in deep lakes, offering new evidence on a previously poorly analyzed topic [4; 6; 7; 8; 9; 10]. An unexpected dynamism was observed, suggesting the existence of rapid cycles (e.g., of the order of a few years) characterized by the ability of macrophytes--both vascular and algae of the Chaophyceae class--to expand or contract colonized areas along the depth gradient by a few meters [7; 8]. These growing depth variations--although of limited magnitude--should be evaluated as very significant, considering that the depth range colonized by macrophytes hardly exceeds 15-20 m in deep oligo-mesotrophic temperate lakes [11]. Accordingly, in large lakes, deviations of a few decimeters of the maximum growing depth of macrophytes can result in large variations of colonized areas (of the order of hectares of surface) [4]. However, despite this relevance, the roles of physical factors (e.g., hydrological disturbance) or biotic interactions (e.g., herbivory) in regulating macrophyte community dynamics remain largely unclear, especially in large, deep lakes [1; 12; 13; 14]. Lake areas exposed to strong winds are characterized by equally significant wave movements, which result in high sediment resuspension rates, and damage, fragmentation, or uprooting of macrophytes [15; 16]. At the same time, the water level fluctuations have huge effects on aquatic vegetation, regulating the depth ranges of aquatic plant colonization [8; 11; 17]. Under increasingly variable lake water level regimes because of climate change, especially in Mediterranean and temperate geographic contexts, evermore complex macrophyte responses are expected as the qualitative status of lakes varies, in particular water transparency [18]. The progressive fall of lake water levels associated with an increase in trophy leads to a reduction of the euphotic zone with the consequent decline/loss of submerged meadows [7]. Herbivorous birds are another key regulator of the distribution of macrophytes in lake littoral areas [6; 19], as well as the recreational boat traffic [20]. Inland waters intensely crossed by boats have macrophytes cover-abundance rates that are 60% lower than control (no traffic) areas. This knowledge can also provide a vital input and role in the assessment of the conservation status of habitats and species of conservation concern. Aquatic habitats, such as submerged or free-floating macrophyte meadows, are generally rare and intensely impacted by anthropogenic pressures, requiring active management to be maintained, especially in overexploited landscapes [21]. Area and range are two key descriptors of habitat conservation status in the frame of the Habitats Directive (92/43/EEC) [22] but are usually difficult to reliably quantify in aquatic ecosystems [23]. Knowing the spatiotemporal dynamics of macrophytes and their main drivers is the first step to counteract the loss of biodiversity in freshwater ecosystems. Macrophytes are important biological indicators of water and sediment quality but monitoring their distribution with standard approaches typically shows some limitations, such as only a small area being investigated by field campaigns, which are unrepresentative of processes at larger scale, time-limited (e.g., not repeated seasonally or even annually), and costly.