# Stochasticity Shapes Microbial Communities in High-Altitude Lakes, Whereas Species Selection and Homogenization Dispersal Are More Important in Lowland Lakes: Case of Benthic Diatoms in Alpine Lakes

F. Rimet, C. Lemonnier, Benjamin Alric

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F. Rimet, C. Lemonnier, Benjamin Alric. Stochasticity Shapes Microbial Communities in High-Altitude Lakes, Whereas Species Selection and Homogenization Dispersal Are More Important in Lowland Lakes: Case of Benthic Diatoms in Alpine Lakes. Ecology and Evolution, 2025, 15 (9), pp.e71977. 10.1002/ece3.71977. hal-05508594

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RESEARCH ARTICLE

OPEN ACCESS

# Stochasticity Shapes Microbial Communities in High-Altitude Lakes, Whereas Species Selection and Homogenization Dispersal Are More Important in Lowland Lakes: Case of Benthic Diatoms in Alpine Lakes

F. Rimet<fnref n="1" />,² | C. Lemonnier<fnref n="1" /> | B. Alric<fnref n="1" />,²

**Correspondence:** F. Rimet (frederic.rimet@inrae.fr)

**Received:** 6 June 2025

| **Revised:**

31 July 2025

| **Accepted:** 1 August 2025

**Funding:** The authors received no specific funding for this work.

**Keywords:** dispersion | homogenization | lake | metabarcoding | microalgae | selection

## ABSTRACT

Lakes are fundamental ecosystems for human well-being, and understanding the ecological processes shaping their biological communities is of prime importance. Among microalgae, diatoms are often dominating the biomass of their benthic habitats, especially in European alpine lakes. We hypothesized that, because of their contrasted hydro-morphometric characteristics, high-altitude and lowland lake communities may have contrasted diversities and may be shaped differently by ecological processes. We sampled benthic diatoms in 46 high-altitude and 12 lowland lakes in the framework of several projects between years 2013 and 2019. Each lake was sampled in several places along their shoreline depending on lake size, for a total of 514 samples. Samples were analyzed with DNA metabarcoding and specific diatom primers. We used a naïve taxonomic approach based on amplicon sequence variant and a method based on null modelling and phylogenetic indices, together with variance partitioning and co-occurrence networks. Lowland lakes had higher alpha diversities, and the irdiatom ecological networks were more connected than high-altitude lakes. These distinct structural patterns between lake types were explained by different contributions of ecological processes. Although dispersal was similarly restricted in both lake types, diatom communities in high-altitude lakes were mainly governed by stochastic processes, which was not the case in lowlands. This pattern can be explained by the extreme conditions at high altitudes, which create major bottlenecks in diatom communities and thus favour stochasticity. Conversely, homogenizing dispersion was greater in lowlands, confirming the hypothesis of greater connectivity via anthropogenic and biotic vectors in lowland lakes. These findings suggest that high-altitude lakes could be less resilient to environmental changes due to lower diversity and network connectivity compared with lowlands. Finally, we advocate the combined use of diversity metrics, statistical analyses to assess ecological processes, and inference of networks because they provide complementary information to understand lakes vulnerabilities.

## 1 | Introduction

Lakes are fundamental ecosystems for human well-being because they provide a number of essential socio-economic

services (Millennium Ecosystem Assessment 2005; Dudgeon et al. 2006). However, they face significant threats from intensified human activities (Mammides 2020). Understanding the ecological processes driving lakes biodiversity is essential for

<footnote n="1">¹Université Savoie-Mont Blanc, INRAE, UMR CARRTEL, Thonon-les-Bains, France | ²Pôle R&D ECLA, INRAE OFB, Thonon-les-Bains, France</footnote>

<footnote>This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.</footnote>

<footnote>© 2025 The Author(s). *Ecology and Evolution* published by British Ecological Society and John Wiley & Sons Ltd.</footnote>
the sustainable management of these ecosystems. Benthic diatoms, a highly diverse group of microalgae (~100,000 species globally; Mann and Vanormelingen 2013), are key contributors in the littoral zone, respond rapidly to environmental changes (Rimet 2012), and are often used as lake ecological indicators (Marchetto et al. 2013).

Selection, dispersal, speciation, and ecological drift are the four fundamental ecological processes regulating the diversity of communities (Vellend 2010). The relative importance of these processes in shaping lake diatom communities has been investigated for the past decades. Traditionally, research on microalgal communities, including diatoms, and the factors driving changes in their composition focused mainly on local environmental changes (Butcher 1947; Fjerdingstad 1950). The ecological process of species selection when referring to environmental filtering (Vellend 2010) has long been described as the most important process in explaining variability in diatom communities, and a large body of research has described this process in freshwater ecosystems (Rimet 2012; Huber et al. 2020). In particular, it has been shown that under the species selection process, parameters such as nutrients and organic matter concentration in water (Griffiths et al. 2002) as well as grazing (de Faria et al. 2017) influenced diatom community composition. These results led to the development of monitoring tools for assessing river (e.g., Prygiel and Coste 1996; Stevenson and Bahls 2002) and lake pollution (e.g., Hoffman 1994; Marchetto et al. 2009).

Spatial factors and dispersal limitation gained attention in diatom research later than species selection, in the 21st century, with the debate on the Baas-Becking ubiquity hypothesis (everything is everywhere) applied to diatoms (Finlay et al. 2002). Observation of endemic diatom taxa in ancient lakes (Kulikovskiy and Lange-Bertalot 2012; Levkov et al. 2007) and lakes located in isolated regions such as Tasmania and New Zealand (Vyverman et al. 2007) challenged this hypothesis. Recent metabarcoding studies revealed limited dispersal capacity at the subspecies level of diatoms, with, for example, high-altitude lakes separated by 3000 km sharing only 13% of subspecies (Rimet, Pinseel, et al. 2023). While diatoms are now recognized to have dispersal limits and geographic patterns (Pinseel et al. 2024), some species, like *Didymosphaenia geminata* (Blanco and Ector 2009) and tropical invasive diatoms (Coste and Ector 2000), exhibit widespread invasions in rivers. Diatom species invasions in lakes are less known but were revealed using a paleolimnological approach (Alverson et al. 2021). The mass-effect process, focused on the dispersal of individuals from source to sink environments, strongly influences lake communities through cells deriving from tributaries into the lake (Benito et al. 2018; Rimet, Canino, et al. 2023).

Speciation (or diversification) is another central process in shaping biodiversity (Vellend 2010), yet often overlooked in community ecology despite its importance (Zhou and Ning 2017). Addressing this gap is crucial for understanding protist and diatom ecology (Pinseel et al. 2024). In ancient lakes, the importance of speciation is evident through “species flocks,” which are rapid diversification events of particular taxa (Kociolek et al. 2017). For instance, in Lake Ochrid, molecular and fossil evidence shows a rapid diversification

of the genus *Aneumastus*, resulting in many endemic species and a particular taxonomic composition of its communities (Stelbrink et al. 2018).

Finally, ecological drift involves stochastic changes in community composition over time due to random processes like birth, death, and reproduction, especially in small or finite populations (Vellend 2010). Although microbial communities are typically large, the many rare taxa within them are vulnerable to ecological drift (Zhou and Ning 2017). Stochasticity has been increasingly studied in diatom communities over the past 15 years, with special attention in alpine rivers affected by stochastic hydrological events (Centis et al. 2010) and during species succession in rivers (Passy and Larson 2011). Its importance grows with geographical scale in dispersal-related factors (Soininen 2023) and is dominant in alpine mountain lakes for littoral and plankton diatom communities (Ossyssek et al. 2023).

Lakes of the Alpine region provide important ecosystem services to neighboring populations (Baulaz et al. 2021). Due to the typological differences (some being large and low-lying, others small and high-lying) of lakes in this region, their biological communities can be structured by different ecological processes. In the current context of global change, understanding which ecological processes control the biological communities of these lakes will enable us to anticipate their evolution. Our aim is to evaluate how ecological processes influence diatom communities in contrasting lake types (high-altitude vs. lowland lakes) within the same climatic (Alpine) and geographical (Western Europe) zone. Given their contrasted hydro-morphometric characteristics (depth, altitude, residence time, lake surface, and catchment area), we hypothesize that these lakes will exhibit distinct alpha, beta, and gamma diversities, with varying ecological processes shaping these patterns. Our working hypotheses are as follows:

1. High-altitude lakes are pioneer ecosystems with harsher climatic and physical conditions (e.g., freezing, drying) compared to lowlands. Therefore, our 1st hypothesis was that stochastic processes (e.g., ecological drift) dominate in high-altitude lakes, while deterministic processes (selection, dispersal) are more significant in lowlands.

2. High-altitude lake communities exhibit high endemism and limited dispersal capacities due to geographical barriers (Rimet, Pinseel, et al. 2023). In contrast, lowland lakes should be less affected by these barriers due to anthropogenic and biotic vectors (e.g., ballast water, animal movements) that facilitate diatom transfer, even between lakes not hydrographically connected. Consequently, our 2nd hypothesis was that lowland lakes share more species, have lower beta-diversity, and show greater community similarity than high-altitude lakes.

3. Diatom communities in lakes are influenced by mass-effect from rivers arriving in them (Rimet, Canino, et al. 2023). Lakes with large catchment areas attract more dispersers than smaller ecosystems, enhancing diversity and richness (Gilpin and Diamond 1976). Since high-altitude lakes usually have smaller catchment areas than lowland lakes, our 3rd hypothesis was that lowland lakes host a higher
<figure><img src="image_3.png" /><figcaption>**FIGURE 1** | Location of sampling sites in the Alps mountains. A total of 12 lowland lakes (black dot) and 46 high-altitude lakes (gray dots) were sampled. Blue lines: rivers; light blue: large lake in; gray lines: countries boundaries.</figcaption></figure>

diversity (when considering each lake's diversity separately) and that there was a correlation between lake diversity and the lake's surface and the lake's watershed surface.

4. If these hypotheses of stronger geographical barriers and stochasticity in high-altitude lakes are confirmed, our 4th hypothesis was that ecological networks were more complex in lowlands with a higher number of co-occurring taxa, as well as stronger connectivity and connectance. Using ecological network metrics will provide complementary insights to diversity metrics, in particular concerning the stability and resilience of ecosystems (Landi et al. 2018).

To test these hypotheses, while avoiding climate-related confounding factors, we sampled 56 high-altitude and lowland lakes located in the same climatic zone, the European alpine region. Benthic diatom communities, sampled in the littoral zone, were analyzed by DNA metabarcoding targeting a 263 base-pairs fragment of a chloroplast gene (rbcL). This fragment is known to be resolutive at the subspecific level (Kermarrec et al. 2013). In addition, the reference barcode library -Diat.barcode- dedicated to this marker gene and curated by a network of experts for 14years is available (Rimet, Gusev, et al. 2019). Since species boundaries can be ambiguous, we used a naïve taxonomic approach based on the sequence variants (ASV, amplicon sequence variants). We compared communities' similarities and alpha and beta diversities between lake types. Using a reference phylogeny where environmental sequences were relocated, we quantified each ecological process for each lake type following the approach proposed by Stegen et al. (2013). Additionally, variance partitioning was used to assess environmental and geographical effects on community variability, and co-occurrence network metrics were compared across lake types.

## 2 | Materials and Methods

### 2.1 | Study Area and Samplings

Two types of lakes were monitored, high-altitude and lowland lakes, where benthic diatoms were sampled according to the European guidelines for diatom metabarcoding sampling (CEN 2025). For each sample, five stones were collected at a depth of 40–50 cm in an area of 20 m², the upper surface of which was scraped with a clean toothbrush (minimal surface of 100 cm²) to recover the biofilms in sterile plastic tubes. We then fixed the biofilms with a minimal final concentration of 70% ethanol before any further treatment.

Forty-six high-altitude lakes were sampled in the northern (23 lakes) and mid-southern (23 lakes) French Alps, above 1500 m a.s.l. in summer 2013 (aquatic ecosystems above 800 m asl are considered high-altitude in system A of the European Water Framework Directive). For each lake, we collected three samples, except eight lakes where only two samples were taken. The position along the shore of the sampling stations was chosen so that the distance between them was maximized. Twelve lowland lakes (below 800 m asl) were sampled in the alpine region of several European countries (Austria, France, Germany, Italy, Slovenia, Switzerland), with altitudes ranging from 65 to 649 m during the summer and early autumn period from 2017 to 2019. For each lake, from 3 to 152 sampling stations were taken (average of 32). These sampling stations were chosen along the shoreline of the lakes in order to capture a maximum variety of situations, the number of sampling sites being adapted to the lake's surface (Rimet, Canino, et al. 2023). The location of the lakes is given in Figure 1; a total of 125 samples
<table><caption>TABLE 1 | Lakes sampled, with their sampling sites position, sampling dates and elevation.</caption><thead><tr><th>Lake name</th><th>Station</th><th>Country</th><th>Latitude (GPS)</th><th>Longitude (GPS)</th><th>Sampling date</th><th>Elevation (m asl)</th></tr></thead><tbody><tr><td>Annecy</td><td>Annecy_1</td><td>FR</td><td>45.86094</td><td>6.14480</td><td>17/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_2</td><td>FR</td><td>45.84714</td><td>6.15560</td><td>16/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_3</td><td>FR</td><td>45.84474</td><td>6.17406</td><td>17/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_4</td><td>FR</td><td>45.83944</td><td>6.17777</td><td>16/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_5</td><td>FR</td><td>45.83398</td><td>6.18392</td><td>16/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_6</td><td>FR</td><td>45.83078</td><td>6.18958</td><td>16/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_7</td><td>FR</td><td>45.82855</td><td>6.20013</td><td>16/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_9</td><td>FR</td><td>45.82148</td><td>6.20773</td><td>16/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_10</td><td>FR</td><td>45.81443</td><td>6.21031</td><td>16/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_11</td><td>FR</td><td>45.80522</td><td>6.21211</td><td>16/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_12</td><td>FR</td><td>45.79317</td><td>6.21585</td><td>16/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_13</td><td>FR</td><td>45.79478</td><td>6.22152</td><td>16/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_14</td><td>FR</td><td>45.79711</td><td>6.22658</td><td>16/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_15</td><td>FR</td><td>45.79996</td><td>6.22906</td><td>16/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_16</td><td>FR</td><td>45.80543</td><td>6.23155</td><td>16/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_17</td><td>FR</td><td>45.81149</td><td>6.23049</td><td>16/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_18</td><td>FR</td><td>45.81597</td><td>6.22860</td><td>16/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_19</td><td>FR</td><td>45.82298</td><td>6.22143</td><td>16/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_20</td><td>FR</td><td>45.82732</td><td>6.21808</td><td>16/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_21</td><td>FR</td><td>45.83656</td><td>6.21500</td><td>16/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_22</td><td>FR</td><td>45.84186</td><td>6.20820</td><td>16/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_23</td><td>FR</td><td>45.84367</td><td>6.18871</td><td>16/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_24</td><td>FR</td><td>45.85323</td><td>6.18737</td><td>17/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_25</td><td>FR</td><td>45.85943</td><td>6.18498</td><td>17/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_26</td><td>FR</td><td>45.86252</td><td>6.18555</td><td>17/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_27</td><td>FR</td><td>45.87101</td><td>6.18060</td><td>17/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_28</td><td>FR</td><td>45.88066</td><td>6.17448</td><td>17/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_29</td><td>FR</td><td>45.89134</td><td>6.16685</td><td>17/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_30</td><td>FR</td><td>45.89874</td><td>6.16200</td><td>17/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_31</td><td>FR</td><td>45.90289</td><td>6.15991</td><td>17/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_32</td><td>FR</td><td>45.90428</td><td>6.15174</td><td>17/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_33</td><td>FR</td><td>45.90206</td><td>6.14475</td><td>17/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_34</td><td>FR</td><td>45.90134</td><td>6.13334</td><td>17/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_35</td><td>FR</td><td>45.89740</td><td>6.13376</td><td>17/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_36</td><td>FR</td><td>45.89235</td><td>6.13850</td><td>17/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_37</td><td>FR</td><td>45.89024</td><td>6.14350</td><td>17/07/2019</td><td>447</td></tr><tr><td>Annecy</td><td>Annecy_38</td><td>FR</td><td>45.87779</td><td>6.14328</td><td>17/07/2019</td><td>447</td></tr></tbody></table>

(Continues)
<table><caption>TABLE 1 | (Continued)</caption><thead><tr><th>Lake name</th><th>Station</th><th>Country</th><th>Latitude (GPS)</th><th>Longitude (GPS)</th><th>Sampling date</th><th>Elevation (m asl)</th></tr></thead><tbody><tr><td>Annecy</td><td>Annecy_39</td><td>FR</td><td>45.87150</td><td>6.14419</td><td>17/07/2019</td><td>447</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN1</td><td>FR/CH</td><td>46.20904</td><td>6.16238</td><td>27/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN10</td><td>FR/CH</td><td>46.30400</td><td>6.18173</td><td>27/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN100</td><td>FR/CH</td><td>46.39892</td><td>6.76829</td><td>14/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN101</td><td>FR/CH</td><td>46.40553</td><td>6.73323</td><td>14/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN102</td><td>FR/CH</td><td>46.40776</td><td>6.71082</td><td>14/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN103</td><td>FR/CH</td><td>46.40783</td><td>6.68956</td><td>14/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN104</td><td>FR/CH</td><td>46.40502</td><td>6.66787</td><td>14/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN105</td><td>FR/CH</td><td>46.40562</td><td>6.64282</td><td>14/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN106</td><td>FR/CH</td><td>46.40442</td><td>6.62526</td><td>14/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN107</td><td>FR/CH</td><td>46.40307</td><td>6.60698</td><td>14/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN108</td><td>FR/CH</td><td>46.40302</td><td>6.60720</td><td>14/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN109</td><td>FR/CH</td><td>46.39977</td><td>6.57290</td><td>14/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN11</td><td>FR/CH</td><td>46.31891</td><td>6.19622</td><td>27/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN110</td><td>FR/CH</td><td>46.39546</td><td>6.54316</td><td>14/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN111</td><td>FR/CH</td><td>46.40203</td><td>6.52576</td><td>14/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN112</td><td>FR/CH</td><td>46.40361</td><td>6.52225</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN113</td><td>FR/CH</td><td>46.40392</td><td>6.51998</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN114</td><td>FR/CH</td><td>46.40427</td><td>6.51875</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN115</td><td>FR/CH</td><td>46.40476</td><td>6.51651</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN116</td><td>FR/CH</td><td>46.40380</td><td>6.50802</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN117</td><td>FR/CH</td><td>46.39529</td><td>6.48699</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN118</td><td>FR/CH</td><td>46.37880</td><td>6.47949</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN119</td><td>FR/CH</td><td>46.37884</td><td>6.47943</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN12</td><td>FR/CH</td><td>46.33671</td><td>6.20551</td><td>27/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN120</td><td>FR/CH</td><td>46.37454</td><td>6.47406</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN121</td><td>FR/CH</td><td>46.36803</td><td>6.45378</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN122</td><td>FR/CH</td><td>46.36423</td><td>6.44355</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN123</td><td>FR/CH</td><td>46.36410</td><td>6.44302</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN124</td><td>FR/CH</td><td>46.36389</td><td>6.44243</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN125</td><td>FR/CH</td><td>46.35923</td><td>6.41189</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN126</td><td>FR/CH</td><td>46.35021</td><td>6.39925</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN127</td><td>FR/CH</td><td>46.34985</td><td>6.39885</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN128</td><td>FR/CH</td><td>46.34864</td><td>6.39874</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN129</td><td>FR/CH</td><td>46.34425</td><td>6.39404</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN13</td><td>FR/CH</td><td>46.34973</td><td>6.20982</td><td>27/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN130</td><td>FR/CH</td><td>46.34331</td><td>6.37656</td><td>15/06/2017</td><td>375</td></tr></tbody></table>

(Continues)
<table><caption>TABLE 1 | (Continued)</caption><thead><tr><th>Lake name</th><th>Station</th><th>Country</th><th>Latitude (GPS)</th><th>Longitude (GPS)</th><th>Sampling date</th><th>Elevation (m asl)</th></tr></thead><tbody><tr><td>Léman (Lake Geneva)</td><td>SYN131</td><td>FR/CH</td><td>46.34314</td><td>6.37570</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN132</td><td>FR/CH</td><td>46.34352</td><td>6.37450</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN133</td><td>FR/CH</td><td>46.35355</td><td>6.35709</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN134</td><td>FR/CH</td><td>46.36232</td><td>6.35038</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN135</td><td>FR/CH</td><td>46.36973</td><td>6.34016</td><td>15/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN136</td><td>FR/CH</td><td>46.36909</td><td>6.31815</td><td>16/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN137</td><td>FR/CH</td><td>46.36274</td><td>6.29873</td><td>16/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN138</td><td>FR/CH</td><td>46.35352</td><td>6.28315</td><td>16/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN139</td><td>FR/CH</td><td>46.34237</td><td>6.27469</td><td>16/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN14</td><td>FR/CH</td><td>46.36075</td><td>6.21972</td><td>27/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN140</td><td>FR/CH</td><td>46.32670</td><td>6.25942</td><td>16/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN141</td><td>FR/CH</td><td>46.31553</td><td>6.25552</td><td>16/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN142</td><td>FR/CH</td><td>46.30458</td><td>6.24208</td><td>16/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN143</td><td>FR/CH</td><td>46.30429</td><td>6.24172</td><td>16/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN144</td><td>FR/CH</td><td>46.30373</td><td>6.24068</td><td>16/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN145</td><td>FR/CH</td><td>46.29086</td><td>6.23679</td><td>16/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN146</td><td>FR/CH</td><td>46.28014</td><td>6.22333</td><td>16/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN147</td><td>FR/CH</td><td>46.26986</td><td>6.21415</td><td>16/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN148</td><td>FR/CH</td><td>46.26431</td><td>6.19999</td><td>16/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN149</td><td>FR/CH</td><td>46.25344</td><td>6.19335</td><td>16/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN15</td><td>FR/CH</td><td>46.37001</td><td>6.23141</td><td>27/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN150</td><td>FR/CH</td><td>46.23676</td><td>6.19235</td><td>16/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN151</td><td>FR/CH</td><td>46.22781</td><td>6.18543</td><td>16/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN152</td><td>FR/CH</td><td>46.21766</td><td>6.17696</td><td>16/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN153</td><td>FR/CH</td><td>46.20894</td><td>6.16259</td><td>27/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN16</td><td>FR/CH</td><td>46.38368</td><td>6.24671</td><td>27/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN17</td><td>FR/CH</td><td>46.38753</td><td>6.24863</td><td>27/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN18</td><td>FR/CH</td><td>46.39102</td><td>6.25405</td><td>27/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN19</td><td>FR/CH</td><td>46.39291</td><td>6.26256</td><td>27/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN2</td><td>FR/CH</td><td>46.21017</td><td>6.15694</td><td>27/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN20</td><td>FR/CH</td><td>46.39125</td><td>6.26712</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN21</td><td>FR/CH</td><td>46.39025</td><td>6.27420</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN22</td><td>FR/CH</td><td>46.40700</td><td>6.28306</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN23</td><td>FR/CH</td><td>46.42246</td><td>6.29075</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN24</td><td>FR/CH</td><td>46.42440</td><td>6.29701</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN25</td><td>FR/CH</td><td>46.42553</td><td>6.29690</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN26</td><td>FR/CH</td><td>46.43260</td><td>6.30967</td><td>26/06/2017</td><td>375</td></tr></tbody></table>

(Continues)
<table><caption>TABLE 1 | (Continued)</caption><thead><tr><th>Lake name</th><th>Station</th><th>Country</th><th>Latitude (GPS)</th><th>Longitude (GPS)</th><th>Sampling date</th><th>Elevation (m asl)</th></tr></thead><tbody><tr><td>Léman (Lake Geneva)</td><td>SYN27</td><td>FR/CH</td><td>46.44326</td><td>6.31924</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN28</td><td>FR/CH</td><td>46.46146</td><td>6.34772</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN29</td><td>FR/CH</td><td>46.46415</td><td>6.36893</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN3</td><td>FR/CH</td><td>46.22596</td><td>6.14949</td><td>27/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN30</td><td>FR/CH</td><td>46.46390</td><td>6.38565</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN31</td><td>FR/CH</td><td>46.46161</td><td>6.38928</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN32</td><td>FR/CH</td><td>46.45978</td><td>6.39139</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN33</td><td>FR/CH</td><td>46.45910</td><td>6.39756</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN34</td><td>FR/CH</td><td>46.45995</td><td>6.40530</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN35</td><td>FR/CH</td><td>46.46712</td><td>6.41748</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN36</td><td>FR/CH</td><td>46.47127</td><td>6.43872</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN37</td><td>FR/CH</td><td>46.47551</td><td>6.45005</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN38</td><td>FR/CH</td><td>46.49107</td><td>6.47923</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN39</td><td>FR/CH</td><td>46.50358</td><td>6.49333</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN4</td><td>FR/CH</td><td>46.24355</td><td>6.15302</td><td>27/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN40</td><td>FR/CH</td><td>46.50403</td><td>6.49456</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN41</td><td>FR/CH</td><td>46.50430</td><td>6.49560</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN42</td><td>FR/CH</td><td>46.51245</td><td>6.50157</td><td>26/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN43</td><td>FR/CH</td><td>46.51512</td><td>6.51330</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN44</td><td>FR/CH</td><td>46.51229</td><td>6.52844</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN45</td><td>FR/CH</td><td>46.50741</td><td>6.53873</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN46</td><td>FR/CH</td><td>46.50724</td><td>6.53919</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN47</td><td>FR/CH</td><td>46.50727</td><td>6.53981</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN48</td><td>FR/CH</td><td>46.50742</td><td>6.54003</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN49</td><td>FR/CH</td><td>46.50761</td><td>6.55827</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN5</td><td>FR/CH</td><td>46.26238</td><td>6.16629</td><td>27/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN50</td><td>FR/CH</td><td>46.51368</td><td>6.57259</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN51</td><td>FR/CH</td><td>46.51766</td><td>6.58531</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN52</td><td>FR/CH</td><td>46.51727</td><td>6.58684</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN53</td><td>FR/CH</td><td>46.51743</td><td>6.58803</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN54</td><td>FR/CH</td><td>46.51487</td><td>6.59951</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN55</td><td>FR/CH</td><td>46.51145</td><td>6.60987</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN56</td><td>FR/CH</td><td>46.50573</td><td>6.62451</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN57</td><td>FR/CH</td><td>46.50574</td><td>6.62461</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN58</td><td>FR/CH</td><td>46.50688</td><td>6.63413</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN59</td><td>FR/CH</td><td>46.50573</td><td>6.65215</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN6</td><td>FR/CH</td><td>46.27388</td><td>6.17142</td><td>27/06/2017</td><td>375</td></tr></tbody></table>

(Continues)
<table><caption>TABLE 1 | (Continued)</caption><thead><tr><th>Lake name</th><th>Station</th><th>Country</th><th>Latitude (GPS)</th><th>Longitude (GPS)</th><th>Sampling date</th><th>Elevation (m asl)</th></tr></thead><tbody><tr><td>Léman (Lake Geneva)</td><td>SYN60</td><td>FR/CH</td><td>46.50398</td><td>6.67302</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN61</td><td>FR/CH</td><td>46.50048</td><td>6.69035</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN62</td><td>FR/CH</td><td>46.49808</td><td>6.70010</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN63</td><td>FR/CH</td><td>46.48850</td><td>6.71840</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN64</td><td>FR/CH</td><td>46.48920</td><td>6.73753</td><td>22/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN65</td><td>FR/CH</td><td>46.48633</td><td>6.75167</td><td>21/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN66</td><td>FR/CH</td><td>46.47880</td><td>6.76451</td><td>21/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN67</td><td>FR/CH</td><td>46.47401</td><td>6.78514</td><td>21/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN68</td><td>FR/CH</td><td>46.47101</td><td>6.80548</td><td>21/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN69</td><td>FR/CH</td><td>46.46837</td><td>6.82820</td><td>21/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN7</td><td>FR/CH</td><td>46.27481</td><td>6.17092</td><td>27/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN70</td><td>FR/CH</td><td>46.46343</td><td>6.83490</td><td>21/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN71</td><td>FR/CH</td><td>46.46079</td><td>6.83489</td><td>21/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN72</td><td>FR/CH</td><td>46.45517</td><td>6.85289</td><td>21/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN73</td><td>FR/CH</td><td>46.44807</td><td>6.87065</td><td>21/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN74</td><td>FR/CH</td><td>46.43974</td><td>6.88882</td><td>21/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN75</td><td>FR/CH</td><td>46.43955</td><td>6.90310</td><td>21/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN76</td><td>FR/CH</td><td>46.43067</td><td>6.90892</td><td>21/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN77</td><td>FR/CH</td><td>46.42297</td><td>6.92359</td><td>21/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN78</td><td>FR/CH</td><td>46.41317</td><td>6.92906</td><td>21/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN79</td><td>FR/CH</td><td>46.40233</td><td>6.92507</td><td>21/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN8</td><td>FR/CH</td><td>46.27518</td><td>6.17083</td><td>27/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN80</td><td>FR/CH</td><td>46.39725</td><td>6.91646</td><td>19/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN81</td><td>FR/CH</td><td>46.39861</td><td>6.90728</td><td>19/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN82</td><td>FR/CH</td><td>46.39606</td><td>6.88567</td><td>19/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN83</td><td>FR/CH</td><td>46.39382</td><td>6.87077</td><td>21/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN84</td><td>FR/CH</td><td>46.39470</td><td>6.86063</td><td>21/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN85</td><td>FR/CH</td><td>46.39539</td><td>6.86017</td><td>21/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN86</td><td>FR/CH</td><td>46.39518</td><td>6.85988</td><td>19/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN88</td><td>FR/CH</td><td>46.39428</td><td>6.85856</td><td>19/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN89</td><td>FR/CH</td><td>46.39455</td><td>6.85813</td><td>19/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN9</td><td>FR/CH</td><td>46.28995</td><td>6.17067</td><td>27/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN90</td><td>FR/CH</td><td>46.39458</td><td>6.85772</td><td>19/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN91</td><td>FR/CH</td><td>46.39380</td><td>6.85717</td><td>19/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN92</td><td>FR/CH</td><td>46.38987</td><td>6.85888</td><td>19/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN93</td><td>FR/CH</td><td>46.38723</td><td>6.85098</td><td>19/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN94</td><td>FR/CH</td><td>46.38674</td><td>6.83632</td><td>19/06/2017</td><td>375</td></tr></tbody></table>

(Continues)
<table><caption>TABLE 1 | (Continued)</caption><thead><tr><th>Lake name</th><th>Station</th><th>Country</th><th>Latitude (GPS)</th><th>Longitude (GPS)</th><th>Sampling date</th><th>Elevation (m asl)</th></tr></thead><tbody><tr><td>Léman (Lake Geneva)</td><td>SYN95</td><td>FR/CH</td><td>46.38906</td><td>6.81755</td><td>19/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN96</td><td>FR/CH</td><td>46.39383</td><td>6.80574</td><td>19/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN97</td><td>FR/CH</td><td>46.39419</td><td>6.80539</td><td>19/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN98</td><td>FR/CH</td><td>46.39431</td><td>6.80436</td><td>19/06/2017</td><td>375</td></tr><tr><td>Léman (Lake Geneva)</td><td>SYN99</td><td>FR/CH</td><td>46.39426</td><td>6.78619</td><td>19/06/2017</td><td>375</td></tr><tr><td>Bled</td><td>Sample10</td><td>SI</td><td>46.36288</td><td>14.08240</td><td>12/08/2019</td><td>475</td></tr><tr><td>Bled</td><td>Sample1</td><td>SI</td><td>46.36191</td><td>14.08485</td><td>12/08/2019</td><td>475</td></tr><tr><td>Bled</td><td>Sample2</td><td>SI</td><td>46.35919</td><td>14.08549</td><td>12/08/2019</td><td>475</td></tr><tr><td>Bled</td><td>Sample3</td><td>SI</td><td>46.36294</td><td>14.09024</td><td>12/08/2019</td><td>475</td></tr><tr><td>Bled</td><td>Sample4</td><td>SI</td><td>46.36269</td><td>14.08961</td><td>12/08/2019</td><td>475</td></tr><tr><td>Bled</td><td>Sample5</td><td>SI</td><td>46.36254</td><td>14.09943</td><td>12/08/2019</td><td>475</td></tr><tr><td>Bled</td><td>Sample6</td><td>SI</td><td>46.36373</td><td>14.10294</td><td>12/08/2019</td><td>475</td></tr><tr><td>Bled</td><td>Sample7</td><td>SI</td><td>46.36503</td><td>14.10622</td><td>12/08/2019</td><td>475</td></tr><tr><td>Bled</td><td>Sample8</td><td>SI</td><td>46.36878</td><td>14.10787</td><td>12/08/2019</td><td>475</td></tr><tr><td>Bled</td><td>Sample9</td><td>SI</td><td>46.36633</td><td>14.08609</td><td>12/08/2019</td><td>475</td></tr><tr><td>Amersee</td><td>A1</td><td>DE</td><td>47.98609</td><td>11.16236</td><td>01/07/2019</td><td>533</td></tr><tr><td>Amersee</td><td>A11</td><td>DE</td><td>48.00937</td><td>11.09907</td><td>09/07/2019</td><td>533</td></tr><tr><td>Amersee</td><td>A13</td><td>DE</td><td>48.04163</td><td>11.09776</td><td>09/07/2019</td><td>533</td></tr><tr><td>Amersee</td><td>A14</td><td>DE</td><td>48.06256</td><td>11.10509</td><td>09/07/2019</td><td>533</td></tr><tr><td>Amersee</td><td>A15</td><td>DE</td><td>48.07385</td><td>11.12242</td><td>09/07/2019</td><td>533</td></tr><tr><td>Amersee</td><td>A16</td><td>DE</td><td>48.06502</td><td>11.13839</td><td>09/07/2019</td><td>533</td></tr><tr><td>Amersee</td><td>A17</td><td>DE</td><td>48.03729</td><td>11.13113</td><td>09/07/2019</td><td>533</td></tr><tr><td>Amersee</td><td>A18</td><td>DE</td><td>48.00858</td><td>11.14056</td><td>10/07/2019</td><td>533</td></tr><tr><td>Amersee</td><td>A19</td><td>DE</td><td>48.00217</td><td>11.15805</td><td>09/07/2019</td><td>533</td></tr><tr><td>Amersee</td><td>A2</td><td>DE</td><td>47.96773</td><td>11.14929</td><td>09/07/2019</td><td>533</td></tr><tr><td>Amersee</td><td>A20</td><td>DE</td><td>47.99891</td><td>11.16727</td><td>01/07/2019</td><td>533</td></tr><tr><td>Amersee</td><td>A3</td><td>DE</td><td>47.95090</td><td>11.15058</td><td>09/07/2019</td><td>533</td></tr><tr><td>Amersee</td><td>A8</td><td>DE</td><td>47.96446</td><td>11.10731</td><td>09/07/2019</td><td>533</td></tr><tr><td>Aiguebelette</td><td>Ai1</td><td>FR</td><td>45.57211</td><td>5.79848</td><td>10/09/2018</td><td>390</td></tr><tr><td>Aiguebelette</td><td>Ai10</td><td>FR</td><td>45.54199</td><td>5.78049</td><td>10/09/2018</td><td>390</td></tr><tr><td>Aiguebelette</td><td>Ai11</td><td>FR</td><td>45.54100</td><td>5.78173</td><td>10/09/2018</td><td>390</td></tr><tr><td>Aiguebelette</td><td>Ai12</td><td>FR</td><td>45.54014</td><td>5.78669</td><td>10/09/2018</td><td>390</td></tr><tr><td>Aiguebelette</td><td>Ai13</td><td>FR</td><td>45.54211</td><td>5.79832</td><td>10/09/2018</td><td>390</td></tr><tr><td>Aiguebelette</td><td>Ai14</td><td>FR</td><td>45.54189</td><td>5.80484</td><td>10/09/2018</td><td>390</td></tr><tr><td>Aiguebelette</td><td>Ai15</td><td>FR</td><td>45.54246</td><td>5.81133</td><td>10/09/2018</td><td>390</td></tr><tr><td>Aiguebelette</td><td>Ai16</td><td>FR</td><td>45.54378</td><td>5.81212</td><td>10/09/2018</td><td>390</td></tr><tr><td>Aiguebelette</td><td>Ai17</td><td>FR</td><td>45.55242</td><td>5.80903</td><td>10/09/2018</td><td>390</td></tr></tbody></table>

(Continues)
<table><caption>TABLE 1 | (Continued)</caption><thead><tr><th>Lake name</th><th>Station</th><th>Country</th><th>Latitude (GPS)</th><th>Longitude (GPS)</th><th>Sampling date</th><th>Elevation (m asl)</th></tr></thead><tbody><tr><td>Aiguebelette</td><td>Ai18</td><td>FR</td><td>45.55840</td><td>5.80499</td><td>10/09/2018</td><td>390</td></tr><tr><td>Aiguebelette</td><td>Ai19</td><td>FR</td><td>45.56690</td><td>5.80855</td><td>10/09/2018</td><td>390</td></tr><tr><td>Aiguebelette</td><td>Ai2</td><td>FR</td><td>45.57191</td><td>5.79675</td><td>10/09/2018</td><td>390</td></tr><tr><td>Aiguebelette</td><td>Ai20</td><td>FR</td><td>45.57502</td><td>5.80528</td><td>10/09/2018</td><td>390</td></tr><tr><td>Aiguebelette</td><td>Ai21</td><td>FR</td><td>45.57497</td><td>5.80231</td><td>10/09/2018</td><td>390</td></tr><tr><td>Aiguebelette</td><td>Ai3</td><td>FR</td><td>45.56791</td><td>5.79544</td><td>10/09/2018</td><td>390</td></tr><tr><td>Aiguebelette</td><td>Ai4</td><td>FR</td><td>45.56566</td><td>5.79622</td><td>10/09/2018</td><td>390</td></tr><tr><td>Aiguebelette</td><td>Ai5</td><td>FR</td><td>45.56089</td><td>5.79506</td><td>10/09/2018</td><td>390</td></tr><tr><td>Aiguebelette</td><td>Ai6</td><td>FR</td><td>45.55620</td><td>5.79524</td><td>10/09/2018</td><td>390</td></tr><tr><td>Aiguebelette</td><td>Ai7</td><td>FR</td><td>45.55269</td><td>5.79172</td><td>10/09/2018</td><td>390</td></tr><tr><td>Aiguebelette</td><td>Ai8</td><td>FR</td><td>45.54792</td><td>5.78324</td><td>10/09/2018</td><td>390</td></tr><tr><td>Aiguebelette</td><td>Ai9</td><td>FR</td><td>45.54327</td><td>5.77618</td><td>10/09/2018</td><td>390</td></tr><tr><td>Bourget</td><td>B1</td><td>FR</td><td>45.65583</td><td>5.86818</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B10</td><td>FR</td><td>45.66459</td><td>5.85908</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B10</td><td>FR</td><td>45.66459</td><td>5.85908</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B11</td><td>FR</td><td>45.67581</td><td>5.85749</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B12</td><td>FR</td><td>45.68594</td><td>5.85865</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B12</td><td>FR</td><td>45.68594</td><td>5.85865</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B1</td><td>FR</td><td>45.65583</td><td>5.86818</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B2</td><td>FR</td><td>45.65182</td><td>5.87566</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B2</td><td>FR</td><td>45.65182</td><td>5.87566</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B3</td><td>FR</td><td>45.65204</td><td>5.88498</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B3</td><td>FR</td><td>45.65204</td><td>5.88498</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B4</td><td>FR</td><td>45.65437</td><td>5.89284</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B4</td><td>FR</td><td>45.65437</td><td>5.89284</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B5</td><td>FR</td><td>45.66486</td><td>5.89462</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B5</td><td>FR</td><td>45.66486</td><td>5.89462</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B6</td><td>FR</td><td>45.67652</td><td>5.89141</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B6</td><td>FR</td><td>45.67652</td><td>5.89141</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B7</td><td>FR</td><td>45.68807</td><td>5.89355</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B7</td><td>FR</td><td>45.68807</td><td>5.89355</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B8</td><td>FR</td><td>45.65624</td><td>5.86561</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B8</td><td>FR</td><td>45.65624</td><td>5.86561</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B9</td><td>FR</td><td>45.65929</td><td>5.85921</td><td>03/10/2018</td><td>232</td></tr><tr><td>Bourget</td><td>B9</td><td>FR</td><td>45.65929</td><td>5.85921</td><td>03/10/2018</td><td>232</td></tr><tr><td>Garda</td><td>CAS</td><td>IT</td><td>45.73623</td><td>10.79145</td><td>19/08/2019</td><td>65</td></tr><tr><td>Garda</td><td>CAS</td><td>IT</td><td>45.73623</td><td>10.79145</td><td>19/08/2019</td><td>65</td></tr></tbody></table>

(Continues)
<table><caption>TABLE 1 | (Continued)</caption><thead><tr><th>Lake name</th><th>Station</th><th>Country</th><th>Latitude (GPS)</th><th>Longitude (GPS)</th><th>Sampling date</th><th>Elevation (m asl)</th></tr></thead><tbody><tr><td>Lugano</td><td>CHST1</td><td>CH</td><td>45.98657</td><td>8.95634</td><td>20/09/2019</td><td>271</td></tr><tr><td>Lugano</td><td>CHST10</td><td>CH</td><td>45.98921</td><td>8.98905</td><td>11/10/2019</td><td>271</td></tr><tr><td>Lugano</td><td>CHST10</td><td>CH</td><td>45.98921</td><td>8.98905</td><td>11/10/2019</td><td>271</td></tr><tr><td>Lugano</td><td>CHST1</td><td>CH</td><td>45.98657</td><td>8.95634</td><td>20/09/2019</td><td>271</td></tr><tr><td>Lugano</td><td>CHST2</td><td>CH</td><td>45.99841</td><td>8.94819</td><td>20/09/2019</td><td>271</td></tr><tr><td>Lugano</td><td>CHST2</td><td>CH</td><td>45.99841</td><td>8.94819</td><td>20/09/2019</td><td>271</td></tr><tr><td>Lugano</td><td>CHST3</td><td>CH</td><td>46.00319</td><td>8.96056</td><td>23/10/2019</td><td>271</td></tr><tr><td>Lugano</td><td>CHST3</td><td>CH</td><td>46.00319</td><td>8.96056</td><td>23/10/2019</td><td>271</td></tr><tr><td>Lugano</td><td>CHST4</td><td>CH</td><td>46.00234</td><td>8.96157</td><td>23/10/2019</td><td>271</td></tr><tr><td>Lugano</td><td>CHST4</td><td>CH</td><td>46.00234</td><td>8.96157</td><td>23/10/2019</td><td>271</td></tr><tr><td>Lugano</td><td>CHST5</td><td>CH</td><td>46.00408</td><td>8.99541</td><td>24/09/2019</td><td>271</td></tr><tr><td>Lugano</td><td>CHST5</td><td>CH</td><td>46.00408</td><td>8.99541</td><td>24/09/2019</td><td>271</td></tr><tr><td>Lugano</td><td>CHST6</td><td>CH</td><td>46.01544</td><td>9.02005</td><td>26/09/2019</td><td>271</td></tr><tr><td>Lugano</td><td>CHST6</td><td>CH</td><td>46.01544</td><td>9.02005</td><td>26/09/2019</td><td>271</td></tr><tr><td>Lugano</td><td>CHST7</td><td>CH</td><td>46.03052</td><td>9.12308</td><td>08/10/2019</td><td>271</td></tr><tr><td>Lugano</td><td>CHST7</td><td>CH</td><td>46.03052</td><td>9.12308</td><td>08/10/2019</td><td>271</td></tr><tr><td>Lugano</td><td>CHST8</td><td>CH</td><td>46.03010</td><td>9.12278</td><td>08/10/2019</td><td>271</td></tr><tr><td>Lugano</td><td>CHST8</td><td>CH</td><td>46.03010</td><td>9.12278</td><td>08/10/2019</td><td>271</td></tr><tr><td>Lugano</td><td>CHST9</td><td>CH</td><td>45.99170</td><td>8.99942</td><td>11/10/2019</td><td>271</td></tr><tr><td>Lugano</td><td>CHST9</td><td>CH</td><td>45.99170</td><td>8.99942</td><td>11/10/2019</td><td>271</td></tr><tr><td>Garda</td><td>CISA</td><td>IT</td><td>45.53159</td><td>10.72594</td><td>19/08/2019</td><td>65</td></tr><tr><td>Garda</td><td>CISA</td><td>IT</td><td>45.53159</td><td>10.72594</td><td>19/08/2019</td><td>65</td></tr><tr><td>Faaker</td><td>Faak1</td><td>AT</td><td>46.56965</td><td>13.92774</td><td>16/09/2019</td><td>554</td></tr><tr><td>Faaker</td><td>Faak2</td><td>AT</td><td>46.57522</td><td>13.93253</td><td>16/09/2019</td><td>554</td></tr><tr><td>Faaker</td><td>Faak3</td><td>AT</td><td>46.57573</td><td>13.92676</td><td>16/09/2019</td><td>554</td></tr><tr><td>Garda</td><td>GAR</td><td>IT</td><td>45.62537</td><td>10.57658</td><td>03/07/2019</td><td>65</td></tr><tr><td>Garda</td><td>GAR</td><td>IT</td><td>45.62537</td><td>10.57658</td><td>03/07/2019</td><td>65</td></tr><tr><td>Garda</td><td>GOL</td><td>IT</td><td>45.84395</td><td>10.82783</td><td>19/08/2019</td><td>65</td></tr><tr><td>Garda</td><td>GOL</td><td>IT</td><td>45.84395</td><td>10.82783</td><td>19/08/2019</td><td>65</td></tr><tr><td>Garda</td><td>MON</td><td>IT</td><td>45.52448</td><td>10.54645</td><td>03/07/2019</td><td>65</td></tr><tr><td>Mondsee</td><td>Mon1</td><td>AT</td><td>47.80826</td><td>13.41693</td><td>12/10/2018</td><td>481</td></tr><tr><td>Mondsee</td><td>Mon10</td><td>AT</td><td>47.84562</td><td>13.37172</td><td>11/10/2018</td><td>481</td></tr><tr><td>Mondsee</td><td>Mon10</td><td>AT</td><td>47.84562</td><td>13.37172</td><td>11/10/2018</td><td>481</td></tr><tr><td>Mondsee</td><td>Mon1</td><td>AT</td><td>47.80826</td><td>13.41693</td><td>12/10/2018</td><td>481</td></tr><tr><td>Mondsee</td><td>Mon2</td><td>AT</td><td>47.79940</td><td>13.42248</td><td>11/10/2018</td><td>481</td></tr><tr><td>Mondsee</td><td>Mon2</td><td>AT</td><td>47.79940</td><td>13.42248</td><td>11/10/2018</td><td>481</td></tr><tr><td>Mondsee</td><td>Mon3</td><td>AT</td><td>47.80140</td><td>13.43838</td><td>11/10/2018</td><td>481</td></tr></tbody></table>

(Continues)
<table><caption>TABLE 1 | (Continued)</caption><thead><tr><th>Lake name</th><th>Station</th><th>Country</th><th>Latitude (GPS)</th><th>Longitude (GPS)</th><th>Sampling date</th><th>Elevation (m asl)</th></tr></thead><tbody><tr><td>Mondsee</td><td>Mon3</td><td>AT</td><td>47.80140</td><td>13.43838</td><td>11/10/2018</td><td>481</td></tr><tr><td>Mondsee</td><td>Mon4</td><td>AT</td><td>47.82743</td><td>13.39087</td><td>11/10/2018</td><td>481</td></tr><tr><td>Mondsee</td><td>Mon4</td><td>AT</td><td>47.82743</td><td>13.39087</td><td>11/10/2018</td><td>481</td></tr><tr><td>Mondsee</td><td>Mon5</td><td>AT</td><td>47.83392</td><td>13.36548</td><td>12/10/2018</td><td>481</td></tr><tr><td>Mondsee</td><td>Mon5</td><td>AT</td><td>47.83392</td><td>13.36548</td><td>12/10/2018</td><td>481</td></tr><tr><td>Mondsee</td><td>Mon6</td><td>AT</td><td>47.84055</td><td>13.34793</td><td>12/10/2018</td><td>481</td></tr><tr><td>Mondsee</td><td>Mon6</td><td>AT</td><td>47.84055</td><td>13.34793</td><td>12/10/2018</td><td>481</td></tr><tr><td>Mondsee</td><td>Mon7</td><td>AT</td><td>47.82017</td><td>13.39128</td><td>12/10/2018</td><td>481</td></tr><tr><td>Mondsee</td><td>Mon7</td><td>AT</td><td>47.82017</td><td>13.39128</td><td>12/10/2018</td><td>481</td></tr><tr><td>Mondsee</td><td>Mon8</td><td>AT</td><td>47.81693</td><td>13.36557</td><td>12/10/2018</td><td>481</td></tr><tr><td>Mondsee</td><td>Mon8</td><td>AT</td><td>47.81693</td><td>13.36557</td><td>12/10/2018</td><td>481</td></tr><tr><td>Mondsee</td><td>Mon9</td><td>AT</td><td>47.84970</td><td>13.34767</td><td>12/10/2018</td><td>481</td></tr><tr><td>Mondsee</td><td>Mon9</td><td>AT</td><td>47.84970</td><td>13.34767</td><td>12/10/2018</td><td>481</td></tr><tr><td>Garda</td><td>MON</td><td>IT</td><td>45.52448</td><td>10.54645</td><td>03/07/2019</td><td>65</td></tr><tr><td>Garda</td><td>PAC</td><td>IT</td><td>45.46369</td><td>10.71086</td><td>20/08/2019</td><td>65</td></tr><tr><td>Garda</td><td>PAC</td><td>IT</td><td>45.46369</td><td>10.71086</td><td>20/08/2019</td><td>65</td></tr><tr><td>Garda</td><td>RIV</td><td>IT</td><td>45.87781</td><td>10.85537</td><td>19/08/2019</td><td>65</td></tr><tr><td>Garda</td><td>RIV</td><td>IT</td><td>45.87781</td><td>10.85537</td><td>19/08/2019</td><td>65</td></tr><tr><td>Bled</td><td>Sample1</td><td>SI</td><td>46.36191</td><td>14.08485</td><td>12/08/2019</td><td>475</td></tr><tr><td>Bled</td><td>Sample2</td><td>SI</td><td>46.35919</td><td>14.08549</td><td>12/08/2019</td><td>475</td></tr><tr><td>Bled</td><td>Sample3</td><td>SI</td><td>46.36294</td><td>14.09024</td><td>12/08/2019</td><td>475</td></tr><tr><td>Bled</td><td>Sample4</td><td>SI</td><td>46.36269</td><td>14.08961</td><td>12/08/2019</td><td>475</td></tr><tr><td>Bled</td><td>Sample5</td><td>SI</td><td>46.36254</td><td>14.09943</td><td>12/08/2019</td><td>475</td></tr><tr><td>Bled</td><td>Sample6</td><td>SI</td><td>46.36373</td><td>14.10294</td><td>12/08/2019</td><td>475</td></tr><tr><td>Bled</td><td>Sample7</td><td>SI</td><td>46.36503</td><td>14.10622</td><td>12/08/2019</td><td>475</td></tr><tr><td>Bled</td><td>Sample8</td><td>SI</td><td>46.36878</td><td>14.10787</td><td>12/08/2019</td><td>475</td></tr><tr><td>Bled</td><td>Sample9</td><td>SI</td><td>46.36633</td><td>14.08609</td><td>12/08/2019</td><td>475</td></tr><tr><td>Staffelsee</td><td>SF12</td><td>DE</td><td>47.69782</td><td>11.17805</td><td>08/07/2019</td><td>649</td></tr><tr><td>Staffelsee</td><td>SF14</td><td>DE</td><td>47.70164</td><td>11.15929</td><td>08/07/2019</td><td>649</td></tr><tr><td>Staffelsee</td><td>SF2a</td><td>DE</td><td>47.67812</td><td>11.15076</td><td>08/07/2019</td><td>649</td></tr><tr><td>Staffelsee</td><td>SF5a</td><td>DE</td><td>47.69153</td><td>11.15798</td><td>08/07/2019</td><td>649</td></tr><tr><td>Staffelsee</td><td>SF8a</td><td>DE</td><td>47.70493</td><td>11.17416</td><td>08/07/2019</td><td>649</td></tr><tr><td>Staffelsee</td><td>SF9</td><td>DE</td><td>47.68980</td><td>11.17914</td><td>08/07/2019</td><td>649</td></tr><tr><td>Garda</td><td>SIR1</td><td>IT</td><td>45.47279</td><td>10.60052</td><td>03/07/2019</td><td>65</td></tr><tr><td>Garda</td><td>SIR1</td><td>IT</td><td>45.47279</td><td>10.60052</td><td>03/07/2019</td><td>65</td></tr><tr><td>Garda</td><td>SIR2</td><td>IT</td><td>45.46284</td><td>10.62006</td><td>03/07/2019</td><td>65</td></tr><tr><td>Garda</td><td>SIR2</td><td>IT</td><td>45.46284</td><td>10.62006</td><td>03/07/2019</td><td>65</td></tr></tbody></table>

(Continues)
<table><caption>TABLE 1 | (Continued)</caption><thead><tr><th>Lake name</th><th>Station</th><th>Country</th><th>Latitude (GPS)</th><th>Longitude (GPS)</th><th>Sampling date</th><th>Elevation (m asl)</th></tr></thead><tbody><tr><td>Starnberger_See</td><td>T1</td><td>DE</td><td>47.87994</td><td>11.28782</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T10</td><td>DE</td><td>47.98122</td><td>11.33359</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T10</td><td>DE</td><td>47.98122</td><td>11.33359</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T11</td><td>DE</td><td>47.99569</td><td>11.34602</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T11</td><td>DE</td><td>47.99569</td><td>11.34602</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T13</td><td>DE</td><td>47.98629</td><td>11.35849</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T13</td><td>DE</td><td>47.98629</td><td>11.35849</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T14</td><td>DE</td><td>47.97844</td><td>11.35676</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T14</td><td>DE</td><td>47.97844</td><td>11.35676</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T15</td><td>DE</td><td>47.96721</td><td>11.34848</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T15</td><td>DE</td><td>47.96721</td><td>11.34848</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T16</td><td>DE</td><td>47.95891</td><td>11.34504</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T16</td><td>DE</td><td>47.95891</td><td>11.34504</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T17</td><td>DE</td><td>47.94940</td><td>11.34139</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T17</td><td>DE</td><td>47.94940</td><td>11.34139</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T18</td><td>DE</td><td>47.93047</td><td>11.33244</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T18</td><td>DE</td><td>47.93047</td><td>11.33244</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T19</td><td>DE</td><td>47.91982</td><td>11.33046</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T19</td><td>DE</td><td>47.91982</td><td>11.33046</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T1</td><td>DE</td><td>47.87994</td><td>11.28782</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T2</td><td>DE</td><td>47.88604</td><td>11.28017</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T20</td><td>DE</td><td>47.90935</td><td>11.33329</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T20</td><td>DE</td><td>47.90935</td><td>11.33329</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T21</td><td>DE</td><td>47.89468</td><td>11.33405</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T21</td><td>DE</td><td>47.89468</td><td>11.33405</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T22</td><td>DE</td><td>47.88537</td><td>11.33308</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T22</td><td>DE</td><td>47.88537</td><td>11.33308</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T23</td><td>DE</td><td>47.86901</td><td>11.33393</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T23</td><td>DE</td><td>47.86901</td><td>11.33393</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T24</td><td>DE</td><td>47.85453</td><td>11.33647</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T24</td><td>DE</td><td>47.85453</td><td>11.33647</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T25</td><td>DE</td><td>47.84118</td><td>11.33833</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T25</td><td>DE</td><td>47.84118</td><td>11.33833</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T27</td><td>DE</td><td>47.82074</td><td>11.31834</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T27</td><td>DE</td><td>47.82074</td><td>11.31834</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T28</td><td>DE</td><td>47.82760</td><td>11.29832</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T28</td><td>DE</td><td>47.82760</td><td>11.29832</td><td>18/07/2019</td><td>584</td></tr></tbody></table>

(Continues)
<table><caption>TABLE 1 | (Continued)</caption><thead><tr><th>Lake name</th><th>Station</th><th>Country</th><th>Latitude (GPS)</th><th>Longitude (GPS)</th><th>Sampling date</th><th>Elevation (m asl)</th></tr></thead><tbody><tr><td>Starnberger_See</td><td>T2</td><td>DE</td><td>47.88604</td><td>11.28017</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T3</td><td>DE</td><td>47.89441</td><td>11.27227</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T30</td><td>DE</td><td>47.85375</td><td>11.29653</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T30</td><td>DE</td><td>47.85375</td><td>11.29653</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T3</td><td>DE</td><td>47.89441</td><td>11.27227</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T4</td><td>DE</td><td>47.90609</td><td>11.27956</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T4</td><td>DE</td><td>47.90609</td><td>11.27956</td><td>18/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T5</td><td>DE</td><td>47.93167</td><td>11.29896</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T5</td><td>DE</td><td>47.93167</td><td>11.29896</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T6</td><td>DE</td><td>47.94164</td><td>11.31050</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T6</td><td>DE</td><td>47.94164</td><td>11.31050</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T7</td><td>DE</td><td>47.95147</td><td>11.31009</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T7</td><td>DE</td><td>47.95147</td><td>11.31009</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T8</td><td>DE</td><td>47.96140</td><td>11.31807</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T8</td><td>DE</td><td>47.96140</td><td>11.31807</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T9</td><td>DE</td><td>47.96926</td><td>11.32602</td><td>19/07/2019</td><td>584</td></tr><tr><td>Starnberger_See</td><td>T9</td><td>DE</td><td>47.96926</td><td>11.32602</td><td>19/07/2019</td><td>584</td></tr><tr><td>Garda</td><td>TRE</td><td>IT</td><td>45.75651</td><td>10.75008</td><td>03/07/2019</td><td>65</td></tr><tr><td>Garda</td><td>TRE</td><td>IT</td><td>45.75651</td><td>10.75008</td><td>03/07/2019</td><td>65</td></tr><tr><td>Lac des Confins</td><td>LA1.1</td><td>FR</td><td>45.91690</td><td>6.47664</td><td>22/07/2013</td><td>1355</td></tr><tr><td>Lac des Confins</td><td>LA1.2</td><td>FR</td><td>45.91512</td><td>6.47567</td><td>22/07/2013</td><td>1355</td></tr><tr><td>Lac Achard</td><td>LA10.1</td><td>FR</td><td>45.11327</td><td>5.90188</td><td>10/07/2013</td><td>1917</td></tr><tr><td>Lac Achard</td><td>LA10.2</td><td>FR</td><td>45.11369</td><td>5.90116</td><td>10/07/2013</td><td>1917</td></tr><tr><td>Lac Achard</td><td>LA10.3</td><td>FR</td><td>45.11511</td><td>5.90196</td><td>10/07/2013</td><td>1917</td></tr><tr><td>Lac Robert Sud-Est</td><td>LA11.1</td><td>FR</td><td>45.13146</td><td>5.91827</td><td>11/07/2013</td><td>1998</td></tr><tr><td>Lac Robert Sud-Est</td><td>LA11.2</td><td>FR</td><td>45.13078</td><td>5.91752</td><td>11/07/2013</td><td>1998</td></tr><tr><td>Lac Robert Sud-Est</td><td>LA11.3</td><td>FR</td><td>45.13077</td><td>5.91880</td><td>11/07/2013</td><td>1998</td></tr><tr><td>petit Lac Bernard, au sud ouest du Lac Longuet</td><td>LA13.1</td><td>FR</td><td>45.15272</td><td>5.93420</td><td>17/07/2013</td><td>2000</td></tr><tr><td>petit Lac Bernard, au sud ouest du Lac Longuet</td><td>LA13.2</td><td>FR</td><td>45.15222</td><td>5.93397</td><td>17/07/2013</td><td>2000</td></tr><tr><td>petit Lac Bernard, au sud ouest du Lac Longuet</td><td>LA13.3</td><td>FR</td><td>45.15249</td><td>5.93332</td><td>17/07/2013</td><td>2000</td></tr><tr><td>Lac Longet de Belledonne</td><td>LA14.1</td><td>FR</td><td>45.15244</td><td>5.93547</td><td>13/07/2013</td><td>2027</td></tr><tr><td>Lac Longet de Belledonne</td><td>LA14.2</td><td>FR</td><td>45.15368</td><td>5.93778</td><td>13/07/2013</td><td>2027</td></tr><tr><td>Lac Longet de Belledonne</td><td>LA14.3</td><td>FR</td><td>45.15280</td><td>5.93759</td><td>13/07/2013</td><td>2027</td></tr><tr><td>Lac David</td><td>LA15.1</td><td>FR</td><td>45.15087</td><td>5.94320</td><td>17/07/2013</td><td>2212</td></tr><tr><td>Lac David</td><td>LA15.2</td><td>FR</td><td>45.15047</td><td>5.94195</td><td>17/07/2013</td><td>2212</td></tr></tbody></table>

(Continues)
<table><caption>TABLE 1 | (Continued)</caption><thead><tr><th>Lake name</th><th>Station</th><th>Country</th><th>Latitude (GPS)</th><th>Longitude (GPS)</th><th>Sampling date</th><th>Elevation (m asl)</th></tr></thead><tbody><tr><td>Lac David</td><td>LA15.3</td><td>FR</td><td>45.15010</td><td>5.94286</td><td>17/07/2013</td><td>2212</td></tr><tr><td>Lac Merlat</td><td>LA16.1</td><td>FR</td><td>45.15848</td><td>5.93099</td><td>14/07/2013</td><td>2044</td></tr><tr><td>Lac Merlat</td><td>LA16.2</td><td>FR</td><td>45.15833</td><td>5.93335</td><td>14/07/2013</td><td>2044</td></tr><tr><td>Lac Merlat</td><td>LA16.3</td><td>FR</td><td>45.15758</td><td>5.93121</td><td>14/07/2013</td><td>2044</td></tr><tr><td>Lac Claret</td><td>LA17.1</td><td>FR</td><td>45.15637</td><td>5.94292</td><td>17/07/2013</td><td>2045</td></tr><tr><td>Lac Claret</td><td>LA17.2</td><td>FR</td><td>45.15553</td><td>5.94203</td><td>14/07/2013</td><td>2045</td></tr><tr><td>Lac Claret</td><td>LA17.3</td><td>FR</td><td>45.15523</td><td>5.94292</td><td>14/07/2013</td><td>2045</td></tr><tr><td>Lac Blanc de l'Herpie</td><td>LA18.1</td><td>FR</td><td>45.11179</td><td>6.10397</td><td>24/07/2013</td><td>2525</td></tr><tr><td>Lac Blanc de l'Herpie</td><td>LA18.2</td><td>FR</td><td>45.11718</td><td>6.10628</td><td>24/07/2013</td><td>2525</td></tr><tr><td>Lac Blanc de l'Herpie</td><td>LA18.3</td><td>FR</td><td>45.11497</td><td>6.10832</td><td>24/07/2013</td><td>2525</td></tr><tr><td>Lac Noir de Poutran</td><td>LA19.1</td><td>FR</td><td>45.11692</td><td>6.08484</td><td>23/07/2013</td><td>2047</td></tr><tr><td>Lac Noir de Poutran</td><td>LA19.2</td><td>FR</td><td>45.11747</td><td>6.08543</td><td>23/07/2013</td><td>2047</td></tr><tr><td>Lac Besson-Rond</td><td>LA20.1</td><td>FR</td><td>45.67938</td><td>6.85323</td><td>23/07/2013</td><td>2070</td></tr><tr><td>Lac Besson-Rond</td><td>LA20.3</td><td>FR</td><td>45.67852</td><td>6.85216</td><td>23/07/2013</td><td>2070</td></tr><tr><td>Lac de Presset</td><td>LA24.1</td><td>FR</td><td>45.65022</td><td>6.66482</td><td>20/07/2013</td><td>2514</td></tr><tr><td>Lac de Presset</td><td>LA24.2</td><td>FR</td><td>45.64934</td><td>6.66396</td><td>20/07/2013</td><td>2514</td></tr><tr><td>Lac de Presset</td><td>LA24.3</td><td>FR</td><td>45.64905</td><td>6.66465</td><td>20/07/2013</td><td>2514</td></tr><tr><td>Lac Sans Fond</td><td>LA29.1</td><td>FR</td><td>45.67608</td><td>6.88848</td><td>14/07/2013</td><td>2456</td></tr><tr><td>Lac Sans Fond</td><td>LA29.2</td><td>FR</td><td>45.67457</td><td>6.88663</td><td>14/07/2013</td><td>2456</td></tr><tr><td>Lac Sans Fond</td><td>LA29.3</td><td>FR</td><td>45.67417</td><td>6.88785</td><td>14/07/2013</td><td>2456</td></tr><tr><td>Lac Longet du petit saint bernard</td><td>LA30.1</td><td>FR</td><td>45.67602</td><td>6.88821</td><td>15/07/2013</td><td>2316</td></tr><tr><td>Lac Longet du petit saint bernard</td><td>LA30.2</td><td>FR</td><td>45.67397</td><td>6.88663</td><td>15/07/2013</td><td>2316</td></tr><tr><td>Lac Longet du petit saint bernard</td><td>LA30.3</td><td>FR</td><td>45.67449</td><td>6.88856</td><td>15/07/2013</td><td>2316</td></tr><tr><td>Lac de la Plagne</td><td>LA31.1</td><td>FR</td><td>45.48579</td><td>6.84170</td><td>11/08/2013</td><td>2145</td></tr><tr><td>Lac de la Plagne</td><td>LA31.2</td><td>FR</td><td>45.48423</td><td>6.84021</td><td>11/08/2013</td><td>2145</td></tr><tr><td>Lac de la Plagne</td><td>LA31.3</td><td>FR</td><td>45.48318</td><td>6.84293</td><td>11/08/2013</td><td>2145</td></tr><tr><td>Grand lac du Chardonnet</td><td>LA32.1</td><td>FR</td><td>45.46612</td><td>6.88511</td><td>16/08/2013</td><td>2384</td></tr><tr><td>Grand lac du Chardonnet</td><td>LA32.3</td><td>FR</td><td>45.46555</td><td>6.88238</td><td>16/08/2013</td><td>2384</td></tr><tr><td>Lac du Grataleu</td><td>LA33.1</td><td>FR</td><td>45.46186</td><td>6.85849</td><td>16/08/2013</td><td>2512</td></tr><tr><td>Lac du Grataleu</td><td>LA33.3</td><td>FR</td><td>45.46097</td><td>6.86004</td><td>16/08/2013</td><td>2512</td></tr><tr><td>Lac Brulet d'archebroc</td><td>LA35.2</td><td>FR</td><td>45.57395</td><td>6.96936</td><td>22/08/2013</td><td>2697</td></tr><tr><td>Lac Brulet d'archebroc</td><td>LA35.3</td><td>FR</td><td>45.57322</td><td>6.96995</td><td>22/08/2013</td><td>2697</td></tr><tr><td>Lac Noir du clou</td><td>LA37.1</td><td>FR</td><td>45.56956</td><td>6.98395</td><td>22/08/2013</td><td>2618</td></tr><tr><td>Lac Noir du clou</td><td>LA37.2</td><td>FR</td><td>45.57111</td><td>6.98449</td><td>22/08/2013</td><td>2618</td></tr><tr><td>Lac Noir du clou</td><td>LA37.3</td><td>FR</td><td>45.56950</td><td>6.98671</td><td>22/08/2013</td><td>2618</td></tr><tr><td>Lac Noir du Carro</td><td>LA38.1</td><td>FR</td><td>45.42187</td><td>7.12494</td><td>12/08/2013</td><td>2750</td></tr><tr><td>Lac Noir du Carro</td><td>LA38.2</td><td>FR</td><td>45.42073</td><td>7.12434</td><td>12/08/2013</td><td>2750</td></tr></tbody></table>

(Continues)
<table><caption>TABLE 1 | (Continued)</caption><thead><tr><th>Lake name</th><th>Station</th><th>Country</th><th>Latitude (GPS)</th><th>Longitude (GPS)</th><th>Sampling date</th><th>Elevation (m asl)</th></tr></thead><tbody><tr><td>Lac Blanc du Carro</td><td>LA39.1</td><td>FR</td><td>45.42139</td><td>7.12742</td><td>13/08/2013</td><td>2753</td></tr><tr><td>Lac Blanc du Carro</td><td>LA39.2</td><td>FR</td><td>45.42020</td><td>7.12597</td><td>13/08/2013</td><td>2753</td></tr><tr><td>Lac Blanc du Carro</td><td>LA39.3</td><td>FR</td><td>45.41983</td><td>7.12750</td><td>13/08/2013</td><td>2753</td></tr><tr><td>Lac des Evettes</td><td>LA40.1</td><td>FR</td><td>45.35593</td><td>7.11486</td><td>05/08/2013</td><td>2539</td></tr><tr><td>Lac des Evettes</td><td>LA40.2</td><td>FR</td><td>45.35506</td><td>7.11653</td><td>05/08/2013</td><td>2539</td></tr><tr><td>Lac des Evettes</td><td>LA40.3</td><td>FR</td><td>45.35455</td><td>7.11477</td><td>05/08/2013</td><td>2539</td></tr><tr><td>Lac de la Leisse (sud)</td><td>LA41.1</td><td>FR</td><td>45.42002</td><td>6.91068</td><td>14/08/2013</td><td>2798</td></tr><tr><td>Lac de la Leisse (sud)</td><td>LA41.2</td><td>FR</td><td>45.41871</td><td>6.91038</td><td>14/08/2013</td><td>2798</td></tr><tr><td>Lac de la Leisse (sud)</td><td>LA41.3</td><td>FR</td><td>45.41843</td><td>6.91115</td><td>14/08/2013</td><td>2798</td></tr><tr><td>Lac des Nettes</td><td>LA42.2</td><td>FR</td><td>45.41367</td><td>6.90014</td><td>14/08/2013</td><td>2641</td></tr><tr><td>Lac des Nettes</td><td>LA42.3</td><td>FR</td><td>45.41288</td><td>6.89832</td><td>14/08/2013</td><td>2641</td></tr><tr><td>Lac Long</td><td>LA43.1</td><td>FR</td><td>45.39696</td><td>6.79092</td><td>16/08/2013</td><td>2467</td></tr><tr><td>Lac Long</td><td>LA43.2</td><td>FR</td><td>45.39618</td><td>6.78960</td><td>16/08/2013</td><td>2467</td></tr><tr><td>Lac Long</td><td>LA43.3</td><td>FR</td><td>45.39574</td><td>6.79153</td><td>16/08/2013</td><td>2467</td></tr><tr><td>Lac Rond</td><td>LA44.1</td><td>FR</td><td>45.38880</td><td>6.79961</td><td>16/08/2013</td><td>2500</td></tr><tr><td>Lac Rond</td><td>LA44.3</td><td>FR</td><td>45.38804</td><td>6.80104</td><td>16/08/2013</td><td>2500</td></tr><tr><td>Lac du Pelve</td><td>LA45.1</td><td>FR</td><td>45.36081</td><td>6.80098</td><td>20/08/2013</td><td>2574</td></tr><tr><td>Lac du Pelve</td><td>LA45.2</td><td>FR</td><td>45.36181</td><td>6.80091</td><td>20/08/2013</td><td>2574</td></tr><tr><td>Lac de Roche ferran</td><td>LA46.1</td><td>FR</td><td>45.35883</td><td>6.79230</td><td>21/08/2013</td><td>2619</td></tr><tr><td>Lac de Roche ferran</td><td>LA46.2</td><td>FR</td><td>45.36030</td><td>6.79214</td><td>21/08/2013</td><td>2619</td></tr><tr><td>Lac de Roche ferran</td><td>LA46.3</td><td>FR</td><td>45.36105</td><td>6.79541</td><td>20/08/2013</td><td>2619</td></tr><tr><td>Plan du lac</td><td>LA48.1</td><td>FR</td><td>45.33839</td><td>6.83222</td><td>07/08/2013</td><td>2362</td></tr><tr><td>Plan du lac</td><td>LA48.3</td><td>FR</td><td>45.33622</td><td>6.83174</td><td>07/08/2013</td><td>2362</td></tr><tr><td>Lac de l'Arpont</td><td>LA49.1</td><td>FR</td><td>45.31523</td><td>6.77605</td><td>28/08/2013</td><td>2666</td></tr><tr><td>Lac de l'Arpont</td><td>LA49.2</td><td>FR</td><td>45.31665</td><td>6.77441</td><td>28/08/2013</td><td>2666</td></tr><tr><td>Lac de l'Arpont</td><td>LA49.3</td><td>FR</td><td>45.31621</td><td>6.77667</td><td>28/08/2013</td><td>2666</td></tr><tr><td>Lac de Lessy</td><td>LA51.1</td><td>FR</td><td>45.98818</td><td>6.44088</td><td>23/07/2013</td><td>1735</td></tr><tr><td>Lac de Lessy</td><td>LA51.2</td><td>FR</td><td>45.98814</td><td>6.43792</td><td>23/07/2013</td><td>1735</td></tr><tr><td>Lac de Lessy</td><td>LA51.3</td><td>FR</td><td>45.98658</td><td>6.43613</td><td>23/07/2013</td><td>1735</td></tr><tr><td>Lac inférieur de Lanserlia</td><td>LA50.1</td><td>FR</td><td>45.33361</td><td>6.85767</td><td>22/08/2013</td><td>2745</td></tr><tr><td>Lac inférieur de Lanserlia</td><td>LA50.2</td><td>FR</td><td>45.33441</td><td>6.85746</td><td>22/08/2013</td><td>2745</td></tr><tr><td>Lac inférieur de Lanserlia</td><td>LA50.3</td><td>FR</td><td>45.33429</td><td>6.85885</td><td>28/08/2013</td><td>2745</td></tr><tr><td>Lac de la Leisse (milieu)</td><td>LA51.1</td><td>FR</td><td>45.42273</td><td>6.91271</td><td>14/08/2013</td><td>2769</td></tr><tr><td>Lac de la Leisse (milieu)</td><td>LA51.2</td><td>FR</td><td>45.42211</td><td>6.91262</td><td>14/08/2013</td><td>2769</td></tr><tr><td>Lac de la Leisse (milieu)</td><td>LA51.3</td><td>FR</td><td>45.42184</td><td>6.91404</td><td>14/08/2013</td><td>2769</td></tr><tr><td>Lac supérieur de Lanserlia</td><td>LA52.1</td><td>FR</td><td>45.33680</td><td>6.85514</td><td>22/08/2013</td><td>2760</td></tr><tr><td>Lac supérieur de Lanserlia</td><td>LA52.2</td><td>FR</td><td>45.33748</td><td>6.85477</td><td>22/08/2013</td><td>2760</td></tr></tbody></table>

(Continues)
<table><caption>TABLE 1 | (Continued)</caption><thead><tr><th>Lake name</th><th>Station</th><th>Country</th><th>Latitude (GPS)</th><th>Longitude (GPS)</th><th>Sampling date</th><th>Elevation (m asl)</th></tr></thead><tbody><tr><td>Lac supérieur de Lanserlia</td><td>LA52.3</td><td>FR</td><td>45.33740</td><td>6.85605</td><td>22/08/2013</td><td>2760</td></tr><tr><td>Lac des Cerces</td><td>LA53.1</td><td>FR</td><td>45.07238</td><td>6.47373</td><td>23/07/2013</td><td>2410</td></tr><tr><td>Lac des Cerces</td><td>LA53.2</td><td>FR</td><td>45.07073</td><td>6.47352</td><td>23/07/2013</td><td>2410</td></tr><tr><td>Lac des Cerces</td><td>LA53.3</td><td>FR</td><td>45.07073</td><td>6.47596</td><td>23/07/2013</td><td>2410</td></tr><tr><td>Lac du Grand Ban</td><td>LA55.2</td><td>FR</td><td>45.08600</td><td>6.47591</td><td>23/07/2013</td><td>2465</td></tr><tr><td>Lac du Grand Ban</td><td>LA55.3</td><td>FR</td><td>45.08550</td><td>6.47217</td><td>23/07/2013</td><td>2465</td></tr><tr><td>Lac du Serpent</td><td>LA56.1</td><td>FR</td><td>45.05269</td><td>6.56178</td><td>31/07/2013</td><td>2448</td></tr><tr><td>Lac du Serpent</td><td>LA56.2</td><td>FR</td><td>45.05205</td><td>6.56346</td><td>31/07/2013</td><td>2448</td></tr><tr><td>Lac du Serpent</td><td>LA56.3</td><td>FR</td><td>45.05087</td><td>6.56198</td><td>31/07/2013</td><td>2448</td></tr><tr><td>Lac Laramon</td><td>LA57.1</td><td>FR</td><td>45.04934</td><td>6.55599</td><td>31/07/2013</td><td>2359</td></tr><tr><td>Lac Laramon</td><td>LA57.2</td><td>FR</td><td>45.04855</td><td>6.55444</td><td>31/07/2013</td><td>2359</td></tr><tr><td>Lac Laramon</td><td>LA57.3</td><td>FR</td><td>45.04786</td><td>6.55643</td><td>31/07/2013</td><td>2359</td></tr><tr><td>Lac Rond des Rochilles</td><td>LA58.1</td><td>FR</td><td>45.08667</td><td>6.48123</td><td>23/07/2013</td><td>2450</td></tr><tr><td>Lac Rond des Rochilles</td><td>LA58.2</td><td>FR</td><td>45.08525</td><td>6.48425</td><td>23/07/2013</td><td>2450</td></tr><tr><td>Lac Rond des Rochilles</td><td>LA58.3</td><td>FR</td><td>45.08470</td><td>6.48112</td><td>23/07/2013</td><td>2450</td></tr><tr><td>Lac des Béraudes</td><td>LA59.1</td><td>FR</td><td>45.58606</td><td>6.50357</td><td>19/07/2013</td><td>2504</td></tr><tr><td>Lac des Béraudes</td><td>LA59.2</td><td>FR</td><td>45.58592</td><td>6.50405</td><td>19/07/2013</td><td>2504</td></tr><tr><td>Lac des Béraudes</td><td>LA59.3</td><td>FR</td><td>45.58580</td><td>6.50368</td><td>19/07/2013</td><td>2504</td></tr><tr><td>Lac Sainte Marguerite du Thabor le plus haut</td><td>LA60.1</td><td>FR</td><td>45.12520</td><td>6.59439</td><td>25/07/2013</td><td>2513</td></tr><tr><td>Lac Sainte Marguerite du Thabor le plus haut</td><td>LA60.2</td><td>FR</td><td>45.12553</td><td>6.59282</td><td>25/07/2013</td><td>2513</td></tr><tr><td>Lac Sainte Marguerite du Thabor le plus haut</td><td>LA60.3</td><td>FR</td><td>45.12662</td><td>6.59363</td><td>25/07/2013</td><td>2513</td></tr><tr><td>Lac des Muandes (Névaches)</td><td>LA62.1</td><td>FR</td><td>45.08839</td><td>6.54384</td><td>01/08/2013</td><td>2387</td></tr><tr><td>Lac des Muandes (Névaches)</td><td>LA62.2</td><td>FR</td><td>45.08824</td><td>6.54483</td><td>01/08/2013</td><td>2387</td></tr><tr><td>Lac des Muandes (Névaches)</td><td>LA62.3</td><td>FR</td><td>45.08768</td><td>6.54400</td><td>01/08/2013</td><td>2387</td></tr><tr><td>Lac Blanc de Polset</td><td>LA63.1</td><td>FR</td><td>45.29405</td><td>6.64986</td><td>26/07/2013</td><td>2433</td></tr><tr><td>Lac Blanc de Polset</td><td>LA63.2</td><td>FR</td><td>45.29434</td><td>6.65388</td><td>26/07/2013</td><td>2433</td></tr><tr><td>Lac Blanc de Polset</td><td>LA63.3</td><td>FR</td><td>45.29342</td><td>6.65308</td><td>26/07/2013</td><td>2433</td></tr><tr><td>Lac inférieur du Merlet</td><td>LA64.1</td><td>FR</td><td>45.35848</td><td>6.64797</td><td>20/07/2013</td><td>2391</td></tr><tr><td>Lac inférieur du Merlet</td><td>LA64.2</td><td>FR</td><td>45.35779</td><td>6.64904</td><td>20/07/2013</td><td>2391</td></tr><tr><td>Lac inférieur du Merlet</td><td>LA64.3</td><td>FR</td><td>45.35753</td><td>6.64701</td><td>20/07/2013</td><td>2391</td></tr><tr><td>Lac de la Partie</td><td>LA66.1</td><td>FR</td><td>45.25788</td><td>6.66348</td><td>17/07/2013</td><td>2458</td></tr><tr><td>Lac de la Partie</td><td>LA66.2</td><td>FR</td><td>45.25896</td><td>6.66321</td><td>17/07/2013</td><td>2458</td></tr><tr><td>Lac du Mont Charvin</td><td>LA9.1</td><td>FR</td><td>45.80901</td><td>6.42210</td><td>16/07/2013</td><td>2011</td></tr><tr><td>Lac du Mont Charvin</td><td>LA9.2</td><td>FR</td><td>45.80833</td><td>6.42304</td><td>16/07/2013</td><td>2011</td></tr><tr><td>Lac du Mont Charvin</td><td>LA9.3</td><td>FR</td><td>45.80895</td><td>6.42345</td><td>16/07/2013</td><td>2011</td></tr></tbody></table>

Note: Complete metadata (with additional physical and chemical data) are given in Supporting Information at https://doi.org/10.57745/0TVDYI.
were collected in high-altitude lakes and 389 in lowland lakes. Table 1 gives the geographical position of the sampling sites as well as the dates of sampling for each lake (for complete metadata with physico-chemical parameters, as well as lake characteristics—altitude, lake depth, surface, watershed surface, and residence time—see Supporting Information S1).

## 2.2 | DNA Extraction and Sequencing

We extracted DNA contained in biofilm samples from each lake following the protocol proposed by Rivera et al. (2020). Briefly, the suspended diatom biofilm (2mL) was centrifuged for 30 min at 13,000 rpm to recover the supernatant from which DNA was extracted using the NucleoSpin Soil kit (Macheray-Nagel) following the manufacturer's protocol. DNA quantity and quality were checked using a NanoDrop 1000 Spectrophotometer (Thermo Fisher Scientific). For PCR, we amplified a 263 bp barcode of chloroplastic DNA, embedded in the rbcL gene, which encodes for ribulose-1,5-bisphosphate carboxylase/oxygenase. This barcode is recommended for diatom species identification (e.g., Kermarrec et al. 2013; Maitland et al. 2020). We used the diatom-specific primers Diat_rbcL_708F_1 (AGGTGAAGTAAAAGGTTCWTACTTAAA), Diat_rbcL_708F_2 (AGGTGAAGTTAAAGGTTCWTAYTTAAA), and Diat_rbcL_708F_3 (AGGTGAAACTAAAGGTTCWTACTTA AA) as forward primers and Diat_rbcL_R3_1 (CCTTCTAA TTTACCWACWACTG) and Diat_rbcL_R3_2 (CCTTCTAATT TACCWACAACAG) as reverse primers (Vasselon et al. 2017). Each DNA extract was amplified in triplicate using equimolar mixes of the three forward and two reverse primers. Additionally, blank samples using water of molecular quality were run in parallel to check for potential contaminations introduced during handling the samples in the lab. The DNA extracts were used as templates for polymerase chain reaction amplification (PCR) from a final volume of 25 µL following mix and thermal cycling conditions used by Rivera et al. (2020). Thermal cycling conditions consisted of 33 cycles of 1 min at 95°C, 1 min at 54°C, and 1 min at 72°C. For each sample, PCR products from the three replicates were pooled, and 50 µL was sent for sequencing to a genomic platform, using MiSeq technology (Illumina) and the V1 reagent kit (2 × 250 bp). Four different runs were carried out at two different platforms: 3 at the GetPlage platform (Toulouse, France, https://get.genotoul.fr), and one at the University of Geneva for Lake Geneva samples (https://id-gene.com).

## 2.3 | Bioinformatic Analysis

To describe diatom diversity, the demultiplexed reads were analyzed with a pipeline combining Cutadapt v3.5 (Martin 2011) to remove primer sequences and DADA2 (Callahan et al. 2016) to delineate ASVs. According to the quality profiles, forward and reverse reads were trimmed at 200 and 170 nucleotides, respectively. Truncated sequences were filtered out using the filterAndTrim() function from the dada2 R-package (Callahan et al. 2016) when they contained ambiguous nucleotides or exceeded a maximum expected error number (MaxEE) greater than two. After applying the DADA2 denoising model to determine an error model for each run using the learnErrors()

function, the forward and reverse reads were merged to obtain the full denoised sequences using the *dada()* function. The preceding steps were applied separately for each sequencing run, which were then merged using the *mergeSequenceTables()* function, and chimeras were removed using the *removeBimeraDe novo()* function.

In the total ASV table, ASVs not matching the target length (263 bp) or with fewer than 10 reads were removed. Since rbcL is a coding region, we used MEGAX (Kumar et al. 2018) to check for indels and stop codons, without finding any. We assigned taxonomy to ASVs using Diat.barcode reference library version 11 (Rimet, Gusev, et al. 2019) with a minimum bootstrap confidence of 60%, and non-Bacillariophyta ASVs were excluded. Samples with fewer than 10,000 reads were removed (8 out of 514), and data were rarefied to 10,958 reads (the lowest number of reads) using the *vegan* R-package (Oksanen et al. 2025). The final database includes 2523 ASVs (1444 in high altitude, 1507 in lowland) and 514 samples, totaling 5,632,412 reads.

## 2.4 | Statistical Analyses

### 2.4.1 | Changes in Shared Taxa and Beta-Diversity With Geographical Distance in Lowland and High-Altitude Lakes

Before analyzing shared taxa between samples, we compared alpha diversities between high-altitude and lowland lake samples with the Kruskal-Wallis test for richness with the vegan R-package (Oksanen et al. 2025) and the Hutcheson *t*-test for the Shannon index with the ecolTest R-package (Salinas 2021).

We calculated the Jaccard's index (Jaccard 1901) to measure the proportion of ASVs shared between samples from different lakes for high-altitude and lowland lakes (excluding comparisons between the two groups) using the *dist.ldc()* function of the adespatial R-package (Dray et al. 2025). Index values were grouped into seven classes of geographical distance between samples: < 200 m, [200 m, 2 km], [2 km, 20 km], [20 km, 50 km], [50 km, 100 km], [100 km, 200 km], [200 km, 654 km].

For each geographical distance class, a Wilcoxon rank sum test was carried out to test the difference between Jaccard index values between high-altitude and lowland lakes. Kruskal-Wallis and Dunn tests were calculated to compare indices between class distances using PAST software (Hammer et al. 2001). An NMDS (Non-metric multimetric dimensional scaling) was calculated using the *metaMDS()* function from the *vegan* R-package based on Jaccard distance to visualize the beta-diversities of lowland and high-altitude lake communities.

### 2.4.2 | Correlations Between Lake Diversity and Lake Surface and Watershed Size

We checked for a relationship between lake, watershed surface, and lake richness (total number of ASVs in each lake) using the "Non-linear fit" option of Past software.
In addition, species accumulation curves were drawn for both high-altitude and lowland lakes by merging samples from the same lake into a single community and summing ASV reads across samples. Accumulation curves were estimated using the *specaccum()* function (the random permutation method and the other default arguments were used), and the *Chao2* (*Chao 1987*) index (asymptotic species richness) was calculated with the *specpool()* function for high-altitude and lowland lakes with the *vegan* R-package.

### 2.4.3 | Evaluation of Assembly Processes and Environmental Factors Shaping Diatom Communities in High-Altitude and Lowland Lakes

Assembly processes were assessed relative to phylogenetic and taxonomic turnover according to Stegen et al. (2013) analytical framework. Briefly, this framework compares in a 1st step phylogenetic turnover of samples' communities to the null model in order to assess selection processes. If communities are significantly phylogenetically over-clustered, environmental filtering is interpreted as the dominant process for these samples. Conversely, if they are significantly over-dispersed, competition is interpreted as the dominant structuring process. Samples that do not differ significantly from the null model are tested in a 2nd step. This 2nd step compares taxonomic turnover to the null model to assess dispersal processes. If sample turnover is significantly higher than expected by chance, this is interpreted as a dispersal limitation, whereas if it is smaller than expected by chance, this is interpreted as dispersal homogenization. For the other samples, which do not differ from the null model, stochastic processes are considered to be dominant.

To this end, a reference phylogeny was constructed using long sequences from the reference library Diat.barcode v12 (Rimet, Gusev, et al. 2019), and an alignment was performed on 1046 nucleotides and 3506 sequences. The construction of this reference phylogeny was based on a maximum likelihood algorithm using raxml-8.2.12 software (Stamatakis 2014) with 100 rapid bootstrap replicates and the GTRGamma model. The phylogeny is provided as Supporting Information S2. ASVs were aligned in a FASTA file and placed in this reference phylogeny using RaxmlGUI (Silvestro and Michalak 2012) with the “enforce constrain mode” and the “backbone option” (Supporting Information S3). This enables getting the phylogenetic distances between ASVs.

Assembly processes were estimated using the *microeco* R-package (Liu et al. 2021). To analyze processes between lakes, samples from the same lake were merged: reads were summed per ASV, averages were calculated for water chemical measurements (pH, conductivity, nitrate, total phosphorus) and geographical coordinates, and lake morphometric measures (lake surface, depth, altitude, residence time, basin surface) remained unchanged. At this stage, the phylogenetic signal was tested for chemical parameters with a Mantel correlogram using the *cal_mantel_corr()* function and default options. This step is essential since a phylogenetic signal conditions the use of NTI indices (Nearest Taxon Index) to estimate assemblage processes. The global dataset was divided into two according

to lake type: high-altitude and lowland lakes. Following the approach of Stegen et al. (2013), selection processes are estimated from null models based on betaNTI (beta-nearest taxon index) distances, calculated between lakes using the ASV table and the phylogenetic distances between ASVs. To assess dispersal processes, null models based on the Raup-Crick metric using Bray-Curtis dissimilarities (RCbray) are calculated between lakes based on the ASV table using the *cal_rcbray()* function and 1000 runs. These processes were estimated separately for high-altitude and lowland lakes. Then we evaluated the proportion of the inferred processes using the *cal_process()* function.

After this first stage of analyses, we quantified the variance of diatom communities explained by the three classes of environmental factors (chemical, hydro-morphological, and spatial) using a variance partitioning analysis and the *varpart()* function of the *vegan* R-package. We performed this analysis for both lake types separately. Chemical and hydro-morphometric data were standardized (mean and variance respectively equal 0 and 1). Spatial parameters were estimated using the approach of principal coordinate analysis of neighbor matrices (PCNM; Borcard and Legendre 2002) using the *pcnm()* function from the vegan R-package), with the three first axes selected and then standardized. We performed a forward selection on the chemical, hydro-morphometric, and spatial parameters separately to estimate the significant explicative variables of each using the *ordistep()* function of the vegan R-package.

### 2.4.4 | Taxa Co-Occurrence in High-Altitude and Lowland Lakes

Between lakes, the number of samplings varied considerably, from two or three samples for high-altitude lakes to 152 samples for Lake Geneva. The large number of samples taken in Lac Geneva may result in a high probability of having the same ASV co-occurring together, compared with high-altitude lakes. In order not to artificially increase the correlations between ASVs when lakes were sampled many times, samples from the same lake were merged into a single community, as done in § 2.4.3.

A co-occurrence network was calculated for each type of lake, using the SparCC (Sparse Correlations for Compositional data) method and the *sparcc()* function from the SpiecEasi R-package (Kurtz et al. 2015, 2025). We chose this method because it has been tailored to genomic data to infer co-occurrence networks between taxa (or genes) from compositional data (Kurtz et al. 2015) and because it has been widely used with success for such kinds of data (Kajihara and Hynson 2024). In both co-occurrence networks, only associations between ASVs with a correlation coefficient greater than 0.5 were retained as significant associations. The final co-occurrence networks were visualized using the *layout_on_grid()* function from the igraph R-package (Csardi and Nepusz 2006). We characterized the structure of networks by calculating their level of connectivity (i.e., number of connected ASVs divided by the total number of ASV in the network) and connectance (i.e., number of edges divided by the number of possible edges in the network), using the *degree()* function and the *edge_density()* function of the igraph R-package, respectively.
<figure><img src="image_4.png" /><figcaption>**FIGURE 2** | Similarity in terms of shared ASVs between communities of different lakes according to geographical distance. The Jaccard index measures the proportion of shared taxa between two samples. The indexes were calculated between communities of high-altitude lakes and between communities of lowland lakes. The indices are presented in box-plots according to classes of geographical distances between communities.</figcaption></figure>

## 3 | Results

### 3.1 | Changes in Shared Taxa and Beta-Diversity With Geographical Distance in Lowland and High-Altitude Lakes

Samples from lowland lakes had significantly higher diversities than those from high-altitude lakes (Shannon with Hutcheson t-test and richness with Kruskal-Wallis test: $p < 2 \times 10^{-16}$). Jaccard indices were consistently higher between groups of high-altitude lakes compared to groups of lowland lakes, regardless of geographic distance class (Figure 2). Therefore, when considering two lakes separated by the same distance range, communities from lowland lakes share more ASVs than communities from high-altitude lakes ($p < 2 \times 10^{-16}$ Wilcoxon test). Within each lake type, Jaccard indices increased with distance class, indicating that the most geographically distant lakes share fewer ASVs (Kruskall-Wallis $p < 0.005$, and all pairwise Dunn tests $p < 0.005$). NMDS analysis based on ASV tables revealed clear differences between samples according to lake type (Figure 3). This difference was supported by the low overlap of ASVs, with only 17% shared between high-altitude and lowland lakes, and 41% being specific to high-altitude lakes and 42% specific to lowland lakes.

### 3.2 | Correlations Between Lake Diversity With Lake Surface and Watershed Size

We found significant positive relationships (Spearman correlation test) between lake diversity (total number of ASVs in each lake) and both lake surface ($r^2 = 0.73, p < 0.005$) and watershed surface ($r^2 = 0.70, p < 0.005$), as shown in Figure 4 for watershed surface. However, these correlations were no longer significant when the tests were restricted to high-altitude or lowland lakes.

In addition, lowland lakes showed a faster increasing accumulation curve than high-altitude lakes and a higher cumulative number of ASVs (Supporting Information S4). Gamma diversities estimated by the Chao2 index are significantly higher in lowland lakes (2273 ASVs $\pm 84$ sd) than in high-altitude lakes (2079 ASVs $\pm 71$ sd). This trend is supported by the observed richness, which is 1444 ASVs for high-altitude lakes and 1507 ASVs for lowland lakes.

### 3.3 | Evaluation of Assembly Processes and Environmental Factors Shaping Diatom Communities in High-Altitude and Lowland Lakes

A significant positive correlation over short phylogenetic distances (Supporting Information S5) was observed for the tested environmental parameters (conductivity, pH, nitrates), indicating that phylogenetically neighboring taxa share similar environmental optima. This correlation supports the use of the betaNTI (measuring phylogenetic turnover) and RCbray (measuring taxonomic turnover) metrics as indicators of selection and dispersal processes, respectively. Null models based on these two metrics showed that ecological drift (i.e., taxonomic turnover of samples was not significantly different from the null model) was the overriding process for both lake types (high-altitude lakes: 82%, lowland lakes: 45%), but to a lesser extent for lowland lakes (Figure 5a). Homogeneous selection (i.e., communities show significant higher phylogenetic over-clustering than the null model) was similar between lowland and high-altitude lakes (10% and 5%, respectively). Dispersal processes were more important for lowland lakes (45%) than for high-altitude lakes (12%). They were driven by the homogenization dispersal; i.e., taxonomic turnover was smaller than the null model (lowland lakes: 32%, high-altitude lakes: 2%). Dispersal limitation (i.e., taxonomic turnover was higher than the null model) was similar between both types of lake (13% and 10%, respectively).
<figure><img src="image_5.png" /><figcaption>**FIGURE 3** | Non-metric multidimensional scaling (NMDS) showing the similarity in terms of ASV composition between communities of high-altitude and lowland lakes. The NMDS is based on the Jaccard distance matrix, stress: 0.191, R² = 0.963 (non-linear fit).</figcaption></figure>

For the variance partitioning analysis, forward selection re-
tained as explanatory variables: total phosphorus, pH, and ni-
trate for chemistry; elevation, depth, and water residence time
for hydro-morphometry; and the first three PCNM axes for
spatial parameters (Figure 5b). The analysis showed that en-
vironmental parameters explained 50% and 8% of community
variability in lowland and high-altitude lakes, respectively.
When excluding spatial parameters (even simultaneous effects),
the variability explained is reduced to 27% for lowland lakes and
6% for high-altitude lakes.

3.4 | Taxa Co-Occurrence in High-Altitude and Lowland Lakes

Based on co-occurrence networks, the number of co-occurring
ASVs was greater in lowland lakes than in high-altitude lakes
(Figure 6), indicating a more complex network in lowlands.
This is supported by a stronger connectance in lowland lakes'
network (edge density = 3.2 × 10⁻²) than in high-altitude (edge
density = 2 × 10⁻⁴), and the same trend is observed for con-
nectivity (node density: high-altitude lakes = 0.89, lowland
lakes = 0.14).

4 | Discussion

4.1 | Stochastic Processes Are More Important in High-Altitude Than in Lowland Lakes

Most of the samples (82%) from high-altitude lakes showed com-
munity structures that did not deviate from those expected under
the null model, compared with only 45% of samples from lowland
lakes. Community structure in high-altitude lakes was mainly
driven by stochastic processes, as already observed (Ossyssek
et al. 2023), unlike in lowland lakes. We can suppose that this
difference between the two types of lakes is probably due to the
extreme meteorological conditions in high-altitude lakes, which
create serious bottlenecks for diatom communities. Most of
these lakes freeze for more than six months (Rivier 1997), which

<figure><img src="image_6.png" /><figcaption>**FIGURE 4** | Relation between lake basin surface and lake richness. Lake richness is the total number of ASVs in a lake. Black dots represent lowland lakes, and gray dots high-altitude lakes. Overall, relationship is significant between lake surface and ASV richness (logarithmic regression, r² = 0.73, *p* < 0.005).</figcaption></figure>

affects the survival of diatom cells trapped in the ice. Moreover,
during the melting season, the massive influx of water from the
melted snow and rain of the watershed causes strong turbulence
and turbidity (Rimet, Feret, et al. 2019), which can strip biofilms
where diatoms live and carry them out of the lake. These two
phenomena are much less common in lowland lakes. However,
when diatoms face unfavorable conditions, they are capable of
producing resting spores (auxospores)—as most protists—and
therefore should not be sensitive to bottlenecks. But less than 1%
of vegetative cells are able to do so in freshwaters (Jewson 1992;
Sutherland et al. 2023), and survival rates of spores are less than
40% in marine sediments (Sanyal et al. 2022). The production
of resting spores is therefore a major bottleneck for diatoms,
given the low probability of survival. These massive extinc-
tion/colonization processes largely favor stochastic processes
(Vellend 2010) and are much more predominant in high-altitude
lakes than in lowland lakes.

4.2 | Dispersal Processes Play Contrasting Roles in
Lowland and in High-Altitude Lakes

Dispersal processes play a major role in lowland and high-altitude
lakes. There are similarities in the way communities are struc-
tured by dispersal in high-altitude and lowland lakes. For exam-
ple, in both types of lake, we observed a decrease in the number of
shared ASVs between lakes as the geographical distance between
them increased. These results indicate that dispersal is limited,
with around 10%–12% of the communities being shaped by this
process. Such a decrease in community similarity with geograph-
ical distance has already been shown for river diatoms with mor-
phological data in different regions of the world (Keck et al. 2018;
Jamoneau et al. 2018; Wetzel et al. 2012) as well as on a global scale
(Martín-Devasa et al. 2024). However, large-scale morphological
databases suffer from a lack of taxonomic homogeneity due to
varying identification skills between experts (Kahlert et al. 2009),
a concern for biogeographical studies (Pinseel et al. 2024). The me-
tabarcoding approach avoids this issue. This relationship between
<figure><img src="image_7.png" /><figcaption>**FIGURE 5** | (a) Contribution of the ecological processes structuring diatom communities in high-altitude and lowland lakes using Stegen et al. (2013) methodology. (b) Contribution of environmental (water chemistry, hydromorphometry) and dispersal filters (spatial distance) to explain communities variability using variance partitioning (unexplained variance: 92% for high-altitude lakes and 50% for lowland lakes).</figcaption></figure>

<figure><img src="image_8.png" /><figcaption>**FIGURE 6** | Co-occurrence networks for lowland and high-altitude lakes. A dot corresponds to an ASV, and an edge indicates a significant correlation between two ASVs above 0.5. ASVs are ordered by increasing abundance from the right bottom corner to the top left corner. Dot size corresponds to ASV reads sum in all samples.</figcaption></figure>

geographical distance and community similarity is now well ad-
mitted based on metabarcoding studies targeting microbial com-
munities like protists (Lentendu and Dunthorn 2021) and bacteria
(Trouche et al. 2021) in a variety of environments, including lakes'
diatoms (Rimet, Pinseel, et al. 2023).

Beyond these similarities in the dispersal processes affecting
communities living in high-altitude and lowland lakes, certain
specificities emerge depending on the type of lake. For exam-
ple, for the same range of geographical distances, communities
in high-altitude lakes shared fewer ASVs than those in lowland
lakes. Indeed, 32% of communities in lowland lakes show ho-
mogeneous dispersal (i.e., communities were more similar than
expected by chance), compared with 2% in high-altitude lakes.
Homogenization in lowland lakes is a much stronger process
than in high-altitude lakes, which validates our hypothesis. We
can suppose that the presence of numerous biotic (e.g., birds)
and anthropogenic (human movement, boat transport, water
ballast) vectors drives this homogenization process through
dispersal. Dispersal of some freshwater diatom species by birds
has already been proven experimentally (Faye et al. 2021), but
it has also been observed in situ with *Silurus glanis*, an invasive

fish in northern Italian rivers (Falasco et al. 2024), as well as
via water ballast for some marine diatom species (MacGillivary
and Kaczmarska 2015; Pfannkuchen et al. 2018). Such dispersal
vectors are more seldom in high-altitude.

A second explanation may be related to mass-effect, gamma
diversity, and lake size. Mass-effect explains an important
part of diatom communities in rivers (Leboucher et al. 2021)
and lakes (Rimet, Canino, et al. 2023), and larger ecosystems
provide a bigger target for dispersers than smaller ecosystems,
which in turn increases their diversity and richness (Gilpin and
Diamond 1976). We showed that there is a correlation between
lake gamma diversity and lake surface as well as watershed sur-
face (Figure 4). Moreover, in our study, surface areas and water-
sheds of lowland lakes were larger than those of high-altitude
lakes. Therefore, we can assume that mass-effect may be of big-
ger importance in lowland lakes, which validates our 3rd hy-
pothesis. Mass-effect usually increases homogeneity between
communities (Mouquet and Loreau 2003) and this homogeni-
zation has also been shown for river diatom communities (Bried
and Vilmi 2022). Therefore, we can suppose that mass-effect
could explain why lowland lakes are more homogeneous with
each other than high-altitude lakes. However, this 2nd explanation needs to be tempered, as small lakes and watersheds were only found at high-altitude, and large lakes and watersheds were found in the lowlands. Indeed, it is likely that the observed correlation between gamma diversity and lake or watershed size has a potential confounding influence with altitude.

The higher homogeneous dispersal processes observed in lowland lakes' communities can be part of the processes explaining the greater connectance and connectivity of lowland ecological networks compared to high-altitude lakes (Figure 6). Analysis of ecological network topologies has been shown to be of great interest *because links* can be established with ecosystem resilience and resistance (e.g., Gao et al. 2022; Xu et al. 2022). In particular, ecosystems hosting ecological networks with higher connectance and connectivity have, in theory, higher resistance and resilience to environmental changes (Landi et al. 2018). Therefore, we can assume that the ecological networks of lowland lakes with higher connectance and connectivity are probably more stable and resilient to environmental changes than high-altitude lakes. This hypothesis is of primary interest to lake managers who recognize that lakes are facing rapid changes (e.g., global warming, tourist overcrowding, water abstraction, and eutrophication).

## 4.3 | Species Selection Is More Important in Lowland Than in High-Altitude Lakes

Communities in high-altitude lakes were less influenced by species selection than those in lowland lakes. This result is supported by the fact that 10% of lowland lakes' communities were shaped by species selection, compared to only 5% for high-altitude lakes according to the approach of Stegen et al. (2013). This is further supported by the variance partitioning analysis showing that 50% of the variability in lowland communities was explained by local factors (chemical and hydro-morphological parameters) compared to only 8% in high-altitude lakes (Figure 6).

Strong environmental gradients generally lead to greater species selection (Lindström and Langenheder 2012; Nemergut et al. 2013), and lowland lakes can have stronger gradients than high-altitude lakes. For example, if we consider lake surface area, that of lowland lakes varies by two orders of magnitude (from 1,450,000 m² for Lake Bled to 580,000,000 m² for Lake Geneva) and only one order of magnitude in high-altitude (from 3806 m² to 131,663 m²). This difference can lead to the presence of a greater variety of niches in large environments than in smaller ones, and therefore to more different species richness and community compositions in lowlands (Bolgovics et al. 2016). In addition, biotic factors *such as grazing of diatoms by invertebrates and fish should be* limited in high-altitude compared to lowland lakes, and this is an additional factor that promotes more species selection in lowland than in high-altitude. Conversely, if we consider nutrients as the level of total phosphorus in lowland and high-altitude lakes, the two types of lake vary similarly by an order of magnitude in lowland (0.004 µgP/l in Lake Faaker to 0.233 µgP/l in Lake Geneva) and high-altitude lakes (0.001 to 0.043 µgP/l). Another counter example is given with residence time, a decisive descriptor of lake functioning,

which varies by two orders of magnitude (from 1.8 to 180 days) in high-altitude lakes, whereas it varies by one order of magnitude in lowlands (620 days in Lake Mondsee to 9809 in Lake Garda), with conductivity (ranging from 9 to 1000 µs/cm in high-altitude and from 174 to 352 µs/cm in lowlands). This tends to moderate this explanation for the smaller influence of species selection in high-altitude.

## 5 | Conclusions

Communities in high-altitude lakes were mostly driven by stochastic processes, unlike those in lowland lakes, supporting the hypothesis on extreme conditions causing a severe community bottleneck in high-altitude lakes. While dispersion was equally limiting in both lake types, homogenizing dispersal was more significant in lowland lakes, supporting the hypothesis of greater connectivity via anthropogenic and biotic vectors in lowland than in high-altitude lakes. Finally, the communities' diversities, connectivity, and connectance of ecological networks in lowland lakes may make them more stable and resilient to environmental changes than high-altitude lakes (Landi et al. 2018). However, we must acknowledge that the spatial distribution of the sampled lakes was heterogeneous, and this may influence our results.

These results have implications on the use of diatom communities for monitoring human impact in lakes. In high-altitude lakes, where stochastic processes dominate, monitoring human activities (through, for instance, nutrient level) would be challenging. However, benthic diatoms remain a useful tool for monitoring lowland lakes and join the long-standing tradition of diatom monitoring in lakes (Hoffman 1994; Marchetto et al. 2009).

Finally, the combined use of metrics estimating diversity, statistical analyses to identify ecological processes structuring communities, and inference of ecological networks provide valuable information on biological communities that, once disseminated to lake managers, will enable them to better understand the vulnerabilities of lakes, which are facing significant global changes.

### Author Contributions

**F. Rimet:** conceptualization (lead), data curation (lead), formal analysis (lead), funding acquisition (lead), investigation (lead), methodology (lead), project administration (lead), resources (lead), visualization (lead), writing – original draft (lead), writing – review and editing (equal). **C. Lemonnier:** writing – review and editing (supporting). **B. Alric:** formal analysis (supporting), investigation (supporting), writing – review and editing (supporting).

### Acknowledgments

We are grateful to the INRAE MIGALE bioinformatics facility (MIGALE, INRAE, 2020. Migale bioinformatics Facility, doi: 10.15454/1.5572390655343293E12) for providing computing and storage resources. Samplings in Lake Geneva were realized in the framework of the Synaqua Interreg FR-CH project. The other lowland lakes were sampled in the framework of the EcoAlpsWater Interreg Alpine-Space project. High-altitude lakes were sampled thanks to E. Dambrine and F. Arthaud.
## Conflicts of Interest

The authors declare no conflicts of interest.

## Data Availability Statement

The data that support the findings of this study and Supporting Information are openly available at: https://doi.org/10.57745/0TVDYI.

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## Supporting Information

Additional supporting information can be found online in the Supporting Information section. Data S1: ece371977-sup-0001-AppendixS1.zip.