First record of quagga mussel, Dreissena bugensis Andrusov, 1897, in Italy: morphological and genetic evidence in Lake Garda

Here, we report the first record of quagga mussel, Dreissena bugensis Andrusov, 1897, in Italy. This mollusc is native of the Dnieper River drainage of Ukraine and is one of the most aggressive invaders in freshwater ecosystems. The spread of quagga mussels throughout Europe and Northern America begun during the 1940s and 1989, respectively. Individuals of quagga mussel were identified in February and March 2022 in two stations located in the shallow (Bardolino) and deeper basins (Castelletto di Brenzone) of Lake Garda. Samples, collected with an Eckman grab, allowed identifying individuals of quagga mussel attached on macrophytes, stones and other mollusc shells. The identification of the individuals was carried out both through the analysis of morphological characters and genetic and phylogenetic analyses using the mitochondrial COI gene. The discovery of quagga mussel is the last of a long series of reports of non-indigenous species introduced into Lake Garda. Lacking direct connection by rivers or canals with other waterbodies colonized by D. bugensis at the northern side of the Alps, a more probable cause of introduction of this new species into Lake Garda can be due to unintentional overland transport through recreational boats and fishing gear. With this new discovery, Lake Garda has confirmed its pivotal role as a southern Alpine corridor for the introduction of non-indigenous species previously established at the northern border of the Alps. Considering its high colonization rate and compared with other invasion patterns observed in Europe and North America, it can be assumed that D. bugensis will soon establish itself with dominant populations throughout Lake Garda. At the same time, it can also be assumed that it will soon spread to other Italian water bodie

Biodiversity patterns of cyanobacterial oligotypes in lakes and rivers: results of a large-scale metabarcoding survey in the Alpine region

In this work, we characterised the cyanobacterial communities in the plankton and littoral biofilm of 38 lakes and in the biofilm of 21 rivers in the Alps and surrounding subalpine regions by 16S rRNA gene metabarcoding. We found little overlap in the distribution of amplicon sequence variants (ASVs) between the three habitats and between water bodies. The differences were caused by environmental filtering acting on the selection of the most abundant ASVs and a high contribution of rare oligotypes. The differentiation of community and genotype composition from specific water bodies was explained to a significant extent by environmental variables and morphometry. The taxonomic consistency of ASVs classified under the same genus name was assessed by phylogenetic analyses performed on three representative dominant genera, namely Cyanobium, Tychonema and Planktothrix. The analyses revealed eco-evolutionary adaptations in lakes and rivers, including some evidence for a polyphyletic nature. Monitoring individual genotypes in relation to environmental conditions will be useful to define the ecological amplitude of these taxa. However, the persistence or ephemeral nature of some of the rarest and most unusual ASVs has remained unknow

Alpine freshwater fish biodiversity assessment: an inter-calibration test for metabarcoding method set up

The analysis of environmental DNA (eDNA) by high throughput sequencing (HTS) is proving to be a promising tool for freshwater fish biodiversity assessment in Europe within the Water Framework Directive (WFD, 2000/60/EC), especially for large rivers and lakes where current fish monitoring techniques have known shortcomings. These new biomonitoring methods based on eDNA show several advantages compared to classical morphological methods. The sampling procedures are easier and cheaper and eDNA metabarcoding is non-invasive and very sensitive, allowing for the detection of traces of DNA. However, eDNA metabarcoding methods need careful standardization to make the results of different surveys comparable. The aim of the EU project Eco-AlpsWater is to test and validate molecular biodiversity monitoring tools for aquatic ecosystems (i.e., eDNA metabarcoding) to improve the traditional WFD monitoring approaches in Alpine waterbodies. To this end, an inter-calibration test was performed using fish mock community samples containing either tissue-extracted DNA, eDNA collected from aquaculture tanks and eDNA samples collected from Lake Bourget (France). Samples were analysed using a DNA metabarcoding approach, relying on the amplification and HTS of a 12S rDNA marker, in two separate laboratories, to evaluate if different laboratory and bioinformatic protocols can provide a reliable and comparable description of the fish communities in both mock and natural samples. Our results highlight good replicability of the molecular laboratory protocols for HTS and good amplification success of selected primers, providing essential information concerning the taxonomic resolution of the 12S mitochondrial marker in describing the Alpine fish communities. Interestingly, different concentrations of species DNA in the mock samples were well represented by the relative DNA reads abundance. These tests confirm the reproducibility of eDNA metabarcoding analyses for the biomonitoring of freshwater fish inhabiting Alpine and peri-Alpine lakes and river

Temperature Effects Explain Continental Scale Distribution of Cyanobacterial Toxins

Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains.Peer reviewe

Vertical and horizontal distribution of the microcystin producer Planktothrix rubescens (Cyanobacteria) in a small perialpine reservoir

Among cyanobacteria, Planktothrix rubescens (De Candolle ex Gomont) Anagnostidis & Komárek is a species that is well adapted to develop in moderately nutrient rich and deep lakes. In this typology of waterbodies, the competitive abilities of this species rely in its capacity to stand and growth in the dimly illuminated metalimnetic layer during the warmer months. In this work, we have studied the seasonal development and distribution of this species in Lake Ledro, a meso-oligotrophic reservoir located in the Eastern Alps. During the last decade, this species has given rise to numerous and extended surface bloom episodes, causing the reddening of vast areas of the lake. In summer, the light intensities in the zone of greater development of this cyanobacterium (the metalimnion, between the euphotic depth and the layer of maximum development of the species) were between 2 and 20 µmol m–2 s–1, i.e. values that were well within the light intensities required to sustain the optimal growth of filaments. The formation of the autumn and winter blooms was triggered by the cooling of surface waters and the deepening of the mixed layer, which, eroding the metalimnion, entrained the filaments of P. rubescens in the surface mixed layers. The formation of the surface blooms was associated with the presence of high amounts of microcystins, which in a few occasions reached concentrations between 10 and 22 µg L–1, posing potential problems for the exploitation of water resources

Biodiversity patterns of cyanobacterial oligotypes in lakes and rivers: results of a large-scale metabarcoding survey in the Alpine region

International audienceAbstract In this work, we characterised the cyanobacterial communities in the plankton and littoral biofilm of 38 lakes and in the biofilm of 21 rivers in the Alps and surrounding subalpine regions by 16S rRNA gene metabarcoding. We found little overlap in the distribution of amplicon sequence variants (ASVs) between the three habitats and between water bodies. The differences were caused by environmental filtering acting on the selection of the most abundant ASVs and a high contribution of rare oligotypes. The differentiation of community and genotype composition from specific water bodies was explained to a significant extent by environmental variables and morphometry. The taxonomic consistency of ASVs classified under the same genus name was assessed by phylogenetic analyses performed on three representative dominant genera, namely Cyanobium , Tychonema and Planktothrix . The analyses revealed eco-evolutionary adaptations in lakes and rivers, including some evidence for a polyphyletic nature. Monitoring individual genotypes in relation to environmental conditions will be useful to define the ecological amplitude of these taxa. However, the persistence or ephemeral nature of some of the rarest and most unusual ASVs has remained unknown

DNA sequence and taxonomic gap analyses to quantify the coverage of aquatic cyanobacteria and eukaryotic microalgae in reference databases: Results of a survey in the Alpine region

30restrictedInternationalInternational coauthor/editorThe taxonomic identification of organisms based on the amplification of specific genetic markers (metabarcoding) implicitly requires adequate discriminatory information and taxonomic coverage of environmental DNA sequences in taxonomic databases. These requirements were quantitatively examined by comparing the determination of cyanobacteria and microalgae obtained by metabarcoding and lightmicroscopy. Weused planktic and biofilm samples collected in 37 lakes and 22 rivers across the Alpine region.We focused on two of the most used and best represented genetic markers in the reference databases, namely the 16S rRNA and 18S rRNA genes. A sequence gap analysis using blastn showed that, in the identity range of 99–100%, approximately 30% (plankton) and 60% (biofilm) of the sequences did not find any close counterpart in the reference databases (NCBI GenBank). Similarly, a taxonomic gap analysis showed that approximately 50% of the cyanobacterial and eukaryotic microalgal species identified by light microscopy were not represented in the reference databases. In both cases, themagnitude of the gaps differed between the major taxonomic groups. Even considering the species determined under the microscope and represented in the reference databases, 22% and 26% were still not included in the results obtained by the blastn at percentage levels of identity≥95% and≥97%, respectively. The main causes were the absence of matching sequences due to amplification and/or sequencing failure and potential misidentification in the microscopy step. Our results quantitatively demonstrated that in metabarcoding the main obstacles in the classification of 16S rRNA and 18S rRNA sequences and interpretation of high-throughput sequencing biomonitoring data were due to the existence of important gaps in the taxonomic completeness of the reference databases and the short length of reads. The study focused on the Alpine region, but the extent of the gaps could be much greater in other less investigated geographic areas.restrictedSalmaso, Nico; Vasselon, Valentin; Rimet, Frédéric; Vautier, Marine; Elersek, Tina; Boscaini, Adriano; Donati, Claudio; Moretto, Marco; Pindo, Massimo; Riccioni, Giulia; Stefani, Erika; Capelli, Camilla; Lepori, Fabio; Kurmayer, Rainer; Mischke, Ute; Klemenčič, Aleksandra Krivograd; Novak, Katarina; Greco, Claudia; Franzini, Giorgio; Fusato, Giampaolo; Giacomazzi, Federica; Lea, Alessia; Menegon, Silvia; Zampieri, Chiara; Macor, Arianna; Virgilio, Damiano; Zanut, Elisa; Zorza, Raffaella; Buzzi, Fabio; Domaizon, IsabelleSalmaso, N.; Vasselon, V.; Rimet, F.; Vautier, M.; Elersek, T.; Boscaini, A.; Donati, C.; Moretto, M.; Pindo, M.; Riccioni, G.; Stefani, E.; Capelli, C.; Lepori, F.; Kurmayer, R.; Mischke, U.; Klemenčič, A.K.; Novak, K.; Greco, C.; Franzini, G.; Fusato, G.; Giacomazzi, F.; Lea, A.; Menegon, S.; Zampieri, C.; Macor, A.; Virgilio, D.; Zanut, E.; Zorza, R.; Buzzi, F.; Domaizon, I