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Data availability Data will be made available on request., Acknowledgements We would like to thank the support of all the citizen volunteers without which this work would not have been possible. We are extremely grateful to the colleagues of the Ecology Department Carmen Pérez, Eloisa Ramos, Jesús Manuel López-Rodríguez and José Antonio Delgado for leading the multidisciplinary research groups. We are indebted to the contribution of Joana Llodrá for lake basins estimations. Dr. Bopaiah Biddanda is acknowledge for his thorough suggestions. We are also grateful to the staff of Sierra Nevada National Park and the Global Change Observatory of Sierra Nevada who have always supported the “74 High Mountain Glacial-Lake Oases” Citizen Science initiative. This research has been funded by a FECYT grant to MVA (FCT- 18-13095), the LifeWatch-ERIC project “Smart EcoMountains” (LifeWatch- 2019-10-832 UGR-01), a FEDER/Junta de Andalucía-Consejería de Transformación Económica, Industria, Conocimiento y Universidades project (P20_00105), and by the Ministerio de Ciencia e Innovación project “REMOLADOX” (PID 2020-118872RB-I00). Funding for open access charge: Universidad de Granada / CBUA., Microplastics have become one of the most serious global threats to animal and human health. While their presence has been documented in all Earth water ecosystems, including remote mountain lakes, the observation that the abundance of microplastics is largely different across nearby lakes has rarely been examined. As part of a citizen science initiative, this study analyzed for the first time the abundance of microplastics in the surface of 35 glacial lakes of Sierra Nevada National Park in Southern Spain with the objective of determining the local factors that control their abundance. First, we described the shape, size, color and nature of microplastics. Second, we tested whether the number of microplastics differed between basins and analyzed environmental and morphometrical features of lakes affecting their abundance. We found that microplastics were common in most lakes, with a maximum abundance of 21.3 particles per liter that akin to some of the most microplastic polluted lakes worldwide. Fragments were the predominant shape (59.7%) followed by fibers (38.8%) and very scarce spheres (1.5%). Microplastics were observed for all size-fractions, but the abundance of particles, FECYT grant to MVA (FCT- 18-13095), LifeWatch-ERIC project “Smart EcoMountains” (LifeWatch- 2019-10-832 UGR-01), FEDER/Junta de Andalucía-Consejería de Transformación Económica, Industria, Conocimiento y Universidades project (P20_00105), Ministerio de Ciencia e Innovación project “REMOLADOX” (PID 2020-118872RB-I00), Funding for open access charge: Universidad de Granada / CBUA

Carnobacteria are common bacteria in cold and temperate environments; they are also reported during fish mortality events. In a previous study, carnobacteria were isolated from the eyes of healthy wild salmonids from a high-mountain lake. To better understand these findings, salmonids were captured from three high-mountain lakes (Lower and Upper Balma Lake, Rouen Lake; northwest Italy) during August 2019 and subjected to bacteriological and histological examination. Although all were healthy, 8.7% (Lower Balma Lake), 24% (Upper Balma Lake), and 32.6% (Rouen Lake) were positive for carnobacteria colonization of the eyes. A Trojan-horse effect was hypothesized to explain carnobacteria isolation in the eye. This immune-escaping macrophage-mediated mechanism has been identified in other Gram-positive bacteria. Biochemical, molecular, and phylogenetic analysis were carried out on isolated bacteria (Carnobacterium maltaromaticum and C. divergens). Based on previous references for carnobacteria isolated from fish, C. maltaromaticum strains were tested for the pisA precursor gene of the bacteriocin piscicolin 126. Carnobacterium maltaromaticum strains were found to display genotypic heterogeneity and a low percentage of pisA positive amplification. Features of geomorphology, geographic isolation, and microbiota common to the three lakes are thought to be possibly related to our findings. Moreover, terrestrial insects collected from the lake shoreline and the stomach contents were screened for the presence of carnobacteria. The salmonids in these high-mountain environments feed mainly on terrestrial insects, which are considered possible vectors for carnobacteria that might catabolize the exoskeleton chitin. All insects tested negative for carnobacteria, but as a small number of samples were analyzed, their role as possible vectors of infection cannot be excluded. Further studies are needed to corroborate our research hypothesis.

The composition of charophyte taxa and their habitat preferences in water bodies of the Artabel Lakes Nature Park were investigated on 15 August 2013 and 13 August 2016. A total of 73 taxa belonging to Conjugatophyceae (Zygnematophyceae) and Klebsormidiophyceae were recorded. The genera Connarium (37), Staurastrum (10) and Closterium (7) were most abundant. 'The partly unexpected presence of certain desmid taxa, i.e., taxa characteristic of eutrophic water, was recorded. Filamentous charophytes were represented by three taxa. The Willis curve for the distribution of species to genera had a trend line of R-2 = 0.9123. Bioindication, statistical methods and comparative floristic results show that water in all of the studied lakes was fresh, of low-conductivity, circum-neutral and with little organic pollution. Four groups of lakes were identified as a result of statistical comparison of their environmental and biological variables. Bioindication results can be used as references for future monitoring of the lakes in protection of the species found in the Artabel Lakes Nature Park and can also be included in the National Water Quality Standard System of Turkey. Karadeniz Technical UniversityKaradeniz Technical University [BAP: FBA-2016-5487] This Project was financially supported by Karadeniz Technical University (BAP: FBA-2016-5487). We are grateful to teacher Vehbi YALCIN for his support in the field. WOS:000526082900002 2-s2.0-85084756618

Climatic change-induced glacier recession has been accompanied by formation and growth of proglacial lakes in the Himalayan region, which pose an emerging significant threat to the downstream communities/settlements in the form of outburst floods. To understand spatiotemporal evolution patterns, sources and driving mechanism of formation and expansion of glacial lakes, a temporal inventory of glacial lakes (area > 2000 m(2)) in Chandra basin has been developed from 2000 to 2014 using IRS LISS-III images. From 2000 to 2014, the total number of glacial lakes in Chandra basin increased from 28 to 46 and area expanded from 1.91 +/- 0.24 km(2) to 3.26 +/- 0.24 km(2). Glacier recession and increased glacier melt runoff due to climate warming led to the formation and expansion of glacial lakes in space vacated by glacier recession. The increase in number and area of ice-dammed lakes at higher elevations confirms the continued glacier retreat in the basin. Lakes in contact or in the proximity of the mother glacier exhibit higher growth and formation rate. The accelerated growth of glacial lakes has resulted in increased hazard and damage potential of glacial lake outburst floods in Chandra basin. Seven potentially dangerous lakes are identified and analysed qualitatively for outburst probability.

As groundwater-fed waterworks clean their raw inlet water with sand filters, a variety of pro- and eukaryotic microbial communities develop on these filters. While several studies have targeted the prokaryotic sand filter communities, little is known about the eukaryotic communities, despite the obvious need for knowledge of microorganisms that get in contact with human drinking water. With a new general eukaryotic primer set (18S, V1-V3 region), we performed FLX-454 sequencing of material from 21 waterworks' sand filters varying in age (3–40 years) and geographical location on a 250 km east–west axis in Denmark, and put the data in context of their previously published prokaryotic communities. We find that filters vary highly in trophic complexity depending on age, from simple systems with bacteria and protozoa (3–6 years) to complex, mature systems with nematodes, rotifers and turbellarians as apex predators (40 years). Unlike the bacterial communities, the eukaryotic communities display a clear distance–decay relationship that predominates over environmental variations, indicating that the underlying aquifers feeding the filters harbor distinct eukaryotic communities with limited dispersal in between. Our findings have implications for waterworks' filter management, and offer a window down to the largely unexplored eukaryotic microbiology of groundwater aquifers.

Filiación institucional de autor: Alejo Cochachín Rapre / Autoridad Nacional del Agua - Unidad de Glaciología y Recursos Hídricos (ANA-UGRH), Huaraz, Peru Original abstract: Changing high-mountain environments are characterized by destabilizing ice, rock or debris slopes connected to evolving glacial lakes. Such configurations may lead to potentially devastating sequences of mass movements (process chains or cascades). Computer simulations are supposed to assist in anticipating the possible consequences of such phenomena in order to reduce the losses. The present study explores the potential of the novel computational tool r.avaflow for simulating complex process chains. r.avaflow employs an enhanced version of the Pudasaini (2012) general two-phase mass flow model, allowing consideration of the interactions between solid and fluid components of the flow. We back-calculate an event that occurred in 2012 when a landslide from a moraine slope triggered a multi-lake outburst flood in the Artizón and Santa Cruz valleys, Cordillera Blanca, Peru, involving four lakes and a substantial amount of entrained debris along the path. The documented and reconstructed flow patterns are reproduced in a largely satisfactory way in the sense of empirical adequacy. However, small variations in the uncertain parameters can fundamentally influence the behaviour of the process chain through threshold effects and positive feedbacks. Forward simulations of possible future cascading events will rely on more comprehensive case and parameter studies, but particularly on the development of appropriate strategies for decision-making based on uncertain simulation results. Artículo en acceso abierto Explora el potencial de la nueva herramienta computacional r.avaflow en relación a la simulación de complejas cadenas de procesos relacionados a la desestabilización de laderas de hielo, rocas o escombros conectadas a lagos glaciares en evolución. Asimismo, realiza el cálculo de un evento ocurrido en 2012 cuando un deslizamiento de tierra provocó una inundación de varios lagos en los valles de Artizón y Santa Cruz (Cordillera Blanca, Perú) con cuatro lagos y una cantidad sustancial de escombros arrastrados a lo largo del camino.

From an ecological approach the physical environment of lakes can be summarized by four components: temperature, light, turbulence and Lhe morphology of the basin and its watershed. The variabWity Lhrough an annual cycle of Lhese components of Lhe physical environment of the Estany Redó is described in the paper and their implicattions for Lhe dynamics of its biota are examined. The ratio between catchment area size (155 hm2 ) and lake volumen (7.75 hm3 ) is extremally small.The value of relaLive depth is extraordinarilly high (1 3 %). Both aspects contribute to the oligotrophy of Lhe lake. Because of the hypsographic configuration of the lake Redó there is a sediment focusing above 40 m and between 15 and 25 m. Production peak s should be linked to the interaction of the mixing layer with these sediment-rich bottoms. Other implications of the temperature, the light and the mixing time scales in the lake biological dynamics are also examined., El medio fisico relacionado con el ecosistema pelágico de un lago profundo de alta montaña (Estany Redó, Pirineos centrales). El medio físico de un lago puede caracterizarse fundamentalmente con cuatro descriptores: temperatura, luz, energía cinética turbulenta y la morfología de la cuenca. En este estudio presentamos estas características para el Estany Redó, un lago de alta montaña situado en el Pirineo central y originado por la acción modeladora de las glaciaciones del Pleistoceno. El lago se encuentra en una cuenca granodiorítica en forma de amfiteatro y de laderas muy pendientes. El suelo y la vegetación están poco desarrollados en toda la cuenca. El lago es profundo (73 m) en relación a su área (24 hm2 ), y su volumen (7.75 hm3 ) es considerable en relación a su cuenca de recepción (155 hm2 ). En los lagos de sus dimensiones Qongitud mínima 655 m), la fuerza del viento sólo tiene un papel. distribuidor de sedimento en un estrecho margen litoral y los procesos de deposición están gobernados por la pendiente. Como en el Redó la pendiente de las paredes es muy acusada el sedimento fino no se deposita de forma estable en las plataformas profundas. El tiempo medio de residencia del agua en el lago es cercano a los cuatro años, que considerado por capas supone unos 2 años para las capa superiores (0-5 m) y más de 15 años para las más profundas ( 40 m). El lago permanece helado durante medio año, de Diciembre a Junio. En el período que está libre de hielo la radiación solar penetra profundamente debido a la transparencia del agua (disco de Secchi hasta 17 m). En invierno, la acumulación de nieve (2 m) impide el paso de luz. Debido al alto tiempo de residencia del agua, la estructura de la columna de agua está gobernada por los intercambios de calor y la acción del viento. Se trata de un lago dimíctico clásico. La mezcla de primavera es más cona que la de otoño. Después del deshielo, rápidamente se forma una incipiente termoclina entre 3 -4 m, que rápidamente se traslada a profundidades mayores (c. 13 m) por la acción del viento. La termoclina permanece estable durante poco más de un mes, mientras el flujo medio de calor es positivo. Cuando el flujo de calor se invierte, la convección debilita y hunde la termoclina rápidamente. Sin embargo, la distinción de dos capas (cpi- e hipolimnion) es válida hasta que prácticamente la mezcla llega al fondo del lago. Desde un punto de vista biológico, la pequeñez de la cuenca en relación al volumen del lago favorece una oligotrofia extrema. Por otro lado, la disposición del sedimento fino (imponante en el reciclado de nutrientes) a profundidades por debajo de la tennoclina estable, favorece una pauta de producción biológica estrechamente relacionada con los períodos de mezcla de la columna. La alta penetración de la luz y la falta de aportes de nutrientes al hipolimnion pueden favorecer la formación de mínimos profundos de clorofila en verano, lejos de las capas fotoinhibidoras superiores. De cualquier modo, la baja temperatura supone en todo momento un límite a la velocidad de los procesos biológicos tanto de producción como de respiración.

Colbricon Superiore and Inferiore are two small adjacent high-mountain lakes located in the Paneveggio Natural Park (Italy). The lakes differ by size and depth while sharing the same bedrock setting and catchment basin. Changes in the phytoplankton communities were studied over a 10-years period to individuate which environmental variables would determine the main differences in biotic assemblages across time and between the two lakes.The study was conducted with fortnightly samplings, assessing the density and biomass of algal taxa. Relationships of each of the biological variables with water temperature, pH, conductivity, transparency, water level, previous week rainfall, and relative water column stability were analyzed by correlation and regression analyses, cluster analysis, and by canonical correspondence analysis. The most significant variables resulted air temperature, hydrologic water level and pH. The smaller Colbricon Inferiore had about double the amount of phytoplankton density and biomass than did the larger Colbricon Superiore. The same lake had higher diversity and lower evenness in structure of the phytoplankton community. Notwithstanding their proximity each lake appears to follow independent species composition dynamics, however parallel patterns were interestingly revealed when data were analyzed by pooling taxa into morpho-functional groups. Morpho-functional groups (MFGs) 1b, 3a, 6b, 7a, 9b were differentially most abundant in warm periods, while 2c, 3b, 11c, 5e, 10a prevailed in cold years. MFGs 1b, 2d, 3a and 3b were more characteristic of Lake Colbricon Superiore, while Colbricon Inferiore preferentially featured MFGs 5a, 5e, 9a, 9b, 10a, 11a and 8a. The role of the meteo-climatic parameters was pointed out in driving the different patterns observed in the two lakes.

We investigated 2500 years of community succession in Cladocera from the sediments of a mountain lake (Lake Piramide Inferiore) located in the Khumbu Valley close to Mt. Everest in the Nepalese Himalayas. Our objective was to determine late Holocene changes in cladoceran species composition and abundance in a biogeographical context and with respect to previous proxy-based paleolimnological data (algal pigments and organic content). The results suggested that cladoceran fauna of Lake Piramide Inferiore was species-poor and dominated by Chydorus cf. sphaericus throughout the sequence. The sediment profile recorded the occurrence of Alona guttata type individuals, which were attributed to Alona werestschagini Sinev 1999 based on their morphology and the species' current distributional range, and this was the first record of its presence in the Himalayas. In addition, a periodic long-term succession of melanic Daphnia (Ctenodaphnia) fusca Gurney, 1907 and non-melanic D. (Daphnia) dentifera Forbes 1893 was observed in the sediments. The millennia-long cladoceran community changes, although subtle due to the C. cf. sphaericus dominance, were in general agreement with the previous proxy-data of lake productivity following the regional paleoclimatic development and apparently partly driven by bottom-up mechanisms. The periodic occurrence and success of D. fusca and D. dentifera throughout the late Holocene in Lake Piramide Inferiore, combined with the knowledge of their phenotypic properties (i.e. carapace melanization) and previous investigations on their contemporary and past distribution in Khumbu Valley, suggested that they may have responded to altered underwater UV radiation regimes. Furthermore, they may have even periodically excluded each other subsequent to changes in the underwater UV environment. The results indicated the usefulness of fossil cladoceran analysis as a tool in biogeographical research, since the occurrence of species in space and time can be observed through sediment records and taxonomic identity of the remains may be resolved with the help of regional faunal distribution.

International audience; In this study, we evaluated the driving forces exerted by a large set of environmental and biological parameters on the spatial and temporal dynamics of archaeal community structure in two neighbouring peri-alpine lakes that differ in terms of trophic status. We analysed monthly data from a 2-year sampling period at two depths corresponding to the epi- and hypolimnetic layers. The archaeal communities seemed to be mainly composed of ammonia-oxidizing archaea belonging to the thaumarchaeotal phylum. The spatio-temporal dynamics of these communities were very similar in the two lakes and were characterized by (1) disparities in archaeal community structure in both time and space and (2) no seasonal reproducibility between years. The archaeal communities were regulated by a complex combination of abiotic factors, including temperature, nutrients, chlorophyll a and dissolved oxygen, and biotic factors such as heterotrophic nanoflagellates and ciliates. However, in most cases, these factors explained

International audience; The origin of perylene, a five-ring polycyclic aromatic hydrocarbon (PAH), in sediments has been a matter of constant debate and its formation mechanisms remain unclear. A perylene record in sediment was described and could support a clear link between perylene and terrigenous organic matter (OM) input. The distributions of PAHs, the variations of organic proxies such as the ratio of terrigenous to aquatic n-alkanes (TAR(HC)) and 5a(H)-stanols/D5-sterols ratio in sediments have been investigated. Sediments were sampled from a pond artificially created during the Middle Ages from a swampy area. In the period prior to the pond creation, for which high contributions of terrigenous OM were evidenced, perylene was found to be the predominant PAH. Furthermore, perylene content was shown to increase in response to the establishment of more reducing conditions. This result supports the common idea that the main source of perylene is natural and derives from biogenic precursors under reducing conditions. The creation of the pond in this wetland is marked by the deposition of a wood rich level characterized both by more oxygenated conditions and higher concentrations of perylene. These high concentrations could result from the introduction of high concentrations of biogenic precursors of perylene under oxidative conditions. Subsequently, the progressive burial of the woody level could have allowed the establishment of oxygen depleted conditions and the formation of perylene. These results validate the use of perylene as a paleoenvironmental marker of terrigenous sources but it must be carefully used as a marker for syn- or post-depositional oxygen depleted conditions in lacustrine environments

11 páginas, 5 tablas, 6 figuras., We assessed the effects of Saharan dust inputs of particulate matter (PM), total phosphorus (TP), total nitrogen, and water soluble organic carbon (WSOC) on bacterial abundance (BA) in two alpine lakes and two reservoirs in the Mediterranean region. We also experimentally assessed the effects of dust inputs on bacterial activity and community composition and explored the presence of airborne bacteria. We found synchronous BA dynamics at least in one of the study years for each corresponding pair of ecosystems, suggesting an external control. The link between BA dynamics and inputs of PM, WSOC, or TP occurred only in those ecosystems with severe P-limitation and low dissolved organic carbon. The response was most intense in the most P-limited ecosystem. Dust addition had a significant positive effect on bacterial growth and abundance, but not on richness, diversity, or composition of the indigenous bacterial assemblages. We also obtained experimental evidence that some airborne bacteria could develop in oligotrophic waters by observing the growth of gamma-proteobacteria, a group poorly represented in natural aquatic environments., This research was supported by the projects ECOSENSOR (Fundación BBVA, BIOCON04/009) and MICROBIOGEOGRAPHY (080-2007) to IR, REN03-03038 (Ministerio de Ciencia y Tecnologı´a) to RMB, and AERBAC (079-2007) to EOC, FPU (Formacio´n del Profesorado Universitario), and FPI (Formacio´n del Personal Investigador) grants from Spanish Government to E. Ortega-Retuerta, E. Pulido-Villena, and O. Romera.

The effects of many environmental stressors such as UV radiation are mediated by dissolved organic matter (DOM) properties. Therefore, determining the factors shaping spatial and temporal patterns is particularly essential in the most susceptible, low dissolved organic carbon (DOC) lakes. We analyzed spatiotemporal variations in dissolved organic carbon concentration and dissolved organic matter optical properties (absorption and fluorescence) in 11 transparent lakes located above tree line in the Sierra Nevada Mountains (Spain), and we assessed potential external (evaporation and atmospheric deposition) and internal (bacterial abundance, bacterial production, chlorophyll a, and catchment vegetation) drivers of DOM patterns. At spatial and temporal scales, bacteria were related to chromophoric DOM (CDOM). At the temporal scale, water soluble organic carbon (WSOC) in dust deposition and evaporation were found to have a significant influence on DOC and CDOM in two Sierra Nevada lakes studied during the ice-free periods of 2000-2002. DOC concentrations and absorption coefficients at 320 nm were strongly correlated over the spatial scale (n = 11, R-2 = 0.86; p < 0.01), but inconsistently correlated over time, indicating seasonal and interannual variability in external factors and a differential response of DOC concentration and CDOM to these factors. At the continental scale, higher mean DOC concentrations and more CDOM in lakes of the Sierra Nevada than in lakes of the Pyrenees and Alps may be due to a combination of more extreme evaporation, and greater atmospheric dust deposition.