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Disentangling the environmental and spatial drivers of biological communities across large scales increasingly challenges modern ecology in a rapidly changing world. Here, we investigate the hierarchical and trait‐based organization of regional and local factors of zooplankton communities at a macroscale of 1240 mountain lakes and ponds spanning western North America (California, USA, to Yukon Territory, Canada). Variation partitioning was used to test the hypothesized importance of climate, connectivity, catchment features, and exotic sportfish to zooplankton beta‐diversity in the context of key functional traits (body size and reproductive dispersal potential) given the pronounced environmental heterogeneity (e.g. thermal gradients), topographic barriers, and legacy of stocked fish in mountainous regions. Dispersal limitation was inferred from multispecies patch connectivity estimates based on nearest and average distances to occupied patches. Environmental heterogeneity best explained community composition as catchment/lake features (morphometry, land cover, and lithology) collectively captured greater variation than did climate (temperature, precipitation, and solar radiation), local stocking, or connectivity; however, single climatic variables captured the most variation individually. Macrospatial variation by larger obligate sexual species was better explained than that by smaller cyclically parthenogenetic asexual species. Our results provide several novel insights into the macroecology of zooplankton of the North American Cordillera, demonstrating their stronger associations to climatically driven aquatic‐terrestrial habitat coupling than dynamics arising from introduced salmonids, human land‐use, or species dispersal. These findings highlight the clear and important role of these communities as bioindicators of the limnological impacts of accelerating rates of climate change, as their responses appear relatively not confounded by local human perturbations or dispersal limitation.

Zooplankton, a group of aquatic animals important as trophic link in the food web, are exposed to high levels of UV radiation (UVR) in clear alpine lakes, while in turbid glacier-fed lakes they are more protected. To study the interplay between behavioral and physiological protection responses in zooplankton from those lakes, we sampled six lakes of different UVR transparency and glacial turbidity. Copepods were absent in the upper water layers of the clearest lake, while in glacier-fed lakes they were more evenly distributed in the water column. Across all lakes, the weighted copepod mean depth was strongly related to food resources (chlorophyll a and rotifers), whereas in the fishless lakes, glacial turbidity largely explained the vertical daytime distribution of these organisms. Up to ~11-times (mean 3.5) higher concentrations of photo-protective compounds (mycosporine-like amino acids, MAAs) were found in the copepods from the clear than from the glacier-fed lakes. In contrast to carotenoid concentrations and antioxidant capacities, MAA levels were strongly related to the lake transparency. Copepods from alpine lakes rely on a combination of behavioral and physiological strategies adapted to the change in environmental conditions taking place when lakes shift from glacially turbid to clear conditions, as glacier retreat proceeds.

Zooplankton, as an important component of mountain river ecosystems, play a crucial role in the cycling of matter and the flow of energy. However, the depth and systematic research on the formation mechanisms and influencing factors of zooplankton communities in mountain streams are poorly understood. Here, we conducted field sampling and investigated the spatiotemporal distribution of the zooplankton community structure and the major environmental factors in mountain streams to explore the principles underlying their effects on the zooplankton community. The results showed that zooplankton community structure exhibited significant seasonal variations. Rotifera and Cladocera were the dominant groups, with Rotifera dominant in warm weather and Cladocera dominant in February. The analysis revealed that temperature and trace elements are the main factors affecting zooplankton diversity. Our model explained 46.50% of the variation in zooplankton through temperature, water properties, nutrients, and trace elements. The results highlighted that temperature acted directly on the zooplankton community and also exhibited indirect and negative effects on zooplankton diversities through altering trace elements. Trace element variables had a significant impact on zooplankton community distribution. Our study systematically quantified these relationships, providing insights into the ecological processes of mountain streams and offering a scientific basis for the ecological protection of mountain streams.

This study investigated the distribution patterns of zooplankton species composition and functional groups, their correlations with aquatic environmental factors, and the mechanisms underlying community stability under the influence of regional barriers in arid areas of Xinjiang, China. The aim was to elucidate the ecological processes driving zooplankton communities in artificial aquatic ecosystems in Central Asia. A systematic survey was conducted on water environmental parameters and zooplankton community structures across 10 artificial water bodies, including the southern foot of the Altai Mountains and both northern and southern slopes of the Tianshan Mountains. The survey encompassed physical and nutrient indicators, and the results revealed significant spatial variation among water bodies across regions. Artificial water bodies in the southern Altai Mountains and northern Tianshan Mountains exhibited substantial fluctuations in temperature, dissolved oxygen (DO), total nitrogen (TN), and total phosphorus (TP). In contrast, water bodies in the southern Tianshan Mountains showed less variation in nutrient indicators. Zooplankton identification results indicated marked differences in zooplankton communities across regions, which were further confirmed by cluster analysis and non-metric multidimensional scaling (NMDS). A total of 19 dominant zooplankton species were identified across the three basins, classified into 6 functional groups. The composition of zooplankton functional groups also varied considerably, which may be closely associated with significant fluctuations in nutrient indicators of aquatic environmental factors across regional barriers. Additionally, there were specific differences in zooplankton diversity among the three basins: the SA region ranged from α-mesosaprobic to polysaprobic and β-mesosaprobic; the NT region was classified as β-mesosaprobic; and the ST region ranged between β-mesosaprobic and lightly polluted. These results may be attributed to differences in regional barriers and glacial meltwater conditions. Canonical Correspondence Analysis (CCA) showed that environmental factors collectively explained 71.1% of the variation in species distribution. Exploring the zooplankton species composition and their relationships with aquatic environmental factors under different regional barriers provides a scientific basis for regional water resource management and environmental protection.

This research was supported by the Spanish Ministries of Science and Innovation (CGL2011-23681/BOS), and Environment, Rural and Marine Affairs (OAPN2009/067); ‘Consejería de Innovación, Ciencia y Empresa – Junta de Andalucía’ (Excelencia CVI-02598; P09-RNM-5376); The Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (FORMAS) and Stockholm University’s strategic marine environmental research program ‘Baltic Ecosystem Adaptive Management’, and a Spanish government ‘Formación de Profesorado Universitario’ fellowship to F.J. Bullejos.

Lakes are essential ecosystems that provide a large number of ecosystem services whose quality is strongly impacted by human pressures. Optimal uses of lakes require adapted magement practices which in turn rely on physico-chemical and biological monitoring. Long-term ecological monitoring provides large sets of environmental data. When such data are available, they have to be associated to metadata and to be stored properly to be accessible and useable by the scientific community. We present a data informatics system accessible to anyone who requests it. Maintained online since 2014 (https://si-ola.inrae.fr), it is origited from the Observatory on LAkes (OLA). It contains long-term data from 4 peri-alpine lakes (Lakes Aiguebelette, Annecy, Bourget, Geneva/Léman) and 24 high-altitude lakes of the northern French Alps. We describe the generated long-term data series, the data type, the methodologies and quality control procedures, and the information system where data are made accessible. Data use is allowed under the condition of providing reference to the origil source. We show here how such a platform clearly enhances data sharing and scientific collaboration. Various studies referring to these data are regularly published in peer-reviewed jourls; providing in fine a better understanding of lakes’ ecosystems functioning under local and global pressures.

Copepods, small aquatic crustaceans, are one of the most abundant zooplankton in the world. These animals play a critical ecological role in aquatic ecosystems such as oceans, streams, or, as in this study, alpine lakes. In these ecosystems, copepods have adapted to stressful and dynamic environments, a process which can be investigated via comparative transcriptomics. An assembled transcriptome is a pre-requisite to applying transcriptomic tools in physiological research, but there are few transcriptome assemblies available for copepods. To address this gap, we assembled a de novo transcriptome of Cyclops abyssorum tatricus by merging Pacific Bioscience long reads from copepods collected in two lakes at two different time points. The final assembly consisted of 52,521 contigs with a BUSCO score of 80.7%. We annotated a total of 26,255 (49.99%) protein sequences using the eggNOG database. Gene ontology analyses revealed that most gene annotations were involved in cellular processes and signaling (34.61%). Comparisons with two other copepod species showed that the transcriptome assembly of C. abyssorum tatricus is enriched for cold acclimation genes, consistent with its long-term adaptation to cold water environments. This de novo transcriptome will enable comparative transcriptomic studies in this species, allowing us to investigate physiological adaptations to alpine environments.

BackgroundChemical pollution forms a severe threat for human and environmental health. While the risks for European lowland water bodies are well known, there is little knowledge on remote aquatic ecosystems and particularly mountain lakes, despite their importance for the provision of freshwater. Here, we critically review the current knowledge on the exposure and risk by chemical pollution for mountain lakes and present a tiered approach on how to advance effectively our understanding in the future.ResultsGenerally, pollutant monitoring data are currently incomplete, with many regions and substances having been only poorly investigated. More reliable data exist only for persistent organic pollutants (POPs). However, there is increasing evidence that even remote mountain lakes are exposed to a wide range of organic pollutants. Among them potent pesticides currently used in agricultural and biocidal applications, such as diazinon and permethrin. The exposure of mountain lakes to pollutants follows a complex pattern. Pollutants are introduced into mountain lakes via the atmospheric deposition and run-off from the watershed, but also local sources, like tourism and pastoralism. Our risk assessment and recent biomonitoring studies suggest that there are widespread chronic toxic risks on crustacean in mountain ranges. If mountain ranges are exposed to tourism and pastoralism, even acute toxic effects on crustacean are possible. Thereby, the vulnerability of mountain lakes to toxic effects has to be expected to be particularly high due to the harsh environmental conditions at high altitudes, the organism’s traits, the insular position of mountain lakes and a lower species richness with increasing altitudes. Furthermore, there is little knowledge on the biological processes leading to the degradation of chemical pollutants under the environmental and ecological conditions of mountain ecosystems.ConclusionWhile the exposure and sensitivity of mountain aquatic ecosystems is currently poorly investigated, the existing data suggest that it is very likely that also water bodies as remote as mountain lakes do suffer from pollution-induced toxicity. To verify this suggestion and expand the existing knowledge, it is necessary that future studies combine a more holistic pollution monitoring with exposure modelling and links to biological effects. Only then will it be possible to obtain a more reliable understanding of the impact of chemical pollution on aquatic mountain ecosystems and to protect these fragile ecosystems.

The trophic niche of invasive species can vary overtime because of different processes related to ecological opportunity and invader activity that condition biological interactions with the native biodiversity. We conducted an annual-based survey of the trophic niche of the mysid Hemimysis anomala in the largest European peri-alpine lake by combining molecular and isotope analyses. We hypothesized that the population trophic niche width would vary seasonally, expanding in warm periods due to greater ecological opportunities and higher mysid metabolic activity. Molecular analyses identified a diversified set of prey throughout the year ranging from autotrophic protists to zooplankton and converged with isotope analyses to support the diet seasonality hypothesis of H. anomala with wider trophic niches and, in a lower extent, richer diets in spring and summer when compared to autumn and winter. Isotope analyses also highlighted a seasonal pattern in resources used with a dominance of pelagic reliance in summer and autumn. These results underlined the significant seasonal variability in the trophic niche of this invasive mysid suggesting that future assessments of its ecological impacts should account for the temporal variations of its trophic interactions with the native biodiversity.

High mountain lakes (HMLs) are considered unique and comparable ecosystems for monitoring global climate change. The food web structure can indicate the response of these ecosystems to ecological threats, such as fish introduction, by analyzing the trophic dynamics. Nonetheless, the food webs of tropical HMLs are less well-studied than temperate HMLs. The present study assessed the food webs of two neighboring (600 m apart) tropical HMLs, El Sol and La Luna, inside the crater of the Nevado de Toluca volcano, Mexico. It used stable isotopes (δ 13 C and δ 15 N) and Bayesian mixing models with different trophic discrimination factors and priors to assess the impacts of introduced rainbow trout, persisting only in the larger lake, El Sol. The food web in Lake El Sol was more complex than in Lake La Luna, mainly due to its larger size, extensive vegetated littoral zone, and being fueled by autochthonous primary production. In contrast, the smaller and fishless Lake La Luna has a reduced and bare littoral zone that harbored a simple food web substantially sustained by allochthonous carbon inputs. The persistence of introduced rainbow trout in Lake El Sol but not in Lake La Luna accentuated the differences between the lakes. The models suggested that rainbow trout fed on key consumers of littoral macroinvertebrates (70–80%) and pelagic zooplankton (20–30%), increasing the linkage between sub-networks. In both tropical HMLs, the species richness and herbivorous fraction were elevated compared with temperate HMLs, while the linkage density and omnivorous fraction were lower. Basal nodes dominated these tropical HMLs, and the vegetated littoral zone of Lake El Sol had more intermediate (omnivore) nodes. Our results showed the convenience of food web analysis to compare the effects of introduced fish in originally fishless lakes in different latitudes.