The littoral zone of polar lakes : inshore-offshore contrasts in an ice-covered High Arctic lake

In ice-covered polar lakes, a narrow ice-free moat opens up in spring or early summer, and then persists at the edge of the lake until complete ice loss or refreezing. In this study, we analyzed the horizontal gradients in Ward Hunt Lake, located in the High Arctic, and addressed the hypothesis that the transition from its nearshore open-water moat to offshore ice-covered waters is marked by discontinuous shifts in limnological properties. Consistent with this hypothesis, we observed an abrupt increase in below-ice concentrations of chlorophyll a beyond the ice margin, along with a sharp decrease in temperature and light availability and pronounced changes in benthic algal pigments and fatty acids. There were higher concentrations of rotifers and lower concentrations of viruses at the ice-free sampling sites, and contrasts in zooplankton fatty acid profiles that implied a greater importance of benthic phototrophs in their inshore diet. The observed patterns underscore the structuring role of ice cover in polar lakes. These ecosystems do not conform to the traditional definitions of littoral versus pelagic zones, but instead may have distinct moat, icemargin and ice-covered zones. This zonation is likely to weaken with ongoing climate change

Dissolved organic matter concentration, optical parameters and attenuation of solar radiation in high-latitude lakes across three vegetation zones

High-latitude lakes are usually transparent, due to their low productivity and low concentration of dissolved organic matter (DOM), but large variations in lake optical properties can be found within and between regions. We investigated the light regimes in relation to DOM in 18 oligotrophic, high-latitude lakes across mountain birch woodland, shrub tundra and barren tundra in north-west Finnish Lapland. In 12 lakes >1% of photosynthetically active radiation (PAR) reached the lake bottom, while 1% UV-B depth ranged from 0.1 to >12 m. Lakes located in barren tundra had highest transparency, lowest dissolved organic carbon (DOC) concentration and lowest DOM absorption (a440) (mean values: Kd PAR 0.3m–1, DOC 2.1mg l–1, a440 0.4m–1), while lakes in shrub tundra and mountain birch forest were less transparent (DOC 4.7 mg l–1, a440 1.4 m–1). Solar attenuation and lake transparency was best explained by a440. Our survey emphasizes the importance of catchment type on DOM characteristics and lake optics. We predict that even small changes in DOM quality may largely change the UV radiation exposure of lakes while changes in PAR may have smaller biological effects in these shallow lakes that are already illuminated to the bottom. Les lacs en hautes latitudes sont généralement transparents due à de faibles productivité et concentration en matière organique dissoute (MOD). Toutefois, ceux-ci présentent une grande variabilité en propriétés optiques. Nous avons étudié le régime lumineux avec la MOD dans 18 lacs oligotrophes des forêts (bouleau pubescent) et toundras (arbustive et herbacée) du nord-ouest de la Laponie finlandaise. Dans 12 lacs, >1% du rayonnement photosynthétique actif (RPA) a atteint le fond, tandis que le UVB 1% atteint entre 0.1 et >12m. Les lacs de la toundra herbacée avaient les transparences les plus élevées mais des concentrations en carbone organique dissout (COD) et en MOD chromophore (a440) les plus faibles (moyennes: RPA Kd 0,3m–1, COD 2,1mg.l –1, a440 0,4m–1), tandis que ceux de la toundra arbustive et des forêts étaient moins transparents (COD 4,7mg.l–1, a440 1,4m–1). L’atténuation de la radiation solaire et la transparence étaient liées à a440. Notre étude montre l’importance du type de bassin versant pour les caractéristiques de la MOD et l’optique des lacs. Nous prédisons que de faibles changements de la MOD pourront causer des changements dans l’exposition aux UV, mais des changements du RPA pourraient avoir de faibles effets biologiques dans ces lacs déjà illuminés jusqu’au fond

Variability in lake bacterial growth and primary production under lake ice: Evidence from early winter to spring melt

Climate change is causing seasonally ice‐covered lakes of the boreal region to undergo changes in their winter regime by altering patterns of precipitation and temperature, often reflected as reduced snow and ice cover duration. The duration, extent and quality of ice, and snow cover have a pivotal role for production and carbon cycling in lakes in winter, with potentially cascading effects for the following open water period. We investigated under‐ice carbon cycling by assessing bacterial growth (including bacterial production, bacterial respiration, and bacterial growth efficiency) and primary production at five water depths during early winter, midwinter, late winter and melting season in a boreal lake, and report significantly different temporal patterns. Bacterial respiration was dominant in early and midwinter, whereas the late winter and melting season were dominated by bacterial production. Multiple linear regression models indicated that high early winter bacterial respiration was associated with senescing phytoplankton, whereas bacterial production was promoted by the onset of spring processes. Collectively, bacterial growth indices were inherently linked with bacterioplankton community composition and specific biomarker taxa. Primary production under ice increased in late winter when light‐blocking snow cover melted, and primary production measured from the lake ice exceeded that of the water column at the melting season. Ice samples hosted diverse eukaryotic communities including photoautotrophs, suggesting that the habitat potential of the understudied lake ice and the role of ice for ecological processes at ice melt should be further explored

Hidden stores of organic matter in northern lake ice : Selective retention of terrestrial particles, phytoplankton and labile carbon

Around 50% of the world's lakes freeze seasonally, but the duration of ice-cover is shortening each year and this is likely to have broad limnological consequences. We sampled freshwater ice and the underlying water in 19 boreal and polar lakes to evaluate whether lake ice contains an inoculum of algae, nutrients, and carbon that may contribute to lake ecosystem productivity. Boreal and Arctic lakes differed in ice duration (6 vs. >10 months), thickness (70 vs. 190 cm), and quality (predominantly snow ice vs. black ice), but in all lakes, there were consistent differences in biological and biogeochemical composition between ice and water. Particulate fractions were often more retained while most dissolved compounds were excluded from the ice; for example, the ice had more terrestrial particulate carbon, measured as fatty acid biomarkers (averages of 1.1 vs. 0.3 µg L−1) but lower dissolved organic carbon (2.2 vs. 5.7 mg C L−1) and inorganic phosphorus concentrations (4.0 vs. 7.5 µg C L−1) than the underlying water. The boreal ice further had three times higher chlorophyll-a, than the water (0.9 vs. 0.3 µg L−1). Of the dissolved fractions, the contribution of protein-like compounds was higher in the ice, and this in all lakes. These labile compounds would become available to planktonic microbes when the ice melts. Our results show that freshwater ice has an underestimated role in storage and transformation in the biogeochemical carbon cycle of ice-covered lake ecosystems

Effects of UV radiation on aquatic ecosystems and interactions with other environmental factors

Interactions between climate change and UV radiation are having strong effects on aquatic ecosystems due to feedback between temperature, UV radiation, and greenhouse gas concentration. Higher air temperatures and incoming solar radiation are increasing the surface water temperatures of lakes and oceans, with many large lakes warming at twice the rate of regional air temperatures. Warmer oceans are changing habitats and the species composition of many marine ecosystems. For some, such as corals, the temperatures may become too high. Temperature differences between surface and deep waters are becoming greater. This increase in thermal stratification makes the surface layers shallower and leads to stronger barriers to upward mixing of nutrients necessary for photosynthesis. This also results in exposure to higher levels of UV radiation of surface-dwelling organisms. In polar and alpine regions decreases in the duration and amount of snow and ice cover on lakes and oceans are also increasing exposure to UV radiation. In contrast, in lakes and coastal oceans the concentration and colour of UV-absorbing dissolved organic matter (DOM) from terrestrial ecosystems is increasing with greater runoff from higher precipitation and more frequent extreme storms. DOM thus creates a refuge from UV radiation that can enable UV-sensitive species to become established. At the same time, decreased UV radiation in such surface waters reduces the capacity of solar UV radiation to inactivate viruses and other pathogens and parasites, and increases the difficulty and price of purifying drinking water for municipal supplies. Solar UV radiation breaks down the DOM, making it more available for microbial processing, resulting in the release of greenhouse gases into the atmosphere. In addition to screening solar irradiance, DOM, when sunlit in surface water, can lead to the formation of reactive oxygen species (ROS). Increases in carbon dioxide are in turn acidifying the oceans and inhibiting the ability of many marine organisms to form UV-absorbing exoskeletons. Many aquatic organisms use adaptive strategies to mitigate the effects of solar UV-B radiation (280–315 nm), including vertical migration, crust formation, synthesis of UV-absorbing substances, and enzymatic and non-enzymatic quenching of ROS. Whether or not genetic adaptation to changes in the abiotic factors plays a role in mitigating stress and damage has not been determined. This assessment addresses how our knowledge of the interactive effects of UV radiation and climate change factors on aquatic ecosystems has advanced in the past four years.Fil: Häder, Donat P.. Universitat Erlangen-Nuremberg; AlemaniaFil: Williamson, Craig E.. Miami University; Estados UnidosFil: Wängberg, Sten Åke. University of Gothenburg. Department of Biological and Environmental Science; SueciaFil: Rautio, Milla. Université du Québec à Chicoutimi. Département des Sciences Fondamentales and Centre for Northern Studies; CanadáFil: Rose, Kevin C.. University Of Wisconsin; Estados UnidosFil: Gao, Kunshan. Xiamen University. State Key Laboratory of Marine Environmental Science; ChinaFil: Helbling, Eduardo Walter. Fundación Playa Unión. Estación de Fotobiología Playa Unión; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Sinha, Rajeshwar P.. Banaras Hindu University. Centre of Advanced Study in Botany; IndiaFil: Worrest, Robert. Columbia University; Estados Unido

Écosystème numérique DESIIR : Données Environnementales et de Santé Intégrées pour une Infrastructure de Recherche

La pandémie de COVID-19 a souligné l’interdépendance des espèces vivantes et de leur environnement, menant au concept de « One Health ». Celui-ci implique une démarche intersectorielle afin de répondre aux enjeux complexes de santé incluant l’impact des changements climatiques sur la santé respiratoire et allergique. Ainsi, ce projet vise à regrouper les données de recherche générées au Saguenay–Lac-Saint-Jean (SLSJ) depuis les années 1970 en environnement, en santé physique et psychosociale et sur la structure populationnelle au sein d’un écosystème numérique nommé DESIIR (Données Environnementales et de Santé Intégrées pour une Infrastructure de Recherche). Le premier volet de ce projet vise à regrouper ces données dans un environnement sécurisé répondant aux principes FAIR et respectant les lois québécoises sur la protection des données. Le deuxième volet utilisera l’asthme comme modèle afin de démontrer l’ampleur des possibilités qu’offrira DESIIR. Le troisième volet aura comme objectif d’évaluer la complétude des différents ensembles de données, de planifier des programmes de recherche pour combler les lacunes identifiées et de développer un plan de valorisation de DESIIR pour maximiser sa visibilité et son utilisation. DESIIR est un vaste projet d’infrastructure qui implique une équipe de 30 chercheuses et chercheurs provenant de 9 établissements universitaires qui sera réalisé en partenariat avec le Centre intégré de santé et de service sociaux du SLSJ, le Cégep de Jonquière, ville Saguenay ainsi que « Secure Data 4 Health » pour la construction de l’infrastructure. Ces chercheurs, chercheuses et partenaires assurent actuellement la gestion des données qui seront regroupées dans DESIIR et la gouvernance du projet. À terme, DESIIR fournira des données conformes aux principes FAIR, de multiples opportunités pour le développement de nouveaux projets de recherche novateurs, des modèles d’analyse qui pourront être élargis à d'autres traits complexes ainsi qu’une preuve de concept de la valeur ajoutée d'un tel écosystème. Il favorisera le développement d’une approche holistique de la recherche en santé durable conduisant au développement et à l’application de nouveaux modèles de prévention et de gestion de la santé. DESIIR contribuera à bâtir un modèle socioéconomique innovant en santé durable pour la population du SLSJ

Piloting gender-oriented colorectal cancer screening with a faecal immunochemical test: population-based registry study from Finland

Objective To assess the feasibility and evaluate the performance of a relaunched colorectal cancer (CRC) screening programme with different cut-offs for men and women. Design Population-based registry study. Setting Nine municipalities in Finland which started CRC screening with faecal immunochemical test (FIT) in April 2019 with cut-off levels 70 mu g Hg/g faeces for men and 25 mu g Hg/g faeces for women. Participants Men (n=13 059) and women (n=14 669) aged 60-66 years invited to screening during the first programme year. Outcome measures Participation rates, positivity rates, detection rates of CRC and advanced adenoma (AA), and positive predictive values (PPV) of FIT for CRC and AA. Results Altogether 21 993 invitees returned stool samples. The participation rate of women (83.4%; 95% CI 82.8 to 84.0) was significantly higher than that of men (74.7%; 95% CI 73.9 to 75.4). The positivity rates were 2.4% (2.2 to 2.7) and 2.8% (2.5 to 3.1), respectively. In total, 37 CRCs and 116 AAs were detected. The detection rates of CRC and AA per 1000 participants were 1.8 (1.1 to 2.9) and 7.2 (5.6 to 9.1) for men and 1.6 (0.9 to 2.4) and 3.8 (2.8 to 5.0) for women. The PPVs per 100 positive tests were 6.6 (4.0 to 10.3) and 25.7 (20.6 to 31.4) for men and 6.4 (3.9 to 9.8) and 15.5 (11.6 to 20.2) for women. Conclusions The chosen FIT strategy narrowed the gap in the diagnostic performance between men and women especially in the detection of CRC. The participation rates were excellent. The levels of positivity and detection rates were moderate and need further action. The results indicate that gender-specific protocols can be introduced to organised CRC screening. It is yet to be seen whether they are more effective than a uniform screening protocol.</p

First circumpolar assessment of Arctic freshwater phytoplankton and zooplankton diversity : Spatial patterns and environmental factors

Arctic freshwaters are facing multiple environmental pressures, including rapid climate change and increasing land-use activities. Freshwater plankton assemblages are expected to reflect the effects of these stressors through shifts in species distributions and changes to biodiversity. These changes may occur rapidly due to the short generation times and high dispersal capabilities of both phyto- and zooplankton. Spatial patterns and contemporary trends in plankton diversity throughout the circumpolar region were assessed using data from more than 300 lakes in the U.S.A. (Alaska), Canada, Greenland, Iceland, the Faroe Islands, Norway, Sweden, Finland, and Russia. The main objectives of this study were: (1) to assess spatial patterns of plankton diversity focusing on pelagic communities; (2) to assess dominant component of beta diversity (turnover or nestedness); (3) to identify which environmental factors best explain diversity; and (4) to provide recommendations for future monitoring and assessment of freshwater plankton communities across the Arctic region. Phytoplankton and crustacean zooplankton diversity varied substantially across the Arctic and was positively related to summer air temperature. However, for zooplankton, the positive correlation between summer temperature and species numbers decreased with increasing latitude. Taxonomic richness was lower in the high Arctic compared to the sub- and low Arctic for zooplankton but this pattern was less clear for phytoplankton. Fennoscandia and inland regions of Russia represented hotspots for, respectively, phytoplankton and zooplankton diversity, whereas isolated regions had lower taxonomic richness. Ecoregions with high alpha diversity generally also had high beta diversity, and turnover was the most important component of beta diversity in all ecoregions. For both phytoplankton and zooplankton, climatic variables were the most important environmental factors influencing diversity patterns, consistent with previous studies that examined shorter temperature gradients. However, barriers to dispersal may have also played a role in limiting diversity on islands. A better understanding of how diversity patterns are determined by colonisation history, environmental variables, and biotic interactions requires more monitoring data with locations dispersed evenly across the circumpolar Arctic. Furthermore, the importance of turnover in regional diversity patterns indicates that more extensive sampling is required to fully characterise the species pool of Arctic lakes.Peer reviewe