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Climate change and other anthropogenic stressors have led to long-term changes in the thermal structure, including surface temperatures, deepwater temperatures, and vertical thermal gradients, in many lakes around the world. Though many studies highlight warming of surface water temperatures in lakes worldwide, less is known about long-term trends in full vertical thermal structure and deepwater temperatures, which have been changing less consistently in both direction and magnitude. Here, we present a globally-expansive data set of summertime in-situ vertical temperature profiles from 153 lakes, with one time series beginning as early as 1894. We also compiled lake geographic, morphometric, and water quality variables that can influence vertical thermal structure through a variety of potential mechanisms in these lakes. These long-term time series of vertical temperature profiles and corresponding lake characteristics serve as valuable data to help understand changes and drivers of lake thermal structure in a time of rapid global and ecological change.

Fishes in northern latitude lakes are at risk from climate-induced warming because the seasonality in water temperature is degrading, which can change ecosystem properties and the phenology of life-history events. Temperature-dependent embryo development models were developed for a group of cold, stenothermic fishes (Salmonidae Coregoninae) to assess the potential impacts of climate-induced changes in water temperature on cisco (Coregonus artedi) from two populations in Lake Superior (Apostle Islands [USA] and Thunder Bay [Canada]) and one in Lake Ontario (USA), vendace (C.albula) in Lake Southern Konnevesi (Finland), and European whitefish (C. lavaretus) in lakes Southern Konnevesi, Constance (Germany), Geneva (France), and Annecy (France). Water temperatures for each study group were simulated and changes in reproductive phenology across historic (1900–2006) and three future climatic-warming scenarios (2007–2099) were investigated. Models predicted that increases in water temperatures are likely to cause delayed spawning, shorter embryo incubation durations, and earlier larval hatching. Relative changes increased as warming scenarios increased in severity and were higher for littoral as compared to pelagic populations. Our simulations demonstrated that slower cooling in the autumn and (or) more rapid warming in spring can translate into substantial changes in the reproductive phenology of coregonines among our study groups. We expect that the changes in reproductive phenology predicted by our models, in the absence of thermal or behavioral adaptation, will have negative implications for population sustainability. Our paper developed and evaluated temperature-dependent embryo development modelsfor a group of cold, stenothermic fishes (Salmonidae Coregoninae) to assess the potential impacts of climate-induced changes in water temperature on cisco (Coregonus artedi) from two populations in Lake Superior (Apostle Islands [USA] and Thunder Bay [Canada]) and one in Lake Ontario (USA), vendace (C. albula) in Lake Southern Konnevesi (Finland), and European whitefish (C. lavaretus) in lakes Southern Konnevesi, Constance (Germany), Geneva (France), and Annecy (France). Water temperatures for each study group were simulated and changes in reproductive phenology across historic (1900-2006) and three future climatic-warming scenarios (2007-2099) were investigated. Models predicted that increases in water temperatures are likely to cause delayed spawning, shorter embryo incubation durations, and earlier larval hatching. Relative changes increased as warming scenarios increased in severity and were higher for littoral as compared to pelagic populations. Our simulations demonstrated that slower cooling in the autumn and (or) more rapid warming in spring can translate into substantial changes in the reproductive phenology of coregonines among our study groups. We expect that the changes in reproductive phenology predicted by our models, in the absence of thermal or behavioral adaptation, will have negative implications for population sustainability. [ABSTRACT FROM AUTHOR]

Toxicological studies were performed to examine silver nanoparticle (AgNP, size: 14.4 ± 2.5 nm) transformation within three different test media and consequent effects on embryos of whitefish (Coregonus lavaretus) and roach (Rutilus rutilus). The test media, namely ASTM very hard water, ISO standard dilution medium, and natural lake water differed predominantly in ionic strength. Total silver was determined using inductively coupled plasma mass spectrometry (ICP-MS), while AgNPs were characterized by transmission electron microscopy and single particle ICP-MS. Silver species distributions were estimated via thermodynamic speciation calculations. Data demonstrated that increased AgNP dissolution accompanied by decreasing ionic strength of the test medium did not occur as noted in other studies. Further, other physicochemical parameters including AgNP size and metallic species distribution did not markedly affect AgNP-induced toxicity. Irrespective of the test medium, C. lavaretus were more sensitive to AgNP exposure (median lethal concentration after 8 weeks: 0.51–0.73 mg/L) compared to R. rutilus, where adverse effects were only observed at 5 mg/L in natural lake water. In addition, AgNP-induced toxicity was lower in the two standard test media compared to natural lake water. Currently, there are no apparent studies assessing simultaneously the sensitivity of C. lavaretus and R. rutilus to AgNP exposure. Therefore, the aim of this study was to (1) investigate AgNP-induced toxicity in C. lavaretus and R. rutilus cohabiting in the same aquatic environment and (2) the role played by test media in the observed effects of AgNPs on these aquatic species. [ABSTRACT FROM AUTHOR]