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Attenuation of ultraviolet radiation in mountain lakes: Factors controlling the among- and within-lake variability / Isabelle Laurion in Limnology and oceanography, 45 (6) (2000) 

Public Citation [article]  inLimnology and oceanography > 45 (6) (2000) . - 1274-1288 Titre : Attenuation of ultraviolet radiation in mountain lakes: Factors controlling the among- and within-lake variability Type de document : Imprimé Auteurs : Isabelle Laurion ; Marc Ventura ; Jordi Catalán ; Roland Psenner (1950-) ; Ruben Sommaruga Année de publication : 2000 Article en page(s) : 1274-1288 Langues : Anglais (eng) Catégories : [CBNPMP-Thématique] Enjeux de conservation des lacs d'altitude Résumé : High-altitude lakes are exposed to high fluence rates of solar ultraviolet radiation (UVR; 29–400 nm) and contain low concentrations of dissolved organic carbon (DOC). While in most lowland lakes, DOC can be used to predict UV transparency with sufficient accuracy, current models fail to estimate UVR in clear alpine lakes. In these lakes, phytoplankton may contribute significantly to the UV attenuation either as particles or as a source of chromophoric dissolved organic matter (CDOM) with distinctive properties. We investigated a series of 26 lakes in the Alps and Pyrenees, situated at elevations ranging from 422 to 2,799 m above sea level and having DOC concentrations ranging from 0.2 to 3.5 mg L−1. CDOM, as measured by the absorptivity of filtered lake water, explained most of the variability in the attenuation of underwater UVR among lakes (r2 = 0.94, P < 0.001). However, within-lake variation in the UV attenuation revealed a significant contribution from phytoplankton in deeper waters (UV attenuation increasing with chlorophyll a concentration; r2 = 0.97, P = 0.002), only apparent when DOC concentrations were low (∼0.3 mg L−1). The DOC-specific absorptivity (ag*) was also important for characterizing the optical conditions in this series of lakes. Epilimnetic values of ag* were significantly lower in lakes located at high elevations (with low allochthonous CDOM inputs from the catchment), compared to lakes surrounded by trees and meadows. Moreover, ag* was generally lower in surface waters than in deeper water layers, suggesting the influence of photobleaching on UV transparency. The slope S of the exponential regression between CDOM absorptivity and wavelength did not show clear patterns, such as found in marine systems, and often presented lower values in the epilimnetic waters (in association with lower ag*). Collectively, our results suggest that in transparent alpine lakes, the dynamics of the CDOM pool and phytoplankton production will have a strong effect on temporal changes in UV underwater attenuation. Lien pérenne : DOI : 10.4319/lo.2000.45.6.1274 Permalink : https://biblio.cbnpmp.fr/index.php?lvl=notice_display&id=150993 Laurion, Isabelle, Ventura, Marc, Catalán, Jordi, Psenner, Roland (1950-), Sommaruga, Ruben 2000 Attenuation of ultraviolet radiation in mountain lakes: Factors controlling the among- and within-lake variability. Limnology and oceanography, 45(6): 1274-1288.

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Climate warming increases vertical and seasonal water temperature differences and inter-annual variability in a mountain lake / Georg H. Nierdrist in Climatic change, 151 (2018) 

Public Citation [article]  inClimatic change > 151 (2018) . - 473-490 Titre : Climate warming increases vertical and seasonal water temperature differences and inter-annual variability in a mountain lake Type de document : Imprimé Auteurs : Georg H. Nierdrist ; Roland Psenner (1950-) ; Ruben Sommaruga Année de publication : 2018 Article en page(s) : 473-490 Langues : Anglais (eng) Catégories : [CBNPMP-Thématique] Enjeux de conservation des lacs d'altitude [LOTERRE-Biodiversité] Changement climatique Résumé : Lakes around the world are warming, but not all water layers are warming at the same rate, and some are even cooling. Most studies have focused on summer lake water surface temperatures or analyzed short-time series. Here, we analyze a 44-year time series of water temperature from nine depths in a small mountain lake using dynamic linear models and temporal trend decomposition. We observe a significant long-term warming trend, but this occurred only from August to December in all water layers. The lake warmed ca. twice as fast (0.23 °C decade−1) as the air, but warming of the epilimnion slowed down remarkably (from 0.65 to 0.10 °C per decade) after 1993, a consequence of changing stratification timing. Deeper water layers even cooled thereafter, pointing to a stronger isolation from surface layers, which were still warming over the whole study period. This differential warming of the lake was accompanied by significant shifts of lake freezing and thawing dates leading to shorter ice-cover periods (~ 5 days decade−1). As a result, the thermal Schmidt stability of the water column strengthened, but also temperature variance in the epilimnion increased significantly, together with increasing variance and extremes of local air temperature. Our results show a significant autumn/winter warming effect of lake water together with an increasing intensity of temperature fluctuations in this seasonally ice-covered mountain lake, suggesting that current broad scale estimates of climate change impacts on lakes, based on summer temperature measurements and surface layers, do not fully reflect the effect of climate change. Lien pérenne : DOI : 10.1007/s10584-018-2328-6 Permalink : https://biblio.cbnpmp.fr/index.php?lvl=notice_display&id=150995 Nierdrist, Georg H., Psenner, Roland (1950-), Sommaruga, Ruben 2018 Climate warming increases vertical and seasonal water temperature differences and inter-annual variability in a mountain lake. Climatic change, 151: 473-490.

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High mountain lakes and atmospherically transported pollutants / Richard William Battarbee (2005)

Public Citation est un extrait de Global change and mountain regions / Uli M. Huber (2005) Titre : High mountain lakes and atmospherically transported pollutants Type de document : Extrait d'ouvrage Auteurs : Richard William Battarbee (1947-) ; Uli M. Huber ; Harald K. M. Bugmann ; Mel A. Reasoner ; Martin Beniston ; Simon Patrick ; Martin Kernan ; Roland Psenner (1950-) ; Hansjoerg Thies ; Joan Grimalt ; Bjoern O. Rosseland ; Bente Wathne ; Jordi Catalán ; Rosario Mosello ; Andrea Lami ; David Livingstone ; Evzen Stuchlik ; Vera Straskrabova ; Gunnar Raddum Editeur : Dordrecht : Springer Netherlands Année de publication : 2005 Importance : 113-121 Catégories : [CBNPMP-Thématique] Enjeux de conservation des lacs d'altitude [CBNPMP-Thématique] Etude d'aménagement, étude d'impact, actions anthropiques et leur impact [CBNPMP-Thématique] Lac d'altitude Résumé : Remote mountain lakes, whether found at high altitudes or high latitudes, usually appear to be in pristine condition. In particular, those lakes that are situated above or beyond the tree-line are rarely disturbed by agricultural or forestry practices and few if any people inhabit their catchments. However, recent research indicates that even the most remote lakes are impacted by atmospherically transported pollutants, and that greenhouse-gas forced climate change is beginning to have a significant influence on ecosystem functioning. UV-B radiation is also increasing and, in interaction with global warming, may already be changing biogeochemical cycles in many mountain lakes (Vinebrooke and Leavitt, this volume). All sites are subject to multiple stresses, and studies of the ecological response of mountain lakes to such combined stress need to consider interactions between all factors, both natural and anthropogenic. In this chapter, we consider acid deposition, toxic substances and climate change as the three main drivers of ecosystem change in high mountain lakes. Lien pérenne : DOI : 10.1007/1-4020-3508-X_12 Permalink : https://biblio.cbnpmp.fr/index.php?lvl=notice_display&id=147857 Battarbee, Richard William (1947-), Huber, Uli M., Bugmann, Harald K. M., Reasoner, Mel A., Beniston, Martin, Patrick, Simon, Kernan, Martin, Psenner, Roland (1950-), Thies, Hansjoerg, Grimalt, Joan, Rosseland, Bjoern O., Wathne, Bente, Catalán, Jordi, Mosello, Rosario, Lami, Andrea, Livingstone, David, Stuchlik, Evzen, Straskrabova, Vera, Raddum, Gunnar 2005 High mountain lakes and atmospherically transported pollutants. In: Global change and mountain regions. Springer Netherlands, Dordrecht: 113-121.