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Thursday, 12 July 2012

Isabel Reche
Department of Ecology, Faculty of Science, University of Granada

Presentation: Dusty Skies and Pristine Lakes.

Biographical Information: Dr. Isabel Reche is an Associate Professor of Ecology and Associate Scientist of the Instituto del Agua at the University of Granada (Spain). She received her doctor degree from this university in 1995 and was a postdoctoral fellow at the Institute of Ecosystems Studies (Millbrook, NY, USA) until 1998. Since then she is at the University of Granada. She has been involved in several projects in remote environments as boreal, and alpine lakes or in the Southern Ocean. Her specific scientific interests are dissolved and particulate organic carbon dynamics in aquatic ecosystems and bacterioplankton activity and structure.

Desertification and land use changes are promoting an increase of dust in the atmosphere. The Sahara-Sahel region is the main source of atmospheric dust accounting for approx. 50% of the dust production in the Earth surface, but other deserts as Gobi and Takla Makan in Asia are also relevant. African dust is mostly exported toward the Atlantic Ocean and the Mediterranean region mobilizing particles, inorganic and organic nutrients, pollutants, and also microorganisms. Remote lakes are usually unaffected by direct human influence and, consequently, are considered as pristine and reference sites very responsive to environmental changes. However, these remote, alpine lakes are also submitted to dust deposition that influences their pool of mineral nutrients, dissolved organic matter, optical properties, and planktonic assemblages.

We have been studying the effects of dust deposition on lake biogeochemistry and microbial biogeography patterns. At the regional scale, in Sierra Nevada (Spain), atmospheric deposition of particulate matter, calcium, total phosphorus, and chromophoric dissolved organic matter is mainly associated to dryfall and shows seasonal patterns similar to Saharan dust exports. These dust inputs are an important source of phosphorous and organic carbon affecting lake stoichiometry and boosting phytoplankton and bacterioplankton. We have quantified bacterial loadings linked to dust deposition and identified viable long-distance airborne bacteria as immigrants in alpine lakes. At the global scale, we have reported significant latitudinal trends in alpine lakes in dissolved organic matter quantity and quality influenced by dust deposition. Our results suggest the current increase in dust export from land may affect the optical quality of dissolved organic matter in clear, alpine lakes and, consequently, their value as pristine reference sites.