Identifying and evaluating the main drivers of change in freshwater ecosystems

点击翻译按钮获取中文摘要

Lake ecosystems are in trouble, threatened by global warming and more immediate anthropogenic activities. Climate change is affecting lakes by altering the thermal gradient of the water column, nutrient cycling, and by increasing greater nutrient and sediment inputs as a result of increasing runoff. The effect of global warming on higher latitude freshwater ecosystems has been identified and studied over recent years but very little is known about the effects of climate change on tropical lakes, where more accelerated warming may be occurring and where anthropogenic impact is spreading rapidly. My research program will bridge this gap by studying tropical lakes distributed along altitudinal gradients and under different types and degrees of anthropogenic influence. An altitudinal gradient in the tropics offers a unique opportunity to study the effects of climate change in aquatic ecosystems, since climatic stressors are more accentuated in the tropics and changes upslope are more contrasting than in higher latitudes. Most of the urban population in the Andes derive their drinking water from high Andean lakes, thus it is of utmost importance to understand the fate of this resource in developing countries. This research program will use paleoecological and paleolimnological reconstructions based on diatoms, complemented by pigments, grain size and stable isotopes, to understand the evolution and trajectories of tropical lakes in the Holocene and Anthropocene, and to reconstruct Holocene climate variability in the tropics. Diatoms are excellent indicators of limnological change, which in most cases reflect the effect of external stressors and interactions with natural internal processes.With this study I will contribute to answer the overarching question: How have freshwater ecosystems changed in response to climate change and anthropogenic impact? Results from this program will be applicable to a wide range of ecosystems not only in the tropics, but also in Canada where boreal forests have shifted latitudinally north and south, similarly to the altitudinal migration of the tropical forest, and where severe human impact is affecting lakes and diminishing their capability to respond to climate change. My program will contribute substantively to the understanding of the behaviour of climatic phenomena of great impact in Canadian climate, such as the Pacific Decadal Oscillation and the El Nio Southern Oscillation, and to scholarly debates regarding Holocene climate variability in the tropics. The objectives of this program are to unravel the long and short-term history of tropical lakes along an altitudinal and vegetation gradient and with varying degrees of anthropogenic impacts, in order to: (1) evaluate the vulnerability of ecosystems to climate change and human impact, and (2) to reconstruct climate variability for the Holocene of the tropics.