Paleolimnology and Environmental Change

点击翻译按钮获取中文摘要

Warmer temperatures over the last century and projections of unprecedented increases in temperature over the next 20-50 years, has led to concern on the potential impacts of climate change on aquatic ecosystems. Research in my lab focuses on understanding how lakes have responded to climate and other natural or human-induced factors in the past, by the analysis of the physical, chemical and biological information preserved in lake sediment cores. Paleolimnological studies can provide important insights on the sensitivity of aquatic and terrestrial ecosystems to climate change. This proposal seeks to provide research and training opportunities to investigate how warmer periods in the past influenced the water balance and aquatic production of boreal lakes from northern Ontario, with a focus on the Holocene Thermal Maximum (HTM), a warmer period circa 8,000 to 4,000 years ago. During the HTM, northwest Ontario was characterized by a parkland-type forest with scrubs and grasses, low lake-levels, and frequent fires. However, information on how lakes responded to the HTM, across the humid regions of northern Ontario from Sioux Lookout to Timmins (a distance of over 700 km) are largely unknown. It is likely that the HTM influenced this entire region, since the easternmost region of northern Ontario, near Timmins, saw white pine replacing spruce c. 7,000 years ago, before returning to a spruce forest circa 4,000 years ago. We propose to develop and apply approaches, using physical, chemical and biological proxies, from both near-shore and deep-water cores, to provide information on how lake levels and production changed across the central and eastern boreal regions of Ontario, as well as provide information on changes in vegetation and fire over the Holocene. Given that the estimated temperature changes during the HTM were small relative to the projected warming, information from this study will provide an assessment of vulnerability to possible droughts, algal blooms, and fires associated with living in a warmer world.**** This proposal also seeks support to provide training and research opportunities to understand the possible role of recent climate change on lakes from the Adirondack region (New York, USA). Most aquatic systems in the northeast are now influenced by multiple local and regional stressors. We have developed a network of 31 reference lakes, that were chosen from over 1400 lakes, to have little impact from local human activities (roads, logging, settlement, fish stocking) and the direct impacts of acid deposition. This network of lakes will be studied to assess how biological assemblages of algae and invertebrates have changed in the absence of the most common environmental stressors to aquatic systems in the northeast (i.e. acid deposition, watershed disturbances, fish stocking), thereby allowing an assessment of recent changes related to climate and other broad-scale regional stressors.**** **