Isotopic Records in Post-Glacial Lake Sediments: Implications for Biota and Landscape Evolution

University Of Vermont & State Agricultural College, Burlington VT

Investigators

Abstract

Lake sediments provide a temporal record of surface and lacustrine processes influenced by environmental and climatic changes. Since environmental changes affect the biological communities in and around lakes, evidence of local and regional environmental histories can be found in the chemical composition of organic material preserved in their sediments. The extreme climatic changes associated with glacial-interglacial transitions had profound ecological impacts, which are recorded in lake sediments. The objectives of this project are to understand how and at what rates lacustrine ecosystems were established in newly created post-glacial lakes, and to investigate the relationship between lake ecosystem and watershed evolution. In order to meet these objectives, sediment cores spanning the whole late Pleistocene-Holocene time interval will be collected from post-glacial lakes in New England. Analyses that will be performed to characterize the sedimentary organic matter include: carbon and nitrogen stable isotopes, organic carbon and nitrogen content, C/N ratios, and hydrogen and oxygen indices. Samples of present-day watershed and lake plants will also be collected for each of the cored lakes. This modern dataset will provide a base for the interpretation of the sedimentary records. The proposed study has significant potential impacts. If, as hypothesized, geochemical records such as those provided by carbon isotopes reflect the individualistic response of the developing lake systems to the local geology, hydrology, and biota, these factors must be considered before attempting correlation of environmental climate proxies on a local, regional, and global scale. Results will also provide constraints on how much time is needed for lake ecosystems to recover from extreme natural or anthropogenic disturbances.