Session 6: Vulnerability of Northern Social Systems 1 Workshop: Vulnerability of Cryospheric and Socio-Economic Systems (Feb. 26 – 28, 2006) Using lake and pond sediments to assess the effects of multiple-stressors in the Arctic Jules M. Blais Director of the Ottawa-Carleton Chemical and Environmental Toxicology Program Associate Professor, Department of Biology, University of Ottawa, 30 Marie Curie Road, Rm. 271, Ottawa, Ont. K1N 6N5, Canada, jblais@science.UOttawa.ca John P. Smol Professor Canada Research Chair in Environmental Change, Paleoecological Environmental Assessment and Research Lab (PEARL), Dept. Biology, 116 Barrie St., Queen's University, Kingston, Ontario K7L 3N6, Canada, SMOLJ@BIOLOGY.QueensU.Ca Ecosystems are being subjected to multiple environmental stressors, but tracking the effects of these problems is very difficult due to the lack of long-term monitoring data. For example, most environmental assessments are based on sampling strategies of three years or less (Smol 2002). The lack of long-term monitoring data is especially acute in Arctic ecosystems, where logistical difficulties and other concerns make frequent sampling difficult. Fortunately, polar regions are often characterized by large numbers of aquatic and semi-aquatic ecosystems, such as ponds, lakes, and bogs. These habitats archive important records of past environmental change in their sedimentary records. The multi-disciplinary field of paleolimnology uses the biological, chemical and physical information in these sediments to reconstruct past environmental conditions, from which hypotheses and models can be evaluated, and from which the natural, pre-anthropogenic conditions and modes of environmental change can be assessed. Paleolimnology is now being used extensively in many polar regions (Pienitz et al. 2004). This presentation will review some of the recent advances that have occurred in the field of arctic paleolimnology, and focus especially on two interacting environmental stressors: climatic change and the transport of contaminants. Recent climatic change is a global problem, but high latitude ecosystems are considered to be especially at risk. Yet, log-term instrumental data are especially sparse for Arctic regions. Beginning with work in the Canadian High Arctic, paleolimnological analyses revealed that diatom assemblages on ponds from east central Ellesmere Island recorded dramatic ecosystem changes beginning in the nineteenth century, which appeared to be linked to limnological changes related to climatic warming (Douglas et al. 1994). Subsequent analyses on many other Canadian arctic lakes, including deeper lakes in the Sub-Arctic regions of Western Canada, also reported marked species changes that were linked to warming (e.g. Rühland et al. 2003). A recent meta-analysis of 55 paleolimnological profiles from Arctic Canada, Lapland, Spitzbergen, and Russia, including 26 co-authors (Smol et al. 2005), concluded that areas of the Arctic expected to have warmed the most have changed the most in species composition; that ecological changes have occurred at several trophic levels; and that the ecological characteristics of species involved indicate that changes are driven primarily by climate warming. Two