How Lake Champlain Got Its Spots
Ann Arbor, MI — Lake Champlain was once solid blue. Today its summer coat is spotted with bright green patches. When did the lake change and why?
An international team of paleolimnologists led by University of Vermont professors Suzanne Levine and Andrea Lini recently answered this question for the lake’s northeastern arm, where the blotches are densest and largest. "Masses of buoyant cyanobacteria (blue green algae) form whenever there is enough nutrient for them to reproduce", says Levine. "For Lake Champlain, the sediment record tells us that human and animal wastes usually are the nutrient source."
Take St. Albans Bay. Cottages along its shoreline attest to its clarity in the past. "We found that water quality in this bay began to decline shortly after 1900, the year that sewage discharge from St. Albans began", says Levine. "The change was minor at first, but became explosive in the 1950s and ‘60s as suburban growth greatly upped sewage volume. Thereafter biomass increased explosively, reaching the high levels of today by 1970. Missisquoi Bay’s story is different. Having escaped major sewage influx, this bay began to deteriorate in the 1970s, responding to changes in agriculture that increased the manure load spread on farm fields. By 1990, algal patches were as or more abundant than in St. Albans Bay. Finally the Northeast Arm, which receives water from both polluted bays began gradual deteriorated in the 1960s, and now supports occasional blooms of limited dimensions. These blooms may become worse should bottom waters become anoxic. Phosphorus carried in from the bays over the past century has been stored at high concentrations in this region, and might move out of the sediments as a large flux should the minerals holding it in place dissolve.
An unexpected aspect of the paleolimnological findings was a lack of correspondence between historical periods of soil erosion, and algal productivity. "We interpret these trends as indicating that the phosphorus attached to river sediments is largely unavailable to algae", says Levine. "Thus we don’t consider river stabilization a major management goal if its purpose is reducing the phosphorus supply to algae."
This study relied on sediment records to learn the history of the lake. Cores from several regions were sliced, dated, and examined for fossils, algal pigments, nutrients, and other indicators of community composition and activity.
Original Publication Information
Results of this study, "The Eutrophication of Lake Champlain’s Northeast Arm: Insights from Paleolimnological Analyses," are reported by Suzanne N. Levine, Andrea Lini, Milton L. Ostrofsky, Lynda Bunting, Heather Burgess, Peter R. Leavitt, Daun Reuter, Andrea Lami, Piero Guilizzoni and Elizabeth Gilles in the special issue on Lake Champlain, of the Journal of Great Lakes Research, published by Elsevier, 2011.
Contacts
For more information about the study, contact Suzanne Levine, Rubenstein School of Environment and Natural Resources, University of Vermont, Burlington, Vermont; slevine@uvm.edu, (802) 656-2515.
For information about the Journal of Great Lakes Research, contact Marlene Evans, Editor, National Water Research Institute, Environment Canada, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada; jglr@ec.gc.ca; (306) 975-5310.
Since 1967, IAGLR has served as the focal point for compiling and disseminating multidisciplinary knowledge on North America's Laurentian Great Lakes and other large lakes of the world and their watersheds. In part, IAGLR communicates this knowledge through publication of the Journal of Great Lakes Research, available to members in print and electronic form. A searchable archive of the journal is available online and includes the abstracts of articles from the journal's inception in 1975 through the most recent issue. In addition, complete articles are available to members who have signed up for an electronic subscription.