Assessing the components of turbidity in a shallow, eutrophic pond

J. Lyon and S.M. Ackroyd. Department of Biology, Merrimack College, North Andover, MA 01845

Water clarity is a primary regulator of biological and ecological functions in aquatic systems. There are several components that can contribute to turbidity in freshwater systems including algae, suspended and re-suspended sediments and dissolved organic compounds. We have been studying the components of turbidity in Martins Pond, a shallow, eutrophic pond in Massachusetts, using a modified model from Scheffer et al. 1993. Martins Pond is located in the North Eastern Coastal Zone Ecoregion in New England and is listed as an impaired water body under section 303(d) of the Clean Water Act due, in part, to high turbidity. The euphotic depth in the pond is approximately 1.2 m. We have been assessing the contribution of algae (chlorophyll-a), suspended solids and tannins to turbidity both seasonally (2002-2003) and spatially. Although tannin levels fluctuate seasonally, with lows in late summer, they are a strong contributor to turbidity in the pond. There is a relatively constant background level of total suspended solids. Algal biomass exhibited temporal peaks in spring and summer. We have also been studying the influence of P, N and Cl on temporal and spatial patterns of turbidity. These results are guiding management strategies aimed to reduce turbidity in the pond.