Vallisneria americana as a Biomonitor of Aquatic Ecosystems: Leaf-to-Root Surface Area Ratios and Organic Contamination in the Huron-Erie Corridor

Abstract

Aquatic macrophytes are useful biomonitors of sub-lethal effects of organochlorine contamination. Ramets of Vallisneria americana were sampled from natural populations at 243 sites in the Huron-Erie corridor in August 1993, and an index of leaf-to-root surface area ratios was determined. Sites were then ranked according to this index. Site rankings based on leaf-to-root surface area ratios were significantly correlated with the ranks of these sites using levels of organochlorine contamination of biota or sediment, reported independently in the published literature. The ratio of leaf-to-root surface areas ranged from 2 to 92, and higher values were found in more polluted sites. At four sites, plants were sampled monthly over one growing season, while at two sites plants were sampled each year for 4 years. The leaf-to-root surface area ratio changed little from year to year. At highly polluted sites there was a progressive increase in ratio over the growing season. Surveyed sites remained in the same relative ranking over the growing season, and a single survey within the same month could compare sites reliably. These results demonstrate that a very simple measure of ratios of leaf-to-root surface areas in Vallisneria may provide a rapid, sensitive, convenient and inexpensive metric of site quality from the perspective of macrophytes and organochlorine contamination. This could be used to prioritize sites for remedial action, and could confirm environmental improvement following remediation.