VALLISNERIA AMERICANA AS A BIOMONITOR OF AQUATIC ECOSYSTEMS - LEAF-TO-ROOT SURFACE-AREA RATIOS AND ORGANIC CONTAMINATION IN THE HURON-ERIE CORRIDOR

Aquatic macrophytes are useful biomonitors of sub-lethal effects of or ganochlorine contamination. Ramets of Vallisneria americana were sampl ed 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 det ermined Sites were then ranked according to this index. Site rankings based on leaf-to-root surface area ratios were significantly correlate d with the ranks of these sires using levels of organochlorine contami nation of biota or sediment, reported independently in the published l iterature. The ratio of leaf-to-root surface areas ranged from 2 to 92 , and higher values were found in more polluted sites. At four sires, plants were sampled monthly over one growing season, while at two site s 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. Sur veyed sites remained in the same relative ranking over the growing sea son, and a single survey within the same month could compare sites rel iably. These results demonstrate that a very simple measure of ratios of leaf-to-root surface areas in Vallisneria may provide a rapid, sens itive, convenient and inexpensive metric of site quality from the pers pective of macrophytes and organochlorine contamination. This could be used to prioritize sites for remedial action, and could confirm envir onmental improvement following remediation.