Date of Award


Publication Type

Doctoral Thesis

Degree Name



Biological Sciences


Biology, Ecology.


Doust, J. L.




Macrophytes form the base of the food web in aquatic ecosystems, and are consumed as fresh biomass or as detritus. They also provide oxygen, mineral nutrients, substrate, habitat, and breeding and nursery areas for numerous biota. In North America, one of the most common and ecologically significant submersed macrophytes is Vallisneria americana Michx. Vallisneria was studied in two, interrelated ways. In the field of population ecology, the objective of several experiments was to identify factors affecting the performance of this plant in situations involving organic contamination. In the area of applied ecology, the objective was to assess the potential of V. americana as a biomonitor of environmental quality using parameters of population biology to measure performance. In a number of laboratory and field experiments, I observed the growth and development of Vallisneria americana in terms of ramet density, rate of clonal growth, number of leaves and turions per ramet, rate of flowering, biomass per ramet, biomass allocation patterns, and surface areas of leaf and root. Plant performance was significantly affected by duration of exposure to contaminants, by seasonal differences and differences between years, sediment type and quality, water column characteristics, water temperature, light levels, and organic contaminant concentrations in the sediment pore-water and water column. The magnitude of plants responses may be modified by their genotype and the history of their earlier exposure to contaminants. Some Vallisneria clones proved to be tolerant to high levels of contamination by the organic solvent trichloroethylene (TCE). Plants exposed in the greenhouse to TCE accumulated it within their tissues, and particularly high concentrations were found in root tissue. In the field study, the concentration of organochlorine contaminants (PCBs) increased with time of exposure over the growing season. A significant correlation was observed in the laboratory experiments, and also in the field studies, between contaminant concentration and plant performance. Thus, Vallisneria americana may be an effective monitor of environmental quality. In a long-term field study, the relative ranking of site quality did not change over four years of exposure to local environmental factors. The most useful measure of environmental quality was the ratio of leaf-to-root surface area. The ratio had greater values at sites more contaminated by organochlorine compounds and lower values at relatively less contaminated sites. The leaf-to-root surface area ratio appears to be independent of plant genotype and of differences in meteorological characteristics. Performance of V. americana was significantly affected by and correlated with contaminant concentrations, and this suggests great potential as a biomonitor. The leaf-to-root surface area ratio may be particularly useful for objective biomonitoring of both short-term and long-term changes in environmental quality at highly contaminated areas.Dept. of Biological Sciences. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1996 .B53. Source: Dissertation Abstracts International, Volume: 59-08, Section: B, page: 3841. Adviser: J. Lovett Doust. Thesis (Ph.D.)--University of Windsor (Canada), 1996.