| Popis: |
This paper assesses the value of American wildcelery, Vallisneria americana, as a biomonitor of organochlorine contamination. Plants provide a valuable indicator of local environmental conditions and sub-lethal effects of contaminants on growth and reproduction provide a means of assessing both acute and chronic contaminant effects. In a field survey, Vallisneria plants in the St. Clair and Detroit rivers were found to accumulate significant amounts of organochlorine contaminants, and the concentration increased over the season. Root tissue contained the highest concentrations on each occasion, suggesting contaminant transfer occurred from sediments to the roots. A factorial experiment was set up at two stations in the channel connecting Lakes Huron and Erie to assess the separate effects of contaminant concentrations in the sediment, water column, and source population of the plants, upon growth and reproduction of Vallisneria plants. Contaminant concentrations in sediment and plant tissues were also measured to correlate contaminant content and demographic effects. A clear relationship between exposure to contaminants and effect (on plant performance) was observed. Results indicated that exposure first to the water column, and secondarily to the sediments from the more contaminated site had detrimental effects on plant performance and survival. Plants at each site appeared to be locally adapted and differed in their apparent resistance to organochlorine contaminants. An “impairment index” (reflecting relative plant performance) was calculated and can be used to calibrate the degree of contamination of different sites relative to a “clean” reference site. This may allow prioritization of remediation of contaminated sites, and should allow field managers to track and document the restoration of environmental quality in recognized Areas of Concern in the Great Lakes. |
