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A SEDIMENT TOXICITY METHOD USING LEMNA MINOR, DUCKWEED
Citation:
Lazorchak, J M., E. M. SuszcynskyMeister, AND M E. Smith. A SEDIMENT TOXICITY METHOD USING LEMNA MINOR, DUCKWEED. Presented at Society of Environmental Toxicology and Chemistry, Nashville, TN, November 12-16, 2000.
Impact/Purpose:
The current goals of this task's research are to (1) develop miniaturized sediment exposure methods using selected marine and freshwater fish and amphipods that can be used for screening contaminants in sediments from surface waters and remediation studies and (2) to modify present sediment toxicity methods to include molecular methods for the detection of sublethal changes associated with exposure to contaminants.
Description:
We developed a Lemna minor sediment toxicity test method to assess sediment contaminants which may affect plants. This 96-hour test used 15 ml of sediment and 2 ml of overlying water which was renewed after 48 hours. Sand was used as the control sediment and also to dilute test sediments. This method was evaluated with sediments from the East River (ERS), NY; the NY/NJ harbor, the Calumet River, IL; and the Little Miami River, OH. In addition to the duckweek method, sediments were also tested using a miniaturized freshwater amphipod method and a fathead minnow embryo-larval (FHM) survival test. Of the three endpoints used in duckweed tests, results indicated that chlorophyll a was a more sensitive measure than either frond number or wet weight. ERS and NY/NJ sediments were toxic to H. azteca and FHM and inhibited L. minor growth. Tests were conducted using diluted NY/NJ harbor sediments, which were known to be uncontaminated by PAHs. Varying the overlying water volumes did not affect plant response to the control or test sediments. Nutrient enrichment of 1% NY/NJ sediment resulted in significantly higher levels of chlorophyll a as compared to unenriched sediments. Chlorophyll a measurements were as sensitive as survival of H. azteca to the Calumet sediments and more sensitive than the FHM survival. Sediments tested from the Little Miami River, which were shown to be inhibitory to H. azteca growth in earlier sediment tests, affected frond number and chlorophyll a content when tested with L. minor. A sediment reference toxicant method has been developed for KCl and Atrazine. The duckweed method is convenient to use and provides an additional sediment toxicity indicator.