T11 AM Aquatic Plants: Methods, Mechanisms and Markers
Tuesday, 15 November 2005: 8:00 AM - 11:40 AM in 343-344

(GAU-1117-828260) Are Duckweed and Algae Equivalent Indicators of Phytotoxicity?

Gausman, M¹, Belanger, S¹, Guckert, J¹, ¹ The Procter & Gamble Company, Cincinnati, OH, USA

ABSTRACT- An extensive amount of literature exists on the use of the floating macrophyte, duckweed (Lemna species) that, as with algae, can potentially give insight into the phytotoxicity of chemicals. However, information on toxicity of consumer product and other high volume chemicals to duckweed is lacking. Traditionally, algae, especially the chlorophytes Scenedesmus (=Desmodemsus) subspicatus and Selenastrum (=Pseudokirchneriella) capricornutum have been used in this application. The objectives of this research are to (1) compare sensitivity of the two test organisms, (2) explore advantages and disadvantages of using duckweed and algae in toxicity testing of chemicals, and (3) experimentally evaluate responses of both algae and duckweed to various surfactants. Literature was compiled for a broad comparison between duckweed species and green algae to understand similarities and differences with respect to toxicity responses, test conditions and experimental designs. An experimental program was also developed to assess the comparative sensitivity of duckweed and green algae. Duckweed and algal data were both available for over 40 different compounds in nearly 200 tests. The majority of chemicals were herbicides (10), metals (7), and pharmaceuticals (10). Only one surfactant comparison was available. For herbicides, duckweed and algae were similarly sensitive; for metals, algae were more sensitive than duckweed; and for pharmaceuticals, duckweed was less sensitive and algae sensitivity varied greatly (possibly reflecting a wider array of modes of toxic action). When algal and duckweed responses were regressed against each other for all compounds combined, algae were somewhat more sensitive (slope = 0.63, r-square = 0.5). For new experimental comparisons of algal and duckweed responses to surfactants it appears that algae are more sensitive to cationic surfactants, but duckweed is more sensitive to anionic surfactants. Results of the literature assessment will be reviewed in detail along with a comparison of the strengths and limitations of both assays.

Key words: duckweed, algae, phytotoxicity, surfactant