TP4 Toxicity of Complex Mixtures
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() Co-contamination of metals and phenanthrene elicit complex non-additive interactions in the meiobenthic copepod, Schizopera knabeni.

Marlborough, S.1, Fleeger, J.1, Gust, K.1, 1 Louisiana State University, Baton Rouge, LA, USA

ABSTRACT- Interactions between phenanthrene, a poly-nuclear aromatic hydrocarbon (PAH) and a mixture of lead, cadmium and mercury in the meiobenthic, harpacticoid copepod Schizopera knabeni were investigated in laboratory bioassay experiments. Adult female copepods were exposed to sediment-associated phenanthrene, a mixture of metals (Pb, Cd and Hg in a 5:3:2 ratio) and combinations of each in separate 4-day LC50 lethality tests. Interactions (non-additive synergisms and antagonisms) between phenanthrene and metals were examined using the Toxic Unit methodology. Combined metal mixture and phenanthrene exposures demonstrated strongly synergistic lethality; metals in combination with phenanthrene were more toxic than either was alone. The 4-d LC50 values for phenanthrene only, Cd only, metals combination only, phenanthrene and metals combination, and phenanthrene and Cd were 342 ppm, 389 ppm, 1392 ppm, 610 ppm (Toxic Unit 0.65), and 162 ppm (Toxic Unit 0.42), respectively. The Toxic Unit assays indicates a greater than additive effect. The greater synergistic response of phenanthrene and Cd compared to that of phenanthrene and the metal mixture, suggests Pb and Hg are antagonistic to the effects of Cd. Previous studies have found non-additive interactions between metals and PAH, however our works shows that interactions may be further modified with increasing contaminant diversity.

Key words: metals, conatminated sediment, pah, synergism

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