REDUCTION IN TOXICITY OF CHROMATED COPPER ARSENATE (CCA)-TREATED WOODAS ASSESSED BY COMMUNITY STUDY

Panels of chromated copper arsenate (CCA)-treated wood and control (un treated) wood were placed into an estuary and examined after one month for differences in settlement of organisms. The community on the CCA wood exhibited greatly reduced species richness, biomass, and diversit y. When the community on each panel (treated and untreated) was remove d and the boards replaced into the estuary, the epibiota settling duri ng the following month showed a smaller difference between the CCA pan els and the control wood. After removal of the community and immersion of the wood for a third month, there were no statistically significan t differences in the community that formed on the two materials. Howev er, qualitative differences were still visible, particularly in the gr owth of the alga Enteromorpha and the bryozoan Conopeum. Differences i n algal and bryozoan cover persisted after a year of submersion. The d ecreased toxicity of the CCA wood with repeated trials is probably rel ated to decreased rate of leaching, as observed earlier in laboratory experiments, and suggests that the treated wood would have reduced env ironmental impact if it were soaked out at the treatment facility befo re being marketed for use in the aquatic environment. Bioaccumulation of the metals in the epibiota on the CCA wood generally declined over time, but remained far above control levels.