Toxicity of Chromated Copper Arsenate (CCA)-Treated Wood to Non-Target Marine Fouling Communities in Langstone Harbour, Portsmouth, UK

The effect of the anti-marine-borer timber preservative chromated copper arsenate (CCA) (a pressure impregnated solution of copper, chromium and arsenic compounds) on non-target marine fouling animals was investigated during a subtidal exposure trial. Panels of Scots pine treated to target retentions of 12, 24 and 48 kg CCA per m−3 of wood, plus untreated controls were submerged at a coastal site on the south coast of the UK for 6, 12 and 18 months. After each exposure period the fouling communities that formed on the surface of panels were assessed both qualitatively and quantitatively. Community structure was similar on panels treated to the three CCA loadings, but was significantly different from community structure on untreated panels. The total number of species (species richness) was similar on all panels, although the number of individual organisms attached to the surface of panels was significantly higher on CCA-treated panels than on untreated panels. k-dominance curves revealed that the difference in numbers of individuals between CCA-treated and untreated panels was caused by higher numbers of the dominant species (Elminius modestus, Hydroides ezoensis, and Electra pilosa) on CCA-treated panels. Other species were present in similar numbers on panels of all treatments. Results indicate that there are no detrimental toxic effects to epibiota caused by the presence of CCA preservative within the matrix of the wood at any of the treatment levels. Differences in community structure between CCA-treated and untreated panels may be due to enhanced larval settlement on CCA-treated timber by some species as a result of modifications to the surface properties of the timber by the CCA preservative.