The Extent of Benthic Impacts of CCA-Treated Wood Structures in Atlantic Coast Estuaries

To ascertain the extent of impacts from CCA-treated wood bulkheads, we sampled sediments along 10-m transects from these bulkheads and from reference sites (either bulkheads made of other materials or unbulkheaded areas nearby) and analyzed the fine fraction for metals. We ascertained metal content in resident biota, and analyzed species richness, Shannon-Wiener diversity index, and biomass of the benthic community. We found accumulation of metals in the fine-grained portion of nearby sediments and reduction in the biotic community nearby (generally at 0 and 1 m); such gradients were generally not seen in reference transects. At two of the sites there was evidence for secondary reduction of the community out further to 3 or 10 m, where the metals in the fines were lower but the percent fines was greatly increased. At all the other sites, impacts were generally limited to 0 and 1 m. The lack of reduction at further distances at the other sites is attributed to factors such as the age of the bulkheads, high energy of the environment, or nature of the sediments at those sites.