Behavioral responses of veliger larvae of Crassostrea gigas to leachate from wood treated with copper-chrome-arsenic (CCA): a potential bioassay of sublethal environmental effects of contaminants

This study examined effects upon swimming behavior of larval oysters (Crassostrea gigas) caused by leachates from timber treated against marine borer attack using CCA (copper, chromium and arsenic bound to the lignocellulose of the wood cells). Early veliger stage larvae were observed to avoid a layer of concentrated leachate. No effect of more dilute leachate on swimming behavior of 2-day-old larvae was detected, but 3- and 7-day-old larvae swam two to three times faster in leachate than in plain seawater and moved up and down more in leachate. The concentrations of leachate used in these experiments considerably exceed likely environmental levels, but behavior could be used to assay improvements to the treatment process and to provide data for models of the impact of treated wood structures. The methodology offers a bioassay for assessment of sublethal effects of toxicants.