The Effect of Sea Surface Microlayer Enrichment on TBT Transport

To assess the biological significance of the release of TBT containing substances the pathways as well as potential concentrating mechanisms must be understood. The sea surface microlayer provides such a pathway and may allow for significant enrichment. TBT compounds are surface active and hence remain surface adsorbed by lowering the Gibb\´s Free Energy. Because TBT also "dissolves" in lipids, petroleum hycrocarbons, and non-polar moieties of proteins and their breakdown products, the surface active nature of many of these compounds serves as an additional enriching mechanism. Conventional surface sampling methods yield enrichment over bulk water concentrations of 2 to 3 orders of magnitude, which reflect much higher surface concentrations. While direct contact by floating fish eggs and ichthyoplankton may be one method of transfer into the food web, the creation of whitecaps and the downwelling of bubble swarms not only may allow redistribution of TBT, but bubble collapse by rectified diffusion, and film collapse by surface stresses converts TBT enriched microlayer organic matter into particulate phases that inturn are able to enter the food web via detrital feeders.