1. Institut des Sciences de la Mer de Rimouski, Université du Québec à Rimouski, Québec, Canada G5L 3A1, Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, Department of Marine Sciences, University of Georgia, Athens, Georgia 30602, and Ecosystems Research Division, National Exposure Research Laboratory, The United States Environmental Protection Agency, Athens, Georgia 30605