Identifying Marine Copper-Binding Ligands in Seawater
Hannah Whitby, University of Liverpool, School of Environmental Sciences, Liverpool, United Kingdom, James T Hollibaugh, University of Georgia, Department of Marine Sciences, Athens, GA, United States, Maria Teresa Maldonado, University of British Columbia, Department of Earth, Ocean and Atmospheric Sciences, Vancouver, BC, Canada, Sachiko Ouchi, University of British Columbia, Vancouver, BC, Canada and Stan MG van den Berg, University of Liverpool, Liverpool, L69, United Kingdom
Abstract:
Complexation reactions are important because they affect the bioavailability of trace metals such as copper and iron. For example, organic complexation can determine whether copper is a limiting or a toxic micronutrient at natural levels. Copper competes with iron for complexing ligands, and when iron is limiting, copper can also substitute for iron in some metabolic pathways. The speciation of copper can be measured using complexing capacity titrations, which provide the concentration of individual ligand classes (L1, L2 etc.) and the complex stabilities (log K).
Using methods recently developed in our laboratory, we show that the ligands within these classes can be measured independently of titrations, thus confirming the titration method and simultaneously identifying the ligands within each class. Thiols were identified as the L1 ligand class and humic compounds as the weaker L2 class in samples from coastal Georgia, USA, collected monthly from April to December. Log K values of the ligand complexes were consistent with values expected for thiols and humic substances.
Recent results from culture studies and from samples collected along Line P, a coastal – oceanic transect in the HNLC region of the NE subarctic Pacific, will be presented in comparison to the estuarine results. This comparison will help to broaden our perspective on copper complexation and the ligands responsible, furthering our understanding of ligand sources and life cycles.
