Partitioning of Cu in estuarine waters, II. Control of partitioning by the biota

In two sets of suspensions containing biotic particles, organisms indirectly controlled the partitioning of added Cu between the dissolved and particulate phases by releasing dissolved organic ligands. Organisms present at total suspended matter concentrations as low as 10 mg/l released enough organic compounds during 1 day to negate the initial removal of the hydrophobic dissolved organic matter by Sep-Pak columns. In these experiments, the coating of particulate inorganic surfaces with organic matter may have also prevented Cu from establishing a chemical equilibrium between these particulate surfaces and the solution. The behavior of added radioactive Cu is consistent with an equilibrium model if the transfer of organic matter between dissolved and particulate phases by organisms is considered. In contrast, the behavior of natural Cu in these biotic suspension indicate that the partitioning of Cu was controlled as much by active biological processes as by chemical equilibria.