title: Diel changes in trace metal concentration and distribution in coastal waters: Catalina Island as a study case.
abstract: Understanding biogeochemical cycling of trace metals in the ocean requires information about variability in metal concentrations and distribution over short, e.g., diel, time scales. Such variability and the factors that influence it are poorly characterized. To address this shortcoming, we measured trace metal concentrations in the total dissolved, colloidal, and soluble fractions every 3-4 h for several consecutive days and nights in surface waters from a coastal station. Our results show that both the concentration and the size partitioning of some biologically essential (Fe, Cu, Co, and Cd) and anthropogenic (Pb) metals are subjected to diel variations that may be related to both inorganic and biological processes (e.g., photolysis of high-molecular-weight dissolved organic matter, photoinduced reduction/oxidation of metal(hydrous)oxides, uptake by growing phytoplankton, degradation of organic matter, lysis, and grazing). The largest fluctuations were observed in the soluble and colloidal pools. Soluble Fe varied during the day-night cycle by a factor of 40, and the contribution of colloidal Pb to the total dissolved fraction increased from 6±3% during the day to as much as 70-80% during the night. Our results suggest that changes occurring over time scales of hours need to be considered when collecting and interpreting trace metal data from the surface ocean.
authors: Department of Earth Sciences and §Department of Biological Sciences and Department of Earth Sciences, University of Southern California , Los Angeles, California 90089-0740, United States.
authors: Paulina
authors: P
authors: Pinedo-Gonzalez
authors: A Joshua
authors: AJ
authors: West
authors: Ignacio
authors: I
authors: Rivera-Duarte
authors: Sergio A
authors: SA
authors: Sañudo-Wilhelmy
mesh_terms: D002140:California; D005591:Chemical Fractionation; D003102:Colloids; D017753:Ecosystem; D005843:Geography; D062312:Islands; D008027:Light; D008670:Metals / Q000032:analysis*; D010839:Phytoplankton / Q000378:metabolism; D012623:Seawater / Q000737:chemistry*; D012995:Solubility; D013499:Surface Properties; D013696:Temperature
chemical_list: D003102:Colloids; D008670:Metals