The detection and biogeochemistry of trace metals in natural waters.

摘要

Trace metal biogeochemistry can have profound impacts on phytoplankton communities as limiting nutrients, potential toxins, and dictators of phytoplankton community structure. Overall, phytoplankton in upwards of 40% of the world's ocean are limited in some way by low availabilities of trace metals, and this limitation is thought to impact global carbon cycling and climate change over glacial time scales. Therefore, it is important that oceanographers better quantify the parameters surrounding trace metal sources, sinks, and chemical factors tied to bioavailability. This can only be done by developing novel analytical methods that streamline trace metal analysis and probe the chemical speciation of trace metals in natural waters.Part this thesis has focused on streamlining and optimizing analytical methods for Fe. Two methods have been developed and optimized so that Fe measurements can be made in nearly all regions of the ocean without sample preconcentration. The first technique built on and optimized a commonly used chemiluminescent technique, while the second method harnesses novel nanotechnology to make Fe measurements using a siderophore modified surface.A second portion of this work is centered around Fe(II) redox dynamics, which likely has major impacts on Fe bioavailability to marine phytoplankton. In short, we found that Fe(II) half-lives can vary widely depending on the region of the ocean, and we believe that the difference in oxidation rates are likely due to differences in natural Fe complexing organic ligands.The remainder of this thesis focuses on trace metal sources and distributions. We find that eddies are responsible for transporting Fe rich waters to the Gulf of Alaska. We estimate that these eddies transport as much Fe to the Gulf of Alaska as atmospheric dust to the region. Further down the western coast of North America, we report dissolved Fe and Cu concentrations in the Washington coast area, an area whose fisheries are frequently decimated by toxic phytoplankton blooms. Finally, we report metal distributions in Lake Bonney, a permanently ice covered lake in East Antarctica. We hypothesize that exceedingly high Ag or Zn levels are causing a collapse in the nitrogen cycle in one lobe of this lake.