Master of Science (M.S.)
Moss Landing Marine Laboratories
This thesis consists of two papers that examine the sedimentation history of the continental shelf of the Central California coast. The first paper is the outcome of a collaborative project between the U.S. Geological Survey and Moss Landing Marine Laboratories. It examines the implications of sediment accumulation rates that are based on profiles of Â²Â¹â°Pb and other short-lived radioisotopes that were measured in sediment cores. This first paper documents the rate of sediment accumulation on a 100-year time scale on the continental shelf, between Pacifica and Monterey. The second paper examines 150cm-long sediment core for evidence of changes in primary productivity in Monterey Bay. Findings from the first paper were used to choose the site of the core that is examined in the second paper. This core comes from a flat part of the shelf in the center of Monterey Bay, at a location where sedimentation is thought to be sufficiently rapid to preserve diatoms and photosynthetic pigments before they are destroyed diagenetically. In the second paper, the abundance of certain diatoms are examined along with supporting data in order to determine if diatom productivity in Monterey Bay has changed significantly over the last 170 years. The abundance of key diatoms such as Chaetoceros sp and Thalassionema nitzschioieds varies significantly with depth. Sedimentary concentrations of Phaeophorbide-a, a decay product of cholorophyll-a, vary significantly with depth in the core. Profiles of phaeophorbide-a and total diatom abundance are similar in shape. Profiles organic carbon and sediment texture show only minor variations. The Pb-210 profile of this core indicates an anomalous sedimentation history. Subsequently, the age control for this core is uncertain.
Lewis, Roger C., "Sediment accumulation and sedimentary diatom abundance on the continental shelf of central California" (2003). Capstone Projects and Theses. 93.