Grantee Research Project Results

Role of Oceanic Primary Production in Glacial-Interglacial Climate Change Based on an Analysis of a Sediment Core Collected From the Gulf of Alaska

EPA Grant Number: U915375
Title: Role of Oceanic Primary Production in Glacial-Interglacial Climate Change Based on an Analysis of a Sediment Core Collected From the Gulf of Alaska
Investigators: Westley, Marian B.
Institution: University of Hawaii at Manoa
EPA Project Officer: Lee, Sonja
Project Period: August 1, 1998 through August 1, 2000
Project Amount: $43,950
RFA: STAR Graduate Fellowships (1998) RFA Text |  Recipients Lists
Research Category: Fellowship - Oceanography , Fellowship - Aquatic Ecology and Ecosystems , Academic Fellowships

Objective:

The objective of this research project is to determine the role of oceanic primary production in glacial-interglacial climate change based on an analysis of a sediment core collected from the Gulf of Alaska (Pederson, et al., 1994).

Approach:

More than 50 times the amount of carbon dioxide in the atmosphere is dissolved in the oceans (Post, et al., 1990); thus, any process that affects carbon dioxide concentrations in surface ocean water is likely to affect the atmosphere. Phytoplankton take up dissolved carbon dioxide and fix it into organic carbon. As a result, if the phytoplankton sink out of the surface mixed layer, they transfer carbon dioxide from the surface water into deep water or sediments. This new production drives the so-called "biological pump." The hypothesis that the biological pump plays a role in regulating carbon dioxide levels in the atmosphere, and thus climate, would be supported by the finding that phytoplankton productivity was higher in periods of low atmospheric carbon dioxide. The carbon stable isotopic composition of phytoplankton has been shown to be a function of growth rate and the concentration of dissolved carbon dioxide (Laws, et al., 1995). Isotopic analysis of preserved phytoplankton organic matter, combined with a knowledge of the carbon isotopic composition of the inorganic carbon pool derived from the study of calcium carbonate shells, can provide information on the ancient levels of dissolved carbon dioxide in surface waters and the growth rates (or productivity) of phytoplankton. My research focuses on diatoms, the class of phytoplankton that is most likely responsible for the new production. Recently, workers have used the stable isotopic composition of organic matter enclosed within diatom frustules to infer paleoproductivity rates (Shemesh, et al., 1993; Singer and Shemesh, 1995; Sigman, et al., 1997). I will validate the use of frustule organic matter as a proxy for diatoms and calibrate the isotopic composition of this organic matter against growth rate and carbon dioxide concentration using diatoms grown in continuous culture under controlled conditions. I will use this information to analyze frustule organic matter in a sediment core from the Gulf of Alaska, studying the relationship between paleoproductivity and ancient levels of dissolved carbon dioxide.

Supplemental Keywords:

fellowship, carbon dioxide, ocean water, dissolved carbon dioxide, Gulf of Alaska, phytoplankton, organic matter, paleoproductivity., RFA, Scientific Discipline, Toxics, Air, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Ecology, Environmental Chemistry, Ecosystem/Assessment/Indicators, Ecosystem Protection, Chemistry, Oceanography, HAPS, climate change, Northwest, Ecological Effects - Environmental Exposure & Risk, Ecological Indicators, atmospheric carbon dioxide, phytoplankton productivity, environmental monitoring, oceanic primary production, sediment core, Gulf of Alaska, phytoplankton, carbon dioxide, phytoplankton production, glacial-interglacial climate change, ecosystem

Progress and Final Reports:

1999

Final