Last Updated:
February 28, 2007

GCRIO Program Overview

Library 
Our extensive collection of documents.

Privacy Policy

Archives of the
Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999

FROM VOLUME 12, NUMBER 2, FEBRUARY 1999

JOURNAL ARTICLES...
OCEANIC PHYTOPLANKTON

Item #d99feb18

“Phytoplankton Community Structure and the Drawdown of Nutrients and CO₂ in the Southern Ocean,” K. R. Arrigo et al., Science 283, 365-367 (Jan. 15, 1999).

Phytoplankton communities in the Ross Sea were found to display preferences in the degree of mixing in the water in which they lived. Diatoms prefer highly stratified waters, whereas Phaeocystis antarctica assemblages preferred deeply mixed waters. The use of CO₂ and nutrients and the rate of new production by diatoms are much lower than by Phaeocystis. Thus, if upper-ocean stratification of the Ross Sea should occur because of climate warming, transport of carbon to the deep ocean could be dramatically curtailed.

“Widespread Iron Limitation of Phytoplankton in the South Pacific Ocean,” M. J. Behrenfeld and Z. S. Kolber, Science 283, 840-843 (Feb. 5, 1999).

Physiological diagnostics were sought for limiting factors on primary productivity in the oceans that can be used to readily survey vast areas. Samples were taken during transects of the South Pacific and the Atlantic oceans. The fluorescence rates, photochemical quantum efficiencies, and functional absorption cross-sections of photosystem II of these samples were measured. A diurnal cycle in photochemical quantum efficiencies was noticed with a rapid decrease at sunset and an increase at sunrise; the functional absorption cross-sections followed a similar course. During each cycle, the fluorescence rates fluctuated widely, indicating that quenching processes were reacting to irradiance saturation. When iron was added to the samples, the decreases in photochemical quantum efficiencies and functional absorption cross-sections disappeared. Tests on the samples gathered indicate that iron deficiency limits primary productivity in much of the South Pacific gyre.