Aquatic Sciences Meeting, Albuquerque 2001

CS41 Phytoplankton: Nutrient Dynamics and Physiology

Date: Friday, February 16, 2001, Time: 8:45:00 AM

Location: Galisteo

Worden, A, Z, Scripps Institution of Oceanography, La Jolla, USA, aworden@ucsd.edu

Binder, B, J, University of Georgia, Athens, USA, bbinder@arches.uga.edu

DYNAMICS OF PROCHLOROCOCCUS AND SYNECHOCOCCUS GROWTH AND GRAZING MORTALITY RATES IN THE SARGASSO SEA AND CALIFORNIA CURRENT.

Although a considerable amount is known about the spatial and temporal distribution of Prochlorococcus and Synechococcus, much less is known about the factors regulating this distribution. To address this issue, growth and grazing mortality rates among picocyanobacterial populations in the Sargasso Sea and California Current were assessed using dilution experiments combined with cell cycle and diel abundance analysis. Growth rates varied from 0.46 to 1 day-1 and 0.42 to 0.75 day-1 for Prochlorococcus and Synechococcus, respectively. Stations with the lowest Prochlorococcus abundance generally had the highest growth and grazing mortality rates. This indicates that the abundance of Prochlorococcus does not necessarily reflect its growth rate nor the contribution of Prochlorococcus to overall productivity. Grazing mortality rates generally balanced growth rates among picocyanobacterial populations. Mortality varied over the day, generally being heaviest during or just after cell division. In some experiments mortality rates determined via the traditional series of nutrient-amended dilution bottles were drastically different from those derived from a non-amended series. These data provoke consideration of prey-selectivity and the influence of food quality on grazing activity.

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Aquatic Sciences Meeting, Albuquerque 2001

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