Microbial communities in the Arabian Sea: Composition,
size spectra and growth rates from individual cell properties
Robert J. Olson
Biology Department
Woods Hole Oceanographic Institution
508 457-2000 x2565
A central mission of the JGOFS project in the Arabian Sea is to determine
how efficiently the carbon pump operates in this region, and how it responds
to changes in physical forcing. To approach these problems we need
to analyze the structure of the food web and determine how it varies with
geographical and temporal gradients in nutrient supply and water column
mixing. The juxtaposition of productive and oligotrophic oceanic
systems in the Arabian Sea, and the regular oscillation between very high
and low rates of nutrient supply under relatively constant conditions of
solar illumination, offers opportunities for us to gain insights into food
web regulation processes.
Specifically, we propose to: (1) Characterize the distribution,
abundance, and light scatter properties of the picoplankton and nanoplankton
at the four intensive stations and at selected intermediate stations, flow
cytometry, and (2) Estimate in situ growth rates of specific groups of
phytoplankton, and grazing pressure on these groups, from diel patterns
in cell number, light scatter properties and DNA content of individual
cells from depth profiles. This information will help to interpret
diel patterns in beam attenuation, a JGOFS core measurement.