Hugh Ducklow, F. Azam, and D. Kirchman; VIMS, SIO, and CMS-DEL

"Bacterial Production Uncoupled from Primary Production: Implication for DOM Fluxes in the Southern Ocean, (JGOFS)"

The joint project of Azam (SIO), Ducklow (VIMS) and Kirchman (CMSDEL) seeks to document and explain in terms of dissolved and particulate organic matter utilization and various mortality terms, the time and space-dependent variations of bacterial biomass and productivity in the U.S. JGOFS SOPS study areas. In doing so, we will contribute core measurements of bacterial abundance, biovolume (biomass) and thymidine/leucine incorporation (production) to the JGOFS database. In our proposal, we hypothesized that bacterial biomass and productivity, would be lower and less temporally variable, relative to phytoplankton, in the PFZ than the Ross Sea, due to differing dynamics of the phytoplankton bacterial coupling as modulated by seasonal cycles of primary production, phytomass and DOM accumulation. Our recent work in the Ross Sea will cause some revision of that hypothesis (there doesn't seem to be much DOM accumulation), but it remains a useful guide for our work.

We propose a comprehensive program of core measurements and directed experiments spanning all seasons and study regions of the program. We hope to participate in Ross Sea Process Studies I, IV and APFZ studies I and II. We will sample the following on each cruise:

Measurement	Method	Depths (* = core meas)
Bacterial abundance	Microscopy	entire water column *
Bacterial biovolume	Image analysis	" *
Bacterial production	3H thymidine incorp	" *
Bacterial production	3H leucine incorp	" *
Amino acid	concentr HPLC	upper 200 m
Monosacc.	conc HPLC	"
DOM utilization	3Hsubstrate uptake	"
DOM utilization	DOC decrease	selected depths
growth dynamics	seawater cultures	"
respiring bacteria	microscopy	"	and expts