Rau, G. H.. IMS, University of California, Santa Cruz, rau4@llnl.gov
Chavez, F. H.. MBARI,
Friederich, G. E.. MBARI,

 
CARBON SUPPLY/DEMAND VERSUS 13C FRACTIONATION BY PHYTOPLANKTON: A STUDY IN MONTEREY BAY, CA
 
Two relationships between biological 13C fractionation (Ep) and [CO2aq] were evident in Monterey Bay, CA over a four year period. One showed high Ep sensitivity to [CO2aq] similar to that frequently seen elsewhere, and anticipated when phytoplankton exclusively use CO2aq which is diffusively transported into their cells. A second trend occurred seasonally when large diatoms dominated the plankton community, with Ep consistently low and relatively insensitive to [CO2aq] even in high-[CO2aq] waters. Also counter to predictions based on diffusive CO2 transport, very weak to non-existent correlations were found between Ep and: i) mean growth rate (+/- day length adjustment), ii) mean cell size, iii) carbon demand (growth rate x mean cell volume), iv) areal primary production, or v) [CO2aq]-normalized functions of these parameters. Such Ep decoupling from both carbon supply and demand may be consistent with a recent report of active (non-diffusive) inorganic carbon transport in central California coast diatom communities (Tortell et al. Nature 390: 243-). If the preceding isotopic behavior can be interpreted in the context of active C transport, this energetically costly process appears to occur even in high-[CO2aq], low-growth-rate waters in Monterey Bay. Comparisons to other recent field, culture, and modeling studies will be made.
 
Day: Monday, Feb. 1
Time: 04:15 - 04:30pm
Location: Eldorado Hotel
 
Code: SS32MO0415E