Tortell, P. Princeton University, ptortell@phoenix.princeton.edu
Rau, G. Institute of Marine Sciences, UC Santa Cruz, rau4@llnl.gov
Morel, F. Princeton University,

 
INORGANIC CARBON METABOLISM AND 13C/12C FRACTIONATION BY PHYTOPLANKTON IN COASTAL AND OCEANIC PACIFIC WATERS
 
Laboratory and field studies indicate that a variety of marine phytoplankton possess inorganic carbon concentrating mechanisms which alleviate potential CO2 limitation through active transport of HCO3- and/or CO2. We have previously shown that zinc is involved in HCO3- utilization in diatoms as a cofactor in the enzyme carbonic anhydrase (CA) and have examined the interaction between CO2 and zinc availability on the growth of these organisms in culture. Here we document the growth responses of coastal and oceanic phytoplankton to natural gradients and experimental manipulations of CO2 and trace metals and examine the effects of carbon concentrating mechanisms on 13C/12C fractionation. Diatom dominated phytoplankton assemblages from the California upwelling regime showed no growth responses to artificial doubling or three-fold reduction of CO2 in incubation bottles. However, the growth of the fastest growing assemblage (u=2.1 /d) was significantly inhibited at the lowest CO2 treatments. In the offshore Northeast Pacific, slow growing phytoplankton were unaffected by CO2 manipulations regardless of trace-metal enrichments to incubation bottles. Despite the lack of growth rate responses, CO2 manipulations appeared to have a strong influence on inorganic carbon acquisition. Bicarbonate uptake and CA synthesis are enhanced at low CO2 and repressed at high CO2. We are currently analyzing organic carbon isotope signatures and relative activities of CA, Rubisco, and PEP-Carboxylase in both incubation experiments and in situ samples
 
Day: Monday, Feb. 1
Time: 04:30 - 04:45pm
Location: Eldorado Hotel
 
Code: SS32MO0430E