title: PHOSPHATE-LIMITED GROWTH OF PAVLOVA LUTHERI (PRYMNESIOPHYCEAE) IN CONTINUOUS CULTURE: DETERMINATION OF GROWTH-RATE-LIMITING SUBSTRATE CONCENTRATIONS WITH A SENSITIVE BIOASSAY PROCEDURE(1).
abstract: The relationship between steady-state growth rate and phosphate concentration was studied for the marine prymnesiophyte Pavlova lutheri (Droop) J. C. Green grown in a chemostat at 22°C under continuous irradiance. A bioassay procedure involving short-term uptake of 10 picomolar spikes of (33) P-labeled phosphate was used to estimate the concentration of phosphate in the growth chamber. The relationship between growth rate and phosphate was well described by a simple rectangular hyperbola with a half-saturation constant of 2.6 nM. The cells were able to take up micromolar spikes of phosphate at rates two to three orders of magnitude higher than steady-state uptake rates. The kinetics of short-term uptake displayed Holling type III behavior, suggesting that P. lutheri may have multiple uptake systems with different half-saturation constants. Chl a:C ratios were linearly related to growth rate and similar to values previously reported for P. lutheri under nitrate-limited conditions. C:N ratios, also linearly related to growth rate, were consistently lower than values reported for P. lutheri under nitrate-limited conditions, a result presumably reflecting luxury assimilation of nitrogen under phosphate-limited conditions. C:P ratios were linearly related to growth rate in a manner consistent with the Droop equation for growth rate versus cellular P:C ratio.
authors.affiliation: Department of Environmental Sciences, School of the Coast & Environment, Louisiana State University, Baton Rouge, Louisiana 70803, USADepartment of Oceanography, School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, Hawaii 96822, USABeaufort Laboratory, National Ocean Service, National Oceanic and Atmospheric Administration 101 Pivers Island Road, Beaufort, North Carolina 28516, USA.
authors.forename: Edward A
authors.initials: EA
authors.lastname: Laws
authors.affiliation: Department of Environmental Sciences, School of the Coast & Environment, Louisiana State University, Baton Rouge, Louisiana 70803, USADepartment of Oceanography, School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, Hawaii 96822, USABeaufort Laboratory, National Ocean Service, National Oceanic and Atmospheric Administration 101 Pivers Island Road, Beaufort, North Carolina 28516, USA.
authors.forename: Shaofeng
authors.initials: S
authors.lastname: Pei
authors.affiliation: Department of Environmental Sciences, School of the Coast & Environment, Louisiana State University, Baton Rouge, Louisiana 70803, USADepartment of Oceanography, School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, Hawaii 96822, USABeaufort Laboratory, National Ocean Service, National Oceanic and Atmospheric Administration 101 Pivers Island Road, Beaufort, North Carolina 28516, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Bienfang
authors.affiliation: Department of Environmental Sciences, School of the Coast & Environment, Louisiana State University, Baton Rouge, Louisiana 70803, USADepartment of Oceanography, School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, Hawaii 96822, USABeaufort Laboratory, National Ocean Service, National Oceanic and Atmospheric Administration 101 Pivers Island Road, Beaufort, North Carolina 28516, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: Grant
authors.affiliation: Department of Environmental Sciences, School of the Coast & Environment, Louisiana State University, Baton Rouge, Louisiana 70803, USADepartment of Oceanography, School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, Hawaii 96822, USABeaufort Laboratory, National Ocean Service, National Oceanic and Atmospheric Administration 101 Pivers Island Road, Beaufort, North Carolina 28516, USA.
authors.forename: William G
authors.initials: WG
authors.lastname: Sunda
keywords: Michaelis-Menten; Monod; Pavlova lutheri; continuous culture; phosphate limitation