Church, M. J. School of Marine Science/College of William and Mary, mattc@vims.edu
Ducklow, H. J. School of Marine Science/College of William and Mary, duck@vims.edu
Hutchins, D. A. College of Marine Studies/University of Delaware, dahutch@udel.edu

 
INVESTIGATION INTO BOTTOM-UP LIMITATION OF BACTERIAL GROWTH IN THE SOUTHERN OCEAN
 
The relative importance of bottom-up controls (organic, inorganic, and trace nutrients) limiting bacterial growth in the subantarctic Southern Ocean were determined experimentally. Experiments were conducted aboard the r/v Aurora Australis throughout March-April 1998. Incubations were set up along a 141 E transect line between 42 S and 55 S. Whole seawater cultures were inoculated with various additions including (separately and in combination): glucose, amino acids, iron, ammonium and phosphate. Inoculated cultures were sampled daily for bacterial production and biomass. Changes in bacterial production, biovolume, and cell number over time were used to estimate bacterial growth rates. Experimental results varied across latitudinal boundaries, but in general, bacterial growth rates increased by the addition of labile organic substrates (amino acids and glucose). Growth rates increased most dramatically by the addition of energy rich organic substrates (amino acids and in one experiment the combination of glucose and ammonium + phosphate), indicating potential energy limitations. Enhancement of bacterial growth by the combined addition of carbon substrates and iron was observed, but the addition of iron alone did not significantly increase bacterial growth. Carbon supply may be a substantial limitation to bacterial growth in the subantarctic Southern Ocean.
 
Day: Wednesday, Feb. 3
Time: Poster
Location: Sweeney Center
 
Code: SS31WE1334S