Herndl, G. J.. Netherlands Institute for Sea Research, herndl@nioz.nl
Stoderegger, K. J.. Netherlands Institute for Sea Research, karen@nioz.nl

Recently, evidence emerged that bacterioplankton-derived dissolved organic matter (DOM) might contribute to the oceanic DOM pool to a larger extent than hitherto assumed. We investigated the potential contribution of bacterioplankton release of capsular material to the oceanic DOM pool. The rate of the release of capsular material and its subsequent utilization by bacteria was investigated. Also the formation of transparent exopolymer particles (TEP) from bacterial-derived capsular material was determined. We found that active bacteria release capsular material at rates equal to about 25 % of their respiratory carbon demand. This released capsular material is utilized by bacteria at rates 3 orders of magnitude lower than glucose. Release capsular material was found to lead to the formation of TEP. Depending on the overall trophic conditions of the waters and on the methods used to quantify TEP, it is estimated that between 5 to 20% of the TEP present in the water column are derived from bacteria. Comparing the grazing efficiency of heterotrophic flagellates on bacterial with and without a capsule, we found that bacterial cells with a capsular envelope are grazed at 5-10 times higher rates than bacteria without a capsule.
Day: Thursday, Feb. 4
Time: 02:30 - 02:45pm
Location: Sweeney Center
Code: SS33TH0230S