Carlson, C. A. Bermuda Biological Station for Research Inc., ccarlson@sargasso.bbsr.edu
Giovannoni, S. A. Oregon State University, giovanns@ava.bcc.orst.edu
Hansell, D. A. Bermuda Biological Station for Research Inc., dennis@sargasso.bbsr.edu
Wheeler, B. R. Bermuda Biological Station for Research Inc., jwheeler@sargasso.bbsr.edu

 
DETERMINING THE RESPONSE OF SURFACE AND DEEP BACTERIOPLANKTON COMMUNITIES TO DOM WHICH ACCUMULATES AT THE BERMUDA ATLANTIC TIME-SERIES STUDY STATION (BATS)
 
DOC dynamics at BATS demonstrate an annual pattern where DOC stocks accumulate rapidly within the surface 100m after spring restratification and stay elevated until the next deep mixing event. As a result of mixing, a portion of this seasonally accumulated DOC is mixed to depth ( >200m) and subsequently removed after restratification. It is hypothesized that microbial remineralization is responsible for deep DOC removal. If true then DOC, which accumulates in the surface, is resistant to rapid microbial degradation by surface bacterioplankton communities but is available to deeper communities. The objective of our work was to simulate a deep mixing event in which deep bacterioplankton communities were mixed with surface water DOM. Experiments consisted of controls and several treatments of organic and inorganic amendments in which 0.2 um filtrate, collected from 10m, was inoculated with natural bacterioplankton assemblages collected from 10m and 250m and incubated at respective in situ temperatures. Bacterioplankton abundances from 10m inoculum (control and inorganic amendments) increased 14% over 3 days while abundances from 250m inoculum (initially lower than 10 m treatments) increased 185% and reached similar abundance levels as 10m inoculum. Changes in DOC, shifts in species composition and implication on DOC dynamics at BATS will be discussed.
 
Day: Thursday, Feb. 4
Time: 09:15 - 09:30am
Location: Sweeney Center
 
Code: SS33TH0915S