Carlson¹, C.A., D.A. Hansell², and S.J. Giovannoni³

¹University of California, Santa Barbara, CA, 93106, USA, Tel: 805-893-2541; Fax: 805-893-8062, E-mail: carlson@lifesci.ucsb.edu, ²Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, USA and ³Oregon State University, Corvallis, OR 97331, USA

A synthesis of bacterioplankton dynamics and interactions with DOC at the BATS site

Throughout the JGOFS era significant progress has been made towards understanding the interactions between heterotrophic prokaryotes and dissolved organic carbon (DOC). Studies conducted at the Bermuda Atlantic Time-series Study (BATS) site demonstrated that bacterioplankton processes and community structure play an important role in the temporal and spatial variability of DOC in open ocean systems. 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 convective overturn event. When mixing is >200m, a portion of this seasonally accumulated DOC is mixed into the upper mesopelagic zone where it is 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. Here we will present a synthesis of field and experimental work that describes or examines: 1. the temporal dynamics of bacterioplankton and DOC at BATS; 2. the effects of enhanced nutrient availability on bacterial production, bacterial community structure and processing of semi-labile DOC; 3. how vertical stratification of bacterial community structure may control the processing of semi-labile DOC and its long term accumulation within the euphotic zone at the BATS site.