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MEPS 369:1-11 (2008)  -  DOI:

Bacterial DMSP metabolism during the senescence of the spring diatom bloom in the Northwest Atlantic

Anissa Merzouk1,*, Maurice Levasseur2, Michael Scarratt3, Sonia Michaud3, Martine Lizotte2, Richard B. Rivkin4, Ronald P. Kiene5

1University of British Columbia, Earth and Ocean Sciences/Oceanography, 1461-6270 University Boulevard, Vancouver, British Columbia V6T 1Z4, Canada
2Université Laval, Département de biologie (Québec-Océan), Pavillon Alexandre-Vachon, Quebec, Quebec G1K 7P4, Canada
3Fisheries and Oceans Canada, Maurice Lamontagne Institute, 850 Route de la mer, Mont-Joli, Quebec G5H 3Z4, Canada
4Ocean Sciences Centre, Memorial University of Newfoundland, St. John’s, Newfoundland A1C 5S7, Canada
5University of South Alabama, Department of Marine Sciences, Mobile, Alabama 36688, USA

ABSTRACT: The impact of the decline of the vernal bloom on the bacterial metabolism of dimethylsulfoniopropionate (DMSP), the precursor of dimethylsulfide (DMS), was investigated during a 7 d Lagrangian study conducted in the Northwest Atlantic in spring 2003. Daily variations in bacterial leucine incorporation, dissolved DMSP (DMSPd) uptake and DMS production rates were measured in the surface mixed layer (SML) and in the deep chlorophyll a maximum (DCM) that formed as the bloom collapsed. Seawater samples were amended with 35S-DMSPd, and the products of bacterial DMSPd degradation were measured during 3 h on-board incubations. The gradual decrease in phytoplankton biomass and diatom abundance measured in the SML was accompanied by a sharp doubling of the bacterial abundance and a peak in leucine incorporation rate on Day 2, suggesting that bacteria responded to a transient pulse in dissolved organic matter. Bacterial DMSPd uptake and DMS production were highest on Days 1 and 2 (1.2 and 0.10 nmol l-1 h-1, respectively), but rapidly decreased by Day 3, suggesting that DMSPd was becoming a less important substrate for the growing bacterial assemblage as other substrates became available. Bacterial DMSPd uptake and DMS production rates were also low in the DCM despite very high DMS yields (40 to 50%), showing that neither the decline of the diatom spring bloom in the SML nor the accumulation of cells in the DCM resulted in a stimulation of bacterial DMSP metabolism or accumulation of DMS. The present study provides new field evidence for the potential uncoupling between bacterial production and DMS dynamics likely due to variations in the availability of other S-containing organic compounds released during the decay of phytoplankton blooms.

KEY WORDS: DMSP cycling · Bacterial metabolism · Bloom senescence · Northwest Atlantic Ocean

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Cite this article as: Merzouk A, Levasseur M, Scarratt M, Michaud S, Lizotte M, Rivkin RB, Kiene RP (2008) Bacterial DMSP metabolism during the senescence of the spring diatom bloom in the Northwest Atlantic. Mar Ecol Prog Ser 369:1-11.

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