Phytoplankton-derived particles represent one of the main sources of organic matter (OM) for marine systems, fuelling heterotrophic life and sequestering C in the ocean interior. The solubilization of sinking particles and the production of recalcitrant dissolved organic matter (RDOM) linked to microbial activities are two of the main processes influencing the ocean C storage capacity. These processes depend on the seasonally-variable makeup of phytoplankton assemblages, however, our understanding of this relationship is hindered by the difficulty of relating the processing of OM at depth with its phytoplanktonic source. To better understand the effects of the phytoplanktonic origin of particles on their degradation process, we performed three experiments using particles from the surface NW Mediterranean covering a wide range of phytoplankton assemblage compositions. The particulate material was added to mesopelagic water containing natural microbial communities and incubated in the dark during 25 days while monitoring particulate and dissolved organic carbon, and microbial concentrations. In addition, using fluorescence spectroscopy, we were able to track the labile and recalcitrant fluorescent fractions of both the dissolved and total (particulate + dissolved) OM pools. We will describe the fluorescent OM dynamics during the degradation process and discuss the results in relation to the source phytoplankton composition, with special focus on the processes of particle solubilization and production of RDOM within the context of the biological and microbial pump efficiencies. 

Primary Presenter: Miguel Cabrera-Brufau, Institute of Marine Sciences (ICM-CSIC) (cabrera@icm.csic.es)

Authors:

Miguel Cabrera-Brufau, Institute of Marine Sciences (ICM-CSIC)  (cabrera@icm.csic.es)

Laura Arin, Institute of Marine Sciences (ICM-CSIC)  ()

Patricia Armero-Jurado, Institute of Marine Sciences (ICM-CSIC)  ()

Mar Caballé Junquera, Institute of Marine Sciences (ICM-CSIC)  ()

Laura Cabrera Vázquez, Institute of Marine Sciences (ICM-CSIC)  ()

Clara Cardelús, Institute of Marine Sciences (ICM-CSIC)  ()

Pedro Cermeño, Institute of Marine Sciences (ICM-CSIC)  ()

Ferran Figueras, Institute of Marine Sciences (ICM-CSIC)  ()

Cèlia Marrasé, Institute of Marine Sciences (ICM-CSIC)  ()

Magda Vila, Institute of Marine Sciences (ICM-CSIC)  ()

Francesc Peters, Institute of Marine Sciences (ICM-CSIC)  ()

Mª Montserrat Sala, Institute of Marine Sciences (ICM-CSIC)  ()