Dynamics of polysaccharides and transparent exopolymer particles during a coccolithophorid bloom in the Bay of Biscay

Carbohydrates comprise a large fraction (~30 %) of organic matter in the ocean (Pakulski and
Benner, 1994). The production of polysaccarides (CCHO) in seawater is mainly linked to autotrophic processes. CCHO serve as structural and storage compounds, or are released by exudation, cell lysis or leakage to the dissolved organic matter pool. Concentrations of total hydrolyzable neutral sugars range from 200-800nM and 20-170nM in surface and deep waters, respectively (Benner, 2002). It has been shown that CCHO, in particular acidic polysaccharides, are involved in aggregation processes, e.g. the formation of transparent exopolymer particles (TEP). Recently, it has been suggested that ocean acidification increases TEP production, and therefore potentially enhances particle aggregation (Engel 2002, Mari 2008). Here, we present data on the abundance and composition of neutral and acidic CCHO and on TEP, obtained from field investigations and from CO2-controlled chemostat experiments that were conducted during a coccolithophore bloom in the Bay of Biscay 2006. Based on our findings, we discuss the partitioning of CCHO into gel particles, potential effects of ocean acidification and related consequences for organic matter export.