Characterization of colloids before, during, and after a phytoplanktonic bloom in Lake Geneva (Switzerland/France)

摘要: Colloids play an important role in trace metal cycling lakes(Morel & Gschwend 1987) due to their high sorptioncapacity and long residence times. Indeed, because of Brow-nian motion, colloids do not settle individually, even stillwater; however, they can aggregate into larger particles andstart entraining bound or embedded compounds.Aggregation, ultimately colloid removal rates, canstrongly be enhanced during a phytoplankton bloom, particu-larly through the production sticking exopolymers (Pas-sow 2002) released by (Jackson Burd1998). Sticking are also known promote dia-tom aggregation both marine (Alldregde Jackson1995 other references this special issue) freshwa-ter systems (Hoffman et al. 2001).In international project aiming assess metalremoval Lake Geneva phytoplanktonic bloom,colloids were extensively studied 3field campaignsbefore, during, after 2006 spring bloom. Changes insize, concentration, composition, rate col-loids with time will presented elsewhere (V.Chanudet, unpubl.). Here we present specifically resultsof second campaign (bloom), which wasexpected most influence colloidal particle size distri-bution significant process.To verify assumption, carried out experiments on col-loid using single counter (SPC), aunique tool allowing measurements sizerange 0.1–2µm at natural concentrations. We able todemonstrate that early phase bloom lakes,small centric diatoms individually rather than as aggre-gates, possibly low concentration exopoly-mers.