We measured flocculation of dissolved organic carbon (DOC) in the water from a humic lake (DOC 5 14.9 mg C L21) and from an adjacent mire (DOC 5 25.7 mg C L21), in in situ enclosure experiments with different light regimes. Light stimulated the formation of organic particles in both waters, and organic particle formation was observed at all incubation depths, even in the dark controls. Producti...