Diurnal variations of dissolved and colloidal organic carbon and trace metals in a boreal lake during summer bloom

► Cyanobacterial bloom occurred in the boreal lake due to exceptionally hot summer 2010. ► Constant concentration of most trace elements (TE) in humic lake during bloom period. ► Mn, Fe, and Ba may be linked to adsorption on cell surface in response to pH change. ► Allochthonous organo-mineral colloids prevent the uptake and adsorption of TEs by phytoplankton.