Contribution of transparent exopolymer particles to carbon sinking flux in an oligotrophic reservoir

Transparent exopolymer particles (TEP) compose an important pool of particulate organic matter (POM) in aquatic systems. However, no studies of TEP contribution to C export to sediment exist for freshwaters. We quantify the contribution of TEP to C sinking fluxes in an oligotrophic reservoir (Quéntar, Southern Spain) by monitoring TEP in the water column and TEP, particulate organic carbon (POC) and dry weight in sedimentation traps. TEP sinking fluxes ranged from 0.73 to 183.23 mg C m^?2 day^?1 and from 0.51 to 177.04 mg C m^?2 day^?1 at the surface and at the bottom layer, respectively. These values represent that, over an annual basis, 5.59 Ton TEP-C (over 61.32 Ton POC) are exported, on an average, from the water column to the sediment of Quentar reservoir. TEP concentrations (average = 48.0 μg XG eq l^?1) were lower than the scarce data reported for freshwaters. No significant relationships between TEP and Chl a concentrations or BA were observed. Average value for daily sedimentation flux (6.63 g Dry Weight m^?2 day^?1) in the study reservoir was higher than that documented for low productive natural aquatic ecosystems as a consequence of the high amount of allochthonous material input characterizing reservoirs. TEP contributed to C export to sediment with a value that range from 0.02 to 31%. Our results show that even in man-made systems, which are predominantly controlled by allochthonous inputs, TEP may be relevant for explaining POM settling fluxes.