Nickel Sorption by Periphyton Exposed to Different Light Intensities

Photosynthetic activity and nickel sorption by stream periphyton were examined in relation to light intensity. Ceramic tiles supporting moderate levels of periphyton were placed in laboratory microcosms and exposed to nickel ion and 14C-labeled sodium bicarbonate. Sorption of nickel increased hyperbolically as light intensity increased from zero to 300 μmol quanta m-2 s-1; this response was similar to the photosynthesis-irradiance relationship for periphyton collected from the same site. Nickel sorption with light was up to 76% greater than nickel sorption in the dark. Dark-related nickel sorption was likely attributable to sorption by hydrous iron and manganese oxides and to passive biotic sorption. These results suggest an important relationship between nickel sorption and photosynthesis, which may be a result of active uptake, adsorption through cation exchange, or nickel precipitation.