Particulate trace metal dynamics in response to increased CO2 and iron availability in a coastal mesocosm experiment

Abstract

Rising concentrations of atmospheric carbon dioxide are causing ocean acidification and will influence marine processes and trace metal biogeochemistry. In June 2012, in the Raunefjord (Bergen, Norway), we performed a mesocosm experiment, comprised of a fully factorial design of ambient and elevated pCO2 and/or an addition of the siderophore desferrioxamine B (DFB). In addition, the macronutrient concentrations were manipulated to enhance a bloom of the coccolithophore Emiliania huxleyi. We report the changes in particulate trace metal concentrations during this experiment. Our results show that particulate Ti and Fe were dominated by lithogenic material, while particulate Cu, Co, Mn, Zn, Mo and Cd had a strong biogenic component. Furthermore, significant correlations were found between particulate concentrations of Cu, Co, Zn, Cd, Mn, Mo and P in seawater and phytoplankton biomass (μ gC L-1), supporting a significant influence of the bloom in the distribution of these particulate elements. The concentrations of these biogenic metals in the E. huxleyi bloom were ranked as follows: Zn < Cu Mn < Mo < Co