Biological responses to CO2-related changes in seawater carbonate chemistry during a bloom of Emiliania huxleyi

One of the most prominent consequences of human activities is the progressive rise in atmospheric pCO_2. This will also cause changes in seawater carbonate chemistry. However, to what extent anthropogenic perturbations in marine growth conditions will affect biological processes like species composition, ecosystem functioning, carbon production and vertical carbon export in the sea, as well as possible feedback mechanisms, is still under debate. In the present study, for the first time CO_2 effects were tested on a natural marine plankton community. In a series of floating mesocosms in a Norwegian fjord a phytoplankton bloom dominated by the coccolithophore Emiliania huxleyi was induced. By covering the enclosures by gas-tight domes, functioning as greenhouses, we were able to maintain CO_2 concentrations in the overlaying atmosphere ranging from pre-industrial to projected year 2100 levels over a three-week period. Here we present an overview of the experiment and report on the development of the bloom under different pCO_2 levels