Abstract
Abstract. Planktonic foraminifera are a major contributor to the deep carbonate-flux and the planktonic biomass of the global ocean. Their microfossil deposits form one of the richest databases for reconstructing paleoenvironments, particularly through changes in their taxonomic and shell composition. Using an empirically-based foraminifer model that incorporates three known major physiological drivers of foraminifer biogeography – temperature, food and light – we investigate (i) the global redistribution of planktonic foraminifera under anthropogenic climate change, and (ii) the alteration of the carbonate chemistry of foraminifer habitat with ocean acidification. The present-day and future (2090–2100) 3-D distributions of foraminifera are simulated using temperature, plankton biomass, and light from an Earth system model forced with historical and a future (IPCC A2) high CO2 emission scenario. The broadscale patterns of present day foraminifer biogeography are well reproduced. Foraminifer abundance and diversity are projected to decrease in the tropics and subpolar regions and increase in the subtropics and around the poles. In the tropics, the geographical shifts are driven by temperature, while the vertical shifts are driven by both temperature and food availability. In the high-latitudes, vertical shifts are driven by food availability, while geographical shifts are driven by both food availability and temperature. Changes in the marine carbon cycle would be expected in response to (i) the large-scale rearrangements in foraminifer abundance, and (ii) the reduction of the carbonate concentration in the habitat range of planktonic foraminifers: from 10–30 μmol kg−1 in the polar/subpolar regions to 30–70 μmol kg−1 in the subtropical/tropical regions. High-latitude species are most vulnerable to anthropogenic change: their abundance and available habitat decrease and up to 10% of their habitat drops below the calcite saturation horizon.