FORAMFLUX M140

Planktonic foraminifera are microscopic zooplankton. They live in the surface layer of the ocean, but produce calcite shells, which accumulate in large quantities on the sea floor, where they produce a large reservoir of carbonate and an archive of past climate change. When empty shells of foraminifera sink, they stick to organic particles and act as ballast for the resulting aggregates. Mineral dust transported from the continent by wind acts in the same way, but its size and production pattern are different. Expedition M140 will combine sampling in the water column with recovery of data and samples from long-term observational platforms (sediment traps and dust collecting buoys) to understand how production of marine particle mineral ballast varies in space and time and how important it is for the marine biological pump, transporting carbon from ocean surface to the sea floor. We will work along a transect from low productive offshore regions to high-productivity coastal upwelling. Observations on biodiversity, species ecology and shell chemical composition of planktonic foraminifera will be used to better decipher their fossil record in the sediment as an archive of past ocean and climate change.

Scientific Programme

Planktonic foraminifera shells in marine sediments are the principle source of information on the state of past oceans. To unlock the signals preserved in these shells, the ecology of the organisms that produced them have to be constrained in detail. Combining observations from sediment traps, plankton samples and on-board experiments, the cruise aims to investigate the extent and scale of population patchiness, ontogenetic and diel vertical migration, synchronisation of reproduction, symbiont presence and physiology and the extent of genetic diversity in the group.

Together with mineral dust and other mineralised plankton, empty shells of planktonic foraminifera act as ballast to sinking particles and thus play an important role in ocean carbon cycling. To evaluate the significance of the ballasting, the scientific programme of the expedition incorporates investigations of particle flux and dust deposition in the same region, mutually linked through shared access to moorings which will provide long records of particle flux, including foraminifera and airborne dust, at unprecedented resolution.