research: Depth habitat of planktonic foraminifera

Setup of a sinking speed experiment with living planktonic foraminifera in culture. (A) The placement of three settling tube that allow for the monitoring of temperature, mixing and the sinking of a single foraminifera. (B) Cartoon schematic of the laboratory based thermocline constructed within the settling tube. Living foraminifera (C) in culture and (D) during settling.

Picture: B. Metcalfe

Planktonic foraminifera are free floating members of the pelagic community, how (and if) they maintain buoyancy or whether or not their depth is passively controlled is important for how we interpret proxies that utilise either their abundance or the geochemical properties of their shells. During life, planktonic foraminifera sink through the water column, eventually upon death settling down to the seafloor where they are collected by micropalaeontologists. Determining the depth habitat of these shells is critical for accurate climate reconstructions. There are numerous questions still unanswered concerning the shells of planktonic foraminifera, such as: What is the shell for? What will be the impact of changing ocean carbonate chemistry?

Research funded by an NWO open round grant ("Digging for density in search of a micropalaentological proxy for seawater density") to Dr. Frank Peeters included settling experiments and the stable isotopic composition of individual chambers of planktonic foraminifera.

Single chamber oxygen isotope results showing the migration through the water column of a single foraminifera (Metcalfe, unpublished).