NESSC_New generation of foraminiferal proxies (WP1)

This is part of Work Package 1 of NESSC (Netherlands Earth System Science Centre)

Proxies for inorganic carbon system

The isotope and elemental composition of foraminiferal calcite is frequently used to reconstruct past seawater conditions. Past temperatures can be reconstructed with relatively great confidence using oxygen isotopes and Mg incorporation, but for the inorganic carbon system (pH, [CO₃^2-], alkalinity, etc.) proxies available are limited and associated with relatively large uncertainties.

Precise and accurate reconstructions of these parameters are, however, essential for reconstructing past atmospheric CO₂ concentrations and in combination with temperature reconstructions climate sensitivity.  For several trace metals it is known that their speciation in sea water mainly depends on the inorganic carbon system, but impact on foraminiferal incorporation of these elements in their tests is still unknown. Calibrating these parameters and impact on trace element incorporation requires a large number of calibrations in which the different parameters of the carbonate system are independently varied.

A novel system to culture foraminifera

This project uses a novel system for manipulating the inorganic carbon system of seawater to culture (a.o.) benthic foraminifera. First culturing experiments focus on incorporation of Co, Zn, Li and Ni, since their activity in seawater is known to vary primarily with pH or other marine carbon cycle parameters. Although the concentration of these elements themselves heavily depends on biogeochemical cycling, isolating the impact of [DIC], pH, saturation state, etc. for the individual elements will set the stage for a suitable proxy for reconstructing past CO₂ concentrations, and will therefore be a valuable tool and improve our understanding of previous ocean acidification events and climate change.

In addition to culture experiments with local, benthic Wadden Sea species such as Ammonia tepida or tropic benthic species such as Amphistegina lessonii, planktic foraminifera sampled during cruises will be analysed and compared with specimens grown under controlled conditions in the laboratory.