Contribution of planktonic foraminifera to the export of carbonate and organic carbon to the deep ocean

Planktonic foraminifera are ubiquitous calcifying zooplankton living in the upper ocean and responsible, globally, for more than 25% of the pelagic carbonate production and up to 50% of the carbonate export flux (Schiebel 2002; McLeod et al., 2010; Salter et al., 2014). After their death, planktonic foraminifera sink rapidly to the deep sea and sediments where their shells are preserved on geological time-scales. Until now, research has concentrated on the understanding of the seasonality in foraminifera shell fluxes (Jonkers and Kucera, 2015), but short-scale variability (e.g., monthly (bi-)), which could have equally important consequences to the carbonate export flux, remains understudied. Similarly, while most efforts concentrated on tracking and calculating C_inorg fluxes of foraminifera, C_org fluxes associated with the export flux of foraminifera have been overlooked or assumed to be negligible. This is unfortunate considering that in contrast to the almost purely mineral coccoliths, foraminifera shells contain organic linings which remain locked in their calcite shell (about 0.7% of shell weigh, Mezger et al., 2019) and could play an essential role in the deposition of organic matter that is not accessible to microbial degradation.

In this project we aim to generate and synthesize data on planktonic foraminifera (individuals and calcite) abundances and distribution in the upper ocean and quantify the export flux using high resolution (3 days) sediment trap material from the North East Atlantic Ocean. This will allow us to quantify short-term variability in carbonate and organic carbon fluxes related to linings and tests of planktonic foraminifera, revealing the mechanisms behind flux variability at different time scales.

References:

Jonkers, L., & Kučera, M. (2015). Global analysis of seasonality in the shell flux of extant planktonic Foraminifera. Biogeosciences, 12(7), 2207-2226.

McLeod, D. J., Hosie, G. W., Kitchener, J. A., Takahashi, K. T., and Hunt, B. P. V. 2010. Zooplankton Atlas of the Southern Ocean: The SCAR SO-CPR Survey (1991–2008). Polar science, 4: 353–385.

Mezger, E. M., Nooijer, L. J. D., Bertlich, J., Bijma, J., Nürnberg, D., & Reichart, G. J. (2019). Planktonic foraminiferal spine versus shell carbonate Na incorporation in relation to salinity.Biogeosciences,16(6), 1147-1165.

Salter, I., Schiebel, R., Ziveri, P., Movellan, A., Lampitt, R., & Wolff, G. A. (2014). Carbonate counter pump stimulated by natural iron fertilization in the Polar Frontal Zone. Nature Geoscience, 7(12), 885.

Schiebel, R. (2002). Planktic foraminiferal sedimentation and the marine calcite budget. Global Biogeochemical Cycles, 16(4), 3-1.