ForamEcoGENIE 2.0: Incorporating symbiosis and spine traits into a trait-based global planktic foraminifera model

Abstract

Abstract. Planktic foraminifera are major marine calcifiers in the modern ocean regulating the marine inorganic carbon pump and generating marine fossil archives of past climate change. Some planktic foraminifera evolved spine and symbiosis, increasing functional trait diversity and expanded their ecological niches. Here we incorporate symbiosis and spine traits into the ForamEcoGENIE model, a trait-based model focusing on functional trait rather than individual species, to enable us to study the importance of foraminifera biodiversity in the palaeoceanographic environment. We calibrated the modelled new traits using Latin Hypercube Sampling. We identified the best model run from an ensemble of 1200 runs compared with observations from global core-top, sediment trap, and plankton nets. The model successfully captures the global distribution and seasonal variation of the 4 major functional groups including dominance of the symbiont-obligate type in subtropical gyres and the symbiont-barren type in the productive subpolar oceans. The carbon export rate is correctly predicted for spinose foraminifera, but the model overestimates the global mean biomass of each group by 8 times and global export rate of non-spinose foraminifera by 4 times. Both the observational bias and the model's limitation in linking biomass to export production likely contributes to the discrepancy. Our model approximates a 3.05 g m-2 yr-1 global mean foraminifer-derived calcite flux and 1.1 Gt yr-1 total calcite export, account for 19 % of the global pelagic marine calcite budget within the lower range of modern calcite estimates. The calcite export is mostly derived from the symbiont-barren non-spinose group (39 %) and the symbiont-obligate spinose group (13 %). Our model overcomes the lack of biodiversity in previous version and offers the potential to explore foraminifera ecology dynamics and its impact on biogeochemistry in modern, future and paleogeographic environments.