Global prediction of planktic foraminiferal fluxes from hydrographic and productivity data

Abstract

Abstract. Understanding and quantifying the seasonal and spatial distribution of planktic foraminiferal fluxes reflected in sedimentary assemblages is key to interpret foraminiferabased proxies in paleoceanography. Towards this goal we present an empirical model to predict foraminiferal fluxes on a global scale.A compilation of planktic foraminiferal flux and export production data from globally distributed sediment traps together with environmental data of sea-surface temperature and mixed-layer depth from online databases is used to calibrate the model that calculates monthly foraminiferal fluxes for the 18 most common species. The calibrated model is then forced with a global data set of hydrographic and productivity data to predict monthly foraminiferal fluxes worldwide. The predictive skills of the model are assessed by comparing the model output with planktic foraminiferal assemblages from globally distributed surface sediments as well as with measured foraminiferal fluxes of sediment traps not included in the calibration data set.Many general distribution patterns of foraminiferal species recognized from the model output compare favorably with observations from coretops or sediment traps, even though the model still produces problematic results in some places. Among others, meridional gradients in species richness and diversity, increased relative abundances of Neogloboquadrina pachyderma (dex.) in upwelling areas, and peak abundances of Globigerinella siphonifera in oligotrophic subtropical gyres show good agreement between model and coretops. Absolute foraminiferal fluxes are significantly underestimated in most cases, while seasonal variations can be reproduced for some species. Interannual differences in foraminiferal fluxes are not reflected by the model which might partly be due to a lack of actual environmental data for the calibration and model experiments.Correspondence to: S.Žarić (zaric@uni-bremen.de)The limited predictive skills of the model suggest that additional parameters should be considered. Export production should probably be replaced by a more realistic representation of food availability for planktic foraminifera. This could be achieved by adding a dynamic component to the model and linking it to an ecosystem model.

Modelling planktic foraminifer growth and distribution using an ecophysiological multi-species approach

“…Previous existing models are based on abundance observations and statistical relationships, and are constrained by hypothesis on unknown population dynamic parameters (predation, competition, reproduction success) (Fraile et al, 2008;Zarić et al, 2006). In contrast, the FORAMCLIM model calibration is mostly based on parameters derived from physiological laboratory observations, with a model complexity limited to demonstrated processes.…”

Modeling seasonal and vertical habitats of planktonic foraminifera on a global scale

“…It is known from observational data that the prevailing environmental conditions, such as temperature, stratification, light intensity, and food availability, affect the growth and distribution of the individual planktonic foraminifera (Fairbanks et al, , 1982Bijma et al, 1990b;Watkins et al, 1996;Schiebel et al, 2001;Field, 2004;Kuroyanagi and Kawahata, 2004;Žarić et al, 2005;Salmon et al, 2015;Rebotim et al, 2017). Based on stratified plankton tow and sediment trap data the seasonal succession of planktonic foraminifera species has been assessed on a local or regional scale (e.g., Kohfeld et al, 1996;Wilke et al, 2009;Jonkers et al, 2013;Jonkers and Kučera, 2015), whereas for a broader regional or global perspective, modeling approaches have been used to study the seasonal variations in the surface (mixed) layer of the ocean (Žarić et al, 2006;Fraile et al, 2008;Fraile et al, 2009a, b;Lombard et al, 2011;Kretschmer et al, 2016). Comparatively less is known about the depth habitat of planktonic foraminifera species and how it varies seasonally.…”

Predicting the global distribution of planktonic foraminifera using a dynamic ecosystem model

“…However, due to the short duration of the collecting periods those data may represent local processes of a particular year rather than a long term mean. We used the global database compiled by Zarić et al (2005Zarić et al ( , 2006. This database contains planktonic foraminiferal fluxes calculated from various sediment-trap investigations across the world ocean.…”

“…The tolerance limits of most species are most likely progressive since a departure from optimal growth conditions causes a gradual reduction of vital processes (Arnold and Parker, 1999). Zarić et al (2005Zarić et al ( , 2006 compiled planktonic foraminiferal fluxes from sediment-trap observations across the World Ocean. They analyzed species sensitivity to temperature by relating fluxes and relative abundances of seven species to sea-surface temperature.…”

“…Previously, Zarić et al (2006) developed an statistical model based on hydrographic and productivity data. In contrast to the model ofZarić et al (2006), we present a dynamic model which, considering ecological processes, calculates the growth rate of the foraminifera population between successive time steps.…”