The Impact of Zooplankton Calcifiers on the Marine Carbon Cycle

Abstract

Shelled pteropods and planktic foraminifers are calcifying zooplankton that contribute to the biological carbon pump via the sinking of their calcareous shells. However, their importance for regional and global plankton biomass and carbon fluxes is not well understood. Here, we modeled global annual patterns of pteropod and foraminifer total carbon (TC) biomass and total inorganic carbon (TIC) export fluxes over the top 200 m using five species distribution models (SDMs). An extended version of the MARine Ecosystem DATa (MAREDAT) of zooplankton abundance observations was used to estimate the biomass of both plankton groups. We found hotspots of mean annual pteropod biomass in the high Northern latitudes and the global upwelling systems, and in the high latitudes of both hemispheres and the tropics for foraminifers. This largely agrees with previously observed distributions. For both groups, temperature is the strongest environmental correlate, followed by chlorophyll‐a. We found mean annual standing stocks of 52 Tg TC (48 to 57 Tg TC) and 0.9 Tg TC (0.6 to 1.1 Tg TC) for pteropods and foraminifers, respectively. This translates to mean annual TIC fluxes of 14 Tg TIC yr−1 (9 to 22 Tg TIC yr−1) for pteropod shells and 11 Tg TIC yr−1 (3 to 27 Tg TIC yr−1) for foraminifer tests. These results are similar to previous estimates for foraminifers, but approximately a factor of ten lower for pteropods. Pteropods contribute 0.2%–3.2% and foraminifers 0.1%–3.8% to global surface carbonate fluxes. Including global coccolithophore fluxes, this leaves 40%–60% of the global carbonate fluxes unaccounted for. Our figures are likely lower‐bound estimates due to sampling data characteristics and uncertainty associated with organism growth rates.

Global gradients in species richness of marine plankton functional groups

“…, 2009 ; Drago et al. , 2022 ; Knecht et al. , 2023 ), it could be less relevant for determining the spatial ranges of zooplankton species, and thus emergent species richness, if those are mainly controlled by temperature ( Fig.…”

Modern planktonic Foraminifera: migrating is not enough

“…However, it remains unclear whether they can reproduce under such conditions. Reduced calci cation would affect marginally the CaCO 3 cycle, as about 0.1% -3.8% of the global surface carbonate uxes in the modern open-ocean originates from PF 47 . Although past large-scale acidi cation events in Earth history (e.g., the PETM, 48 ) have not shown signi cantly altered long-term calcite uxes to the sea oor, the exceptional magnitude and pace of the current acidi cation, combined with other potential stressors, means that PF are entering an uncharted era of environmental changes, and that a global-scale negative impact on calci cation is plausible 18 .…”

Large-scale culturing of the subpolar foraminifera Globigerina bulloides reveals tolerance to a large range of environmental parameters associated to different life-strategies and an extended lifespan

“…Planktic foraminifera are calcifying marine protists living in the upper water column of the world’s oceans. They are collectively responsible for 0.1%—3.8% of the global carbonate export flux over the upper 200 m ( Knecht et al., 2023 ), with local and seasonal fluxes up to several orders of magnitude higher ( Anglada-Ortiz et al., 2021 ; Tell et al., 2022 ). Schiebel (2002) estimated that their contribution to the global open marine flux at 100 m depth could be as high as 56%.…”