Upper-ocean flux of biogenic calcite produced by the Arctic planktonic foraminifera Neogloboquadrina pachyderma

Abstract

Abstract. With ongoing warming and sea ice loss, the Arctic Ocean and its marginal seas as a habitat for pelagic calcifiers are changing, possibly resulting in modifications of the regional carbonate cycle and the composition of the seafloor sediment. A substantial part of the pelagic carbonate production in the Arctic is due to the calcification of the dominant planktonic foraminifera species Neogloboquadrina pachyderma. To quantify carbonate production and loss in the upper water layer by this important Arctic calcifier, we compile and analyse data from vertical profiles in the upper water column of shell number concentration, sizes and weights of this species across the Arctic region during summer. Our data are inconclusive on whether the species performs ontogenetic vertical migration throughout its life cycle or whether individual specimens calcify at a fixed depth within the vertical habitat. The base of the productive zone of the species is on average located below 100 m and at maximum at 300 m and is regionally highly variable. The calcite flux immediately below the productive zone (export flux) is on average 8 mg CaCO3 m−2 d−1, and we observe that this flux is attenuated until at least 300 m below the base of the productive zone by a mean rate of 6.6 % per 100 m. Regionally, the summer export flux of N. pachyderma calcite varies by more than 2 orders of magnitude, and the estimated mean export flux below the twilight zone is sufficient to account for about a quarter of the total pelagic carbonate flux in the region. These results indicate that estimates of the Arctic pelagic carbonate budget will have to account for large regional differences in the export flux of the major pelagic calcifiers and confirm that substantial attenuation of the export flux occurs in the twilight zone.

The distribution and abundance of planktonic foraminifera under summer sea-ice in the Arctic Ocean

“…A4). This pattern would be consistent with gametogenesis taking place at the base of the productive zone, located at or below 100m, and would provide some evidence that N. pachyderma does perform ontogenetic vertical migration (Tell et al, 2022). On the other hand, large individuals were present at all depths, but rare (Fig.…”

“…On the other hand, large individuals were present at all depths, but rare (Fig. 11), perhaps substantiating that N. pachyderma performs both ontogenetic vertical migration as well as test growth at fixed depths, in line with the findings of Tell et al (2022). Nevertheless, this result is to be confirmed and further analysed with a comprehensive analysis of N. pachyderma morphotypes in a follow-up study.…”

“…Important to note is that a distinction should be made between the 'main depth habitat' of N. pachyderma, and the depth at which the secondary calcite is secreted, which is more important when it comes to interpreting geochemical signatures of fossil test in paleoceanography (Tell et al, 2022). At all stations, test size increased from the surface to 100-200m depth, and at six out of eight stations no statistical difference was found between the 100-200 m and 200-500 m depth interval (Fig.…”

Interannual variability (2000–2013) of mesopelagic and bathypelagic particle fluxes in relation to variable sea ice cover in the eastern Fram Strait

“…Previous studies have highlighted the importance of cold-water-adapted coccolithophores (Coccolithus pelagicus) to deepwater PIC fluxes in the Fram Strait (Samtleben and Bickert, 1990). Similarly, foraminifera fluxes are typically higher in deeper sediment traps in the Fram Strait (Ramondenc et al, 2022) and biogenic calcite export from the sea-ice-associated species Neogloboquadrina pachyderma is of known importance in the Arctic (Tell et al, 2022).…”

Large-scale culturing of Neogloboquadrina pachyderma, its growth in, and tolerance of, variable environmental conditions

“…Neogloboquadrina pachyderma is the dominant species in the polar oceans where it is a key planktic calcifier responsible for up to 25% of the inorganic carbon export above 50° (e.g. Tell et al. , 2022 ).…”