The reproductive strategy of planktonic foraminifera, key pelagic calcifiers, has long remained elusive, hampering efforts to understand and model their population dynamics. This is particularly critical in polar oceans where their success relies on rapid population growth after the polar night. Here, we provide field and laboratory observations constraining the reproductive cycle of the dominant polar species Neogloboquadrina pachyderma in Antarctic and Arctic waters. We observe that asexual reproduction is a rare but persistent element of the reproductive strategy and that it is reflected in a dimorphism in proloculus and in the ratio of shell size versus the number of chambers between sexually and asexually produced individuals. This dimorphism in natural populations reveals that asexual reproduction supplies more than 75% of adult individuals. This indicates a multigenerational reproduction strategy, where the majority of the population releases gametes to facilitate recombination, while a minority persistently reproduces asexually, allowing rapid population growth as a prerequisite for success in the polar oceans.

The trophic strategies of cold-water planktonic foraminifera are not well understood due to the challenge of culturing them in polar conditions. Here, we identify previously unknown ectoplasmic and cytoplasmic projections in three species of planktonic foraminifera thriving in polar and subpolar marine environments: Globigerina bulloides, Neogloboquadrina incompta and Neogloboquadrina pachyderma. These structures were observed during routine monitoring of cultured specimens sampled from the Norwegian coast, Greenland Sea and Baffin Bay. Two types of projections were discovered, including permanent and non-permanent structures such as ectoplasmic roots, twigs and twig-like projections, similar to those observed in benthic taxa Cibicides and Cibicidoides. Additionally, a previously undescribed filopodia-like projection was observed in N. pachyderma. We discuss the function, the ecological significance and the potential impact on pelagic processes of the presence of these structures in foraminifera species that occupy diverse niches in the water column. Our findings suggest that these structures may play an important role in the trophic strategies of cold-water planktonic foraminifera, and further research and observations are necessary to fully comprehend their significance in the carbon cycle.

From the morning of June 28th to the morning of July 3rd 2021, the Department of Geosciences at UiT The Arctic University of Norway, arranged a scientific cruise on R/V “Helmer Hanssen aimed at sampling living planktic foraminifera (primarily Neogloboquadrina pachyderma) for culturing experiments both onboard and continued at the culturing laboratory at the Department. The purpose is to investigate the physiological and calcification responses of this species to a wide range of temperature, salinity and carbonate chemistry as well as to establish proxy calibration for paleoceanographic reconstructions.  The cruise may be known as: CAGE21_2

From the morning of June 23rd to the morning of June 30th 2022, the Department of Geosciences at UiT the Arctic University of Norway, arranged a scientific cruise on R/V “Helmer Hanssen aimed at sampling living planktic foraminifera (Neogloboquadrina pachyderma and Globigerina bulloides) for culturing experiments both onboard and continued at the culturing laboratory at the Department. The purpose is to investigate the physiological and calcification responses of this species to a wide range of temperature, salinity and carbonate chemistry as well as to establish Arctic-tailored proxy calibrations for paleoceanography reconstructions