Tali Lea Babila

This study investigates the impact of Essential Climate Variables (ECVs) on the respiration rate of polar planktonic foraminifera Neogloboquadrina pachyderma and subpolar Turborotalita quinqueloba and Neogloboquadrina incompta to advance our understanding of foraminifera physiology and geochemical proxy interpretation for species living in understudied subpolar and polar environments. Respiration rates were measured on a total of 166 specimens collected during two field campaigns to the Nordic Seas. To size-normalise respiration rates we measured cavity volume and maximum diameter using x-ray microcomputed tomography (micro-CT) (³√cavity volume = (0.56 (max Ø)−0.38)). Our results show that the physiological response of foraminifera sharing overlapping environments is diverse, with N. pachyderma exhibiting remarkable stability over large gradients in temperature, salinity, carbonate chemistry, dissolved oxygen and nutrients. Conversely, N. incompta and T. quinqueloba have a much stronger thermal response. The difference between species is best described by their respective Q₁₀ (the factor by which the rate of respiration changes with a 10 °C increase in temperature) values of 1.41 for N pachyderma and 3.45 and 4.55 for N. incompta and T. quinqueloba, respectively. We also find a significant relationship between cavity volume and respiration rate (Log₁₀ respiration rate = 0.399 (Log₁₀ cavity volume) − 5.785)) for all three species analysed here, which is consistent with marine protists globally. We conclude that respiration is unlikely to influence geochemical proxies and therefore past climate reconstructions derived from N. pachyderma, however, this may not apply to N. incompta and T. quinqueloba.

This study investigates the impact of Essential Climate Variables (ECVs) on the respiration rate of polar planktonic foraminifera Neogloboquadrina pachyderma and subpolar Turborotalita quinqueloba and Neogloboquadrina incompta to advance our understanding of foraminifera physiology and geochemical proxy interpretation for species living in understudied subpolar and polar environments. Respiration rates were measured on a total of 166 specimens collected during two field campaigns to the Nordic Seas. To size-normalise respiration rates we measured cavity volume and maximum diameter using x-ray microcomputed tomography (micro-CT) (³√cavity volume = (0.56 (max Ø)−0.38)). Our results show that the physiological response of foraminifera sharing overlapping environments is diverse, with N. pachyderma exhibiting remarkable stability over large gradients in temperature, salinity, carbonate chemistry, dissolved oxygen and nutrients. Conversely, N. incompta and T. quinqueloba have a much stronger thermal response. The difference between species is best described by their respective Q₁₀ (the factor by which the rate of respiration changes with a 10 °C increase in temperature) values of 1.41 for N pachyderma and 3.45 and 4.55 for N. incompta and T. quinqueloba, respectively. We also find a significant relationship between cavity volume and respiration rate (Log₁₀ respiration rate = 0.399 (Log₁₀ cavity volume) − 5.785)) for all three species analysed here, which is consistent with marine protists globally. We conclude that respiration is unlikely to influence geochemical proxies and therefore past climate reconstructions derived from N. pachyderma, however, this may not apply to N. incompta and T. quinqueloba.

This study investigates the impact of Essential Climate Variables (ECVs) on the respiration rate of polar planktonic foraminifera Neogloboquadrina pachyderma and subpolar Turborotalita quinqueloba and Neogloboquadrina incompta to advance our understanding of foraminifera physiology and geochemical proxy interpretation for species living in understudied subpolar and polar environments. Respiration rates were measured on a total of 166 specimens collected during two field campaigns to the Nordic Seas. To size-normalise respiration rates we measured cavity volume and maximum diameter using x-ray microcomputed tomography (micro-CT) (³√cavity volume = (0.56 (max Ø)−0.38)). Our results show that the physiological response of foraminifera sharing overlapping environments is diverse, with N. pachyderma exhibiting remarkable stability over large gradients in temperature, salinity, carbonate chemistry, dissolved oxygen and nutrients. Conversely, N. incompta and T. quinqueloba have a much stronger thermal response. The difference between species is best described by their respective Q₁₀ (the factor by which the rate of respiration changes with a 10 °C increase in temperature) values of 1.41 for N pachyderma and 3.45 and 4.55 for N. incompta and T. quinqueloba, respectively. We also find a significant relationship between cavity volume and respiration rate (Log₁₀ respiration rate = 0.399 (Log₁₀ cavity volume) − 5.785)) for all three species analysed here, which is consistent with marine protists globally. We conclude that respiration is unlikely to influence geochemical proxies and therefore past climate reconstructions derived from N. pachyderma, however, this may not apply to N. incompta and T. quinqueloba.

This study investigates the impact of Essential Climate Variables (ECVs) on the respiration rate of polar planktonic foraminifera Neogloboquadrina pachyderma and subpolar Turborotalita quinqueloba and Neogloboquadrina incompta to advance our understanding of foraminifera physiology and geochemical proxy interpretation for species living in understudied subpolar and polar environments. Respiration rates were measured on a total of 166 specimens collected during two field campaigns to the Nordic Seas. To size-normalise respiration rates we measured cavity volume and maximum diameter using x-ray microcomputed tomography (micro-CT) (³√cavity volume = (0.56 (max Ø)−0.38)). Our results show that the physiological response of foraminifera sharing overlapping environments is diverse, with N. pachyderma exhibiting remarkable stability over large gradients in temperature, salinity, carbonate chemistry, dissolved oxygen and nutrients. Conversely, N. incompta and T. quinqueloba have a much stronger thermal response. The difference between species is best described by their respective Q₁₀ (the factor by which the rate of respiration changes with a 10 °C increase in temperature) values of 1.41 for N pachyderma and 3.45 and 4.55 for N. incompta and T. quinqueloba, respectively. We also find a significant relationship between cavity volume and respiration rate (Log₁₀ respiration rate = 0.399 (Log₁₀ cavity volume) − 5.785)) for all three species analysed here, which is consistent with marine protists globally. We conclude that respiration is unlikely to influence geochemical proxies and therefore past climate reconstructions derived from N. pachyderma, however, this may not apply to N. incompta and T. quinqueloba.

This study investigates the impact of Essential Climate Variables (ECVs) on the respiration rate of polar planktonic foraminifera Neogloboquadrina pachyderma and subpolar Turborotalita quinqueloba and Neogloboquadrina incompta to advance our understanding of foraminifera physiology and geochemical proxy interpretation for species living in understudied subpolar and polar environments. Respiration rates were measured on a total of 166 specimens collected during two field campaigns to the Nordic Seas. To size-normalise respiration rates we measured cavity volume and maximum diameter using x-ray microcomputed tomography (micro-CT) (³√cavity volume = (0.56 (max Ø)−0.38)). Our results show that the physiological response of foraminifera sharing overlapping environments is diverse, with N. pachyderma exhibiting remarkable stability over large gradients in temperature, salinity, carbonate chemistry, dissolved oxygen and nutrients. Conversely, N. incompta and T. quinqueloba have a much stronger thermal response. The difference between species is best described by their respective Q₁₀ (the factor by which the rate of respiration changes with a 10 °C increase in temperature) values of 1.41 for N pachyderma and 3.45 and 4.55 for N. incompta and T. quinqueloba, respectively. We also find a significant relationship between cavity volume and respiration rate (Log₁₀ respiration rate = 0.399 (Log₁₀ cavity volume) − 5.785)) for all three species analysed here, which is consistent with marine protists globally. We conclude that respiration is unlikely to influence geochemical proxies and therefore past climate reconstructions derived from N. pachyderma, however, this may not apply to N. incompta and T. quinqueloba.

The boron isotopic composition of planktonic foraminifera is a powerful tool to reconstruct ocean pH and CO₂ in the past. Applications to the high-latitude and polar oceans are however limited as robust calibrations between the δ¹¹B of foraminifera and ocean pH in these regions are lacking. Here, we present a new empirical calibration for the high latitude Arctic species Neogloboquadrina pachyderma and the sub-polar to temperate species Neogloboquadrina incompta using towed specimens from the Labrador Sea, Baffin Bay, and the Nordic Seas. When paired with in situ hydrographic data, this approach allows us to avoid key assumptions used in traditional core top calibrations that are required to link shell geochemical composition to hydrographic conditions during their formation. We show that the foraminifera δ¹¹B of the species analysed is well correlated with the δ¹¹B of seawater borate ion. Further, the foraminiferal δ¹¹B values are consistently lower than seawater equilibrium borate values, consistent with the interpretation of more acidic seawater in the microenvironment due to respiration. However, unlike published calibrations for non-spinose species to date the slope of the δ¹¹B foraminifera to δ¹¹B borate calibration is >1. We discuss several drivers of this higher sensitivity to pH and describe the possible role of vital effects in determining the boron isotopic composition of N. pachyderma and N. incompta. Finally, we apply the tow calibration to core top samples from the Nordic Seas to validate the calibration for use in the paleorecord.

Since atmospheric carbon dioxide (CO ₂ ) is a key driver of global temperatures over geological time, determining past CO ₂ and fluxes among Earth's carbon reservoirs is critical in resolving drivers and feedbacks within Earth's climate system. Such CO ₂ reconstructions are challenging prior to ice core records of the last 800 kyrs, and yet it is beyond this time where the most promising analogs for our warmer, higher CO ₂ future lie. Amongst proxies for past CO ₂ reconstruction, boron isotopes (δ ¹¹ B, primarily measured in foraminiferal carbonate) have become one of the most well‐established, having demonstrated their ability to replicate atmospheric CO ₂ during periods where ice core estimates are available for comparison. Although analytical reproducibility across laboratories has greatly improved in recent years, the approaches taken to derive CO ₂ estimates from these boron isotope measurements remain variable. For example, there are significant inconsistencies in how seawater temperature, boron isotope, and elemental composition are estimated, in how a second carbonate system parameter is used to constrain the carbonate system, in how ecophysiological imprints on proxy signals are accounted for, and in how uncertainties are quantified and propagated. The need to better harmonize practices in the community motivated a series of virtual workshops and a PAGES‐supported meeting, and ultimately this AGU Special Collection “Advances and Best Practices in Boron‐based Paleo‐CO ₂ Reconstruction.” In this synthesis article, we briefly summarize the history of approaches to address these issues, current limitations and strengths of the proxy, and highlight some important points to consider when applying the boron isotope proxy.