Calcification, Dissolution and Test Properties of Modern Planktonic Foraminifera From the Central Atlantic Ocean

Abstract

The mass of well-preserved calcite in planktonic foraminifera shells provides an indication of the calcification potential of the surface ocean. Here we report the shell weight of 8 different abundant planktonic foraminifera species from a set of core-to sediments along the Mid-Atlantic Ridge. The analyses showed that near the equator, foraminifera shells of equivalent size weigh on average 1/3 less than those from the middle latitudes. The carbonate preservation state of the samples was assessed by high resolution X-ray microcomputed tomographic analyses of Globigerinoides ruber and Globorotalia truncatulinoides specimens. The specimen preservation was deemed good and does not overall explain the observed shell mass variations. However, G. ruber shell weights might be to some extent compromised by residual fine debris internal contamination. Deep dwelling species possess heavier tests than their surface-dwelling counterparts, suggesting that the weight of the foraminifera shells changes as a function of the depth habitat. Ambient seawater carbonate chemistry of declining carbonate ion concentration with depth cannot account for this interspecies difference. The results suggest a depth regulating function for plankton calcification, which is not dictated by water column acidity.

Retrieving planktonic foraminifera from lithified rocks, examples from the Eocene limestones and marls (External Dinarides, Croatia)

“…Their high abundance is the result of the dominance of this group of foraminifera during the sedimentation [24] , when the inhabitants of the mixed layers ( Acarinina sp., Morozovella sp.,) were less abundant. In addition, it is known that foraminifera that are surface dwellers are much more susceptible to dissolution, which may also be the reason why acarininids and morozovellas were present in very low numbers [25] .…”

A New Look at Physico-Chemical Causes of Changing Climate: Is the Seasonal Variation in Seawater Temperature a Significant Factor in Establishing the Partial Pressure of Carbon Dioxide in the Earth’s Atmosphere?

“…6.023x10 23 molecules), equivalent to ppmv. However, the idea of a heterogeneous mole of air made up of a total of 6.022x10 23 different molecules is not useful in thermodynamic terms. The mean partial pressure (pi) of each gas per molecule can be given in terms of its number density (N) and the temperature (T).…”

“…The thermodynamic stoichiometry of reactions ( 7) and ( 8) may be questioned, although the overall reaction favoring emission of CO2 is qualitatively correct. Recent data from Zarkogiannis et al [23] showed that planktonic foraminifera from the central Atlantic Ocean had larger, denser shells in cooler water compared to tropical, possible a result of reduced competition for calcification.…”

Precise bulk density measurement of planktonic foraminiferal test by X-ray microcomputed tomography

“…The application of µCT for estimating the carbonate solubility and calcification capacity of marine calcareous materials has recently been widely discussed (Johnstone et al, 2010;Iwasaki et al, 2015;2019a;Todd et al, 2020;Zarkogiannis et al, 2020;Kinoshita et al, 2021;Kuroyanagi et al, 2021;Ofstad et al, 2021;Charrieau et al, 2022). Furthermore, ambitious attempts have been made to estimate the concentration of carbonate ions in past seawater by quantifying the dissolution of foraminifera tests (e.g., Iwasaki et al, 2019b;, habitat depth (Zarkogiannis et al, 2022), and to detect the biological effects of anthropogenic environmental changes since the Industrial Revolution (Fox et al, 2020).…”