Biovolume Method for Foraminiferal Biomass Assessment: Evaluation of Geometric Models and Incorporation of Species Mean Cell Occupancy

Abstract

Foraminifers are widespread, highly abundant protists and active participants in marine carbon cycling. Their biomass might represent almost half of the total meiobenthic biomass in the deep sea. Foraminiferal biomass is frequently assessed through geometric models and biovolume estimates due to its non-destructive nature, which allows estimates of individuals from palaeoecological, museum, and living samples. To increase the accuracy of foraminiferal biovolume and biomass assessment we evaluate and propose geometric models for 207 foraminiferal taxa and the species’ average cell occupancy of the test. Individual test dimensions were measured to calculate volume (µm³), and the percent of cell occupancy (PCO) of the test was measured to assess the biovolume (µm³). These data were converted into individual biomass measurements (µg Corg ind−1). Our high intra- and interspecific PCO variance suggest that a mean PCO for each species represents the natural variability of occupancy more accurately than a predetermined fixed percentage for the whole assemblage, as previously asserted in the literature. Regression equations based on the relationship between test dimensions and volumes are presented. The geometric models, the PCO adjustment, and the equations will reduce time, effort, and discrepancies in foraminiferal biovolume and biomass assessments. Therefore, these results can improve the use and reliability of foraminiferal biomass in the future, facilitating its use in (1) distinct approaches including carbon flux estimations, (2) determining the effects of climate change on the marine trophic webs, and (3) environmental monitoring programs.

Reviews and syntheses: Review of proxies for low-oxygen paleoceanographic reconstructions

“…In most cases, analyses of basic morphology (size, circularity, ornamentation, and sometimes porosity, pore size and pore density) can be carried out using a lighted stereo microscope, equipped with a camera and/or micrometer. This approach can also be automated, using a motorized microscope stage and image acquisition and processing software (e.g., NI Vision software, ImageJ, the R package forImage, Freitas et al, 2021) for automatically reconstructing and measuring pore density, pore surface area, volume and various test measurements (e.g., ImageJ, the MorFo_.ijm plugin available at https://doi.org/10.5281/zenodo.4740079 (Tetard et al, 2021;Freitas et al, 2021). Higher resolution analyses, or precise measurements of small features such as pores, sometimes require SEM imaging.…”

Reply on RC1

“…In most cases, analyses of basic morphology (size, circularity, ornamentation, and sometimes porosity, pore size and pore density) can be carried out using a lighted stereo microscope, equipped with a camera and/or micrometer. This approach can also be automated, using a motorized microscope stage and image acquisition and processing software (e.g., NI Vision software, ImageJ, the R package forImage, Freitas et al, 2021) for automatically reconstructing and measuring pore density, pore surface area, volume and various test measurements (e.g., ImageJ, the MorFo_.ijm plugin available at https://doi.org/10.5281/zenodo.4740079 (Tetard et al, 2021;Freitas et al, 2021). Higher resolution analyses, or precise measurements of small features such as pores, sometimes require SEM imaging.…”

Reply on RC3

“…In most cases, analyses of basic morphology (size, circularity, ornamentation, and sometimes porosity, pore size and pore density) can be carried out using a lighted stereo microscope, equipped with a camera and/or micrometer. This approach can also be automated, using a motorized microscope stage and image acquisition and processing software (e.g., NI Vision software, ImageJ, the R package forImage, Freitas et al, 2021) for automatically reconstructing and measuring pore density, pore surface area, volume and various test measurements (e.g., ImageJ, the MorFo_.ijm plugin available at https://doi.org/10.5281/zenodo.4740079 (Tetard et al, 2021;Freitas et al, 2021). Higher resolution analyses, or precise measurements of small features such as pores, sometimes require SEM imaging.…”