Constant shell density of hyaline large benthic foraminifers under thermal stress

Abstract

Recently, increased concentrations of anthropogenic atmospheric CO2 have caused ocean warming and acidification, leading to swift environmental alterations. In coral reef regions, bleaching and death of symbiotic calcifying organisms have been distressing. Generally, large benthic foraminifers (LBF), a principal symbiotic calcifying organisms in coral reefs, have gained popularity because thermal stress impedes their growth and ecological functions. Nevertheless, due to the complex nature of the shell structure, it is unclear whether indicators (shell volume, density, and size) influence the calcification rate. Micro X-ray computed tomography (MicroCT) has been efficiently used to study these parameters on porcelaneous LBF; however, hyaline LBF remained largely unexplored. In this research, reproducing populations of LBF Calcarina gaudichaudii were grown asexually under six varying temperatures (19 °C–29 °C). They were then determined using MicroCT. Shell weight and volume is reduced under high and low thermal stress with an optimal water temperature of 26 °C. However, the density of the shell was sustained at a continual level. These outcomes indicate that C. gaudichaudii can sustain a continual shell density given circumstances of growth inhibition due to thermal stress.