Abstract
Corals are the backbone of coral reefs, essential for coastline protection and both regional and global economies. However, the future of these animals and the habitats they support are uncertain, due to the continuously rising global temperature and ocean acidification. However, corals are complicated organisms to study, existing as a holobiont with an assembly of numerous microbes that include bacteria, archaea, viruses, protists, and fungi. This contributes to a lack of thorough understanding of the cellular and molecular makeup of scleractinians, or stony corals; what is known has been gleaned from histological and microscopic practices or assumptions made on closely related non-scleractinian hexacorallians. In this dissertation, applications of flow cytometry are explored to better describe cellular diversity. While this technique has historically been used primarily for genome size estimation, cell counting, and measurement solely of the zooxanthellae, an advanced approach known as fluorescence-activated cell sorting (FACS) was applied to identify, isolate, and study various coral cell types, including previously undescribed phagocytes and a putative population of stem/progenitor cells. The morphological and functional descriptions were further paired with gene expression profiles generated from single-cell RNA sequencing, providing candidate gene markers for different flow cytometry-identified cell populations. Gene expression analysis of these populations also strengthened the evidence for the novel identification of specialized immune cells. While this dissertational work describes novel methodologies for studying coral cell biology, most importantly it provides new avenues of research to be considered for improving coral restoration and conservational efforts.