Corals regulate the distribution and abundance of Symbiodiniaceae and biomolecules in response to changing water depth and sea surface temperature

Abstract

The Scleractinian corals Orbicella annularis and O. faveolata have survived by acclimatizing to environmental changes in water depth and sea surface temperature (SST). However, the complex physiological mechanisms by which this is achieved remain only partially understood, limiting the accurate prediction of coral response to future climate change. This study quantitatively tracks spatial and temporal changes in Symbiodiniaceae and biomolecule (chromatophores, calmodulin, carbonic anhydrase and mucus) abundance that are essential to the processes of acclimatization and biomineralization. Decalcified tissues from intact healthy Orbicella biopsies, collected across water depths and seasonal SST changes on Curaçao, were analyzed with novel autofluorescence and immunofluorescence histology techniques that included the use of custom antibodies. O. annularis at 5 m water depth exhibited decreased Symbiodiniaceae and increased chromatophore abundances, while O. faveolata at 12 m water depth exhibited inverse relationships. Analysis of seasonal acclimatization of the O. faveolata holobiont in this study, combined with previous reports, suggests that biomolecules are differentially modulated during transition from cooler to warmer SST. Warmer SST was also accompanied by decreased mucus production and decreased Symbiodiniaceae abundance, which is compensated by increased photosynthetic activity enhanced calcification. These interacting processes have facilitated the remarkable resiliency of the corals through geological time.

Mucus carbohydrate composition correlates with scleractinian coral phylogeny

“…Furthermore, changes in microbial communities due to environmental conditions 31 and ex situ culturing 49 , 50 (i.e., for M. digitata and M. confusa colonies in the present study) may influence coral mucus compositions, and thus should be included in future studies due to expected interaction of mucosal carbohydrates with associated microbes 9 , 51 . Lastly, endosymbiotic Symbiodiniaceae likely influence coral mucus compositions 36 , 37 and the taxonomic composition of Symbiodiniaceae communities can vary widely among and within species of scleractinian corals 52 , 53 . We did not analyze the Symbiodiniaceae communities associated with the investigated corals in the present study, so we do not know which taxa of endosymbionts were present.…”

“…Secondly, microbial communities associated with coral mucus can vary with environmental conditions 31 , potentially resulting in composition adaptations. Finally, endosymbiotic dinoflagellates of the family Symbiodiniaceae 32 are majorly involved in mucus production 33 – 35 , and likely contribute to shaping mucus composition 36 , 37 .…”

The Unseen Drivers of Coral Health; Coral Microbiome; The Hope for Effective Coral Restoration

“…They also help corals get rid of their waste. Corals use these provided substances to produce carbohydrates, fats and proteins in addition to the synthesis of calcium carbonate (CaCO 3 ) needed for their skeleton building [40]. The breakdown of this symbiosis by any mean of environmental disturbances such as elevated temperatures, acidification or water pollution would lead to coral bleaching and propably death of the host.…”

Cellular adaptations leading to coral fragment attachment on artificial substrates in Acropora millepora (Am-CAM)

“…Live and static imaging is an effective way to detail the structures of reef-building corals at the organismal, tissue and cellular levels 6 , 38 , 40 – 45 . Recent advancements in imaging techniques have provided vital insight into coral calcification, biomechanics and cellular plasticity 38 , 40 – 43 , including non-invasive techniques for dynamic temporal imaging at high resolution, such as in vivo video and time-lapse microscopy 46 – 48 and novel static imaging 41 – 43 . The use of in vivo observations is maximised when used in combination with static microscopy to increase the resolution of observation in characterising soft tissue and skeletal development 6 , 43 , 49 .…”