Transcriptomic Changes in Coral Holobionts Provide Insights into Physiological Challenges of Future Climate and Ocean Change.
Tropical reef-building coral stress levels will intensify with the predicted rising atmospheric CO2 resulting in ocean temperature and acidification increase. Most studies to date have focused on the destabilization of coral-dinoflagellate symbioses due to warming oceans, or declining calcification due to ocean acidification. In our study, pH and temperature conditions consistent with the end-of-century scenarios of the Intergovernmental Panel on Climate Change (IPCC) caused major changes in photosynthesis and respiration, in addition to decreased calcification rates in the coral Acropora millepora. Population density of symbiotic dinoflagellates (Symbiodinium) under high levels of ocean acidification and temperature (Representative Concentration Pathway, RCP8.5) decreased to half of that found under present day conditions, with photosynthetic and respiratory rates also being reduced by 40%. These physiological changes were accompanied by evidence for gene regulation of calcium and bicarbonate transporters along with components of the organic matrix. Metatranscriptomic RNA-Seq data analyses showed an overall down regulation of metabolic transcripts, and an increased abundance of transcripts involved in circadian clock control, controlling the damage of oxidative stress, calcium signaling/homeostasis, cytoskeletal interactions, transcription regulation, DNA repair, Wnt signaling and apoptosis/immunity/ toxins. We suggest that increased maintenance costs under ocean acidification and warming, and diversion of cellular ATP to pH homeostasis, oxidative stress response, UPR and DNA repair, along with metabolic suppression, may underpin why Acroporid species tend not to thrive under future environmental stress. Our study highlights the potential increased energy demand when the coral holobiont is exposed to high levels of ocean warming and acidification.
Australian Institute of Marine Science, PMB 3, Townsville MC, Queensland, Australia; School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia.
Paulina
P
Kaniewska
School of Agriculture and Food Sciences, The University of Queensland, St Lucia, Queensland, Australia.
Chon-Kit Kenneth
CK
Chan
School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia; Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, United States of America.
David
D
Kline
University of Queensland Centre for Clinical Research, The University of Queensland, Herston, Queensland, Australia.
Edmund Yew Siang
EY
Ling
School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia.
Nedeljka
N
Rosic
School of Agriculture and Food Sciences, The University of Queensland, St Lucia, Queensland, Australia.
David
D
Edwards
Global Change Institute and ARC Centre of Excellence for Coral Reef Studies, The University of Queensland, St Lucia, Queensland, Australia.
Ove
O
Hoegh-Guldberg
School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia; Global Change Institute and ARC Centre of Excellence for Coral Reef Studies, The University of Queensland, St Lucia, Queensland, Australia.
Sophie
S
Dove
D000704:Analysis of Variance; D000818:Animals; D037421:Anthozoa / Q000235:genetics* / Q000502:physiology*; D002245:Carbon Dioxide / Q000032:analysis; D057231:Climate Change; D020869:Gene Expression Profiling; D063990:Gene Ontology; D009792:Oceans and Seas; D011485:Protein Binding; D060066:Protein Interaction Maps; D012623:Seawater; D013696:Temperature; D059467:Transcriptome / Q000235:genetics*
D002245:Carbon Dioxide