Phosphate Enrichment Hampers Development of Juvenile Acropora digitifera Coral by Inhibiting Skeleton Formation
Coral reef degradation due to various local stresses, such as nutrient enrichment and terrestrial run-off into coastal waters, is an increasing global concern. Inorganic phosphates have been considered to possibly inhibit skeleton formation in corals. Despite many studies available on the effects of nutrients on corals, a clear consensus on how nutrients exert deteriorative effects on corals has not been established satisfactorily. In this study, we examined the effects of phosphates and nitrates on in vitro aragonite CaCO3 formation by using biogenic polyamines and in vivo aragonite formation in the skeleton of juvenile Acropora digitifera corals. We showed that the phosphates at similar concentrations clearly inhibited both in vitro and in vivo CaCO3 formation. In contrast, nitrates inhibited neither in vitro aragonite CaCO3 formation nor in vivo aragonite formation in juvenile coral skeleton. Furthermore, our findings showed that inhibition of coral skeleton formation was due to absorption of phosphate on the skeleton, which inorganically inhibited normal development of juvenile coral skeleton.
KeywordsAragonite formation Calcification Coral skeleton Phosphate enrichment Stress
We thank Dr. Sakai and Ms. Kinjo of the Tropical Biosphere Research Centre at the University of the Ryukyus Sesoko Station for their assistance in obtaining A. digitifera coral larva.
This study was supported in part by grants-in-aids from the Japan Society for the Promotion of Science (KAKENHI Grant Numbers 25850145, 15K07587, 16K00518, and 18K19237) and by the funding from Kitasato University for Young Researchers.
Compliance with Ethical Standards
Conflict of Interests
The authors declare that they have no competing interests.
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