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Unexpected high abundance of aragonite-forming Nanipora (Octocorallia: Helioporacea) at an acidified volcanic reef in southern Japan


Nanipora Miyazaki & Reimer, 2015 is a recently discovered genus of aragonite-skeleton producing octocorals closely related to the blue coral genus Heliopora de Blainville, 1830. Since its discovery, Nanipora has been reported from coral reefs in Okinawa, Japan, and Thailand, and from seagrass beds in the northern South China Sea. However, it remains little known and studied. Here, we report on the unexpected discovery of an abundance of Nanipora colonies in shallow waters less than 2-m deep around a CO2 vent from the uninhabited volcanic island of Iwotorishima, Okinawa, in southern Japan. Nanipora colonies were found covering both coral rubble and hard substrates, alongside a few soft coral and zoantharian species. Polyps were pale white in color with none brown or darker in coloration as in some recent reports. As the original description of N. kamurai from Zamami Island in Okinawa describes the species as azooxanthellate, as the current Iwotorishima specimens also appear to be, and recently reported specimens from Thailand, Dongsha Atoll, and Yaeyama are zooxanthellate, it may be that there are more than one Nanipora species; the type species N. kamurai that is also likely at Iwotorishima, and a zooxanthellate species that constitutes the other records. Although Nanipora is not well studied, its presence at this volcanic CO2 seep suggests it has the ability to survive under unique and extreme environmental conditions, rendering it as a potentially important subject of study in the face of increasing ocean acidification.

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The authors thank the captain and crew of the Yosemiya III for their support and advice. The first author obtained permission for sampling from Okinawa Prefecture (Permit Number 2-34). Comments from two reviewers and the editor improved an earlier version of this manuscript.


The authors were supported by an OIST KICKS grant entitled “Japanese volcanic CO2 vents – natural laboratories to study the behavior and adaptation of marine organisms to acidifying oceans”, and by a JSPS Kakenhi grant to H. Kayanne (#16H01766).

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Corresponding author

Correspondence to James Davis Reimer.

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The authors declare that they have no conflict of interest.

Ethical approval

All applicable international, national, and/or institutional guidelines for animal testing, animal care and use of animals were followed by the authors.

Sampling and field studies

All necessary permits for sampling and observational field studies have been obtained by the authors from the competent authorities and are mentioned in the acknowledgements, if applicable. The study is compliant with CBD and Nagoya protocols.

Data availability

Specimens have been deposited in the Fujukan University of the Ryukyus museum under specimen numbers RUMF-ZG-04458~04462. No other data are present in this research.

Authors’ contributions

JDR and all authors conceived and designed the research. JDR, H Kurihara, H Kayanne, and TR acquired funding. JDR, H Kurihara, YI, and MI conducted benthic surveys. JDR identified specimens and wrote the first draft of the manuscript. All authors read, edited, and approved the manuscript.

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Reimer, J.D., Kurihara, H., Ravasi, T. et al. Unexpected high abundance of aragonite-forming Nanipora (Octocorallia: Helioporacea) at an acidified volcanic reef in southern Japan. Mar. Biodivers. 51, 19 (2021).

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  • Ocean acidification
  • CO2 vent
  • Ryukyu Islands
  • Okinawa
  • Lithotelestidae