Vol. 50 No. 4, 2011
Distribution Patterns of Five Zoanthid Species at Okinawa
Irei1,*, Yoko Nozawa2, and James D. Reimer3
Invertebrate Systematics and Ecology Laboratory, Graduate School of
Marine Science, Univ. of the Ryukyus, Senbaru 1, Nishihara, Okinawa
2Biodiversity Research Center, Academia Sinica,
Nankang, Taipei 115, Taiwan
3Molecular Invertebrate Systematics and Ecology
Laboratory, Rising Star Program, Transdisciplinary Research
Organization for Subtropical Island Studies (TRO-SIS), Univ. of the
Ryukyus, Senbaru 1, Nishihara, Okinawa 903-0213, Japan
Yuka Irei, Yoko Nozawa, and James D. Reimer (2011)
(Anthozoa, Hexacorallia) are distributed worldwide, especially in
shallow tropical and subtropical waters. In fringing reefs of Okinawa
I., southwestern Japan, zoanthids are common benthic organisms. Despite
their abundance, even basic ecological information such as favorable
habitats based on quantitative surveys is still lacking. Accordingly,
we investigated the distribution patterns of 5 common zooxanthellate
zoanthid species in shallow reef waters (< 10 m) of Okinawa I.: Palythoa tuberculosa, P. mutuki, Zoanthus sansibaricus, Z. kuroshio, and Z. gigantus. The survey was
conducted using the belt transect method in 3 reef environments (moat,
reef crest, and reef slope) at 10 reef sites in 2008. As a result, 2404
zoanthid colonies were observed, and Z.
sansibaricus and P.
tuberculosa were the 2 most dominant species, respectively
comprising 52% and 41% of the total zoanthids observed. The environment
where the highest numbers of colonies were observed was the reef crest
(1615 colonies) followed by the reef slope (687 colonies), while
zoanthids were rare in the moat environment (102 colonies). There were
significantly more Z. sansibaricus
colonies on reef crests than reef slopes, but no significant difference
was seen in the frequencies of the other 4 species between the reef
crest and reef slope. As to the zoanthid colony size, most colonies
(> 86%) of the 5 zoanthid species were < 10 cm in diameter, and
only 2 colonies of > 50 cm in diameter were observed in the survey.
The absence of zoanthids in moats suggested that sedimentation or weak
currents may be factors limiting zoanthid distribution; however,
detailed investigations are necessary to confirm this. Since
zooxanthellate zoanthids are a major benthic group on coral reefs,
further research focusing on the relationships between zoanthid
distribution and environmental conditions will foster a better
understanding of coral reef ecosystems.
Key words: Zoanthid,
Distribution, Shallow reef environment, Belt transect.
*Correspondence: Tel: 81-98-8958542. Fax: 81-98-8958577.