Invertebrates found on floating Sargassum horneri (Fucales, Sargassaceae) under the Kuroshio Current in the Pacific Ocean

ABSTRACT

The ecology and biogeography of the invertebrate epifauna related to floating Sargassum in the East China Sea were studied. Floating algal rafts composed of only Sargassum horneri (Turner) C. Agardh were collected in the East China Sea in March 2012 when the rafts were distributed not only on the continental shelf but also, unusually, south and east of the Kuroshio Current in the Pacific Ocean. In total, 71 samples collected at 11 stations were studied. Of the 11 invertebrate taxa recognized, harpacticoid copepods were most abundant, followed by malacostracans, and cirripedes. The densities of these three taxa were higher than those of other invertebrates. The number of invertebrate taxa was not correlated with the algal wet weight. There were more invertebrate taxa in the coastal area around Amami-Oshima Island than in other areas. The trajectories of drifting buoys indicated that the algal rafts collected in this area floated longer than those in other areas, allowing the colonization of invertebrates from the surrounding water.

KEYWORDS:

• Dispersal
• drifting algae
• East China Sea
• epifauna
• satellite-tracked buoy

Acknowledgements

The authors would like to express their gratitude to Dr. M. N. Aoki (Tohoku University), Y. Kuramochi (Sangetsu Co., Ltd), A. Kantachumpoo (Kasetsart University), N. Alabsi (Ricoh Technology Center), T. Otaki (Japan Fisheries Information Service Center), H. Suzuki (National Institute for Environmental Studies, Japan), E. A. Rothäusler (University of Turku) and the crew members of R/V Tansei-maru for their support and help in sampling the floating algae. Further, Dr. A. Kantachumpoo kindly gave us valuable comments that helped us improve a previous version of the manuscript. Special thanks also to Dr. H. Ikezawa of Ibaraki Nature Museum who helped to identify the bryozoans.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was supported partially by a grant-in-aid for scientific research (A) of the Japan Society for the Promotion of Science [grant number 22255010].