Preliminary report on diatoms attached to pumice clasts that originated from the 2021 eruption of the Fukutoku-Oka-no-Ba submarine volcano and drifted to Okinawa Island, southwestern Japan

抄録

A large amount of pumice was produced by the eruption of the Fukutoku-Oka-no-Ba submarine volcano in the Ogasawara Islands in August 2021. The pumice formed pumice rafts that drifted westward on the Pacific Ocean and washed ashore along the coast of Okinawa Island, more than 1000 km away, in October 2021. In this study, we observed surface scrapings of pumice clasts that had drifted onto Okinawa Island by light microscopy and surface of the pumice clast by scanning electron microscopy, and revealed the presence of attached diatoms. Sixteen diatom taxa were observed on the pumice clasts. The genus Mastogloia was the most abundant, with 10 taxa, and accounted for more than 80% of the diatom assemblage on all pumice clasts observed. The second most abundant taxon was Rhopalodia pacifica, accounting for 5–10% of the diatom assemblages. Our results suggest that drifting pumice may contribute to the dispersal of some attached marine diatoms.