Massive Drift of Pumice Stones Might Trigger Coastal Ecological Transitions

Abstract

An intensive underwater volcanic eruption occurred in the Ogasawara Islands on 13–15 August 2021, bringing unprecedented amounts of pumice to the coast of Okinawa Island in the Ryukyu Archipelago, 1,300 km west of the eruption site, approximately 2 months later. The coast of Okinawa Island, especially along the northern part, is home to many typical subtropical seascapes, including coral reefs and mangrove forests, so the possible impact of the large amount of pumice is attracting attention. Here, we report early evidence of ecosystem changes that may be the result of large-scale pumice shoaling on coastal beaches, estuaries, coral reefs, and mangrove forests. Massive pumice drift is a major obstacle to fishing activities and ship traffic, but possible future long-term changes in coastal ecosystems should also be noted. The phenomena observed on Okinawa Island are expected to occur not only in the Ryukyu Islands but also along the coasts of Kyushu, Shikoku, Honshu Islands, where pumice is expected to drift later.