Pumice rafting and biota dispersal across the Southwest Pacific following the 9-11 August 2006 Home Reef submarine volcanic eruption, Tonga.

The research in this 'Urgency Application' has been prompted by the brief opportunity to study pumice raft(s) that were recently generated by a shallow marine explosive eruption at the Home Reef volcano in the Tongan Islands. The eruption occurred from August 9-11, 2006, and pumice raft(s) from the eruption have reached Fiji and are progressing westward following a similar trajectory of previous rafts to eastern Australia. The rafts will reach eastern Australia within the next year where a large proportion of the pumice will be stranded along the coastline, and the rafting event will largely be completed. Floating rafts of pumice are an important, but poorly understood natural phenomena, from their generation by silicic explosive eruptions and dispersal by wind and ocean currents, to their recruitment and long-range transport of biota. Pumice rafts provide an important natural vector for the long-range dispersal of many marine species, overcoming physiological limitations on their dispersal range, and allow intermittent contact and exchange between shallow marine ecosystems that otherwise remain extremely isolated by vast stretches of deep ocean. Pumice rafting will have been an important process in the geological past, and in the future, it may serve as a natural mechanism for ecosystems damaged by human activity to recover species and biodiversity. In many cases, pumice rafts also represent the only record with which to understand the petrogenetic origins and eruptive processes of shallow marine explosive eruptions of silicic magma in island arc settings. The Southwest Pacific is a key area to study these phenomena with pumice rafts being generated once every five to fifteen years from relatively small-volume explosive eruptions from volcanoes in the Tonga-Kermadec islands. The pumice rafts, generated from the submarine explosive eruption at the Home Reef volcano beginning August 9, are currently passing through important areas of tropical reefs, the timing of which will correspond to the late Spring spawning events, as well as the summer cyclone season. These pumice rafts therefore provide a brief window of opportunity to understand in much greater detail, the mechanisms of pumice rafting, how this vector is exploited by a range of biota, and how successful it is for the long-range dispersal of biota to the Great Barrier Reef, an important area of global biodiversity.