Raft of pumice floats past Low

Port Douglas & Mossman Gazette - - FRONT PAGE -

A HUGE float­ing raft of pumice, teem­ing with marine hitch­hik­ers has trav­elled more than 4000 kilo­me­tres and was spot­ted off the coast of Low Isles re­cently.

The pumice was cre­ated by an un­der­wa­ter vol­canic erup­tion near New Zealand and has been trav­el­ling for around 12 months. Rafts of por­ous vol­canic rock are re­mark­able, but poorly un­der­stood, nat­u­ral phe­nom­e­non which play a unique role in trans­port­ing marine species across oceans.

The float­ing is­land of pumice is thought to have trav­elled more than 4000 kilo­me­tres across the Tas­man and the Coral Sea be­fore be­ing spot­ted off Low Isles, by Low Isles care­taker Wayne Fox.

‘‘On Thurs­day 21st, we no­ticed a lot of pumice wash­ing up on the beach and saw it was com­ing from a 600 square me­tre raft, sit­ting about two nau­ti­cal miles away from Low Isles,’’ Wayne said.

‘‘It was un­usual for so much pumice to wash up on the shore. Some of the pieces were quite big, about the size of a hu­man head, and I hadn’t seen any­thing like it be­fore.

‘‘On closer in­spec­tion you could see the pieces of pumice had be­come home to a vast amount of marine life.

‘‘It was spec­tac­u­lar to see it, it has trav­elled so far and so quickly. ‘‘It was truly unique.’’ Dr Scott Bryan, a world ex­pert in pumice rafts from the Queens­land Univer­sity of Tech­nol­ogy, said the pumice was the re­sult of an erup­tion by the Havre Seamount in July 2012 in the Ker­madac Is­lands, north of New Zealand.

The un­der­wa­ter vol­cano spewed out a large amount of pumice, cre­at­ing a raft es­ti­mated to be more than 20,000 square kilo­me­tres in size.

‘‘Pumice rafts are the only process in evo­lu­tion­ary his­tory that can trans­port species fairly rapidly up to 30 kilo­me­tres per day across deep oceans that would nor­mally act as ge­o­graphic bar­ri­ers,’’ Dr Bryan said.

‘‘Species such as goose and acorn bar­na­cles, mol­luscs, ane- mones, bris­tle worms, hy­droids and crabs are just some of the crea­tures float­ing on this vol­canic rock. In the past we’ve seen rafts be­come home to mi­cro com­mu­ni­ties of more than 80 species in­clud­ing corals, and some­times the weight of the hitch­hik­ers is so great it sinks the pumice.’’

The raft had pre­vi­ously been spot­ted south-east Queens­land, north­ern New South Wales be­fore mak­ing its way to Heron Is­land and even­tu­ally into Far North wa­ters.

While pumice can float for many years, it can also ac­cu­mu­late on beaches or sink af­ter be­com­ing wa­ter­logged or over­loaded with dif­fer­ent species.

WASHED UP: erup­tion

Wayne Fox with pumice from New Zealand un­der­wa­ter vol­canic

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