Pink Barnacles on Pumice

by Hazel Britton and Julie Serafin

barnacle on pumice 1
Julie's piece of pumice¹
barnacle on pumice 2
Hazel's pumice²

Whilst on Flinders Island in November 2014, Hazel Britton picked up a piece of pumice with beautiful pink barnacles attached, the shells of small crustaceans that had lived and travelled on the pumice. She had never seen these barnacles before despite many years of opportunistic beachcombing. When showing the piece of pumice to Julie Serafin, she was surprised to find that Julie had an almost identical, but slightly larger piece, also found on Flinders Island at the end of April 2014.

We were obviously curious to find out more about these barnacles, but could find no mention of pink barnacles in Between Tasmanian Tide Lines (2010) or online. Australian Marine Life (2005) states that the Class Cirripedia (Barnacles) comprises about 1000 species, and that Acorn Barnacles like our specimens, include the great majority of Cirripede species.

Barnacles are known to survive where other sea life fails because their conical forms deflects waves and they adhere to a surface with a natural cement, making them ideal long distance travellers (Carson, 1998).

Sarah Lloyd suggested that we contact David Maynard, natural science curator at the Queen Victoria Museum and Art Gallery, for more information.

David very kindly supplied the following interesting information on the barnacles and directed us to a website regarding pumice being washed up on Tasmanian shores since 2013, related to the Havre eruption.

'I am cautious to give a definitive identification for the barnacles. This is because I am not that familiar with them but also, it likely they may have come from east of New Zealand or further afield. These large barnacles are likely to be from the genus Megabanalus, a group of barnacles that grow to over 7 cm in length and inhabit the lower intertidal zone, where they would be exposed to the air for a short period of time each day (and you can imagine that bobbing around on a piece of pumice would be similar).

The colour is unusual, but not uncommon. I have found links to Hawaiian specimens of similar shell form and colour. The colour may relate to the animals’ diet or the colour inside the shell. I think it would normally be purple.'

After watching a media item on the local ABC that asked people on the east coast of Tasmania to be on the lookout for pumice as it washes up on our shores, we sent our photos to Dr Rebecca Carey, a Senior Lecturer in Earth Sciences at the University of Tasmania.

Dr Carey (pers. com.) said that pumice has been arriving on the north east coast of Australia since 2013 related to the Havre eruption which occurred in 2012. Havre is a submarine volcano about 1000 km north of Auckland that lies at a depth of about 700 meters. The eruption produced a gigantic pumice raft that slowly made its way around the Pacific Ocean. In March 2014, twenty months after the eruption, pieces of pumice were being found on beaches in north east Tasmanian. The two photos on the ABC website were of pieces of pumice with gooseneck barnacles (above), members of the other major group of cirripede species Lepadomorpha. The article also mentions that up to 80 different marine species have been found on some pieces of pumice.

Dr Carey supplied two websites where we could find further information. Perusal of these sites provided a wealth of information on the formation of pumice from volcanic eruptions and expeditions and investigations by scientific institutions to the site of the Havre volcano. They also included links to other websites and other scientists working on pumice that has been washed up at other places in eastern Australia. On another website supplied by Sarah we noted that Dr Scott Bryan, Assistant Professor from the School of Earth, Environmental and Biological Sciences at the Queensland University of Technology, was heading a study investigating marine creatures found on pumice off the coast of Queensland. We decided to send him our photographs in the hope that he might be able to add to the information we had so far received.

Dr Bryan kindly replied immediately agreeing that the pumice looked like Havre pumice sourced from the 2012 eruption. He also added the following information:

'This pumice made its way via a rather circular route down the east coast of Australia to Tasmania. We have recognised for example, some corals (mainly Pocillopora) and also a gastropod (Litiopia sp.) on pumice collected in Tasmania which are species well outside their normal geographic ranges. David noted this in his correspondence to you.'

In his email referred to above, David Maynard mentioned that the barnacle larvae could have settled on the pumice in distant waters:

'This is a great example of how new species can be naturally introduced to new environments. The dangerous thing these days is that warming waters, cause by climate change, will allow more of the natural incursions of species to survive in our region, when previously the cold winter waters would have killed them off.'

Dr Bryan added the following:

'The barnacles are definitely of the Acorn barnacle group and I am no expert, but David’s suggestion of Megabanalus seems fairly good. Based on the size of the barnacles, I would expect that they attached while in warm water (probably off Queensland, if not further afield?) and have been transported to Tasmania. Not sure if growth rates are well known for this species.* Based on the size, you could then work out how long they were on the pumice. We have certainly identified acorn barnacles on pumice we have collected here. But they were almost always very small (<0.5 cm in diameter), suggesting recent recruitment and therefore embarkation around Queensland/northern NSW would make some sense for your samples.'

*Unfortunately we have not been able to identify the species and could find photographs of only a few of the hundreds of species that are known to exist.

For more information about the July 2012 Havre eruption please refer to the websites below.

¹Barnacle 1. This piece of pumice has shells of very small barnacles attached to the larger barnacle. There is also a small piece of coral and signs of other marine life. Photo Julie Serafin.
²Barnacle 2. The largest barnacle has a diameter of 2 cm at the widest point. Minute shells, coral and what appears to be larval cases were found inside the shell. Photo Hazel Britton.

We would like to thank Sarah Lloyd for showing interest in our beachcombing finds and for suggesting we contact David Maynard at the Queen Victoria Museum and Art Gallery; also for sending a link to an article on Dr Scott Bryan’s work titled ‘Floating Pumice Seeding Aussie Reefs’.

David Maynard, Dr Rebecca Carey and Dr Scott Bryan all replied promptly to our requests with enthusiasm and information, as well as directing our attention to various websites. Their replies stimulated us to find out as much as possible about our beachcombing finds and we thank them for encouraging us to be inquisitive.

- Carson, Rachel L. (1998). The Edge of the Sea. First Mariner Books Edition.
- Edgar, Graham J. (2000). Australian Marine Life Revised Edition, The Plants and Animals of Temperate Waters. Reed New Holland. - Between Tasmanian Tide Lines. A Field Guide. 2010 Edition 3. A Production of the Tasmanian Marine Naturalists Association Inc. in association with The Tasmanian Museum and Art Gallery.
- Scientists on lookout for volcanic rock on Tasmania's east coast
- Mapping, Exploration, & Sampling at Havre

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