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Pumice the answer to seabird death mystery


The mysterious deaths of up to three million seabirds in a horrific discovery dating back to 2013 have been partially answered in research by the CSIRO.

Australia’s national science agency, along with Queensland University of Technology (QUT), examined the bodies of 172 short-tailed shearwaters to find 96.7 per cent of the seabirds had ingested pumice or plastic.

With such unnatural behaviour accounted for, the next question left unanswered was which came first – starvation, or non-food ingestion?

In a news article by QUT, research paper lead author Dr Lauren Roman said it was likely the former.

“We found that in the instance of the shearwater bird deaths in 2013, these birds were starving, and in their starved state had reduced prey discrimination,” Roman said to QUT.

With the knowledge the birds were starving, researchers then worked on learning where the pumice originated.

QUT associate professor Scott Bryan had been studying pumice rafts for two decades when he considered the seabird mystery and made the complex process of answering the question sound simple.

“We combined the tracking information data of the short-tailed shearwaters, using location tags on migrating birds, and the geological signature of the ingested pumice,” Bryan said.

The pumice was found to have come from the 2012 Havre eruption in the Kermadec arc north of New Zealand.

“By October 2013 when the shearwaters were returning to Australia on their annual migration from the North Pacific, the floating pumice was now located along their flight path as they approached Australia,” Bryan added.

The fact the birds’ starvation led to non-food ingestion led the researchers to ask further questions around why the birds were in such a state.

“With a projected increase in challenging times for wildlife because of threats such as climate change, marine pollution and over-exploitation of resources, this study has implications for mass mortalities and exacerbation of existing threats to marine species,” Roman said.

What is pumice?

When molten lava erupts from underwater volcanoes, it is rapidly cooled and turned into the bubbly rock known as pumice. The stones can end up forming free-floating rafts that host microscopic organisms and tiny sea creatures.

A pumice stone deposit the size of Manhattan that emerged from underwater volcanoes in the Pacific in the past two years has had positive and negative effects on marine and other wildlife in the region.

In quarrying, pumice is deposited on the surface of the earth in loose aggregate form and therefore blasting is unnecessary because it is unconsolidated and can be ripped up by dozers and excavator shovels. Scalping screens are used to filter the pumice from organic soils and unwanted rocks and crushers are used to achieve desired grades, including lump, coarse, intermediate, fine and extra fine.

As an end product, pumice has been employed for centuries in construction, medicine and the cosmetics industry. It is also used as an abrasive, especially in polishes, pencil erasers, and the production of stone-washed jeans. Pumice was also used in the early book making industry to prepare parchment paper and leather bindings. Today, there is still high demand for pumice, particularly for water filtration, chemical spill containment, cement manufacturing, horticulture and the pet industry.

More reading

A geological haven for marine life – but a headache for humans

Pumice the heart of Japanese construction


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