Can we use barnacles to find people missing at sea? Scientists think so

By Angela Heathcote 3 March 2021
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By counting and measuring barnacles on floating debris, we may be able to track missing people.

In 2015, barnacles were touted as a possible solution to finally pinpointing the location of the missing Malaysia Airlines Flight MH370 aircraft that crashed into the Indian Ocean in early 2014. Although it didn’t quite come to any definitive conclusions, Aussie researchers saw great potential. 

“In that case the barnacles weren’t all that helpful, but that may change in the future as marine forensics develops as a field,” says UNSW marine researcher Thomas Mesaglio. 

Developing the field of marine forensics is something Thomas is at the forefront of. This month, he’s published a paper in the journal Marine Biology detailing the ways barnacles may assist authorities in locating missing persons at sea. 

“If you look at terrestrial forensics, it’s a science that’s been around for over a hundred years and they really have things down to a tee. They can use flies, beetles and other arthropods to estimate how long since a person died or whether a body has been moved. 

“The issue with marine forensics is that things can be transported thousands of kilometres by ocean currents and they decompose and break down a lot differently in the ocean. But we thought we could develop a parallel to the beetles and flies, and it seemed that barnacles were what we were looking for.”

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Given the widespread distribution of goose barnacles, the scientists decided it was the best option. From there, they had to work out some fundamental information including daily growth rates. Despite being extremely common, very little research has actually been conducted on them in comparison to other marine creatures and much of the research around growth rates is from the 1940s and 50s, which has been republished since then. 

In November 2018, a mooring was erected off the Sydney coast and over the course of 178 days, scientists checked the barnacles every three to five weeks. From this and other existing moorings along the NSW coast, they found the average daily growth rate for one common goose barnacle species was 1.05mm – faster than even the maximum previously recorded growth rate.  From there, they identified three key ways barnacles could be used to find missing persons; by counting the amount of barnacles on a piece of debris, analysing the length of the barnacles and by conducting isotopic analysis on the barnacle’s shell.

“Let’s say a fisherman out on his boat goes missing, but we don’t know exactly where or when his boat sank,” Thomas says. 

“Two weeks later, debris from his boat washes up ashore. We can measure and count the barnacles to give a minimum estimate for how long that debris was drifting. 

“This would give us a smaller and more accurate time window of when he may have sunk, therefore also narrowing down the range in which he may have sunk.”

By grinding up a barnacle’s shell, scientists can measure the oxygen isotopes, which reflect the sea temperature at the time the barnacle was forming its shell. 

“You can say when these barnacles were floating in the water, it experienced a water temperature of 24 degrees during this week. You ask, ‘during this week, in this particular area, where was the water 24 degrees?’. In all the areas that weren’t 24 degrees at that time can be ruled out.”

When you use these techniques individually, you’ll get some error, Thomas admits. However, when you combine them, it becomes a powerful suite of tools for deducing where a boat may have sunk. The next step is to see if the equation can be applied in other areas off Australia’s coast. 

“If there as an incident in Sydney or somewhere off the NSW coast, then you can probably apply our data and equations, and it would be useful and accurate, but if you had a similar incident on the Western Australian coast, Gulf of Carpentaria or way down in Tasmanian waters, it’s not clear all of our equations will be useful,” Thomas says. “This is because those areas will have different water temperatures, salinity and nutrients, all factors which influence barnacle growth. The most important step for the future will be conducting the same experiment in different areas.”