Fascinatingly Mysterious New Flaperon Barnacle Data


Last month Robyn Ironside, the National Aviation Writer at the News Corp Australia Network, published what struck me as an extremely important article in the Daily Telegraph about the work of scientist Patrick De Deckker, who had obtained a sample of a Lepas anatifera barnacle from the French judicial authorities and conducted an analysis to determine the temperature of the water in which the barnacle grew. A snippet:

The same 2.5 centimetre barnacle was used by both French and Australian examiners — but different techniques applied. “For my analysis, I used a laser to create little holes of 20 microns, over the length of the barnacles. In all we did 1500 analyses,” said Professor De Deckker.

Intrigued, I reached out to Ironside, asking if she could tell me more about De Deckker’s work. She very graciously did just that, and shared this extremely interesting nugget, a verbatim quote from De Deckker:

The start of the growth was around 24 degrees (Celsius) and then for quite some time, it ranged between 20 and 18 degrees (Celsius). And then it went up again to around 25 degrees.

This is surprising. The graphic above shows the water temperature in July 2005, which I take to be a rough proxy for the water temperature in March 2014. (I would be extremely grateful if someone could extract granular sea-surface temperature maps for March 2014 to July 2015 from NASA or NOAA databases available online.) It shows that the waters in the seabed search area are about 12-14 degrees Celsius. To find 24 degree water would mean trekking 1000 miles north, above the Tropic of Capricorn.

It has long been known that Lepas anatifera do not grow in waters below about 18 degrees Celsius, and that in order to begin colonizing the flaperon (if it began its journey in the search zone) would have had to first drift northwards and wait for warmer months and warmer latitudes. What’s peculiar is that this particular Lepas would have to have waited a good while beyond that, until the flaperon arrived in water six degrees above its minimum. As I’ve written before, Lepas naupali are common in the open sea and in general are eager colonizers of whatever they can glue their heads to.

Peculiarity number two is that after this period of initial growth the flaperon then found its way into significantly colder water, where most of its total growth took place. What’s weird is that every drift model I’ve ever seen shows currents going through warm water before arriving at Réunion. Where the heck could it have gone to find 18-20 degree water? And how did it then get back to the 25 degree waters of Réunion Island, where it finished its growth?

I’m frankly baffled, and am appealing to readers to ponder historical surface temperature data and drift models to help figure out what kind of journey this plucky Lepas might have found itself on.