Recently two pieces of debris that may have come from missing Malaysia Airlines Flight 370 were found on the coast of Mozambique.

The first piece was discovered on February 27 by American lawyer Blaine Alan Gibson on a sand bar near the town of Vilankulo (top left). Composed of fiberglass skin around an aluminum honeycomb core, and bearing the words “no step,” the piece is widely presumed to be a part of a 777 horizontal stabilizer. A fastener found attached to the part carried an identifying number that is consistent with, though not exclusive to, a 777. Soon after the find was made public Malaysia’s transport minister Liow Tiong Lai tweeted that there was a “high possibility debris found in Mozambique belongs to a B777.”

The second object was reported on March 11 by South African teenager Liam Lötter, who found it on a beach near the resort town of Xai Xai in southern Mozambique in December. Approximately a meter long, it carries the stencilled code “676EB,” which is written on the right-hand outboard flap farings of Boeing 777s. Its material, a hybrid of fiberglass and carbon fiber, is also consistent with a 777 flap fairing.

The fact that MH370 was the only Boeing 777 lost over the ocean lends weight to the supposition that both parts come from that aircraft.

The pieces’ appearance, however, is quite different from that of the first (and so far, only confirmed) piece of MH370, the plane’s right-hand flaperon, which was found on Réunion on July 29, 2015. Every edge of the flaperon, and much of its broad surface area, was encrusted with goose barnacles of the genus Lepas. The flaperon also had been settled across much of its surface by a brownish algae. Both of the recently discovered pieces are relatively free of marine growth.

This article will explore what the presence or absence of marine growth indicates about how the three pieces traveled through the ocean.

Marine Fouling

When man-made material is immersed in an oceanic ecosystem, a number of plant, animal, and microbial species will begin to settle and grow upon its surface, a process known as “marine biofouling” because historically the process has attracted the most attention as a nuisance to mariners.

Marine biologists study the process using devices called “settling plates” or “fouling panels,” rectangles of material which are put in the water and then observed as time goes by. “The first thing that settles is microalgae, which looks like a slimy brown scummy scuzz,” says Cathryn Clarke Murray, a marine biologist who studies floating debris at the North Pacific Marine Science Organization. Out in the open ocean, microalgae is followed by bryozoans, moss-like filter feeders, and goose barnacles of the genus Lepas. “I’ve found paper bags that have blown into the Pacific and have barnacle larvae on them,” says Bloomsburg University professor Cynthia Venn, who has been studying marine organisms for decades.

Given the great size of the Earth’s oceans, and the relatively slow speed at which objects drift (on the order of dozens of miles per day), objects encountered on the open sea have plenty of time to become colonized. During a survey of debris in the Pacific, marine biologist Miriam Goldstein collected 242 objects and found that all had organisms growing on them except for two that were one square inch in size. University of Florida biologist Mike Gil conducted a similar survey voyage in the eastern Pacific and says that “we didn’t find any clean debris, bottle cap size and larger.”

The mix of species present on an object can yield clues about how it has drifted, a process that renowned invertebrate biologist James Carlton, director of the Williams-Mystic Maritime Studies Program, has labeled “bioforensics.” In his study of marine debris washed out to sea during the Japanese tsunami of 2011, Carlton says, he found “we can track debris across the ocean using two species of bryozoans. One’s cold water, one’s warm water. When I get a boat that lands in Washington or Oregon and has the warm-water bryozoan, it tells me that it went well south before turning north.” Similarly, Carlton has been able to identify debris that traveled south along the coast of Japan before crossing the Pacific by the presence of sea life endemic to that area.

Unfortunately, the flaperon discovered on Réunion Island has been closely held by French investigators since its discovery, so is not known if such a bioforensic analysis has been conducted.

While the presence of certain species can indicate the route its home drifted, the size of individuals can indicate how long an object has been at sea—with some important caveats. Water temperature and the presence of nutrients both affect how quickly an organism will grow. Those on tsunami debris that was carried along through the nutrient-rich waters of the Aleutian chain and wound up in the Pacific Northwest grew faster, and in greater profusion, than those which grew on debris that followed a more tropical route and came ashore in Hawaii.

In order to gauge the time that an object has been in the water, then, it’s important to have a baseline against which to measure. For instance, here’s a boat that spent eight months drifting from Australia to the island of Mayotte in the western Indian ocean.

By comparing the size of the barnacles with the known dimensions of the boat, it is possible to ascertain that they have a maximum capitulum length of 3.5 cm.

And here are Lepas barnacles that grew on the Réunion flaperon.

Given the similarity in latitudes between Réunion and Mayotte, and the fact that the flaperon is believed also to have begun its journey off the west coast of Australia, the temperatures and nutrient levels experienced by both objects should be roughly the same. Applying the same photographic analysis yields a capitulum length of 2.3 cm. Adjusting known Lepas growth rates for the age and size of the Mayotte Lepas specifimens, the size of the Lepas barnacles on the Réunion flaperon suggests it was in water between four and six months.

This technique cannot be applied to the objects found in Mozambique because there are no identifiable forms of marine life visible on them. This absence of visible growth, however, allows us to put an upper bound on the amount of time they were in the water.

“If I put a piece of fiberglass into the ocean, I would expect to see that kind of scummy scuzz about a month after,” says Murray. However, in photographs the pieces of Mozambique debris “look pretty clean to me,” she says.

Shown an image of the new debris and asked how long the pieces look like they’ve been in the water, Jim Carlton says, “My gut instinct would be [that these pieces have been] not long at sea. Not long at sea, because we presume that if you are at sea, you’re going to get Lepas and bryozoans and other oceanic species on you. If you drift in the coastal zone, you’ll pick up coastal barnacles.” Given all that, he cites a possible immersion time of “a couple of days.”

Sam Chan, who studies invasive species at Oregon State University and regularly conducts settling plate experiments on the Pacific coast, says that he finds the clean condition of the honeycombs to be telling. “Not to see marine growth in the honeycomb structure was surprising to me,” he says. “The settling plates we put in the water actually look very much like the honeycomb structure, because it’s a good environment for them to settle.” He says the amount of time the objects have been in the water “could be a couple of weeks. It’s certainly not indicative of something that has been in the water for multiple years, let alone even half a year.” He adds, “If there’s no fouling, was it even in the water?”

Local Mozambique officials who were able to examine the Gibson piece firsthand were similarly skeptical. Joao de Abreu, the director of Mozambique’s National Civil Aviation Institute, was quoted by his government’s official news agency as saying that the object was too clean to have been in the ocean for two years.

Henry Carson, a marine biologist at the Washington Department of Fish and Wildlife, points out that fish sometimes congregate around floating debris in the ocean and can reduce the populations of organisms growing on it. “A colleague of mine encountered a piece of a boat in the middle of the Pacific–I believe also made of fiberglass–that had very few barnacles–and a lot of fish,” he says. “Presumably the grazing fish had kept the barnacles from becoming established. Your pieces could also have sheltered a substantial fish community. Not sure the fish would keep it 100% clean, though, especially of all algae and bryozoans.”

In the Pacific Northwest, it’s not uncommon for beachcombers to find pieces of tsunami debris that have no significant accumulation of marine life on them, but these tend to be highly buoyant objects like pieces of polystyrene foam or smooth, round buoys and floats. “I can only think this stuff rolls on the sea surface,” says Carlton. “Between the UV and getting baked and dried out, dessication’s going to do a job, these things come in whistle clean.”

Obviously that neither of the Mozambique pieces would fit that description, but Carlton points out that it might be possible to imagine a scenario in which they floated across an ocean and then became beached, whereupon it dried out, was foraged upon by terrestrial animals and scoured by wind and sand, then washed out to sea again for a few days before becoming beached again. “One can imagine these scenarios,” he says. “Their probability is another matter.”

Other biologists disagree that weathering and predation could plausibly erase all trace of prior colonization. “We usually see some evidence left, even if it’s been dried out on the beach for a while,” says Murray. “You would see barnacle shells, or the byssal threads from the mussels, even if the mussel’s gone. Usually you see something. I can’t see anything in these pictures.”

“Even if beached and tumbled and baked for some time, I would expect to see a lattice of bryozoan skeletons, barnacle attachment scars, and some staining from where algae had grown. A lot of those things are pretty resilient,” says Carson. “I don’t see any of that in the close-up pictures.”

Says Chan, “There could be some time of feeding or predation, but within that honeycomb structure you would probably still see some remnants, and I just don’t see any.”

Carlton agrees that the condition of the Mozambique debris is puzzling. “Without any bioforensic evidence,” he says, “it’s just a headscratcher.”

Conclusion

The absence of biofouling on a piece of suspected aircraft debris recovered in Mozambique in December, 2015 suggests that it entered the water no earlier than October of that year. The absence of biofouling on a piece of suspected aircraft debris recovered in Mozambique in February, 2016 suggests that it entered the water no earlier than January, 2016. It is entirely possible that one or both of the Mozambique objects were never in the ocean at all.

All of these results counterindicate a scenario in which these pieces of debris were generated by a crash on March 8, 2014 near the area currently being searched by the ATSB. It is incumbent on all the relevant authorities to make public the details of a close examination of the parts, in order to determine how these objects could have arrived in the western Indian Ocean.

Update 3-17-16

I’m adding a couple of videos that Blaine very graciously shared with me, to show how his piece floated in the water. It should be fairly clear that this is not a spherical-float kind of situation. One end of the piece is denser than seawater and is going to be submerged whether or not the piece is occasionally flipped by waves.

Update 3-18-16

David Griffin, an oceanographer with Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO), has expended considerable effort working with drift models to understand how ocean currents may have dispersed debris from a crash site in the southern Indian Ocean. In response to Blaine Alan Gibson’s Mozambique find, he writes on the CSIRO web site: “this item is not heavily encrusted with sea life” and therefore “time at sea is therefore possibly much less than the 716 days that have elapsed since 14 March 2014.”

A number of readers have speculated about various factors that may have kept marine organisms from taking up residence on these objects. The fact is that unless a piece is made entirely of smooth unbroken plastic (and usually even then), it is going to acquire a coating of marine life after a certain amount of time at sea. To see a lot of examples of how objects of different size, shape, and material accumulate debris, here is a gallery of Japanese tsunami debris found washed up in Hawaii. And here is a gallery of stuff that washed up in the Pacific Northwest of the USA.