Almost immediately upon Blaine Alan Gibson’s discovery of the “No Step” debris fragment in Mozambique, questions were raised about the relative scarcity of marine life growing on it. These questions were redoubled after two more finds came to light, one from South Africa and the other from Mozambique, which both looked surprisingly pristine for objects that had been in the water for two years. I explored the issue in a post on this site entitled “Bioforensic Analysis of Suspected MH370 Debris.”
This weekend IG member Richard Godfrey addressed the question in a post on Duncan Steel’s website. “One possible explanation for this obvious difference between the flaperon and the other items,” he wrote, “might be linked to the differing routes taken by the floating debris.”
As a point of reference, I’ve reproduced the current chart from that post (above). Though in reality the currents are not nearly as deterministic as depicted–there is a randomness to the motion of floating objects that causes them to spread out, like a drop of ink in a bucket of water–it does accurately portray the overall movement of things. The black bar represents the area where Godfrey thinks the plane most likely impacted the water, northeast of the current seabed search zone. He points out that to get to the locations where they were found on the coast of Africa, the pieces would have to have either passed around the northern end or the southern end of Madagascar.
In the image below I’ve sketched out what these paths might look like, more or less. The pink oval represents the central gyre seen in the current map above. The yellow line is a hypothetical path proposed by Godfrey that the flaperon might have taken on route to Réunion. The orange line is a hypothetical path that the capsized boat which washed up on Mayotte may have taken during its eight-month drift from northwestern Australia in 2013-2014. I suggest this is a plausible example of a “north route.” The purple line is an even more hypothetical proposal for a “south route” that I just sketched out freehand after watching some drift simulations.
In the first part of his post, Godfrey tackles the question of whether the African debris might have traveled through water too cold to allow the growth of Lepas anatifera, the species of goose barnacle found on the Réunion flaperon:
If floating debris took a path passing slightly further south of Madagascar then it could remain in colder waters (especially between July and October) below 30S, under which circumstance barnacle attachment and growth is contra-indicated. Thus it might be that the three items found on the coast of Africa reached their destinations via such more-southerly routes… The Paindane item (‘676EB’) discovered at around 24S may well show some evidence of marine life, even though it most probably arrived via the southern route past Madagascar, mainly occupying cooler waters… The Mossel Bay find (‘Rolls Royce’) might not be expected to show evidence of marine life because it was discovered at around 34S and may well have spent most of its ocean transport time in the cooler waters below 30S.
To evaluate this idea, I consulted the newly published paper “Endorsing Darwin – Global biogeography of the epipelagic goose barnacles Lepas spp. (Cirripedia, Lepadomorpha) proves cryptic speciation” by Philipp H. Schiffer and Hans-Georg Herbig of Cologne University in Germany (preprint available here). According to this source, Lepas anatifera can be found in waters where the temperature is greater than 15 degrees Celsius. South of this line a sister species, Lepas australis, is found:
To get a sense of where this transition zone occurs, I traced it out on Google Earth and superimposed a surface-temperature chart lifted from Godfrey’s post along with the previously described drift routes.