At first, it seemed ilke a mystery. As of last Sunday (6th June), beachgoers in southern Maine were complaining that after visiting the shore at Wells Beach and also at York Beach, their feet were stained black on the soles. The substance was difficult to remove and clung tenaciously to the skin.
Initially it seemed that the "black goo" might be algae or some kind of seaweed by-product, but it turned out to be neither of those things. It was, however, still an organic stain. The cause? "Beach bugs."
The first person to put the black goo under a microscope was John Lillibridge, an oceanographer (albeit recently retired), who thought that it would turn out to be algae or an oil spill. He said he was very surprised when he examined the substance closely and it revealed itself to be "a whole bunch of bugs".
Each individual bug has wings smaller than a pinpoint, but in huge numbers, their crushed corpses create the black goo that had coated beachgoers' feet.
A marine biologist at the Maine Geological Society, Steve Dickson, undertook further research into the phenomenon, fearing initially that as well as being unsightly the discoloration might turn out to be unsafe. But no. It's just the crushed bodies of millions of bug corpses. No biggie.
This is the first time I’ve seen or heard of this in my 35 years. Normally this time of year we get calls about too much seaweed (wrack) on the beach and the swarming flies that hang around the decaying seaweed. This wasn’t that. - Steve Dickson
Apparently, they're likely to be harmless kelp flies (which feed on decaying seaweed), and were probably on the surface of the ocean before being washed onto the shore. The black stains they produce are a by-product of the kelp they eat, which is a dark green and even darker when decayed.
Even though they're harmless and it's a natural phenomenon, and even though they'll probably disappear back out to sea again when the winds change so it'll probably be a short-lived inconvenience for beachgoers, this appearance of so many bugs en masse on one beach is a rare and unusual occurrence. I wrote recently about how cicadas are having a rare (once every 17 years) Brood X emergence around New York and other mid-Atlantic states, and it seems a strange coincidence that on the American coast, another type of insect is also having a rare moment in the sun.
Maybe this is the year that the millions of insects around us start to make their presence more widely felt?! I hope not.