Mysterious "fairy rings" that occasionally form off the coast of Denmark on the bottom of the Baltic Sea aren't of a mythological nature but the last signs of life from eelgrass, a flowering plant that grows on ocean floors, Mother Nature Network reported.
First captured by tourists in 2008, the phenomenon (which may be a strong word) couldn't be explained at the time because it simply hadn't been studied. Its origins were finally explained to the world by biologists Marianne Holmer from the University of Southern Denmark and Jens Borum from the University of Copenhagen and published this month in the journal Marine Biology.
Eelgrass grows in a widening circle; thus, its oldest parts are around the outside. Only those survive when the sand and mud below become over-saturated with sulfide, poisonous for the plant when in excess. The younger, middle growth dies while the older, outside border persists, leaving what appears to be a ring from the perspective of, say, a tourist looking through the surface.
"The result is an exceptional circular shape, where only the rim of the circle survives - like fairy rings in a lawn," Holmer and Borum said.
In a way, eelgrass fuel their own demise by trappping sulfide-infused mud.
"Most mud gets washed away from the barren, chalky seabed, but like trees trap soil on an exposed hillside, eelgrass plants trap the mud," Holmer and Borum explained. "And therefore there will be a high concentration of sulfide-rich mud among the eelgrass plants."
"Fairy rings" also form on grass (where their name was first coined). In some cases, like the rings imprinted in the grasslands of Namibia, scientists still don't have a concrete explanation, according to Mother Nature Network.
