Fairy Rings Beneath the Sea

RingAroundTreeIn 2008 photographer Jacob T. Johansen snapped a photo of strange circles in the shallows off of Mons Island in Denmark. Mons Island is surrounded by the Baltic sea. Some people thought they were fairy rings. Others, crop circles under water. Perhaps they were marks left by alien spaceships. No one knew for sure.

So biologists Marianne Homer (University of Southern Denmark) and Jens Borum (University of Copenhagen) set out to solve the mystery. Here’s what the underwater fairy rings looked like; Johansen’s photo:


The Clues Add Up

Turns out the solution lies in an ecological problem experienced by eelgrass. This undersea grass grows from a central point and radiates outward forming a circle. The older plants are inside the circle while the younger sprouts live around the edges. (See photo below.)

eelgrass-fairy-rings-denmarkThe scientists were able to determine that an excess of sulfide in the mud in which the grass grows was actually killing the plants. Normally sulfides in the ocean bond with naturally occurring iron. However in the Baltic sea around Denmark, the waters are iron poor. So the sulfide drops to the floor of the sea, accumulating in the mud and spelling disaster for the eelgrass. Making the situation worse, as the eelgrass dies, it decomposes leaving even more sulfur in the undersea soil.

One important factor causing low iron levels in the sea is pollution. Phosphorus and nitrogen run off the land into the surrounding waters and reduce the levels of iron while fostering a boom in algae growth. The more algae in the water, the more sunlight gets blocked at the sea floor, and the eelgrass takes another hit.

AmeliaJaneMurrayFairiesInPeapodWhy Care About Eelgrass?

You may wonder what all the fuss is about the eelgrass. Well, it’s an important habitat for sea creatures like crabs especially when they are molting and small fish until they are big enough to enter the waters on their own. Algae also grows on the eelgrass leaves and this is an important food source for other undersea creatures. (Artwork above “Fairies in a Peapod” by Amelia Jane Murray.)

In addition, eelgrass protects the land around it by preventing erosion. It also helps clean the waters by filtering out particles and sediments that would otherwise mess up that ecosystem.

The good news is that the University of South Denmark is coordinating a research project called NOVA GRASS. Their goal is to restore the undersea habitat so the eelgrass can thrive once more.

SeashoreFairySo, No Fairies?

I like the fairy connection to this story because, according to legend, fairies in general are good stewards of the planet. These “fairy rings” formed by the die-off of eelgrass were an excellent way to get our attention so that a fix could be found. The scientists are still working on that “fix,” but they will probably find a way to rectify the problem soon.


I’m still looking for fairies, though. I’ll let you know when I find them!

Til the next time!


LetMeInUh, I don’t think so! Someone get the fly swatter please!

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