A week ago, my boyfriend and I spent the afternoon playing at Walden Pond. While I was in the water, I saw what I thought was a bubble swimming up and down in the water. When I knelt down to get a closer look, I realized it was a freshwater jellyfish. The little squish was a couple cm long and clear except for a white marking on the top in the shape of a diamond. I was fascinated and got a little deeper in the water to play with it. As I moved, I accidentally knocked a rock over and out came a pretty big crayfish.
I was excited! Crayfish are a sign of good water quality, and despite the many people that hike, swim, and boat around and in Walden Pond, the water is still and clean. A local couple living in the area said, “During the 1980s and 90s, the Pond was pretty bad; you couldn’t swim in it. So the Concord government set to work cleaning it up, and now we can all enjoy it. It’s so wonderful.”
What’s a better way to show A+ effort on river clean up than by seeing such sensitive creatures as the crayfish swimming around, and by the plenty! Almost every turned rock revealed a crayfish. Though they have claws, the shy creatures preferred swimming away, which they did by doing the backstroke. So anyway, the crayfish were a good sign, but what about the jellies?
“The jellyfish are nonnative,” says Pete, Walden Pond’s park ranger. “They came to the states sometime in the early 19th century and have populated pretty much every state in the U.S.” According to Pete, the little jellyfish do not seem to be invasive. In fact no one is sure what they really do to or for the area at all.
“We have no idea if the fish eat them, if they’re overpopulating the pond, anything. No one’s really done research on them, and they seem to just swim mainly in the middle where it’s deep. Most people don’t even know they’re in the pond.
That is, unless you swim through them during one of their population booms. Last summer, the jellyfish population exploded. Says Pete, “This year, there were so many that some people said it was like swimming through clear jell-o.” However, the jellies have no stingers so, at least to humans, they’re harmless. For the most part, the jellyfish are little clear/white globs bobbing in the water, adding a little extra intrigue to Thoreau’s Walden Pond.