Monday, June 21, 2010

Mystery of Laurel Hill Creek

I knelt in the 2 foot deep water and clouds of silt swirled from the bottom. The July temperatures meant that wearing a wet suit in this shallow, warm creek was thermal overkill, but I wished I had one on, at least to give me the impression of separation from what appeared to be a dead stream. Route 31 was to my back and I could hear the traffic bang across the bridge. I reluctantly put my masked face into the water and took a few hard breaths as I adjusted to the water temperature and stark view. The traffic noise was replaced with the sound of my breath rushing through my snorkel. Fine sickly grayish brown silt enveloped the bottom. The water was clear, but there was no life. Not even the usual thin algal mat that covers everything in many of the streams I have visited. The algal growth is a sign of eutrophication. Ecosystems, especially aquatic ones, need algae. They form the foundation of food webs. But too much algae create an unhealthy system. Algae are essentially a kind of plant. They are different of course since they have a hold fast instead of roots, but they serve the same role: they produce food that fuels the rest of the ecosystem. They need nutrients, specifically nitrogen and phosphorous, to grow. Too much nitrogen and phosphorous means too much algae. Most algae are short lived and when they die, they rob oxygen from the water as they decompose, which results in water that can’t support much life. The excess nitrogen and phosphorous come from us in the form of sewage, lawn fertilizer, farm fertilizer and car exhaust. Everything we do on land, and in the air affects fresh water systems and we are over fertilizing most of them on the planet, which causes widespread eutrophic conditions.

But Laurel Hill Creek didn’t even have that eutrophic algal mat growing in it. I crawled my way upstream along the bottom in a foot of water. Rock masses formed other-worldly shapes in this lifeless realm. No fish. I thought that I would at least see a sucker. Why was this rural stream in such a degraded state? I picked up a small rock and found a young crayfish. At least this stream isn’t completely devoid of life. The small crustacean took its time backing into its hole. A large disjointed dead crayfish claw lay near the base of another stone.

Rock, apparently imported to this stream for some construction project – maybe the route 31 bridge, littered the bottom, didn’t fit with the native geology, and gave the place a very strange artificial feel. A pipeline marker loomed out of the four foot murk. This stream was obviously harshly used. Finally I came upon a mass of brilliant green filamentous algae that rested like a large wad of cotton on a rock.

I returned to the stream later that night as lightning flashed in the distance, with the hunch that Laurel Hill Creek is loaded with crayfish. I was right. As soon as my light hit the water, dozens of pairs of orange reflecting eyes shone back. Laurel Hill creek isn’t all dead. There is life here, and the life here is just as fascinating as the life in a more pristine creek. But the question of why Laurel Hill is degraded remains, which will lead to the important answer of what can be done to restore the damage. Crayfish deserve better.

No comments:

Post a Comment