Mayflies, riffle beetles and water striders might be unpleasant sights in drinking water, but their presence in streams means the water is free of pollutants.
Children on a "stream discovery" outing in Piney Run Park on Thursday found those aquatic insects in a small feeder stream on the outskirts of the park.
"There are a lot of pollution-intolerant organisms which only inhabit healthy streams in this water," said Amy Hess, a park intern and leader of the discovery group. "I would call this stream pretty healthy."
That's an important discovery, since the stream feeds into what eventually will be a reservoir, said Ms. Hess, who majors in environmental biology at Western Maryland College.
"Intolerant organisms won't adapt to any pollution," she said. "They die."
The children spent an hour taking organisms and water samples from the stream, which flows into Piney Run Lake.
Richie France, 11, trawled a net through the "misty" stream water and poured his findings into a tray. In about 45 minutes, he had netted two salamanders, two crawfish and a few insect larvae.
"The hardest part was finding specimens; catching them was easy," said Richie, who found only "babies" for his specimen tray.
A frequent visitor to Piney Run Park, he said, "I have seen foot-long crawfish here."
Andrew Oldham, 11, decided the water was "fairly clean" as he moved rocks along the shore, hoping to find a snake.
"It's too shady here for snakes," said Karen Platte, 11. "They like the sun."
Besides, she added, snakes offer no clue as to the water's health.
As she lined up trays of the water samples across a small bridge, Ms. Hess said she found no pollution-tolerant animals. After identifying the animal life captured from the stream, the children pronounced the water clean and healthy.
"Piney Run is not in trouble," said Eileen Kasda, 11. "I knew we would only find healthy stuff."
The children hiked back to the Nature Center, where they tested the water samples for oxygen, nitrogen, phosphates and acidity.
"Phosphate is the bad one," Eileen said. "If it gets in the water, it can kill the animals. It makes a cover on the water surface and sunlight can't get through."
Karen said detergents and shampoos should be phosphate-free. they aren't phosphate-free, write to the company and tell them you are refusing to buy their product," she said.
At the Nature Center, the children viewed their stream findings under microscopes. Kristin Henline, 12, said she could see how the mayfly attaches itself to rocks.
Chris Jones, 10, said he saw gills moving as a tiny specimen swam in the petri dish.
Ellsworth Acker, a member of the Citizens Water Quality Monitor group, showed the children how to test water samples. The monitors have studied area streams for four years and kept records from monthly tests, he said.
Even before 30 minutes of tests proved the water to be of near-perfect quality, Mr. Acker said, the presence of healthy aquatic insects indicated nothing would be wrong.