Distinguishing Macros from Debris at Dry Mill Branch Site

Loudoun Wildlife’s Stream Team welcomes newly certified stream monitors Tracy and Cooper Niess, who established the first stream monitoring location on Dry Mill Branch just outside of Leesburg. Loudoun Wildlife’s 19^th stream site this year, the Dry Mill Branch location is the furthest upstream in a series of six sites that follow the tributary system from Dry Mill Branch to Tuscarora Creek to the main stem of the Goose Creek.

After collecting, identifying and tallying the benthic macroinvertebrates from the riffles at the site, the team calculated a multimetric index score of 9 out of 12 for the stream – which just passed the threshold for acceptable ecological conditions. This score is in line with the scores from other sites along this tributary system, which were 8 out of 12 (indeterminate ecological conditions) or 9 out of 12.

One of the challenges of conducting stream health surveys during the fall season is the amount of debris, such as leaves and seed pods, that can accumulate in the net. Some seeds pods look very similar to certain types of macros – especially the Isonychia Mayfly (pictured below). As macros love to cling to leaf debris, our monitors and volunteers often place the leaves in a small tub of stream water to help expose these masters of camouflage.