Sorting macroinvertebrates, Little Falls Branch
The numbers are in. Caddisflies rule the creek. Over 50% of the macroinvertebrates found during our winter creek survey were common net spinners larvae. These little critters build shelters on the sides of rocks called retreats, and at the end of their retreats, they spin little nets to catch their food. Unfortunately these net spinners are quite pollution tolerant, so an abundance of them is not a good sign for the health of the creek.
A caddisfly with its retreat and silk net structure holding stream gravels together. Photo credit: Benjamin B. Tumolo.
Little Falls Branch Scores Fair
Every 3 months, we survey the creek to see what type of macroinvertebrates are living there. These small critters give us a good picture of the biological health of the creek. We are looking for both diversity and numbers. A good diversity indicates a healthy creek; and the numbers show how many organisms it can support. By combining that data, we can compute a number for the Benthic Index of Biotic Integrity (BIBI Score). Little Falls Branch scored 2.14 this winter, in the very low end of Fair.
We partner with Nature Forward for this effort. The results are shared with the Maryland Department of Natural Resources. To learn more about our macroinvertebrate survey program and view past results, visit HERE.
Notes from the Field
From Frank Sanford, our team leader.
Thanks to our small but efficient crew we completed our winter monitoring. The salt level - 231 PPM was not great, BUT much less than a week before. Here are totals:
Aquatic worm - 1
Planaria - 6
Sowbugs - 5
Midges - 13
Black Fly - 23
Common netspinner 53
