Ecology

Sue deVeer,
Friends of Toms Creek

(5/2019) On March 29, the Friends of Toms Creek held their spring macroinvertebrate count of aquatic insects found in Toms Creek. About twenty volunteers peered into white bins of water samples, spoons and pipettes in hand, watching for something to move. The counts, which have taken place in the spring and fall every year since 2014, aim to increase community awareness and introduce participants to hands-on citizen science.

Friends of Toms Creek is a non-profit group working to protect the headwaters

of Toms Creek, a rare, High-Quality cold water fishery in southwest Adams County, Pennsylvania. The grassroots group monitors and protects the environment and watershed of Toms Creek. The fifty square mile Toms Creek watershed begins in Adams County, and travels twenty-one miles southeast through Frederick County, Maryland where it joins the Monocacy River. The Monocacy River is a tributary to the Potomac River, contributing to the health of the Chesapeake Bay, and ultimately, the Atlantic Ocean.

All of Adams County’s water begins here, with no rivers or streams flowing into Adams county, so we are called to be the stewards of these pristine headwaters. Adams County is fortunate that our water resources are generally of good quality. Nevertheless, how do you know? Some of the most "pristine" streams in Pennsylvania look beautiful, but there is not a living thing in them because of acid or copper-tainted or silty mine drainage. Water quality simply cannot be determined by casual observance. It requires some detective work.

The detective work starts by examining the aquatic life in the stream. Most folks are aware of fish in streams and that fish are an indicator of water quality, with wild trout being the best indicator. Of course, trout and other fish must consume something to survive and aquatic insects are the next thing down on the food chain. As it turns out, aquatic insects are actually a better indicator of water quality than fish and the detective work starts getting serious with macroinvertebrate sampling.

"Macro," meaning big (and everything is relative), and "invertebrate," meaning no backbone, is a big word for aquatic insects. By collecting and analyzing a sample of aquatic insects from a stream, you can determine the quality of the water in the stream. Some insect larva, like mayflies and stoneflies, absolutely refuse to live in polluted water, so if you find those, the water quality is good. Other insect larva, like black fly and midges, tolerate lower water quality, so if you find those, the water quality is suspect. If you find nothing in your sample, you have a toxicity problem.

A growing team of interested and dedicated volunteers has been surveying Toms Creek twice yearly in spring and fall since 2014 to determine the water quality and, over time, determine any trends to the health of the stream. At the Friends of Toms Creek volunteer event in March, participants ranged in age from 8 to 70-plus. Using laminated identification sheets, aquatic insects were sorted by kind into white ice cube trays for a water biologist to count and identify. Some of the critters try to hide in the leaf debris, or under the stones or cobbles, and some try to crawl right out of the ice cube trays! Volunteers were amazed at the variety and quantity of water critters living in the creek. This spring, several species of mayfly nymphs and some large stonefly nymphs were observed. These sensitive species are positive indicators of stream health. In one sample the children even found a sculpin, a tiny fish – not an invertebrate, but another great indicator of the stream’s health and diversity. The children loved running the sculpin back to the stream to be released!

The macroinvertebrate counts are done using the Environmental Alliance for Senior Involvement (EASI) method, which is very accessible to non-scientists. For macroinvertebrate assessment, this method enables watershed groups to easily monitor the long-term biological condition of streams. The EASI method utilizes an easy to understand tally sheet. An example can be viewed in the Biological Monitoring Manual developed by The Alliance for Aquatic Resource Monitoring at Dickinson College. By following established sampling protocols, volunteers can develop a score that indicates the health of a stream. An even better indicator results from sampling a stream several times over an extended period. Testing needs to continue to determine long-term trends in stream health.

The macroinvertebrate counts completed over the years provide a good repeated snapshot of the health of Toms Creek. In general, the quality of the water in the creek is good, which is the expectation since the Pennsylvania Department of Environmental Protection has rated Toms Creek as a High-Quality, cold water fishery, and the Pennsylvania Fish and Boat Commission continues to stock the stream with 1,000 trout each spring. Dedicated trout fishermen may also know that the Mummasburg Sportsmen’s Club stocks 125 trophy trout each spring here in Toms Creek!

During the Friends of Toms Creek macro count, the children were especially excited about the caddis fly nymphs, some of which were a beautiful bright green color. A caddis fly nymph is one of nature’s tiny architects. On top of the stones or cobbles, they build tiny fishing nets to catch edible morsels floating by. Under the creek stones, they each build a tiny home out of pebbles or tiny twigs and pieces of leaf, depending on the species of caddis fly. They go inside to pupate, hatching out, to the delight of the trout, into adult caddis flies.

While trout love to snatch the adult caddis flies and mayflies that are hatching out at this time of year, they also love to turn over the cobble stones in the stream bed to catch the macroscopic invertebrates hiding there. So aquatic insects, sensitive to pollution of any kind, are important food for trout at all stages of the insect’s life cycle. Sediment, which can be carried into streams from agriculture, home construction or mining operations, can fill in between and bury the cobbles, killing off sensitive insect life which should be found there in a balanced healthy and diverse pristine stream.

In addition to our twice-yearly macro count, our nonprofit utilizes a stream monitoring plan. The goals are simple: (1) to measure the health of Toms Creek, and (2) determine if anything is impacting or affecting the health of Toms Creek. Preparing a monitoring plan was an important step in organizing our monitoring effort because:

• It helps you focus on what you are trying to achieve with your monitoring program.
• It allows you to learn all of the components of the monitoring program before "getting your feet wet."
• It clearly documents your sampling and analysis methods along with your quality assurance procedures.
• It helps you to select the most appropriate monitoring strategy to address the issues that are important to you, your group, and your community.
• It helps to inform new members about your monitoring activities.

We invite you to learn more about Friends of Toms Creek and our mission!