Let’s Talk Bugs: an Overview of Benthic Collection and the Benefits of Good Bugs

Let’s talk about bugs! Specifically, aquatic insects, also known as benthic macroinvertebrates. The word benthic refers to anything relating to or occurring at the bottom of a body of water, and that’s exactly where we find these little bugs! These macroinvertebrates are visible to the naked eye and live in a variety of habitats on stream bottoms, like large woody debris, undercut banks, fine root mats, instream structures that promote leaf pack formation, and emergent sticks and rocks within riffles.

But why is it so beneficial to keep track of these bugs? Benthic macroinvertebrates have a wide range of ecological functions, like being the primary processors of organic material and being sensitive to pollution. Depending on their presence and diversity in our streams, it suggests that the water quality of our stream is healthy enough to support a flourishing aquatic community. In other words, if the bugs are present, that’s a great indicator that our streams are healthy.

Wildlands Engineering (Wildlands) established our own biological monitoring program in 2014, and benthic macroinvertebrate collection is a huge part of that. Our mitigation projects are designed to improve biological function and ecological health, which we achieve by alleviating water quality stressors and improving in-stream habitat. These projects have significant impacts, and this monitoring program helps us keep track of their long-term effects. To do this, our scientists collect samples and data from sites over time—from project pre-construction to project close-out—a process that can take upwards of 10 years! The data collected is then analyzed using metrics, like the NCBI, which rates a stream on a scale of “poor” to “excellent” based on a species’ tolerance to pollution. We also use the EPT richness metric—which stands for Ephemeroptera (Mayflies), Plecoptera (Stoneflies), and Trichoptera (Caddisflies)—which indicates the presence of bugs that cannot tolerate pollution. Using this metric, we know that if we are not seeing Mayflies, Stoneflies, and Caddisflies, poor habitat or pollutants are most likely present in our stream ecosystems.

Wildlands recently completed a benthic study on our Candy Creek Mitigation Site, located in Guilford County, NC. Benthic samples were collected beginning in the pre-construction phase [January 2015] through the project closeout phase [March 2024]. The project restored 17,085 linear feet of stream along Candy Creek, and one of the site-specific goals was to improve stream habitat for the bugs! This was accomplished by excluding cattle from the streams and creating stable stream channels, which ultimately reduced pollutants and created habitat for the bugs. Wildlands’ scientists collected benthic samples at four different locations along project streams at Candy Creek during multiple phases of the project: pre-construction, two years post-construction, five years post-construction, and seven years post-construction. At each site visit, the scientists would walk the streams with nets and buckets to collect bugs from rocks, logs, leaf packs, and undercut banks. The bugs were then transferred to a lab where they were identified, and NCBI and EPT metrics were calculated.

What we found in our study on Candy Creek is that benthic communities are sensitive to disturbance and require time to reestablish themselves within our streams as the habitats stabilize and the fine sediments flush out following construction. The NCBI and EPT metrics show that Candy Creek had an immediate decline post-construction, followed by gradual improvement through the closeout phase as the ecosystem reacclimated. At the closeout phase of the project, most streams had an NCBI rating of Good to Excellent and an EPT rating of Fair. While there is still room for improvement for sensitive EPT species, the overall quality of bugs in the streams is improving. Stream restoration and environmental conservation are ever-evolving processes, and our biological monitoring program is one way Wildlands works to keep our restoration projects informed, innovative, and beneficial.