Abstract

In January, we take our nets to a no-name stream in the foothills of the Blue Ridge Mountains of Virginia to do a special kind of macroinvertebrate monitoring—looking for winter stoneflies (Allocapnia). Winter stoneflies have an unusual life cycle. Soon after hatching in early spring, the larvae bury themselves in the streambed. They spend the summer lying dormant in the mud, thereby avoiding problems such as overheated streams, low oxygen concentrations, fluctuating flows, and heavy predation. In later November, they emerge, grow quickly for a couple of months, and then lay their eggs in January. January monitoring of winter stoneflies helps in interpreting the results of spring and fall macroinvertebrate surveys. In spring and fall, a thorough benthic survey is conducted based on Protocol II of the U.S. Environmental Protection Agency’s Rapid Bioassessment Protocols for Use in Streams and Rivers (Plafkin et al., 1989). Some sites on various rural streams have poor diversity and sensitive families. Is the lack of macroinvertebrate diversity because of specific warm-weather conditions, high water temperature, low oxygen, or fluctuating flows, or is some toxic contamination present? In the January screening, if winter stoneflies are plentiful, seasonal conditions could probably be blamed for the earlier results; if winter stone-flies are absent, the site probably suffers from toxic contamination (based on the rural location, probably emanating from nonpoint sources) that is present all year. Though different genera of winter stoneflies are found in the region of southwestern Virginia, Allocapnia is sought because it is present even in the smallest streams (Figure 12.1).