Quantitative Macroinvertebrate Survey of Pen Branch and Indian Grave Branch.

摘要

A total of 82 species were collected at all sites on Pen Branch and Indian Grave Branch during the 28 day period for colonization of the multiplate artificial substrate samplers. Upstream site 2 demonstrated the highest species richness (32), followed by site 3 (31). The average number of species per replicate (14.3) was slightly lower than during March 1989 sampling, a trend noted at all sites except site 3. Species richness at site 3 increased during May sampling, most notably with the presence of numerous mayflies, which were not collected previously at this site. Densities of organisms were lower than in March sampling, with the greatest changes observed at sites 3, 4, and 5. Biomass was greatest at downstream sites 2 and 4, and smallest at sites 3 and 6. Compared to upstream site 2, as well as Upper Three Runs Creek (a nearby stream of similar size), the species richness and density of organisms at downstream sites continues to be suppressed. However, the more pronounced impact at the first downstream sites (3) noted previously, was not found during May collection. As during the previous month's sampling, results suggest substantial but incomplete recovery of the macroinvertebrate community. 19 tabs.