Relative abundance, temporal distribution, and functional feeding groups of aquatic insects in two first-order southwestern Pennsylvania streams.

摘要

Two first to second order streams (Kent Run and Munnell Hollow) at Ryerson Station State Park, Greene County, Pennsylvania, were compared as to water parameters (dissolved oxygen, hardness, temperature, pH, and current velocity), species diversity, and abundance of both immature and adult insects. Samples were taken biweekly for one year from May, 1999 through April, 2000 for a total of 26 sampling periods. Data were analyzed using a repeated measures ANOVA. Kent Run had lower dissolved oxygen, higher pH and hardness, lower temperatures, and higher current velocity. A total of 137 taxa were collected at both streams. Of the total 3,299 individuals collected at Kent Run, 1,166 were adults and 2,133 were immatures. Munnell Hollow had 1,273 adults and 890 immatures for a total of 2,163 individuals. For the adult and immature community metrics, there was a higher number of shredder taxa and a greater percentage of shredders at Munnell Hollow, both a higher number of taxa and a higher percentage of both collector-filterers and collector-gatherers at Kent Run, a higher number of scraper taxa and a greater percentage of scrapers at Kent Run, an equal number of predator taxa at each stream, and a higher percentage of predators at Munnell Hollow. Overall, community metrics were significantly higher for May 12–14, 1999 and April 24–26, 2000, indicating an optimal time for sampling for assessment of community metrics. The combination of the water parameters at Kent Run and its wider area and higher number of leaf packs, snags, and debris dams contributed to the higher numbers of individuals collected.