Benthic Macroinvertebrate Community Comparison of Four Streams in the Juneau, Alaska Area

摘要

A benthic macroinvertebrate bioassessment was completed in 1995 for Steep, Salmon, Gold and Sheep creeks in Juneau, Alaska. This survey was completed to examine any differences in stream benthic communities. Prior benthic surveys were done in areas of logging activity and hardrock mining in Southeast Alaska, but there were no data on local Juneau streams. The four similarly sized creeks selected were located in areas with varying levels of past and present human activities. Benthic samples were collected from five riffle habitats in each creek using a modified Hess stream bottom sampler with a 500- micron mesh net. Sampling was conducted in spring and fall for each creek. Ephemeroptera, Plecoptera, and Tricoptera (EPT) specimens were identified to genera. Specimens from other taxa were identified to at least family level for community similarity indices. Benthic communities of these four streams were compared through quantitative analyses. Data summary included the total EPT genera, total EPT number, EPT/total individual ratio, percent dominant taxa, and a family biotic index (FBI) for taxa tolerance indices. Water quality metrics showed some differences among streams. Steep, Gold and Sheep Creeks are healthy waterbodies with good representation of EPT taxa, a general absence of pollution-tolerant species such as chironomids and oligochates, and overall high taxa richness. Only Salmon Creek has a benthic community that indicates a degree of impairment based on various measures of Ephemeroptera, Plecoptera, and Tricoptera taxa.