Date of Award

2014

Document Type

Honors Thesis (Colby Access Only)

Department

Colby College. Environmental Studies Program

Advisor(s)

F. Russell Cole

Abstract

Headwater streams have some of the best quality water in the country (Dissmeyer 2000). Because headwaters eventually flow into other downstream water bodies like rivers and lakes, they are important places to focus research and conservation efforts. All streams in this study had good water quality based on several assessments of macroinvertebrate communities.

1. Judging from metrics of abundance, richness, EPT, and HBI, all study streams had very good water quality. Thirty-nine total families were observed among the three streams. Whittier Stream was the least healthy of the three, most likely as a result of human disturbances such as a road crossing, fishpond, and mill remnants. It is probable these habitat alterations are having an effect on downstream benthic communities.

2. The riparian zone of each stream was forested and stable, but there were some eroding banks at some points along the study reaches. The abundance of sensitive macroinvertebrates (measured using representative Orders Ephemeroptera, Plecoptera, and Trichoptera) increased with increasing percent canopy cover and decreased with high percentages of sand characterizing the streambed.

3. Macroinvertebrates can be categorized into functional feeding groups based on feeding behavior. Shredders should hypothetically be in high abundance in headwater streams due to high riparian organic matter inputs. However, observed shredders were limited. This may be due to seasonal changes in functional feeding group ratios. In addition, all study streams had a predator/prey ratio that was higher than the ratio expected for a typical stream, which suggests that there might be an abundance of prey biomass in the study stream headwaters.

4. Based on results from stable isotope analysis of carbon and nitrogen, most macroinvertebrates within the study streams seem to be omnivorous. The most complex food web was observed at Stony Brook. Food webs of Beaver Brook and Stony Brook showed similar trophic clustering, a pattern that might be indicative of streams with excellent water quality.

Comments

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Keywords

headwater, diversity, feeding groups, community

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