Longitudinal and seasonal distribution of benthic invertebrates in the Little Lost River, Idaho

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A yearlong investigation of the Little Lost River, ldaho (five sites), was conducted to determine the environmental conditions and benthic invertebrate community composition of the stream and to discover factors responsible for distribution of the benthos. All chemical constituents measured showed a tendency to increase from headwaters to mouth. Stream temperatures ranged from 0–15 ˚C near the headwaters and 0–22 ˚C near the mouth. Chlorophyll a content of the periphyton was low (1–19 mg/m2) following heavy winter ice cover and spring runoff, but attained relatively high levels (12–68 mg/m2) by the end of September. Allochthonous detritus levels were highest (64–96 g/m2) near the headwaters; the lowest levels (16–24 g/m2) were found in areas where the riparian vegetation was restricted largely to sagebrush and grass. The study revealed a fauna comparable in richness to other Rocky Mountain streams. Sixty-two of the 68 taxa collected were insects. Ephemeroptera was the predominant group in terms of both species (29% of total) and number (62% of total). The most common species were Rhithrogena robusta, R. hageni, and Baetis tricaudatus (Ephemeroptera); Nemoura sp., Alloperla sp., and Isoperla fulva (Plecoptera); and Glossosoma sp. and Hydropsyche sp. (Trichoptera). Mean number of invertebrates was between 1500 and 5000/m2 at the various sites. Local environmental conditions exerted a strong influence on the structure of the invertebrate community at the various locations in the river. Foremost among these were ice formation, temperature, volume of flow, and food. Even though the volume of flow in the Little Lost River gradually recedes as it percolates into the substratum, the invertebrate community does not show a reversion to headwater conditions. Only 46% of the mayflies, 33% of the stone flies, 38% of the caddis flies, and 14% of all others found in the headwaters also occurred near the downstream terminus, and all of those were widely distributed in the river.

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ELECTRONIC FILE - Zoology: Invertebrates

SWAP (2/19/16) citation:
Andrews DA, Minshall GW. 1979. Longitudinal and seasonal distribution of benthic invertebrates in the Little Lost River, Idaho. [accessed 2015 Jun 1]; American Midland Naturalist. 102(2):225–226. http://www.ephemeroptera-galactica.com/pubs/pub_a/pubandrewsd1979p225.pdf