Cow manure in headwater streams: Tracing aquatic insect responses to organic enrichment
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Authors: R. B. Del Rosario, E. A. Betts, and V. H. Resh
Date: 2002
Journal: Journal of the North American Benthological Society
Volume: 21
Number: 2
Pages: 278-289
Summary of Methods: The response of aquatic insect populations to manure inputs in stream channels was measured in two distinct California stream systems in the Coastal (37˚ 57’ N; 122˚ 43’ W) and Sierra Nevada (38˚ 55’ N; 120˚ 40’ W) mountain ranges. Three treatments varying the levels of manure input were applied to each stream (manure-enriched, placebo-experimental manipulation without manure-enrichment, and control). Manure was deposited into streams weekly for 8 weeks and was typical of manure deposited by 6 cows in one day (14 kg wet weight). Physical and stream characteristics were measured at 4 stations along each reach. Stream discharge, velocity, width, depth, pH, temperature, dissolved oxygen, and conductivity were measured 2, 4 and 8 weeks after treatment began. Insect densities and species richness were also measured.
Article Summary / Main Points: The Sierran stream had a faster velocity than the Coastal stream, causing there to be less of an impact of manure enrichment by insects in those streams. Insects classified as gathers and filterers assimilated the greatest percentage of manure and shredders assimilated the least. Aquatic insects in the Coastal stream assimilated more manure and were more abundant than insects in the Sierran stream. Uptake of manure by insects occurred within 3 m downstream of the manure input. The addition of manure from cattle grazing did not alter the composition of aquatic insects in either stream system; however the density of certain aquatic insects increased in the Coastal stream.
Vegetation Types: Riparian and Wetlands
MLRA Ecoregions: 15 Central California Coast Range 22A Sierra Nevada Mountains
Agrovoc Control Words: Riparian zones Grazing Aquatic insects
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: aquatic insects, organic enrichment, carbon isotopes, streams, cattle grazing, manure
Annotation: This study was conducted in California but is applicable to any riparian system. Keep in mind that these findings are for manure input into the system and are independent of the physical alterations to the stream that occur from trampling or foraging.
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