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LAND USE AND NATURAL HYDRAULIC CONTROLS ON STREAM SUBSTRATE AND MACROINVERTEBRATE ASSEMBLAGES IN REGIONAL SURVEYS
Citation:
Kaufmann, P R. LAND USE AND NATURAL HYDRAULIC CONTROLS ON STREAM SUBSTRATE AND MACROINVERTEBRATE ASSEMBLAGES IN REGIONAL SURVEYS. Presented at Amer. Soc. of Limnology & Oceanography (ASLO) 2000 Conf, Copenhagen, Denmark, 6/5-9/00.
Description:
In large regions, human land uses typically overlay wide ranges of natural geomorphic factors that control stream habitat characteristics and benthic macroinvertebrate assemblages. Many macroinvertebrate measures of stream "health" show strong association with substrate size, a characteristic controlled by both natural and anthropogenic factors. Critical to assessing alterations in substrate size are stream gradient, size, and large scale roughness, which together determine the stream bottom shear stress. Uncorrected for natural gradients in shear stress, biotic assemblage metrics may show spurious relationship or lack of relationship with watershed disturbances. Based on substrate and channel data collected by the U.S. EPA's Environmental Monitoring and Assessment Program (EMAP) in the Pacific Northwest, Central, and Mid-Atlantic regions of the U.S., I estimated reach average backfull shear stress, adjusting it for energy losses due to large scale roughness. Substrates finer than those predicted by this model suggest sediment supplies are large in relation to a stream's sediment transport capability. Within a given ecoregion or lithology, sediment textural "fining" and associated variation in macroinvertebrate assemblage composition were associated with basin and riparian land disturbances, suggesting that these disturbances generally augmented fine bedload sediment particle supply and altered stream biota.