Environmental factors accounting for benthic macroinvertebrate assemblage structure at the sample scale in streams subjected to a gradient of cattle grazing |
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Authors: | Amy Braccia J Reese Voshell Jr |
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Institution: | (1) Department of Entomology, Virginia Tech, 300A Price Hall, Blacksburg, VA 24061, USA |
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Abstract: | Macroinvertebrate assemblages were related to environmental factors that were quantified at the sample scale in streams subjected
to a gradient of cattle grazing. Environmental factors and macroinvertebrates were concurrently collected so assemblage structure
could be directly related to environmental factors and the relative importance of stressors associated with cattle grazing
in structuring assemblages could be assessed. Based on multivariate and inferential statistics, measures of physical habitat
(% fines and substrate homogeneity) had the strongest relationships with macroinvertebrate assemblage structure. Detrital
food variables (coarse benthic and fine benthic organic matter) were also associated with assemblage structure, but the relationships
were never as strong as those with physical habitat measures, while autochthonous food variables (chlorophyll a and epilithic biomass) appeared to have no association with assemblage structure. The amount of variation explained in taxa
composition and macroinvertebrate metrics is within values reported from studies that have examined macroinvertebrate metric–sediment
relationships. The % Coleoptera and % crawlers had consistent relationships with % fines during this study, which suggests
they may be useful metrics when sediment is a suspected stressor to macroinvertebrate assemblages in Blue Ridge streams. Findings
from this study also demonstrate the importance of quantitative sampling through time when research goals are to identify
relationships between macroinvertebrates and environmental factors. |
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Keywords: | agriculture benthic macroinvertebrates environmental stress habitat sample scale sediment |
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