Riffle-pool geomorphology disrupts longitudinal patterns of stream benthos |
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Authors: | Peter P Brussock Arthur V Brown |
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Institution: | (1) Environmental Liability Management, Inc., Research Park, 218 Wall Street, 08540 Princeton, NJ, USA;(2) Zoology Department, University of Arkansas, 72701 Fayetteville, AR, USA |
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Abstract: | An Ozark Plateau stream was studied to determine the influence of distinct pool and riffle geomorphology on the longitudinal zonation of macroinvertebrate species assemblages and functional group classification. All study sites were dominated by alluvial pool and riffle channel form and the first two orders became intermittent during summer months. Nine benthos samples were collected seasonally from riffles and pools at each of five sites using a vacuum benthos sampler. Diel temperature pulse and coarse particulate organic matter (CPOM) were measured at each site also. Water temperature was most variable in second order, and CPOM on riffles was not more abundant in upstream reaches. Annual average density and biomass of invertebrates were highest in third and fourth orders, respectively. Diversity was depressed in the intermittent headwaters sites. Macroinvertebrate functional groups did not exhibit strong longitudinal trends as predicted by the river continuum model, with species assemblages apparently more strongly affected by the segment-level physical template, although shredders were more abundant in the headwaters during fall and winter. This study indicates that a reach-level perspective based on channel form is a necessary complement to holistic stream ecosystem models, especially in alluvial gravel streams. |
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Keywords: | stream benthos distribution functional groups riffle-pool channel form |
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