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Tuesday, May 19, 2009
211
Meiofauna densities among riffles, pools, and flats in a gravel bed stream
Arthur V. Brown and Adam Franklin. Biological Sciences, University of Arkansas, Fayetteville, AR 72701
Gravel bed streams have predictable structure with riffles spaced at 5-7 bankfull stream widths, conferring some predictability of percentages among the three principal habitats: riffles, pools, and flats. Physical disturbances (gravel mining) alter these percentages, usually widening stream channels, increasing spacing between riffles, and thereby reducing riffle habitat per reach, with considerable consequences. Macroinvertebrates, fish, and algae are generally denser in riffles than pools. Flats have seldom been assessed. We performed this study to determine benthic densities of meiofauna among riffles, pools, and flats hypothesizing that they would also be densest in riffles. In fact, they were denser in flats (1277/L) than in riffles (1097/L) or pools (967/L). Rotifers were most abundant comprising 67% of permanent meiofauna and 30% of the total. Small chironomids and mayflies together accounted for nearly 67% of temporary meiofauna and 36% of the total. Chironomidae, Ephemeroptera, Hydrachnida, and Nematoda densities increased from pools to flats to riffles. Copepoda, Rotifera, Cladocera, and Mollusca densities were highest in flats, with Copepoda and Rotifera denser in pools than riffles. Accounting for total habitat areas of riffles (1362 m2), flats (4087m2), and pools (4436m2) in our study stream, riffles had significantly fewer meiofauna per reach than other habitats.
Web Page: meiofauna, distribution, disturbance
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