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Communication at the NABS Annual meeting, Keystone, 2000
(383) DIATOMS AS AN INDICATER OF HUMAN DISTURBANCE IN OREGON'S CASCADE STREAMS.
P. Gill. Environmental Sciences and Resources, Portland State University, Portland, OR 97207. USA
A study was conducted to investigate the relationship between diatom assemblages and environmental conditions in Oregon's Cascade Mountain streams. Periphyton was collected from natural rock substrate in riffle habitat in 16 streams as part of the Regional Environmental Monitoring and Assessment Program by Oregon's Department of Environmental Quality. A total of 56 diatom species and varieties were identified. The diatom assemblages were dominated by Achnanthes minutissima (38.7%), Gomphonema minuta (14%), Achnanthes lanceolata (12%) and Achnanthes suchlandtii (11%). Canonical correspondence analysis showed that diatom species distribution correlates highly with ionic strength; i.e. total solids (r = 0.70), alkalinity as CaCO3 (r = 0.66) and conductivity (r = 0.61). Our results suggest that the diatom distribution pattern in Oregon's Cascade Range, which has streams with relatively low conductivity and low human disturbance, is primarily a function of basin geochemistry. This study has implications on land use in the region, as ionic strength can be considered a surrogate for human disturbance.
Presented at 1:00 PM on Wednesday, May 31, 2000 in Periphyton
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