Epilithic diatom assemblages in headwaters streams of North Carolina and Virginia

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Title: Epilithic diatom assemblages in headwaters streams of North Carolina and Virginia
Author: Karoly, Cynthia Bell
Advisors: James Gregory, Committee Chair
JoAnn Burkholder, Committee Member
James Gilliam, Committee Member
Abstract: Using data collected by the Environmental Protection Agency during synoptic sampling for the Environmental Monitoring and Assessment Program, I studied the quantitative composition of diatom communities in 112 samples distributed in first through third-order streams within the Blue Ridge, Southeastern Plain, Coastal Plain and Piedmont ecoregions of the eastern U.S. The sampling sites studied were located predominantly in North Carolina and Virginia. The main objective was to identify dominant diatom species using both species density values and importance values incorporating estimated biovolumes. A secondary goal was to determine whether distinct diatom assemblages could be defined within the set of streams studied. Six diatom assemblages were defined based upon increasing diversity, richness and evenness of species within the groups. No trends could be detected in the cluster separation associated with ecoregions, sample years, and instream habitats, and paired riffle/pool samples. Diatoms were observed in all 112 samples, and 390 diatom species were identified. Achnanthes biasolettiana was the dominant species, comprising 54% of the relative density of the total dataset and observed in 89% of all samples. Only twelve additional species equaled or exceeded 1% of the total sample relative density or importance value. Use of estimated biovolume size classes for entire diatom genera did not alter the determination of dominant species. The same species were considered dominant using either measure of dominance. Within samples, the ten most dominant species consistently contributed > 50-75% of the total relative density of the sample.
Date: 2003-07-01
Degree: MS
Discipline: Forestry
URI: http://www.lib.ncsu.edu/resolver/1840.16/2788


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