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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Wetlands II
USING DIATOM ASSEMBLAGES TO ASSESS FRESHWATER WETLAND HEALTH IN THE COLUMBIA RIVER BASIN, OR.
C.L. Weilhoefer and Y. Pan. Environmental Sciences and Resources, Portland State University, Portland, OR 97207
The objectives of this study were to examine diatom distributional patterns in relation to dominant vegetation and proximity to open water, characterize changes over time and determine the number of samples necessary to accurately characterize wetland diatom assemblages. Diatoms were identified from 29 surface sediment samples and within a sediment core from a 5 ha Scirpus validus-dominated wetland. A total of 186 species were identified and assemblages were dominated by Fragilaria construens (16%) and Nitzschia palea (12%). Average species richness was 44 (range 26-60). Non-metric multidimensional scaling techniques did not clearly show patterns in diatom assemblages based on location within the wetland or dominant vegetation. However, diatom richness was greatest at locations with the highest richness of emergent macrophyte species and the abundance of Navicula and Nitzschia species increased with proximity to open water areas. A total of 118 diatom species were found within the sediment core. The top of the core was dominated by periphytic species (e.g. Fragilaria) while the bottom was dominated by planktonic species (e.g. Aulacoseira and Cyclotella). These results indicate that changes in wetland diatom assemblages over time may reflect changes in wetland hydrology and vegetation and therefore, diatoms may be useful indicators of wetland condition.
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