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An examination of the periphytic algae in the sheyenne river, north dakota, usa, and the factors influence the community structure

Abstract

The Sheyenne River is a third order stream in central and eastern North Dakota. The algae in this river had not been previously studied. For this study, periphytic algal samples were collected Fall 1997, April–November 1998, and May–October 1999. Two hundred sixteen periphytic algal taxa were identified. These taxa included 137 Bacillariophyceae, 33 Cyanophyta, 40 Chlorophyta, 8 Xanthophyceae, and 3 Euglenophyta. Several species of algae found in the river appear to be previously undescribed taxa. Two of these organisms were described as new species, Nitzschia sheyennensis and Nitzschia dakotensis (Bacillariophyceae). The distribution of the periphytic algae was correlated to changes in the selected environmental variables using canonical correspondence analysis (CCA) and mult‐dimensional scaling (MDS). The statistically significant environmental variables were nitrite‐nitrate, pH, arsenic, potassium, magnesium, manganese, and total dissolved solids. A reservoir, Lake Ashtabula on the river was formed by a dam in 1954. In the initial statistical analysis, the effects of this reservoir on the periphytic algae downstream were so great that an upstream/downstream covariable had to be used. Further statistical analysis was used to determined that this effect could be correlated to changes in the nutrient levels rather than hydrologic changes.