Document Type



benthic diatoms, epiphyton, epipelon, epilithon, plankton, streams, Iowa


This is the first detailed report on the taxonomy and ecology of diatoms in the portion of the upper reaches of the Cedar River basin in Iowa. This paper describes the diatom taxa from shallow benthic substrata collected quarterly between 11 October 1975 and 19 February 1977 at 14 sampling stations. Just over 500 frustules were counted from each of the 216 samples obtained. Analysis of water samples collected at the same time as the diatoms indicates these screams have alkaline hard waters rich in nutrients with extreme turbidity level fluctuation at irregular intervals.

The 281 diatom taxa identified represented 34 genera, the most diverse being Navicula, Nitzschia, Gomphonema, and Fragilaria (including Synedra). Over 10% of all diatoms counted were Cyclotella meneghiniana. Other diatoms most often reported as "plankton" but found in this study at greater than 4% total abundance in the haptobenthos included Stephanodiscus parvus, S. hantzschii var. tenuis, Nitzschia acicularis, and Cyclotella atomus. Diatoma vulgare was the only nonmotile pennate so abundant. Thirty-four taxa not previously reported from Iowa were found.

The Cedar River and its tributaries have regular seasonal changes in water conditions plus irregular fluctuations reflecting flood effects from storm events or from spring melting. The benthic diatoms respond to these changes in ways similar to diatoms in streams with more predictable disturbance regimes. However regular patterns in distribution and abundance of attached and motile diatoms are unlikely. The data presented strongly suggests that irregular erosion of diatom films and subsequent deposition of upstream benthic and planktonic diatoms along with silt determines the composition of the diatom portion of benthic communities as much as does seasonal succession or substrate affinity.

Publication Date

September 1988

Journal Title

Journal of the Iowa Academy of Science





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© Copyright 1988 by the Iowa Academy of Science, Inc.



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