Plankton diatom assemblages of the Iowa Lakes Region

The plankton diatom communities in five of the major lakes of the Iowa Lakes Region (Lake West Okoboji, Lake East Okoboji, Center Lake, Spirit Lake and Silver Lake) were investigated during 1979 and 1980, in order to provide a definitive plankton diatom flora for the Region. The relative abundance and patterns of seasonal periodicity for the taxa were determined for each lake;Two-hundred and forty-eight diatom taxa encompassing 33 genera, 11 families, and 7 orders were identified from the plankton communities of the study lakes. Spirit Lake had the greatest number of taxa recorded and Center Lake had the fewest. The plankton diatom flora of the Region was characterized by an abundance of pennate taxa. Species of the Araphidineae generally dominated the plankton. The centric diatoms were the second most abundant group;The majority of the taxa recorded for the Region were either meroplanktonic or pseudoplanktonic forms. The pseudoplankton had the greatest diversity, while the meroplankton had the greatest relative abunDance; The occurrence of pseudoplanktonic forms in the plankton was a function of the percent littoral development for each lake. Lake morphometry, fetch, and transparency were important to this relationship;While the dominant species varied spatially and temporally within each lake, the overall species composition between the lakes was remarkably similar. Classification of the lakes with respect to the abundance of diatom taxa, however, indicated that the diatom community structure in the lakes of the Region was markedly different. Lake West Okoboji and Lake East Okoboji were the most similar with respect to the abundance of diatom taxa;The diatom flora of the Region contained entities characteristic of nutrient enrichment. Pollution tolerant diatoms have increased their importance in the plankton. Indicator species suggest that water quality is not improving within the lakes of the Region