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Open Access Thesis

Keywords

Diatoms--Iowa--Lake West Okoboji;

Abstract

Diatom communities were studied that became attached to glass slides suspended at 1 m and 7 m depths in Lake West Okoboji, Iowa during an eight week period in the summer of 1974. Each community was analyzed at two week intervals for colonization, succession, and alternating depth stress manipulation (transfer) responses, Colonization communities were obtained from a series of slides exposed at each depth for each two week interval. Succession communities consisted of a slide series acquired from each depth with exposure times of from two to eight weeks, Diatom communities on a series of slides from each level were physically transferred to the alternate level for analysis of depth stress effects. Each slide was analyzed for taxa, percentage composition, density and similarity indes (SIMI) comparisons between communities. Community aliquots were permanently mounted in Hyrax and each sampled for approximately 1000 diatom valves. A total of 55,426 diatoms were enumerated and represented 83 taxa in 21 genera with 17 dominant taxa (greater than 5% of community), The values for two replicates were averaged for each community. All colonization and succession communities had greater organism density at the 1 m depth. Although the absolute density differed considerably, both depths increased or decreased in approximate unison, The stressed (transferred) communities exhibited three density patterns. First, community density was always greater in the control community (same exposure time but not transferred) than in the pre-transfer community, Second, all communities transferred from 1 m to 7 m decreased in density. While third, all communities transferred from 7 m to 1 m increased in density. SIMI values indicated that distinctly different communities developed at each level. Both colonization and succession slides demonstrated the shortest duration of exposure and the most temporally proximate communities within each level produce the highest similarity values, Both of the reciprocally transferred communities exhibited high SIMI values when compared to the upper level control communities and low SIMI values when compared to lower level control communities, The 17 dominant taxa revealed complex patterns of relative abundance for the colonization, succession and stress tolerance experiments, Taxon dominance may be a function of calendar time rather than duration of exposure, Several taxa exhibited greater tendencies toward either the colonizer or successor habit. The growth morphology, temporal dynamic habit (colonizer or successor attribute), level "preference" (number of occurrences and percent of community for those occurrences), and stress tolerence characteristics were compiled into a profile for each dominant taxon. Transferred (stressed) diatom communities exhibited the greatest change in composition when moved from the lower to the upper level, Communities transferred from the lower level to the upper level always increased in density, while those transferred from the upper level to the lower level always decreased in density. Tolerance to stress was greatest for those taxa transferred to the depth where they were most abundant, whereas taxa transferred from their most abundant depth were generally intolerant of stress.

Year of Submission

1978

Degree Name

Master of Arts

Department

Department of Biology

First Advisor

Paul Whitson

Second Advisor

Lawrence J. Eilers

Third Advisor

Warren E. Picklum

Comments

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Date Original

1978

Object Description

1 PDF file (81 leaves)

Language

en

File Format

application/pdf

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