Date of Award

2010

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Jeffrey Johansen

Second Advisor

Christopher Sheil (Committee Member)

Third Advisor

Carl Anthony (Committee Member)

Abstract

The capacity of diatom species to survive gastrointestinal passage through the algivorous minnows Pimephales notatusand Campostoma anomalum was studied. From a site on the Grand River in northeastern Ohio, 27 minnows and 7 epilithic diatom samples were taken. In order to determine whether diatom taxa varied in digestibility, live/dead ratios of diatom cells taken from the minnows’ feces were compared with live/dead ratios of cells taken from immersed rocks. Diatoms that were live/undigested at the time of collection were differentiated from dead/digested cells under light microscopy by noting the presence of chloroplasts and/or lipid droplets. Seventy-seven percent of the diatom taxa observed in the fish feces had at least one frustule in the “living” condition. The results of this study were used to determine the effect of enrichment culture on various diatom taxa, and which taxa have a special resistance to digestion.

Cluster analyses hint that there may be selective dying off as the diatoms pass through the gut. With the use of Student’s ttests, the percent living of diatoms at the sites was compared to the percent living in the fish, suggesting that Cymbella affinis, Cymbella caespitosa, Nitzschia sinuata var. tabellaria, Cyclotella meneghiniana, Navicula capitatoradiata, Navicula veneta, and the Cymbella, Reimeria and Gomphonema genera, survive gut passage more frequently than other species and genera.

Achnanthes linearis and A. minutissima appear to be less resistant to digestion than other species, but also less accessible to the piscine grazers than are certain Cymbella species. The ratios of living to dead cells at the sites and in the fish indicate that certain Cymbella species are more resistant to digestion than are Achnanthes linearis and A. minutissima.

Diatom species that are readily available to grazers are more resistant to digestion, and vice versa. Diatoms that are less available to grazers are less resistant to digestion.

Comments

70 p.

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