The Repository @ St. Cloud State

Open Access Knowledge and Scholarship

Date of Award


Culminating Project Type


Degree Name

Biological Sciences - Cell and Molecular: M.S.




College of Science and Engineering

First Advisor

Matthew Julius

Keywords and Subject Headings

Diatom, PIV, Fluid Dynamics, Algae, Cell Outline, Biology


Cell outline has been used as the principle metric for taxon recognition in diatoms, a single celled aquatic primary producer. This investigation examines the fluid dynamic implications of three stalk forming diatom outlines. This was accomplished by examining large scale shape differences between the gomphonemoid taxa Gomphoneis herculeana, and the Cymbelloid taxa Cymbella mexicana, as well as small morphological changes to the diatom Gomphonema acuminatum. Fluid dynamic investigations of microscopic diatoms were made possible through the production of scale models of selected diatoms using an atomic force microscope and 3-D rapid prototype printer, flows around these models were quantified through particle image velocimetry. In all cases the shape of the diatom cell influenced the fluid forces experienced. A comparison between the gomphonemoid and cymbelloid shapes demonstrated the potential for the gomphonemoid shape to exhibit a more streamlined body in unidirectional flow. The gomphonemoid shape, although less streamlined than the cymbelloid model in the dorsal leading edge orientation, has the potential advantage of minimal orientation effects due to its symmetry in the valve and girdle views. Outside of large differences in outline between taxa, small changes in ornamentation were also shown to have a measurable effect on the single taxa Gomphonema acuminatum. In this case the loss of the headpole apiculate end had a measurable effect on the wake properties downstream of the model. This investigation has made possible first hand observations into the unique fluid behavior in the understudied environment of the micro-benthos, as well as demonstrated fluid dynamic differences between common diatom morphologies.


This work represents a large cooperative effort in which many need to be acknowledged for their part in its success. I would like to thank Bob Janisch, Jim Nicholson, and Asylum Research for making possible the first atomic force images and printed 3-D models of diatoms. To Russ Lidberg and John Harlander for their assistance and expertise in the laser systems which made the particle image velocimetry analysis possible. I would like to extend a special thank you to my committee for their input and guidance throughout a project which often tread on new and unexpected ground. Most importantly I need to thank my wife Diana and my entire family for their support throughout the last 2 years.

Included in

Biology Commons



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