Date of Award

8-2011

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Oceanography

Advisor

Lee Karp-Boss

Second Committee Member

Peter A. Jumars

Third Committee Member

Eric Landis

Abstract

Most diatoms live as single cells, but formation of chains is common. Adaptive advantages of chains and processes that control their formation have remained enigmatic despite the dominance of chain-forming species in primary production and sinking fluxes in temperate and high-latitude regions. Morphological and mechanical properties of chains affect their interactions with the physical environment and can provide important insights into chain ecology and evolution such as adaptive strategies of cells in the ocean. Although morphological characteristics of chains are largely documented in the literature and diverse, information on their mechanical properties is scarce. I calculated the flexural stiffness of four morphologically diverse species of diatom chains, Lithodesmium unduatum, Stephanopyxis turris, Lauderia annulata, and Guinardia delicatula, by measuring their bending moments in a characterized flow and applying simple beam theory. These species spanned four orders of magnitude in flexural stiffness (from 2.0 x 10-13 to 4.0 x 10-17 N m2) and also differed in their susceptibility to breakage under flow. I further applied a finite-difference analysis of curvature to examine the flexural stiffness at multiple sections along the chain. Although there is variability between segments within chains, the median flexural stiffness by finite-difference methods is similar to that from beam theory. Further experiments suggest that effects of nutrient limitation on susceptibility of chains to breakage under flow depend on the type of connection between cells. These results allow design of more realistic models of diatom chains to study flow effects on nutrient uptake, encounter with grazers, and aggregate formation.

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