Graduation Year


Document Type




Degree Name

Master of Science (M.S.)

Degree Granting Department

Biology (Integrative Biology)

Major Professor

Deby Cassill, Ph.D.

Committee Member

Michelle Green, Ph.D.

Committee Member

Deborah Howard


carbon fixation, climate change, photosynthesis, primary producer


Diatoms are unicellular, eukaryotic, photosynthetic algae responsible for the production of 20% of our atmospheric oxygen. Diatoms contribute to several important biogeochemical functions. Diatoms contribute to the carbon cycle, sequestering carbon and forming oxygen as a product of photosynthesis. Moreover, by converting abiotic forms of energy such as sunlight into organic compounds (i.e., sugars, starches and lipids), primary producers including diatoms, plants, and phytoplankton feed organisms at higher trophic levels. Consequently, changes in temperature, light intensity, nutrients, salinity and other stress factors that affect primary producers can generate a potentially catastrophic ripple effect at higher trophic levels In this study I quantified the impact of increased surface-water temperatures on the population growth and photosynthetic ability of an abundant marine diatom, Thalassiosira pseudonana. To test the effects of temperature on population growth, T. pseudonana, cultures were standardized to 0.005 OD600 and incubated at eight different temperatures from 14°C to 28°C. To test the effect of temperature on population growth and gene expression, T. pseudonana cultures were standardized and incubated at four temperatures from 14°C to 26°C. I show that population growth and gene expression for carbon fixation in the marine diatom, T. pseudonana, increased with temperature. I conclude that T. pseudonana is capable of adjusting its reproductive and photosynthetic ability within the predicted increases in global temperature over the next century.

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