My Ph.D. research with Dr. E. Virginia (Ginger) Armbrust focused on understanding the influence of photorespiration on carbon and nitrogen cycling in diatom cells. I used quantitative RT-PCR as a rapid method for looking at the transcription of a suite of genes involved in the photorespiratory pathway as well as pathways that link to photorespiration through carbon and nitrogen products. Specifically, I was interested in knowing whether photorespiration could be used as an alternate energy sink for diatom cells in high light. Previous work by Mike Lomas and Pat Glibert (see for example L&O 1999, 44: 556-572) suggested diatoms could use luxury uptake and metabolism of nitrate as a mechanism for dissipating excess light energy in high light, particularly at low temperatures when the photosynthetic capacity of cells appears to be lower. Furthermore, studies in higher plants demostrated a role for photorespiration in protection of cells from photoinhibition. The results of my research were synthesized into a hypothetical model of electron and reductant flow under different light, temperature and nitrogen sources:
For my M.S. research, I worked with
Dr. Peter A. Jumars on the population genetics of two local clam species. I was interested in the movement of early life history stages of benthic invertebrates through the water column. Specifically, I was interested in how the hydrology of
Puget Sound,WA affects the population dynamics of two different bivalve species,
Protothaca staminea and
Macoma balthica. The movement of the water can help determine the structure of the adult populations by influencing the dispersal of the larvae. The water in Puget Sound is predominantly forced by the tides, river input, and winds. The Sound is a fjord-like estuarine system composed of five main basins with many constrictions and sills that strongly influence the tidally driven currents. I suspect that the sills in Puget Sound might act as partial barriers to the movements of the clam larvae from one basin to the next, thereby limiting gene flow between the populations. Population genetic theory demonstrates that only a few migrants per generation can homogenize geographically separated populations. By investigating the degree of genetic differentiation between individuals from each basin, I could determine whether or not these two species are panmictic in Puget Sound. To address the question of population genetic differentiation, I looked at variation in allozymes using protein electrophoresis. Allozymes are enzymes that have the same activity (ex. peptidase, dehydrogenase) and are coded for by the same gene. Hence, differences found among allozymes are due to differences in the alleles of the gene. Using starch gel electrophoresis and stains that detect specific enzymatic activity, one can visualize the variation in the allozymes (and thereby the different alleles) of each individual. If two populations do not share the same allele frequencies, it might be hypothesized that a barrier to gene flow exists.
