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MaryLove Ward - Photobiology Lab

Winthrop University, Rock Hill, SC

The Effect of UVR and CO2 Supply on

Membrane Permeability of Thalassiosira pseudonana

The influence of increasing CO2 levels and UVR are of significant interest in aquatic marine species. Particularly because changes in CO2 and UVR can affect primary production in the oceans, influencing potential changes to the global carbon cycle and food web interactions. Phytoplankton research on these factors has shown CO2 affects carbon concentrating mechanism (CCM) activity and UVR can damage various molecules and mechanisms within the cell, including membranes. To compare the synergistic effect of CO2 and UVR in phytoplankton, a study conducted last year in the photobiology lab at SERC, studied these factors in species with different CCMs. The study concluded that there were significant differences in the response to UVR depending on the type of CCM. These results led to the necessity to investigate how membrane permeability might be interacting with the response to UVR. For this investigation we chose Thalassiosira pseudonana, an estuarine diatom, to assess how changes in UVR and CO2 supply were affecting membrane permeability. We used a low (0.03%) and a high (0.1%) CO2 supply paired with damaging (UVA and UVB+ PAR) and non damaging light (PAR only) treatments. To asses changes in membrane integrity (permeability) we used DIBAC3(4) a molecular probe dye. It was concluded that the UVR conditions in this experiment, set to approximately simulate 10-15% of natural solar irradiance, where not significantly influencing changes in permeability. However, the high CO2 treatment did significantly increase the permeability of the cells. The high CO2 also decreased the chlorophyll per cell and increased the growth rate. These results correspond to a parallel study with the same samples, which suggest that the high CO2 treatment may cause down regulation of metabolic processes. The down regulation of the cell may be related to why  we observed an increase in permeability, however further investigation is needed to determine these interactions.

Before this internship I was only vaguely aware of marine ecosystems and the importance they have for geochemical and energy cycles in the biosphere. Now, I am fascinated with this area of study and I plan on returning to the south to pursue a master's degree in marine sciences.