1. Competition between Thalassiosira weissflogii (Diatoms) and Emiliania huxleyi (Coccolithophores) under different light regimes Emily Rogalsky, Oscar Schofield, Michael Garzio, Jillian Conicella evrogalsky@gmail.com Rutgers University, the State University of New Jersey, New Brunswick NJ USA ResultsIntroduction The process of photosynthesis creates a net exchange between the carbon in the atmosphere and the carbon in the water column. During photosynthesis, coccolithophores can increase the alkalinity of the water by releasing calcium carbonate into the water column, which may decrease the efficiency of the biological pump (Cermeno et al, 2010). Coccolithophores prefer to live near the top of the water column in nutrient poor waters while diatoms thrive in high nutrient waters and can withstand high levels of turbulence (Dubinsky and Schofield, 2009) When looking at competition, global regions may introduce other elements that may limit a varying resource such as light. As the sea ice melts in Antarctica particular environmental variables, such as available light intensity, begin to shift. In high latitude region, such as the Antarctic, are characterized for having strong vertical mixing and high nutrient composition (Cermeno et al, 2009). Purpose and Hypothesis Understanding the dynamic that the varying light has on the community structure in these different global regions coupled with competition, is one of the many links needed to understand the carbon cycle and the biological pump as a whole. The ability to survive under low nutrient levels will allow the coccolithophores to maintain their population level and then increase after the diatoms have consumed most of the available nutrients. The rate at which this occurs and the peak population level of coccolithophores will alter depending on the different light regimes. Methods NaNHDILDI NaNHDIDI NaNHCILCI NaNHCILCI Cultures grown under F/2 Media Daily Fire Machine, Coulter Counter, and Hemocyptometer reading Chlorophyll measurement every 2-3 days Conclusion Acknowledgement: This research could not have been conducted without the support of the National Science Foundation and the guidance of /Dr. Oscar Schofield References Cermeno et al Competitive dynamics of phytoplankton under non-equilibrium conditions 2010 Dubinsky, Z., Schofield, O. 2009. Photosynthesis under extreme low and high light in the world’s oceans. Hydrobiologia. DOI 10.1007/s10750-009-0026-0 Under all of the light conditions the diatom populations surpassed that of the coccolithophores In nature, the ability for coccolithophores to have successfully grow during a phytoplankton bloom may be attributed to their armor plates, which would allow them to defend themselves. In the lab, the diatoms may have absorbed all of the nutrients into their vacuoles limiting the nutrients available to the coccolithophores when the diatom population started to deplete. There was an observed difference in the population growth of both the diatoms and the coccolithophores. Under constant light both organisms had higher population counts at their peak. The organisms may have had the ability to acclimate to the light level, while they only acclimated to a mean light intensity under the dynamic light regime limiting their population peak. Under the high light intensity the organisms absorbed the nutrients faster and therefore reached exponential growth faster. The coccolithophore population lived longer under the low light regimes than under the high light Left: Cell response to a dynamic low light regime. Phytoplankton Response Under Constant Light Regime Top: Respond under high light Bottom: Response under low light Phytoplankton Response Under Constant Light Regime Top: Response under high light Bottom: Response under low light Left: graphical representation of the light regime Right: Picture of the experiment set up