Rubisco CO2 fixing capacity

Consequently, we do not know to what extent the photosynthetic rates of Rubisco in the marine microalgae are limited by the relatively low amount of dissolved CO2 in the surface ocean or by the energetic expense of concentrating of CO2 at the site of Rubisco by carbon concentrating mechanisms.

In one facet of this project, we are working on better characterizing the temperature sensitivity of the Rubisco enzyme rates in three species of widespread marine eukaryotic phytoplankton, to estimate the potential degree of carbon limitation and pressure on carbon concentrating mechanisms across the diverse temperature range of ocean photic zone habitats. The Rubisco enzyme also has one of the largest carbon isotopic fractionations in plant metabolism. The Rubisco fractionation itself has been used to evaluate potential reaction mechanisms of Rubisco, and its manifestation in biomass from plants and algae is a widely used proxy for ecophysiology and paleoclimate. We evaluate the Rubisco carbon isotopic fractionation in multiple species of marine phytoplankton to evaluate if it is sensitive to temperature or environmentally selected changes in Rubisco conformation, which will aid interpretation of photosynthetic carbon isotopic fractionation to infer phytoplankton growth rate, carbon limitation, and atmospheric pCO₂.
Additionally, we are conducting experiments and developing process models to evaluate how the hydrogen isotope composition of acyl lipids from marine phytoplankton reflect the intensity of the carbon concentrating mechanism. With our deeper understanding of algal physiology and environmental drivers of its regulation, we can better interpret consequences for ocean nutrient distribution and the ocean carbon cycle.