Award: OCE-1536581

Two different species of marine microscopic algae, Synechococcus sp. and Thalassiosira pseudonana, were grown in the laboratory under conditions that simulated what we expect the ocean will be like by the year 2100 as a result of the accumulation of carbon dioxide in the atmosphere. The surface waters of the ocean are expected to become warmer by several degrees Celsius, and the concentration of carbon dioxide (CO2) in the seawater will of course increase. Synechococcus, which is a very small unicellular, prokaryotic organism, did not benefit in any way from an increase of CO2, but it did benefit greatly from an increase of temperature. It grew most rapidly at a temperature of about 35 Celsius, which is 95 Farenheit. T. pseudonana is a much larger cell and under ideal or nearly ideal temperature conditions, it grew more rapidly when the CO2 concentration was increasedn because it could more easily acquire the inorganic carbon it needed for photosynthesis. However, when the temperature was too low or too high, the increae of CO2 concentration was detrimental because it was associated with the production of carbonic acid, which adversely affected the ability of T. pseudonana to produce a silica frustule, which is the solid matrix that surrounds each cell. The respiratiion rate of T. pseudonana also increased dramatically when the temperature was increased, and hence it grew less efficiently at high temperatures. Our results clearly showed that Synechococcus would be at an advantage relative to T. pseudonana if the climate changes according to projections. Such changes in the composition of the community of photosynthetic organisms in the ocean will adversely affect the ability of the ocean to sequester CO2 and hence its ability to serve as a buffer against climate change effects associated with anthropogenic CO2 emissions and global warming. Last Modified: 07/25/2020 Submitted by: Edward A Laws