You are investigating a spring algae bloom that formed in the North Atlantic, when the seasonal mixed layer shoaled to 50 m. This bloom lasted for 10 days and was dominated by coccolithophores (algae that photosynthesize, and also produce calcite shells) that were rapidly exported to deeper depths. Fluxes of sinking organic carbon and calcium carbonate during these blooms were measured using sediment traps placed at the base of the mixed layer, and were found to be 80 mmol C m-2 d-1 and 20 mm C m-2 d-1 respectively. The temperature of the water was 20C throughout the bloom, and the salinity was 35 PSU. a. Given that the initial dissolved inorganic carbon (DIC) and carbonate alkalinity (Ac) are 2.15 mmol L-1 and 2.40 mmol L-1 respectively, estimate [CO32-] and pH at the beginning of the bloom? (Note, that the the first (Ka,1') and second (Ka,2) apparent dissociation constants of carbonic acid are available in Pilson, Appendix E; Tables E.3a,b). Carefully state your assumptions. b. Given the flux of sinking organic carbon and calcium carbonate out of the mixed layer as well as the mixed layer depth, calculate the change in DIC and the change in alkalinity per liter of water per day (answer should be in mmol L-1 day-1). (tip: the rate of concentration change can be determined by dividing the mixed layer depth by the sediment trap flux, and then converting units). Assume that the rate of CO2 gas exchange with the atmosphere is slow compared to export of carbon as sinking particles. c. What are the final concentrations of DIC and Ac in the mixed layer after the 10 days? d. Approximate the total change in [CO32-] during the bloom (be clear whether it increased or decreased), stating any assumptions made in the calculation. Did pH rise or fall? Is the precipitation of calcium carbonate more or less thermodynamically favorable due to the changing conditions of the bloom?