| The ocean is the dominant source of methyl iodide (CH3I) to the atmosphere which plays an important role in stratospheric ozone destruction. Marine CH3I production mechanisms are not well explained. A previous laboratory and field study suggested Prochlorococcus marinus, an ubiquitous marine cyanobacterium, is a globally significant biological producer of CH3I (Smythe-Wright et al., 2006, Global Biogeochem. Cycles, 20). In my study, methyl halide (CH 3I, CH3Br, CH3C1) concentrations were measured from cultures of P. marinus (MED4) and Synechococcus. Cell-normalized production rates from P. marinus cultures ranged from 2 to 5 molecules of CH3I cell-1d -1; these rates were 1000 fold lower than production rates reported for the previous study. Extrapolating CH3I production rates from the current study yields a global production rate of 0.7 Gg yr-1 which accounts for 0.6% of the estimated global CH3I production, suggesting P. marinus is not a globally significant source of CH3I. |
