Hydroxide decomposition of dimethylsulfoniopropionate to form dimethylsulfide

The kinetics of DMS production resulting from reaction of OH − with DMSP were investigated as a function of hydroxide concentration and temperature. The reaction was first‐order with respect to DMSP and OH − . The second order rate constant at 20+/−1°C is 0.0044 M −1 sec −1 . The activation energy for this reaction is 14.4 kcal mole −1 . Our investigation indicates that the rate of reaction of DMSP with OH − is very slow at the pH of seawater (half‐life of about 8 years at 10°C), suggesting that DMSP, which may be a major precursor of DMS in seawater, decomposes in the ocean by other mechanisms. We have cultured a bacterium which produces DMS from DMSP quantitatively at rates many orders of magnitude higher than indicated by OH −1 decomposition, suggesting that enzymatic processes accelerate the production of DMS from DMSP in seawater.