Hydrogen peroxide lifetimes in south Florida coastal and offshore waters

Hydrogen peroxide is ubiquitous in the surface mixed layer of the ocean and is an important chemical intermediate of aerobic systems. Due to its reactive nature and numerous chemical redox processes, H2O2 decomposition has been suggested to occur mainly through abiotic pathways involving various seawater constituents. Its decomposition rates in natural seawater show considerable spatial variability and generally obey first order kinetics with half-lives ranging from less than 10 hours in coastal waters to greater than 120 hours in surface waters of the open ocean. This study demonstrates that hydrogen peroxide decomposition in natural seawater appears primarily to be biologically mediated by microorganisms less than 1 mu m diameter. Cultured microorganisms added to seawater, especially the prokaryotes Vibrio pelagius and Synechococcus sp. were very efficient mediators of H2O2 decomposition.