The decomposition of hydrogen peroxide by marine phytoplankton

All nine species of marine phytoplankton tested (a cyanobacterium: Synechococcus sp., three diatoms: Chaetoceros simplex, Thalassiosira oceanica and Skeletonema costatum, two prymnesiophytes: Pleurochrysis carterae and Isochrysis galbana, a prasinophyte: Tetraselmis sp., a green alga: Dunaliella tertiolecta, and a dinoflagellate: Amphidinium carterae) were able to decompose hydrogen peroxide in the dark. Since these phytoplankton species can be found widely in a variety of marine sub-environments, this indicates that the dark decomposition of hydrogen peroxide by phytoplankton is a general phenomenon in the oceans. The decomposition rates were first order with respect to the concentration of hydrogen peroxide and biomass. The second-order rate constants for these nine species of phytoplankton ranged between 2 × 10^–4 and 2.7 × 10^–2 μg Chl-a^–1 1 h^–1. Synechococcus sp. and S. costatum were the most efficient, while P. carterae and D. tertiolecta were the least efficient decomposers. While the magnitudes and patterns in the changes were species-dependent, in general, increasing salinity, temperature, the presence of light and the depletion of nutrients enhanced the decomposition of hydrogen peroxide. The effect of growth phase was small.