title: Extensive Dark Biological Production of Reactive Oxygen Species in Brackish and Freshwater Ponds.
abstract: Within natural waters, photodependent processes are generally considered the predominant source of reactive oxygen species (ROS), a suite of biogeochemically important molecules. However, recent discoveries of dark particle-associated ROS production in aquatic environments and extracellular ROS production by various microorganisms point to biological activity as a significant source of ROS in the absence of light. Thus, the objective of this study was to explore the occurrence of dark biological production of the ROS superoxide (O2(-)) and hydrogen peroxide (H2O2) in brackish and freshwater ponds. Here we show that the ROS superoxide and hydrogen peroxide were present in dark waters at comparable concentrations as in sunlit waters. This suggests that, at least for the short-lived superoxide species, light-independent processes were an important control on ROS levels in these natural waters. Indeed, we demonstrated that dark biological production of ROS extensively occurred in brackish and freshwater environments, with greater dark ROS production rates generally observed in the aphotic relative to the photic zone. Filtering and formaldehyde inhibition confirmed the biological nature of a majority of this dark ROS production, which likely involved phytoplankton, particle-associated heterotrophic bacteria, and NADH-oxidizing enzymes. We conclude that biological ROS production is widespread, including regions devoid of light, thereby expanding the relevance of these reactive molecules to all regions of our oxygenated global habit.
authors: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution , Woods Hole, Massachusetts 02543, United States.
authors: Tong
authors: T
authors: Zhang
authors: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution , Woods Hole, Massachusetts 02543, United States.
authors: Colleen M
authors: CM
authors: Hansel
authors: Department of Chemistry and Geochemistry, Colorado School of Mines , Golden, Colorado 80401, United States.
authors: Bettina M
authors: BM
authors: Voelker
authors: Department of Ocean Sciences, University of California-Santa Cruz , Santa Cruz, California 95064, United States.
authors: Carl H
authors: CH
authors: Lamborg
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D001688:Biological Products; D052836:Heterotrophic Processes; D006861:Hydrogen Peroxide / Q000737:chemistry; D008027:Light; D010100:Oxygen; D061005:Ponds / Q000737:chemistry*; D017382:Reactive Oxygen Species / Q000737:chemistry*; D014871:Water Microbiology
chemical_list: D001688:Biological Products; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D010100:Oxygen