About this Research Topic
The photochemical formation of ROS, including hydrogen peroxide (H2O2), superoxide (O2−), hydroxyl radical (OH), and singlet oxygen (1O2), has long been recognized as a significant process in surface waters. ROS are important in that they help poise the chemical redox state of aquatic systems and can have variable impacts on aquatic organisms and ecosystem structure. Despite their significance, robust in situ measurements are surprisingly rare for all ROS but H2O2. Recently, reports of extracellular H2O2 and O2− production by healthy and diverse microbes have raised new questions as to the relative role of photochemistry and biology for ROS production in natural waters. Taken together, it appears that past models using purely photochemical sources and biological sinks for these reactive compounds are overly simplistic. New studies challenge the assumption that ROS represent a suite of detrimental metabolic byproducts, and now show that extracellular ROS may also have beneficial physiological role(s) in living systems.
Overall, our knowledge of ROS in aquatic systems is rapidly evolving but remains limited. The timing is right to re-examine the relative strength of different sources, specific reaction mechanisms, biogeochemical impacts, and feedbacks between abiotic and biotic ROS dynamics in aquatic systems. Settling these issues will have critical implications for understanding aquatic redox chemistry, ecosystem structure and health, and the coupled global cycles of many elements, including metals and carbon, and thus, by extension, climate.
The objective of this Research Topic in Marine Sciences is to integrate and update our current understanding of quantitative ROS dynamics and impacts. In particular, manuscripts that cover the distributions, sources, sinks, and mechanistic roles for ROS in aquatic systems are encouraged.
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