Beyond the Light: The Biological Production and Biogeochemical Consequences of Dark Reactive Oxygen Species in the Ocean
Abstract
Reactive oxygen species (ROS) are oxygen intermediates formed via a number of photochemical, abiotic, and biotic processes. With typical lifetimes on the order of minutes or less, obtaining true measures of ROS within the environment is limited using conventional water retrieval and shipboard instrumentation. The concentrations, distributions, and fate of ROS within natural waters therefore remain poorly constrained. Despite a paucity of direct measurements, ROS are believed to play central roles in carbon degradation, metal cycling, and organismal health. More recently, production of the ROS superoxide by particles within natural waters and extracellularly by axenic phytoplankton cultures provided circumstantial evidence that microbes are unappreciated sources of superoxide within aquatic environments. Yet, the distributions and sources of superoxide within natural systems, the physiological role and regulation of biological production, and the impact of dark superoxide on ocean (bio)geochemistry remain poorly understood. This presentation will summarize our current progress in addressing these knowledge gaps through investigations of superoxide dynamics within laboratory and shipboard incubations coupled with field-based measurements. We find that marine microbes, including bacteria, cyanobacteria and diatoms, produce substantial levels of extracellular superoxide in both the presence and absence of light, at rates that greatly contribute to in situ superoxide fluxes within the ocean. Further, some coral species maintain extracellular levels of superoxide that are up to two orders of magnitude higher than surrounding marine waters. We suggest this biogenic extracellular superoxide production is decoupled from stress and instead is tightly controlled at the cellular level with a possible link to growth regulation and health. We further find that dark biogenic ROS production is coupled to the cycling and mineralization of manganese and may represent an overlooked O2 sink within the ocean. Through our recent developments of new submersible ROS sensors, we are beginning to shed light on in situ ROS levels and distributions, with the ultimate goal of understanding their connection to the chemistry, function, and health of ocean.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B43L..01H
- Keywords:
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- 0498 General or miscellaneous;
- BIOGEOSCIENCES;
- 4599 General or miscellaneous;
- OCEANOGRAPHY: PHYSICAL