Abstract
Based on knowledge of their production pathways, and limited discrete observations, a variety of short-lived chemical species are inferred to play active roles in chemical cycling in the sea. In some cases, these species may exert a disproportionate impact on marine biogeochemical cycles, affecting the redox state of metal and carbon, and influencing the interaction between organisms and their environment. One such short-lived chemical is superoxide, a reactive oxygen species (ROS), which undergoes a wide range of environmentally important reactions. Yet, due to its fleeting existence which precludes traditional shipboard analyses, superoxide concentrations have never been characterized in the deep sea. To this end, we have developed a submersible oceanic chemiluminescent analyzer of reactive intermediate species (SOLARIS) to enable continuous measurements of superoxide at depth. Fluidic pumps on SOLARIS combine seawater for analysis with reagents in a spiral mixing cell, initiating a chemiluminescent reaction that is monitored by a photomultiplier tube. The superoxide in seawater is then related to the quantity of light produced. Initial field deployments of SOLARIS have revealed high-resolution trends in superoxide throughout the water column. SOLARIS presents the opportunity to constrain the distributions of superoxide, and any number of chemiluminescent species in previously unexplored environments.
Highlights
One of the greatest advantages of in situ chemical sensors is their ability to enable observations under ambient conditions that could otherwise not be made [1,2,3,4,5]
Monovalent reduction reactions yielding measurable O2 – in seawater occur through a plethora of pathways including photoreactions with chromophoric dissolved organic matter, abiotic reactions involving reduced metals and sulfide, and numerous extracellular production pathways tied to the activity of various phytoplankton, bacteria, and shallow-water coral species, among others [11,12]
In the photon counts resulting from the chemiluminescent reaction between methyl Cypridina luciferin analogue (MCLA) and solutions of increasing SOTS-1 concentration
Summary
One of the greatest advantages of in situ chemical sensors is their ability to enable observations under ambient conditions that could otherwise not be made [1,2,3,4,5]. Many traditional measurement methods in observational oceanography require the retrieval of water samples for later analyses. For some measurements this approach may skew the representation of natural conditions, and for others, such as the measurement of shortlived chemical species, is impractical or entirely impossible. Monovalent reduction reactions yielding measurable O2 – in seawater occur through a plethora of pathways including photoreactions with chromophoric dissolved organic matter, abiotic reactions involving reduced metals and sulfide, and numerous extracellular production pathways tied to the activity of various phytoplankton, bacteria, and shallow-water coral species, among others [11,12].
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