Manganese (Mn) is a required element for oceanic phytoplankton as it plays a critical role in photosynthesis, through its unique redox chemistry, as the active site in photosystem II, and in enzymes that act as defenses against reactive oxygen species (ROS), most notably for protection against superoxide (O₂^–), through the action of superoxide dismutase (SOD), and against hydrogen peroxide (H₂O₂) via peroxidases and catalases. The distribution and redox speciation of Mn in the ocean is also apparently controlled by reactions with ROS. Here we examine the connections between ROS and dissolved Mn species in the upper ocean using field and laboratory experimental data. Our results suggest it is unlikely that significant concentrations of Mn(III) are produced in the euphotic zone, as in the absence of evidence for the existence of strong Mn(III) ligands, Mn(II) reacts with O₂^– to form the short-lived transient manganous superoxide, MnO₂⁺, which may react rapidly with other redox species in a manner similar to O₂^–. Experiments with the strong Mn(III) chelator, desferrioxamine B (DFB), in seawater indicated that the Mn(III) species are unlikely to form, as formation of the precursor Mn(II) complex is hindered due to the stability of the Ca complex with DFB.

Item Type:	Refereed Article
Research Division:	Earth Sciences
Research Group:	Oceanography
Research Field:	Chemical oceanography
Objective Division:	Environmental Management
Objective Group:	Other environmental management
Objective Field:	Other environmental management not elsewhere classified
UTAS Author:	Wuttig, K (Dr Kathrin Wuttig)
ID Code:	103235
Year Published:	2013
Web of Science® Times Cited:	38
Deposited By:	CRC-Antarctic Climate & Ecosystems
Deposited On:	2015-09-29
Last Modified:	2017-11-01
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