Fate of Phosphorus during Photochemical Cycling of Iron Oxyhydr(oxides) in the Upper Ocean

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Terrestrially-derived dust is an important source of the micronutrient iron (Fe) to nutrient-depleted regions of the oceans. The Fe from aeolian inputs is predominantly in the form of ferric oxyhydroxide which because of its strong affinity for phosphorus (P) have significant amounts of this nutrient associated with it. Together these nutrients can impact primary production. Once dust is introduced to sunlit surface waters, the ferric oxyhydroxide particles are subject to photoreductive dissolution which enhances bioavailable Fe but the impact of this process on the associated P is unknown. Researchers at the University of Hawaii plan to carry out a series of laboratory experiments using synthetic ferric oxyhydroxides and natural dust samples to determine the fate of P associated with these particles once they are photochemically reduced. Results from this study will establish whether Fe-rich dust is a source to the existing bioavailable pool of P or a sink due to removal via sorptive scavenging as a consequence of repetitive photochemical dissolution/re-precipitation cycles of ferric oxyhydroxides in the marine environment. Broader Impacts: Besides providing new insights on the phosphorus cycle, this research would support and train one graduate student of Hawaiian descent.