title: Effect of nitrate enrichment and diatoms on the bioavailability of Fe(III) oxyhydroxide colloids in seawater.
abstract: The photoconversion of colloidal iron oxyhydroxides was a significant source of bioavailable iron in coastal systems. Diatoms dominate phytoplankton communities in coastal and upwelling regions. Diatoms are often exposed to eutrophication. We investigated the effects of different species of diatom, cell density, illumination period, and nitrate additions on the bioavailability of Fe(III) oxy-hydroxide colloids in seawaters. With the increase of illumination period from 1 to 4 h, the ratios of concentrations of total dissolved Fe (DFe) to colloidal iron oxyhydroxides and Fe(II) to DFe increased up to 24.3% and 23.9% for seawater without coastal diatoms, 45.6% and 30.2% for Skeletonema costatum, 44.3% and 29.7% for Thalassiosira weissflogii, respectively. The photochemical activity of coastal diatoms themselves (excluding the dissolved organic matter secreted by algae) on the species transformation of iron in seawater (including the light-induced dissolution of Fe(III) oxyhydroxide colloids and the photo-reduction of Fe(III) into Fe(II)) was confirmed for the first time. There was no significant difference of the ability of S. costatum and Thalassiosira weissflogii on the photoconversion of colloidal iron oxyhydroxides. The photoproduction of dissolved Fe(II) and DFe in the seawater with or without diatoms could be depressed by the nitrate addition.
authors.affiliation: Key Laboratory of Coastal and Wetland Ecosystems, Ministry of Education, Xiamen University, 361005, China; Fujian Provincial Key Laboratory of Coastal Ecology and Environmental Studies, Xiamen University, 361005, China.
authors.forename: Feng-Jiao
authors.initials: FJ
authors.lastname: Liu
authors.affiliation: Key Laboratory of Coastal and Wetland Ecosystems, Ministry of Education, Xiamen University, 361005, China; Fujian Provincial Key Laboratory of Coastal Ecology and Environmental Studies, Xiamen University, 361005, China. Electronic address: bqhuang@xmu.edu.cn.
authors.forename: Bang-Qin
authors.initials: BQ
authors.lastname: Huang
authors.affiliation: Fujian Provincial Key Laboratory of Modern Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou, 363000, China. Electronic address: shunxing_li@aliyun.com.
authors.forename: Shun-Xing
authors.initials: SX
authors.lastname: Li
authors.affiliation: College of Chemistry and Environment, Minnan Normal University, Zhangzhou, 363000, China; Fujian Provincial Key Laboratory of Modern Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou, 363000, China.
authors.forename: Feng-Ying
authors.initials: FY
authors.lastname: Zheng
authors.affiliation: College of Chemistry and Environment, Minnan Normal University, Zhangzhou, 363000, China; Fujian Provincial Key Laboratory of Modern Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou, 363000, China.
authors.forename: Xu-Guang
authors.initials: XG
authors.lastname: Huang
mesh_terms: D001682:Biological Availability; D003102:Colloids; D017377:Diatoms / Q000187:drug effects* / Q000378:metabolism; D005290:Ferric Compounds / Q000378:metabolism* / Q000528:radiation effects; D008027:Light; D009566:Nitrates / Q000494:pharmacology*; D010084:Oxidation-Reduction; D010839:Phytoplankton / Q000187:drug effects* / Q000378:metabolism; D012623:Seawater
chemical_list: D003102:Colloids; D005290:Ferric Compounds; D009566:Nitrates; C021024:ferric hydroxide
keywords: Bioavailability; Coastal seawater; Iron; Macronutrient enrichment; Marine phytonlankton; Photoreduction