Organic matter controls of iron incorporation in growing sea ice

• Published in: Frontiers in Earth Science
• Main Authors: Janssens, JP, Meiners, KM, Townsend, AT, Lannuzel, D
• Format: Article in Journal/Newspaper
• Language: English
• Published: Frontiers Research Foundation 2018
• Subjects: Earth Sciences; Oceanography; Chemical oceanography; Sea ice
• Online Access: https://doi.org/10.3389/feart.2018.00022; http://ecite.utas.edu.au/130924

This study presents the first laboratory-controlled sea-ice growth experiment conductedunder trace metal clean conditions. The role played by organic matter in the incorporationof iron (Fe) into sea ice was investigated by means of laboratory ice-growth experimentsusing a titanium cold-finger apparatus. Experiments were also conducted to understandthe role of extracellular polymeric substances (EPS) in the enrichment of ammonium insea ice. Sea ice was grown from several seawater solutions containing different quantitiesand qualities of particulate Fe (PFe), dissolved Fe (DFe) and organic matter. Sea ice andseawater were analyzed for particulate organic carbon and nitrogen, macro-nutrients,EPS, PFe, and DFe, and particulate aluminum. The experiments showed that biogenicPFe is preferentially incorporated into sea ice compared to lithogenic PFe. Furthermore,sea ice grown from ultra-violet (UV) and non-UV treated seawaters exhibits contrastingincorporation rates of organic matter and Fe. Whereas, the effects of UV-treatments werenot always significant, we do find indications that the type or organic matter controlsthe enrichment of Fe in forming sea ice. Specifically, we come to the conclusion thatthe incorporation of DFe is favored by the presence of organic ligands in the sourcesolution.