Persistence of Fe(II) in Seawater Due to the Effect of Organic Exudates from D. tertiolecta
Aridane Gonzalez1,2, Magdalena Santana-Casiano2, Melchor González-Dávila3, Milagros Rico-Santos2, Aroa Lopez2, Norma Perez-Almeida2, Miguel Angel Suarez de Tangil2 and Antera Martel-Quintana2, (1)Institut Universitaire Européen de la Mer (IUEM), Laboratoire des Sciences de l'Environnement Marin (LEMAR), Brest, France, (2)Facultad de Ciencias del Mar. Universidad de Las Palmas de Gran Canaria., Departamento de Quimica, Las Palmas, Spain, (3)IOCAG. Universidad de Las Palmas de Gran Canaria., Las Palmas de Gran Canaria, Spain
Abstract:
The chemistry of iron is highly affected by the presence of organic ligands in solution, where the exudates produced by microorganisms play a key role. In this sense, the Fe(II) oxidation was studied in the presence of exudates produced by
Dunaliella tertiolecta. The Fe(II) oxidation rate was studied at different stages of growth, where the Dissolved Organic Carbon (DOC) increased from 2.1 to 7.1 mg L
-1. The oxidation of Fe(II) was also studied as a function of pH (7.2 - 8.2), temperature (5-35 °C) and salinity (10-37). The presence of exudates invoked a decrease in Fe(II) rate constant with respect to the control seawater.
On the other hand, the phenolic profile of the exudates and extracts of D. tertiolecta were studied in the stationary phase (8 days of culture) and compared with the control seawater. The phenolic profile revealed an enrichment in phenolic compounds that are able to reduce Fe(III) to Fe(II) acting as a source of Fe(II) in the surface waters.
The two phenolic compounds, catechin and sinapic acid, were selected to study the reduction of Fe(III) in seawater from pH 8.0 to 6.0. The reduction of Fe(III) by these two phenolic compounds was a pH-dependent process.
The organic exudates of D. tertiolecta favoured the persistence of Fe(II) in surface waters. This must be factored under ocean acidification conditions due to the key role played by them on the Fe(II) oxidation rate at lower pH values. As they are responsible for decreasing the Fe(II) oxidation rate, these experiments indicated that the exudates of D. tertiolecta can act as an important Fe(II) supplier to other marine organisms.
