Effect of aging time on the availability of freshly precipitated ferric hydroxide to coastal marine diatoms
- 132 Downloads
Cell growth and iron uptake of the coastal marine diatoms Chaetoceros sociale and Thalassiosira weissflogii were studied in the presence of short-aged amorphous ferric hydroxide (am-Fe(III)) media. These were prepared by aging for 1 day, 3 days, and 3 weeks after adding a small amount of ferric iron acidic stock solution to autoclaved filtered seawater and were experimentally measured in culture experiments at 10°C for C. sociale and 20°C for T. weissflogii. The order of cell yields for both species was: 1-day aged am-Fe(III) >3-day aged am-Fe(III) >> 3-week aged am-Fe(III) media. The iron uptake rates by C. sociale during 0–1 day in 1 day and 3-day aged am-Fe(III) media were about two-thirds and one-fourths, respectively, lower than that in the direct Fe(III) input medium containing C. sociale into which an acidic Fe(III) stock solution was added directly. The longer aging time of am-Fe(III) in media results in reducing the supply of bioavailable iron in the media by the slower dissolution rate of am-Fe(III) with the longer aging time. These results suggest that the chemical and structural changes of freshly precipitated amorphous ferric hydroxide with short aging time affect their ability, such as iron solubility and dissolution rate to supply bioavailable iron for the phytoplankton growth. The chemical and structural conversion of solid iron phases with time is one of the most important processes in changing the supply of available iron to marine phytoplankton in estuarine and coastal waters and in iron fertilization experiments.
KeywordsPhytoplankton Iron Uptake Initial Growth Rate Longe Aging Time Short Aging Time
We thank Dr. K. Suzuki (ES, Hokkaido University) for supplying coastal diatom species and for helpful comments. We also are grateful to anonymous reviewers for their constructive and helpful comments on this work. Partial support was provided by Grant-in-Aids for Environmental Research (No. 023039) from the Sumitomo Foundation and Scientific Research (No. 17651001) from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
- Campbell PGC (1995) Interactions between trace metals and aquatic organisms: A critique of the free-ion activity model. In: Tessier A, Turner DR (eds) Metal speciation and bioavailability in aquatic systems. Wiley, New York, pp 45–102Google Scholar
- Chen M, Wang W-X, Guo L (2004) Phase partitioning and solubility of iron in natural seawater controlled by dissolved organic matter. Global Biogeochem Cycle 18:GB4013; doi: 10.1029/2003GB002160269Google Scholar
- Morel FMM, Hering JG (1993) Principles and applications of aquatic chemistry. Wiley-Interscience, New YorkGoogle Scholar
- Pankow JE (1991) Aquatic chemistry concepts. Lewis, New YorkGoogle Scholar
- Stumm W, Morgan JJ (1996) Aquatic chemistry, 3rd edn. Wiley-Interscience, New YorkGoogle Scholar
- Sunda WG (2001) Bioavailability and bioaccumulation of iron in the sea. In: Turner DR, Hunter KA (eds) The biogeochemistry of iron in seawater. Wiley, New York, pp 41–84Google Scholar
- Takata H, Kuma K, Iwade S, Isoda Y, Kuroda H, Senjyu T (2005) Comparative vertical distributions of iron in the Japan Sea, the Bering Sea and the western North Pacific Ocean. J Geophys Res 110:C07004; doi: 10.1029/2004JC002783Google Scholar
- Waite TD (2001) Thermodynamics of the iron system in seawater. In: Turner DR, Hunter KA (eds) The biogeochemistry of iron in seawater. Wiley, New York, pp 291–342Google Scholar