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Publication Title

Journal of Geophysical Research-Oceans








Dissolved iron and manganese and total dissolvable iron were measured in water column samples from the Polynya Region of the southern Ross Sea in cruises in Nov.-Dec. 1994 (spring 1994) and Dec. 1995 to Jan. 1996 (summer 1995). Iron and manganese addition bottle incubation experiments were also performed on these cruises to assess the nutritional sufficiency of ambient iron and manganese concentrations for phytoplankton growth. Generally high dissolved iron concentrations (>0.5 nM) and relatively complex iron and manganese vertical profiles were obtained in spring 1994 vs. summer 1995. Dissolved iron concentrations in the upper water column averaged 1.0 nM in spring 1994 and 0.23 nM in summer 1995, excluding 2 stations where concentrations exceeding 1 nM were attributed to inputs from melting sea ice. The Observed differences in the iron and manganese distribution between spring 1994 and summer 1995 were attributed to seasonal decreases in bottom water upwelling and sea ice melting, which supplied these metals to the upper water column, combined with the cumulative removal of iron and manganese from the water column throughout the spring and summer, due to biological uptake, vertical export, and scavenging by suspended and sinking particles. Results of metal addition bottle incubation experiments indicated that ambient dissolved Iron concentrations were adequate for phytoplankton growth requirements in spring and early summer, when algal production is highest and Phaeocystis antarctica dominates the algal community, whereas low dissolved Iron concentrations limited algal community growth later in the summer, except in stratified, Iron enriched water near melting sea ice, where diatoms are able to bloom. Observations and inferred seasonal distribution of P. antarctica and diatoms in this water suggested that iron availability and vertical mixing (i.e., irradiance) exert the primary controls on phytoplankton growth and community structure in the southern Ross Sea in spring and summer.

Original Publication Citation

Sedwick, P.N., DiTullio, G.R., & Mackey, D.J. (2000). Iron and manganese in the Ross Sea, Antarctica: Seasonal iron limitation in antarctic shelf waters. Journal of Geophysical Research-Oceans, 105(C5), 11321-11336. doi: 10.1029/2000JC000256