Resource limitation of phytoplankton growth in the Crozet Basin, Subantarctic Southern Ocean
By P. Sedwick, S. Blain, B. Quéguiner, F. Griffiths, M. Fiala, E. Bucciarelli, M. Denis. 2002
88 citations recorded by the source corpus.
In January–February 1999, we performed shipboard iron- and macronutrient-addition experiments in the Crozet Basin, Indian sector of the Subantarctic Southern Ocean, to evaluate the sufficiency of ambient iron and macronutrient concentrations for algal growth. Experiments were conducted with near-surface seawater collected from three locations in a narrow latitudinal band characterized by relatively low algal biomass (o0.7m gl � 1 chlorophyll a), low dissolved iron concentrations (o0.33 nM), and strongmeridional g radients in temperature, salinity and macronutrient concentrations: (1) the Polar Frontal Zone (PFZ) near 461S, 651 E( B19mM nitrate and 1.2mM silicic acid); (2) the confluence of the Subantarctic and Subtropical Fronts (SAF/STF) near 44112 0 S, 63123 0 E( B5.4mM nitrate and 0.5mM silicic acid); and (3) the southern Subtropical Zone (STZ) near 43118 0 S, 62131 0 E( o0.1mM nitrate and B1.4mM silicic acid). Our experimental results reveal three distinct regimes of resource limitation of phytoplankton growth. In the PFZ, iron availability exerted the primary limitation on nitrate drawdown and biomass accumulation, thus community growth, with silicic acid availability exerting a secondary limitation on diatom growth and biogenic silica production. Within the SAF/STF, iron deficiency was also the primary limitation on algal community growth; however, here we observed evidence of secondary limitation of nitrate drawdown and biomass accumulation by silicic acid deficiency, via control of algal community structure—such that iron addition preferentially stimulated the growth of non-diatom nanoplankton—suggesting that the algal community was poised close to co-limitation by iron and silicic acid. As expected, our experimental results indicate that macronutrients (nitrate/phosphate) were the primary limitation on community growth in the STZ waters; however, our results also suggest that iron deficiency imposed a significant secondary limitation on community growth, particularly diatom growth, such that the algal community was poised close to co-limitation by macronutrients and iron. We conclude that these same regimes of resource limitation are likely to regulate phytoplankton growth and export production over much of the open-ocean Subantarctic region during the
Subfields: Ecology, Oceanography
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Citations in the corpus
- Fe and Zn effects on the Si cycle and diatom community structure in two contrasting high and low-silicate HNLC areas (2005, background): “It has been suggested that Fe is the proximate limiting nutrient for community production and nitrate drawdown, while Si can exert a secondary control on diatom community structure and Si production (Hutchins et al., 2001; Blain et al., 2002; Sedwick et al., 2002).”
- ENVIRONMENTAL FACTORS CONTROLLING PHYTOPLANKTON PROCESSES IN THE SOUTHERN OCEAN1 (2002, unknown): “Experiments were conducted in subpolar waters in spring (Boyd et al. 1999) and summer when silicic acid levels less than 1 M were recorded (Sedwick et al. 1999, Hutchins et al. 2001, Sedwick et al. 2002).”