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Photosynthetic maximum quantum yield increases are an essential component of the Southern Ocean phytoplankton response to iron

Publication ,  Journal Article
Hiscock, M; Lance, V; Apprill, A; Bidigare, RR; Mitchell, BG; Smith, WO; Johnson, ZI; Barber, RT
Published in: PNAS
2008

It is well established that an increase in iron supply causes an increase in total oceanic primary production in many regions, but the physiological mechanism driving the observed increases has not been clearly identified. The Southern Ocean iron enrichment experiment, an iron fertilization experiment in the waters closest to Antarctica, resulted in a 9-fold increase in chlorophyll (Chl) concentration and a 5-fold increase in integrated primary production. Upon iron addition, the maximum quantum yield of photosynthesis (!m) rapidly doubled, from 0.011 to 0.025 mol C!mol quanta"1. Paradoxically, this increase in light-limited productivity was not accompanied by a significant increase in light-saturated productivity (Pmax b ). Pmax b , maximum Chl normalized productivity, was 1.34 mg C!mg Chl"1!h"1 outside and 1.49 mg C!mg Chl"1!h"1 inside the iron-enriched patch. The importance of !m as compared with Pmax b in controlling the biological response to iron addition has vast implications for understanding the ecological response to iron. We show that an iron-driven increase in !m is the proximate physiological mechanism affected by iron addition and can account for most of the increases in primary production. The relative importance of !m over Pmax b in this iron-fertilized bloom highlights the limitations of oftenused primary productivity algorithms that are driven by estimates of Pmax b but largely ignore variability in !m and lightlimited productivity. To use primary productivity models that include variability in iron supply in prediction or forecasting, the variability of light-limited productivity must be resolved.

Duke Scholars

Published In

PNAS

Publication Date

2008

Volume

105

Issue

12

Start / End Page

4775 / 4780

Related Subject Headings

  • Time Factors
  • Phytoplankton
  • Photosynthesis
  • Oceans and Seas
  • Models, Biological
  • Iron
  • Chlorophyll
  • Chemical Fractionation
  • Carotenoids
  • Analysis of Variance
 

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Hiscock, M., Lance, V., Apprill, A., Bidigare, R. R., Mitchell, B. G., Smith, W. O., … Barber, R. T. (2008). Photosynthetic maximum quantum yield increases are an essential component of the Southern Ocean phytoplankton response to iron. PNAS, 105(12), 4775–4780.
Hiscock, M., V. Lance, A. Apprill, R. R. Bidigare, B. G. Mitchell, W. O. Smith, Z. I. Johnson, and R. T. Barber. “Photosynthetic maximum quantum yield increases are an essential component of the Southern Ocean phytoplankton response to iron.” PNAS 105, no. 12 (2008): 4775–80.
Hiscock M, Lance V, Apprill A, Bidigare RR, Mitchell BG, Smith WO, et al. Photosynthetic maximum quantum yield increases are an essential component of the Southern Ocean phytoplankton response to iron. PNAS. 2008;105(12):4775–80.
Hiscock M, Lance V, Apprill A, Bidigare RR, Mitchell BG, Smith WO, Johnson ZI, Barber RT. Photosynthetic maximum quantum yield increases are an essential component of the Southern Ocean phytoplankton response to iron. PNAS. 2008;105(12):4775–4780.

Published In

PNAS

Publication Date

2008

Volume

105

Issue

12

Start / End Page

4775 / 4780

Related Subject Headings

  • Time Factors
  • Phytoplankton
  • Photosynthesis
  • Oceans and Seas
  • Models, Biological
  • Iron
  • Chlorophyll
  • Chemical Fractionation
  • Carotenoids
  • Analysis of Variance