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Boyce et al. reply


Replying to A. McQuatters-Gollop et al. Nature 472, 10.1038/nature09950 (2011); D. L. Mackas Nature 472, 10.1038/nature09951 (2011); R. R. Rykaczewski & J. P. Dunne Nature 472, 10.1038/nature09952 (2011)

In their thoughtful responses to our article on global chlorophyll (Chl) trends1, Mackas2, Rykaczewski and Dunne3, and McQuatters et al.7 suggest that some of the variation observed in our analysis may be explained by a possible bias, whereby transparency-derived chlorophyll (CT) measurements overestimate phytoplankton abundance relative to direct in situ chlorophyll (CI) measurements. Although we cannot entirely discount the possibility that changes in sampling methods may introduce fractional bias, extensive sensitivity analyses detailed below show that this is not responsible for the observed Chl declines. Furthermore, the accuracy of CT as a proxy of surface Chl has been independently verified4,5, and indicates that CT explains only 0.5–1.5% less of the variance in surface Chl than precision measurements of water-leaving radiance (remotely sensed ocean colour)5.

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  1. Boyce, D. G., Lewis, M. R. & Worm, B. Global phytoplankton decline over the past century. Nature 466, 591–596 (2010)

    Article  ADS  CAS  Google Scholar 

  2. Mackas, D. L. Does blending of chlorophyll data bias temporal trend? Nature 472 10.1038/nature09951 (2011)

    Article  ADS  CAS  Google Scholar 

  3. Rykaczewski, R. R. & Dunne, J. P. A measured look at ocean chlorophyll trends. Nature 472 10.1038/nature09952 (2011)

  4. Lewis, M. R., Kuring, N. & Yentsch, C. Global patterns of ocean transparency: implications for the new production of the open ocean. J. Geophys. Res. 93, 6847–6856 (1988)

    Article  ADS  Google Scholar 

  5. Falkowski, P. & Wilson, C. Phytoplankton productivity in the North Pacific ocean since 1900 and implications for absorption of anthropogenic CO2 . Nature 358, 741–743 (1992)

    Article  ADS  Google Scholar 

  6. Ripley, B. D. & Thompson, M. Regression techniques for the detection of analytical bias. Analyst (Lond.) 112, 377–383 (1987)

    Article  ADS  CAS  Google Scholar 

  7. McQuatters, A. et al. Is there a decline in marine phytoplankton? Nature 472 10.1038/nature09950 (2011)

  8. Tarran, G. A., Zubkov, M. V., Sleigh, M. A., Burkhill, P. H. & Yallop, M. Microbial community structure and standing stocks in the NE Atlantic in June and July of 1996. Deep Sea Res. Part II Top. Stud. Oceanogr. 48, 963–985 (2001)

    Article  ADS  Google Scholar 

  9. Gregg, W. W., Conkright, M. E., Ginoux, P., O’Reilly, J. E. & Casey, N. W. Ocean primary production and climate: global decadal changes. Geophys. Res. Lett. 30, 1809–1813 (2003)

    Article  ADS  Google Scholar 

  10. Behrenfeld, M. J. et al. Biospheric primary production during an ENSO transition. Science 291, 2594–2597 (2001)

    Article  ADS  CAS  Google Scholar 

  11. Martinez, E., Antoine, D., D’Ortenzio, F. & Gentili, B. Climate-driven basin-scale decadal oscillations of oceanic phytoplankton. Science 326, 1253–1256 (2009)

    Article  ADS  CAS  Google Scholar 

  12. Behrenfeld, M. J. et al. Climate-driven trends in contemporary ocean productivity. Nature 444, 752–755 (2006)

    Article  ADS  CAS  Google Scholar 

  13. Henson, S. A. et al. Detection of anthropogenic climate change in satellite records of ocean chlorophyll and productivity. Biogeosciences 7, 621–640 (2010)

    Article  ADS  CAS  Google Scholar 

  14. Gregg, W. W. & Conkright, M. E. Decadal changes in global ocean chlorophyll. Geophys. Res. Lett. 29, 1730–1734 (2002)

    Article  ADS  Google Scholar 

  15. Reid, P. C., Edwards, M., Hunt, H. G. & Warner, A. J. Phytoplankton change in the North Atlantic. Nature 391, 546 (1998)

    Article  ADS  CAS  Google Scholar 

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Correspondence to Daniel G. Boyce.

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Boyce, D., Lewis, M. & Worm, B. Boyce et al. reply. Nature 472, E8–E9 (2011).

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