Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

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.

This is a preview of subscription content

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


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

    ADS  CAS  Article  Google Scholar 

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

    ADS  CAS  Article  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)

    ADS  Article  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)

    ADS  Article  Google Scholar 

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

    ADS  CAS  Article  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)

    ADS  Article  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)

    ADS  Article  Google Scholar 

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

    ADS  CAS  Article  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)

    ADS  CAS  Article  Google Scholar 

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

    ADS  CAS  Article  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)

    ADS  CAS  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

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

    ADS  CAS  Article  Google Scholar 

Download references

Author information

Authors and Affiliations


Corresponding author

Correspondence to Daniel G. Boyce.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

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

Download citation

  • Published:

  • Issue Date:

  • DOI:

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing