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Does blending of chlorophyll data bias temporal trend?


Arising from D. G. Boyce, M. R. Lewis & B. Worm Nature 466, 591–596 (2010)10.1038/nature09268; Boyce et al. reply

Phytoplankton account for about half of global and nearly all of marine primary productivity; consequently, any widespread drop in phytoplankton biomass would almost certainly have severe ecological consequences. Boyce et al.1 have reported strong (1% per year) and sustained declines in marine phytoplankton biomass at local, regional and global scales. However, I suggest that some or much of their reported declines are attributable to bias between the two data types used by Boyce et al.1. Although real changes may have occurred, their proper quantification requires removal of the bias component.

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Figure 1: Evidence for bias between the transparency-based and in-situ estimates of chlorophyll concentration used by Boyce et al.1.


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

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Correspondence to David L. Mackas.

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Mackas, D. Does blending of chlorophyll data bias temporal trend?. Nature 472, E4–E5 (2011).

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