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 approximately 50% of global primary production, form the trophic base of nearly all marine ecosystems, are fundamental in trophic energy transfer and have key roles in climate regulation, carbon sequestration and oxygen production. Boyce et al.1 compiled a chlorophyll index by combining in situ chlorophyll and Secchi disk depth measurements that spanned a more than 100-year time period and showed a decrease in marine phytoplankton biomass of approximately 1% of the global median per year over the past century. Eight decades of data on phytoplankton biomass collected in the North Atlantic by the Continuous Plankton Recorder (CPR) survey2, however, show an increase in an index of chlorophyll (Phytoplankton Colour Index) in both the Northeast and Northwest Atlantic basins3,4,5,6,7 (Fig. 1), and other long-term time series, including the Hawaii Ocean Time-series (HOT)8, the Bermuda Atlantic Time Series (BATS)8 and the California Cooperative Oceanic Fisheries Investigations (CalCOFI)9 also indicate increased phytoplankton biomass over the last 20–50 years. These findings, which were not discussed by Boyce et al.1, are not in accordance with their conclusions and illustrate the importance of using consistent observations when estimating long-term trends.

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Author information


  1. *Sir Alister Hardy Foundation for Ocean Science, The Laboratory, Citadel Hill, Plymouth, PL1 2PB, UK

    • Abigail McQuatters-Gollop
    • , Philip C. Reid
    • , Martin Edwards
    • , Peter H. Burkill
    • , Claudia Castellani
    •  & Sonia Batten
  2. †University of Groningen, ESRIG, Dept. Ocean Ecosystems, Nijenborgh 4, NL – 9747 AG Groningen, The Netherlands

    • Winfried Gieskes
  3. ‡Wageningen IMARES, Fisheries Department, Haringkade 1, 1976 CP Ijmuiden, The Netherlands

    • Doug Beare
  4. §University of Hawaii, Center for Marine Microbial Ecology and Diversity, 1680 East-West Road, Honolulu, Hawaii 96822 USA

    • Robert R. Bidigare
  5. Fisheries and Oceans Canada, Bedford Institute of Oceanography, PO Box 1006, Dartmouth, Nova Scotia B2Y 4A2, Canada

    • Erica Head
  6. ¶Bermuda Institute of Ocean Sciences, St. George’s, GE 01, Bermuda

    • Rod Johnson
  7. #Scripps Institution of Oceanography, UCSD, 9500 Gilman Dr., La Jolla, California 92093, USA

    • Mati Kahru
    •  & J. Anthony Koslow
  8. Institute of Ocean Sciences, Fisheries and Oceans Canada, PO Box 6000, Sidney, British Columbia V8L 4B2, Canada

    • Angelica Pena


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Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Abigail McQuatters-Gollop.


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