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Upwelling-driven nearshore hypoxia signals ecosystem and oceanographic changes in the northeast Pacific


Seasonal development of dissolved-oxygen deficits (hypoxia) represents an acute system-level perturbation to ecological dynamics and fishery sustainability in coastal ecosystems around the globe1,2,3. Whereas anthropogenic nutrient loading has increased the frequency and severity of hypoxia in estuaries and semi-enclosed seas3,4, the occurrence of hypoxia in open-coast upwelling systems reflects ocean conditions that control the delivery of oxygen-poor and nutrient-rich deep water onto continental shelves1. Upwelling systems support a large proportion of the world's fisheries5, therefore understanding the links between changes in ocean climate, upwelling-driven hypoxia and ecological perturbations is critical. Here we report on the unprecedented development of severe inner-shelf (<70 m) hypoxia and resultant mass die-offs of fish and invertebrates within the California Current System. In 2002, cross-shelf transects revealed the development of abnormally low dissolved-oxygen levels as a response to anomalously strong flow of subarctic water into the California Current System. Our findings highlight the sensitivity of inner-shelf ecosystems to variation in ocean conditions, and the potential impacts of climate change on marine communities.

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Figure 1: Location of the 2002 hypoxic zone and hydrographic transects off Oregon.
Figure 2: Timeline of observations, both continuous (ac) and discrete (1–6).
Figure 3: Impact of hypoxia on rockfish communities.
Figure 4: Dissolved-oxygen profiles.


  1. Naqvi, S. W. A. et al. Increased marine production of N2O due to intensifying anoxia on the Indian continental shelf. Nature 408, 346–349 (2000)

    ADS  CAS  Article  Google Scholar 

  2. Diaz, R. J. Overview of hypoxia around the world. J. Environ. Qual. 30, 275–281 (2001)

    CAS  Article  Google Scholar 

  3. Rabalais, N. N. & Turner, R. E. in Coastal Hypoxia: Consequences for Living Resources and Ecosystems (eds Rabalais, N. N. & Turner, R. E.) 1–36 (American Geophysical Union, Washington DC, 2001)

    Google Scholar 

  4. National Research Council. Coastal Waters: Understanding and Reducing the Effects of Nutrient Pollution (National Academy Press, Washington DC, 2000)

    Google Scholar 

  5. Pauly, D. & Christensen, V. Primary production required to sustain global fisheries. Nature 374, 255–257 (1995)

    ADS  CAS  Article  Google Scholar 

  6. Chavez, F. P., Ryan, J., Lluch-Cota, S. E. & Niquen, M. From anchovies to sardines and back: Multidecadal change in the Pacific Ocean. Science 299, 217–221 (2003)

    ADS  CAS  Article  Google Scholar 

  7. Bakun, A. Global climate change and intensification of coastal ocean upwelling. Science 247, 198–201 (1990)

    ADS  CAS  Article  Google Scholar 

  8. Roemmich, D. & McGowan, J. Climatic warming and the decline of zooplankton in the California Current. Science 267, 1324–1326 (1995)

    ADS  CAS  Article  Google Scholar 

  9. Wheeler, P. A., Huyer, A. & Fleischbein, J. Cold halocline, increased nutrients and higher productivity off Oregon in 2002. Geophys. Res. Lett. [online] 30, 8021 (2003) (doi:10.1029/2003GL017395)

    ADS  Google Scholar 

  10. Freeland, H. J., Gatien, G., Huyer, A. & Smith, R. L. Cold halocline in the northern California current: an invasion of subarctic water. Geophys. Res. Lett. [online] 30, 1141 (2003) (doi:10.1029/2002GL016663)

    ADS  Article  Google Scholar 

  11. Diaz, R. J. & Rosenberg, R. Marine benthic hypoxia: a review of its ecological effects and the behavioural responses of benthic macrofauna. Oceanogr. Mar. Biol. Ann. Rev. 33, 245–303 (1995)

    Google Scholar 

  12. National Marine Fisheries Service. Our Living Oceans (NOAA Technical Memo NMFS-F/SPO-41, US Department of Commerce, Washington DC, 1999)

    Google Scholar 

  13. Dillman, T. Abundance of Fish on Area Reefs Delights, Puzzles Divers (Newport News-Times, Newport, Oregon, 2002)

    Google Scholar 

  14. Huyer, A. Coastal upwelling in the California current system. Prog. Oceanogr. 112, 259–284 (1983)

    ADS  Article  Google Scholar 

  15. Kamykowski, D. & Zentara, S. J. Hypoxia in the world ocean as recorded in the historical data set. Deep-Sea Res. 37, 1861–1874 (1990)

    ADS  CAS  Article  Google Scholar 

  16. Fleischbein, J. Northeast Pacific long term observation program. US GLOBEC〉 (2003)

  17. Huyer, A., Smith, R. L. & Pillsbury, R. D. Observations in a coastal upwelling region during a period of variable winds (Oregon coast, July 1972). Tethys 6, 391–404 (1974)

    Google Scholar 

  18. Oke, P. R. et al. A modelling study of the three-dimensional continental shelf circulation off Oregon. Part I: Model-data comparisons. J. Phys. Oceanogr. 32, 1360–1382 (2002)

    ADS  Article  Google Scholar 

  19. Thomas, A. C., Strub, T., Brickley, P. & James, C. Anomalous satellite-measured chlorophyll concentrations in the northern California Current in 2001–2002. Geophys. Res. Lett. [online] 30, 8022 (2003) (doi:10.1029/2003GL017409)

    ADS  Google Scholar 

  20. Bailey, G. W., Beyers, C. J. B. & Lipschitz, S. R. Seasonal variation of oxygen deficiency in waters off southern south west Africa in 1975 and 1976 and its relation to the catchability and distribution of the cape rock lobster Jasus lalandii. S. Afr. J. Mar. Sci. 3, 197–214 (1985)

    Article  Google Scholar 

  21. Morales, C. E., Hormazabal, S. E. & Blanco, J. L. Interannual variability in the mesoscale distribution of the depth of the upper boundary of the oxygen minimum layer off northern Chile (18–24S): Implications for the pelagic system and biogeochemical cycling. J. Mar. Res. 57, 909–932 (1999)

    CAS  Article  Google Scholar 

  22. Strub, P. T. & James, C. Altimeter estimates of anomalous transports into the northern California Current during 2000–2002. Geophys. Res. Lett. [online] 30, 8025 (2003) (doi:10.1029/2003GL017513)

    ADS  Google Scholar 

  23. Barth, J. A. Anomalous southward advection during 2002 in the northern California Current: evidence from Lagrangian surface drifters. Geophys. Res. Lett. [online] 30, 8024 (2003) (doi:10.1029/2003GL017511)

    ADS  Google Scholar 

  24. Kosro, P. M. Enhanced southward flow over the Oregon shelf in 2002: a conduit for subarctic water. Geophys. Res. Lett. [online] 30, 8023 (2003) (doi:10.1029/2003GL017436)

    ADS  Google Scholar 

  25. Murphree, T., Bograd, S. J., Schwing, F. B. & Ford, B. Large-scale atmosphere–ocean anomalies in the northeast Pacific during 2002. Geophys. Res. Lett. [online] 30, 8026 (2003) (doi:10.1029/2003GL017303)

    ADS  Google Scholar 

  26. Fox, D. S., Amend, M., Merems, A. & Appy, M. Near-shore rocky reef assessment. Oregon Dept. Fish Wildl. Mar. Prog.〉 (2000)

  27. O'Malley, R. SeaSoar observations during the Coastal Ocean Advances in Shelf Transport (COAST) mesoscale surveys I and II. 〈〉 (2003).

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We thank A. Kirincich for ADCP analyses, S. Oda and A. Walters for assistance and A. Pazar for crab fishery data. The Partnership for Interdisciplinary Studies of Coastal Oceans, funded by the David and Lucile Packard Foundation, and the US GLOBEC program, jointly funded by NSF and NOAA, both contributed to this work. J.A.B. acknowledges additional funding from NSF. ODFW ROV survey work was funded in part by the Oregon Department of Land Conservation and Development through NOAA.

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Correspondence to Francis Chan.

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Supplementary information

Supplementary Table S1

Average, minimum and maximum DO and chl-a concentrations along the SH hydroline. (DOC 24 kb)

Supplementary Figure S1

Dissolved oxygen source properties and depletion patterns across the shelf. (DOC 1209 kb)

Supplementary Figure S2

Composite cross-shelf profiles of temperature, salinity, density, nitrate+nitrite, chlorophyll-a, and dissolved oxygen, SH line, 11-12 August, 2002. (DOC 78 kb)

Supplementary Figure S3

Chl-a concentration (mg l-1) at 5 meters depth over Heceta Bank from 9-11 August 2002. (DOC 214 kb)

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Grantham, B., Chan, F., Nielsen, K. et al. Upwelling-driven nearshore hypoxia signals ecosystem and oceanographic changes in the northeast Pacific. Nature 429, 749–754 (2004).

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