{"id":1380,"date":"2026-03-04T16:25:13","date_gmt":"2026-03-04T16:25:13","guid":{"rendered":"https:\/\/cordellfoundation.org\/resourcecenter\/?p=1380"},"modified":"2026-03-19T15:36:22","modified_gmt":"2026-03-19T15:36:22","slug":"what-is-hypoxia-and-why-it-is-important-to-study-hypoxic-events-at-cordell-bank-national-marine-sanctuary","status":"publish","type":"post","link":"https:\/\/cordellfoundation.org\/resourcecenter\/what-is-hypoxia-and-why-it-is-important-to-study-hypoxic-events-at-cordell-bank-national-marine-sanctuary\/","title":{"rendered":"What is hypoxia and why it is important to study hypoxic events at Cordell Bank National Marine Sanctuary"},"content":{"rendered":"\n

Photo: NOAA\/GFNMS\/CBNMS<\/em><\/p>\n\n\n\n

What is Hypoxia?<\/h2>\n\n\n\n

Hypoxia is a term used to describe conditions when the dissolved oxygen concentration in a body of water becomes low and starts to affect aquatic organisms that require oxygen to survive.  In scientific literature, hypoxia usually refers to dissolved oxygen levels below a certain threshold, most commonly 5mg\/L or 2mg\/L.  However, the effects of hypoxia vary greatly across different animals; some species are extremely sensitive to hypoxia (fish and benthic invertebrates), while others thrive in low-oxygen environments (iron- and sulfur-reducing bacteria).  Animals\u2019 responses to hypoxia range from reduced health to death and are greatly dependent on the intensity (how low the concentration of dissolved oxygen gets) and how long the hypoxia event lasts.<\/p>\n\n\n\n

Hypoxia events on Cordell Bank are relatively common, occurring about 20 times a year [DL1] on average and most frequently in late summer.  Most are short-lived, lasting days to weeks at a time. There are several reasons why hypoxia may be observed at this location. The first is driven by coastal upwelling, a process by which water masses from the deep ocean, which are rich in nutrients (e.g., nitrogen and phosphorus) but low in oxygen, are brought to the surface in the spring and summer.  These low-oxygen waters pass over Cordell Bank on their way to the surface, leading to hypoxia events.  The second is that, following upwelling, phytoplankton blooms occur when the ocean becomes calm (termed \u201crelaxation\u2019). As that phytoplankton dies and sinks to the ocean floor, the decomposition process removes oxygen from the water.<\/p>\n\n\n

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Photo Credit: NOAA\/CBNMS\/GFNMS<\/em><\/p>\n\n\n\n

Hypoxia Monitoring at Cordell Bank<\/h2>\n\n\n\n

Since 2014, Cordell Marine Sanctuary Foundation (CMSF) has helped fund  a joint project  of Cordell Bank National Marine Sanctuary (CBNMS) and the University of California Davis Bodega Marine Laboratory to study hypoxia on Cordell Bank. After 10 years of monitoring, these efforts have produced a valuable long-term dataset that can help us understand the conditions animals living on Cordell Bank are experiencing, and if these conditions are changing over time. .<\/p>\n\n\n\n

CMSF is currently funding a graduate student at Bodega Marine Laboratory to analyze the dataset and help inform conservation efforts within CBNMS.  Beyond aiding in conservation efforts, the Cordell Bank hypoxia dataset can serve as the basis for future scientific work and can help oceanographers answer longstanding questions about oxygen levels in coastal and offshore environments. <\/p>\n\n\n\n

Hypoxia Monitoring at Cor<\/strong>dell Bank<\/h2>\n\n\n\n
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What is hypoxia?<\/h2>\n\n

\n Hypoxia refers to low dissolved oxygen (DO) conditions in seawater. It is best understood as a relative condition rather than a single universal threshold, because oxygen sensitivity varies by taxonomic group and life stage. Some organisms can tolerate, or even thrive under, low-oxygen conditions, while others experience rapid stress.\n <\/p>\n\n

Low dissolved oxygen and biological thresholds<\/h3>\n