Hypoxia occurs when an area of the ocean has insufficient dissolved oxygen to support most marine life. When oxygen levels plummet, most animals suffocate if they cannot escape. Hypoxic areas are thus often termed “dead zones”. Since 2002, hypoxic waters have appeared and recurred during the summer along the coastal fringes of the northern California Current Large Marine Ecosystem (off Oregon and Washington). For in-depth information, see Frequently Asked Questions ( also available as a 63 KB, pdf).
Research using over 50 years of oceanographic information is now showing that prior to 2002, these events were completely unprecedented. Hypoxia is closely linked to shifting wind patterns and changing ocean conditions. Scientists believe that hypoxia in these coastal ocean waters is becoming the “new normal” during the summertime.
Researchers tracked the most severe hypoxic event yet recorded in Oregon’s coastal waters in 2006. Oxygen levels fell to zero for the first time on record. (‘Anoxia’ is the term used to mean ‘no oxygen.’) This sudden change had broad ecological impacts. Using a robotic submersible, PISCO researchers and biologists from the Oregon Department of Fish and Wildlife revealed the disappearance of fish and mass die-off of many bottom-dwelling marine organisms in near-shore rocky reef habitats. Monitoring efforts by NOAA scientists further indicated the presence of severely low oxygen water along much of the Oregon and Washington coasts.
In response to this recent rise of hypoxia and anoxia in nearshore, shallow waters, a new network of researchers now monitors the coastal ocean off Washington and Oregon to track the appearance and consequences of hypoxia. This ocean-observing effort involves both research vessels and new state-of-the-art moored oceanographic sensors and autonomous underwater vehicles called "gliders" that patrol the coastal ocean around the clock. In 2007, this monitoring effort detected the reappearance of near-shore severe hypoxia along the Oregon coast.
Ocean areas from southern Oregon to northern Washington were surveyed in 2007 with collaborations across academic institutions and governmental agencies (PISCO, NOAA Fisheries, Oregon Department of Fish and Wildlife, and NOAA Olympic Coast National Marine Sanctuary). The central Oregon coastline, near Newport, was the focus of intense oceanographic and ecological studies. A large number of Remotely Operated Vehicle (ROV) surveys documented the ways in which rocky reef fish and other marine life recovered from the severe 2006 event and responded to 2007 hypoxia. Frequent surveys in summer 2007 showed that, as the dead zone receded, fish species moved back onto the reefs. For long-lived and less mobile bottom-dwelling marine life, scientists have continued to see long lasting impacts from the 2006 event. Continued research will be essential for charting the long term course of recovery for these ecosystems.
Surveys showed partial recovery of a few species and continued depression of others. The process of ecosystem recovery from the extreme 2006 event was likely compromised by the return of hypoxia in 2007. Researchers suggest that recurring hypoxia may create long-lasting changes to the ecosystem.
Research is underway to monitor changes and to understand the causes and consequences of these hypoxic events.