Hypoxia

Ocean Facts!
Below 30 percent oxygen saturation, water is considered hypoxic. Low oxygen conditions in marine habitats can be natural or induced by human activities, but have similar impacts in either case.

Hypoxia (reduction in the dissolved oxygen content of water) has dramatic impacts on aquatic ecosystems. At oxygen levels below 30% saturation, species intolerant of hypoxia (e.g. cod) either migrate to other geographic regions or die.

DFO scientists are studying hypoxia on all three of Canada's coasts:

  • Atlantic: In the St. Lawrence marine ecosystem, changes in oxygen levels are primarily caused by changes in the proportion of higher-oxygen Labrador current water and lower-oxygen Gulf Stream water. Maps of bottom oxygen concentrations in the Gulf of St. Lawrence, Scotian Shelf and Gulf of Maine have been produced.
  • Pacific: On the west coast of Canada, changes in wind patterns and coastal up welling, as well as increasing stratification in offshore waters are contributing factors. DFO scientists are examining historical oxygen data for the Pacific Ocean and British Columbia coastal waters to determine mean oxygen levels and trends.
  • Arctic: In the Arctic Ocean, there is no reason to believe that hypoxic areas exist, but knowing the present levels of oxygen could be useful to establish benchmarks. With accelerated warming, hypoxia may become an issue since increases in primary productivity and vertical fluxes of organic matter may become more common.

DFO scientists will also explore ecosystem impacts of hypoxia by studying the distribution of various groundfish species in relation to oxygen in the Northeast Pacific, Gulf of St. Lawrence and Scotian Shelf-Gulf of Maine. Commercial fishers on the west coast of Vancouver Island and in the Gulf of St. Lawrence, where oxygen levels below 30% saturation are encountered, will benefit from this research.

DFO scientists working on hypoxia science activities can be found here.