Our Oceans Losing Oxygen

An international team of oceanographers, including a scientist from the esteemed Scripps Institution of Oceanography, has determined that expanded areas of tropical oceans are suffering from oxygen depletion as the waters warm globally.  This significant study, entitled “Expanding Oxygen-Minimum Zones in the Tropical Oceans,” was published and appears in the May 2 issue of the journal Science.  The research group was headed by Lothar Stramma from the Leibniz Institute of Marine Sciences (IFM-GEOMAR) in Kiel, Germany and was co-authored by Janet Sprintall, a physical oceanographer at Scripps.  Lower oxygen levels in the oceans limits the areas in which predatory fishes and other marine organisms can live or enter in search of food.  Warming oceans caused by climate change could gradually starve parts of our essential tropical oceans of oxygen, damaging fisheries and coastal economies.

 

The researchers found through analysis of a database of ocean oxygen measurements that levels in tropical oceans at a depth of 300 to 700 meters have declined during the past 50 years.  Problems of lower oxygen supply likely will add to the already mounting problems caused by over-fishing as the world struggles to feed an expanding population. 

 

In undertaking their research, the team selected ocean regions for which they could obtain the greatest amount of data to document the decline in oxygen. Some of the more recent data came from oxygen sensors which have been added to about 150 of the profiling floats used in Argo, a worldwide network of sensors that track basic ocean conditions such as temperature and salinity. There are more than 3,000 Argo floats operating in the world’s oceans, and it has been suggested that more units in the network should be outfitted with oxygen sensors.

 

The ecological impacts of warmer oceans causing more widespread oxygen depletion in our oceans could very well have substantial biological and economical consequences.