by Kristen Minogue

Brown Chromis fish in Flower Garden Banks National Marine Sanctuary. (Credit: Emma Hickerson/NOAA)

The ocean is losing its breath. Two years ago, an international team of scientists known as GO₂NE (the Global Ocean Oxygen Network) published a report in Science with a stark picture of oxygen loss in Earth’s waters: In the open ocean, the amount of water with zero oxygen has spiked fourfold since the mid-20^th century. In coastal water bodies, places with dangerously low oxygen (2 milligrams per liter or less) have increased more than 10-fold. It’s a problem not just for animals, but for people and economies—especially those that rely on tourism or subsistence fishing.

On Dec. 7, a new report emerged from the International Union for the Conservation of Nature. The ocean could lose 3-4% of its total oxygen by the end of the century if nothing changes, with losses even higher in the top, biodiversity-rich 1,000 meters. Large fish like tuna, sharks and marlin are among the most vulnerable. In the closing chapter, led by Denise Breitburg of the Smithsonian Environmental Research Center, they created a massive blueprint for resuscitating the ocean.

We’ve pulled out the highlights below, but the key lies in cracking two global conundrums—nutrient pollution and climate change. Nutrient pollution happens when chemicals like nitrogen and phosphorus stream into the water and fertilize massive growths of algae, which suck oxygen out of the water. Climate change’s role is more subtle, but just as powerful: Warmer water can’t hold as much dissolved oxygen. Warm water also doesn’t mix as well, so oxygen from the atmosphere that’s abundant near the ocean surface doesn’t reach everywhere that needs it.

Fortunately, these two problems are linked. Cleaning up nutrient pollution can help solve climate change, and vice-versa—and the ocean will breathe easier for it. Here are eight highlights from the new report: Click to continue »

by Kristen Minogue

Low oxygen caused the death of these corals and others in Bocas del Toro, Panama. The dead crabs pictured also succumbed to the loss of dissolved oxygen.
(Credit: Arcadio Castillo/Smithsonian)

In the past 50 years, the amount of water in the open ocean with zero oxygen has gone up more than fourfold. In coastal water bodies, including estuaries and seas, low-oxygen sites have increased more than 10-fold since 1950. Scientists expect oxygen to continue dropping even outside these zones as Earth warms. To halt the decline, the world needs to rein in both climate change and nutrient pollution, an international team of scientists asserted in a new paper published Jan. 4 in Science.

“Oxygen is fundamental to life in the oceans,” said Denise Breitburg, lead author and marine ecologist with the Smithsonian Environmental Research Center. “The decline in ocean oxygen ranks among the most serious effects of human activities on the Earth’s environment.”

Click to continue »