OCEAN & OXYGEN: Low oxygen levels in oceans may affect fishing worldwide. Is global warming to blame?

Oxygen levels in many areas of the world's oceans are declining. These “low-oxygen zones” gradually expanded during the last 50 years. Lothar Stramma and colleagues at the University of Kiel in Germany released a study recently that suggests global warming may be at the root of the problem.

Is Global Warming to Blame?

• Global warming is gradually raising the temperature of the world’s oceans.
• Water starting out at the poles and flowing toward the equator is warmer from the get-go.
• Since warmer water is lower in oxygen, the whole process begins with less oxygen and ends up with less by the time the water makes it to the equator.
• Low-oxygen zones form columns in the ocean, and they’re expanding.

Fish Need Oxygen

Some marine animals thrive in or near water with reduced oxygen. Many others—such as some of the fish we find at the market—need lots of oxygen to survive. As global warming continues to heat the oceans and low-oxygen columns expand, these fish will be forced to move elsewhere, or die.

Lisa Levin of Scripps Institution of Oceanography says, “Certainly, where this [low oxygen] occurs on our continental shelf, we will see major changes in our ecosystems, including in the distribution and abundance of fishery species.”

If large numbers of fish move away from low-oxygen zones in common fishing areas or die, fisheries and coastal economies, not to mention plenty of dinner menus, could suffer.

Copyright © 2009 Informify

Sources

"Fishing for Oxygen in Warming Oceans " (Scientific American)

"Expanding Oxygen-Minimum Zones in the Tropical Oceans [abstract]" (Science)

"Low-Oxygen Zones Spreading to Deep Ocean " (NPR)

Question for Readers:

With the current global food crisis, does this potential threat to the world’s fisheries affect your thinking about what you’re willing to eat?