Ocean Dead Zones Might be Worse Than Originally Thought

Well, you didn’t think things were actually better than we initially thought, did you? Frighteningly, dead zones in oceans around the world – which are oxygen-starved areas that can’t support most life – are greater than originally thought in coastal areas that support fishing industries. More than 400 dead zones have formed along continental coastlines since the mid-20th century.  They occur when fertilizer pollution causes algal blooms, whose decomposition feeds oxygen-consuming bacteria.

From Wired Science:

These so-called hypoxic regions now cover an area roughly equivalent in size to Oregon. Compared to Earth’s total ocean area, that’s relatively small, but they’re grouped in places critical to commercial fishing. They’re also spreading, in both size and frequency: Since the 1960s, the number of hypoxic areas has doubled every 10 years.

And as significant as the problem is, it’s based on what may be outdated, overly permissive standards. The new study is a review of nearly 900 studies of 206 ocean floor-dwelling species, and suggests that the level of oxygen considered hypoxic needs to be raised.

“These results imply that the number and area of coastal ecosystems affected by hypoxia and the future extent of hypoxia impacts on marine life have been generally underestimated,” write Carlos Duarte and Raquel Vaquer-Sunyer of the Mediterranean Institute for Advanced Studies. The paper was published yesterday in the Proceedings of the National Academy of Sciences.

Duarte and Vaquer-Sunyer believe that we need to replace the outdated oxygen baseline, set in 1983, to 4.6 milligrams per liter, if not higher, in order to preserve the biodiversity of bottom-dwellers.  This benchmark would probably double the number of hypoxic zones, or at least increase it by 100.

Robert Diaz, a Virginia Institute of Marine Science biologist who has been studying dead zones since 1995, says “Everything is pointing towards a more desperate situation in all aquatic systems, freshwater and marine.  That’s pretty clear.  People should be worried, all over the world.”

We sure have managed to mess things up, haven’t we?

Link [Wired Science]

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