Dead zones in the Atlantic — so called because their lack of oxygen can’t sustain life — have been seen for the first time by scientists.
These areas of extremely low oxygen occurred in the tropical North Atlantic. The levels of oxygen were the lowest ever recorded in the open Atlantic. And while some microorganisms can live in these zones, most sea life can’t, which could lead to massive fish kills…
The oxygen levels found in the open North Atlantic had about 1/2 the concentrations scientists expected to see, lead-author Johannes Karstensen said…
Most dead zones are found near inhabited coastlines, after rivers carry fertilizers and other chemicals that cause algae blooms. When the algae die, they’re decomposed by bacteria that take up the oxygen.
The Atlantic dead zones, by contrast, appear to form in large (60 to 100 miles) eddies, “with the dead zone taking up the upper 100 meters or so,” explains Karstensen, a researcher at GEOMAR, the Helmholtz Centre for Ocean Research Kiel, in Kiel, Germany.
“The fast rotation of the eddies makes it very difficult to exchange oxygen across the boundary between the rotating current and the surrounding ocean. Moreover, the circulation creates a very shallow layer — of a few tens of meters — on top of the swirling water that supports intense plant growth similar to coastal algae blooms,” Karstensen said. “From our measurements, we estimated that the oxygen consumption within the eddies is some five times larger than in normal ocean conditions.”
“Given that the few dead zones we observed propagated less than 100 kilometers north of the Cape Verde archipelago, it is not unlikely that an open-ocean dead zone will hit the islands at some point. This could cause the coast to be flooded with low-oxygen water, which may put severe stress on the coastal ecosystems and may even provoke fish kills and the die-off of other marine life.”
But, hey, as long as there’s sufficient cheap labor available from the local unemployed to clean the hulls of every Cruise Line skyscraper pulling into souvenir harbors – why worry?