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Growing low-oxygen zones in oceans worry scientists

Posted by Enkill_Eridos on March 9, 2010


McClatchy Newspapers

WASHINGTON — Lower levels of oxygen in the Earth’s oceans, particularly off the United States’ Pacific Northwest coast, could be another sign of fundamental changes linked to global climate change, scientists say.

They warn that the oceans’ complex undersea ecosystems and fragile food chains could be disrupted.

In some spots off Washington state and Oregon, the almost complete absence of oxygen has left piles of Dungeness crab carcasses littering the ocean floor, killed off 25-year-old sea stars, crippled colonies of sea anemones and produced mats of potentially noxious bacteria that thrive in such conditions.

Areas of hypoxia, or low oxygen, have long existed in the deep ocean. These areas – in the Pacific, Atlantic and Indian oceans – appear to be spreading, however, covering more square miles, creeping toward the surface and in some places, such as the Pacific Northwest, encroaching on the continental shelf within sight of the coastline.

“The depletion of oxygen levels in all three oceans is striking,” said Gregory Johnson, an oceanographer with the National Oceanic and Atmospheric Administration in Seattle.

In some spots, such as off the Southern California coast, oxygen levels have dropped roughly 20 percent over the past 25 years. Elsewhere, scientists say, oxygen levels might have declined by one-third over 50 years.

“The real surprise is how this has become the new norm,” said Jack Barth, an oceanography professor at Oregon State University. “We are seeing it year after year.”

Barth and others say the changes are consistent with current climate-change models. Previous studies have found that the oceans are becoming more acidic as they absorb more carbon dioxide and other greenhouse gases.

“If the Earth continues to warm, the expectation is we will have lower and lower oxygen levels,” said Francis Chan, a marine researcher at Oregon State.

As ocean temperatures rise, the warmer water on the surface acts as a cap, which interferes with the natural circulation that normally allows deeper waters that are already oxygen-depleted to reach the surface. It’s on the surface where ocean waters are recharged with oxygen from the air.

Commonly, ocean “dead zones” have been linked to agricultural runoff and other pollution coming down major rivers such as the Mississippi or the Columbia. One of the largest of the 400 or so ocean dead zones is in the Gulf of Mexico, near the mouth of the Mississippi.

However, scientists now say that some of these areas, including those off the Northwest, apparently are linked to broader changes in ocean oxygen levels.

The Pacific waters off Washington and Oregon face a double whammy as a result of ocean circulation.

Scientists have long known of a natural low-oxygen zone perched in the deeper water off the Northwest’s continental shelf.

During the summer, northerly winds aided by the Earth’s rotation drive surface water away from the shore. This action sucks oxygen-poor water to the surface in a process called upwelling.

Though the water that’s pulled up from the depths is poor in oxygen, it’s rich in nutrients, which fertilize phytoplankton. These microscopic organisms form the bottom of one of the richest ocean food chains in the world. As they die, however, they sink and start to decay. The decaying process uses oxygen, which depletes the oxygen levels even more.

Southerly winds reverse the process in what’s known as down-welling.

Changes in the wind and ocean circulation since 2002 have disrupted what had been a delicate balance between upwelling and down-welling. Scientists now are discovering expanding low-oxygen zones near shore.

“It is consistent with models of global warming, but the time frame is too short to know whether it is a trend or a weather phenomenon,” Johnson said.

Others were slightly more definitive, quicker to link the lower oxygen levels to global warming rather than to such weather phenomena as El Nino or the Pacific Decadal Oscillation, a shift in the weather that occurs every 20 to 30 years in the northern oceans.

“It’s a large disturbance in the ecosystem that could have huge biological changes,” said Steve Bograd, an oceanographer at NOAA’s Southwest Fisheries Science Center in Southern California.

Bograd has been studying oxygen levels in the California Current, which runs along the West Coast from the Canadian border to Baja California and, some scientists think, eventually could be affected by climate change.

So far, the worst hypoxic zone off the Northwest coast was found in 2006. It covered nearly 1,200 square miles off Newport, Ore., and according to Barth it was so close to shore you could hit it with a baseball. The zone covered 80 percent of the water column and lasted for an abnormally long four months.

Because of upwelling, some of the most fertile ocean areas in the world are found off Washington and Oregon. Similar upwelling occurs in only three other places, off the coast of Peru and Chile, in an area stretching from northern Africa to Portugal and along the Atlantic coast of South Africa and Namibia.

Scientists are unsure how low oxygen levels will affect the ocean ecosystem. Bottom-dwelling species could be at the greatest risk because they move slowly and might not be able to escape the lower oxygen levels. Most fish can swim out of danger. Some species, however, such as chinook salmon, may have to start swimming at shallower depths than they’re used to. Whether the low oxygen zones will change salmon migration routes is unclear.

Some species, such as jellyfish, will like the lower-oxygen water. Jumbo squid, usually found off Mexico and Central America, can survive as oxygen levels decrease and now are found as far north as Alaska.

“It’s like an experiment,” Chan said. “We are pulling some things out of the food web and we will have to see what happens. But if you pull enough things out, it could have a real impact.”

Pollution does have a negative impact on the planet, industrial waste, off shore oil drilling, on shore oil drilling. They all have a negative impact on our environment. Gasoline and Diesel based vehicles also have a negative impact. Not only are we pumping CO2 and Carbon Monoxide in environments that do not have a lot of trees.(They thrive on such things yet we cut them down. Then we wonder why we have smog, and lung cancer patients who never smoked a day in their life.)Is it causing this ecosystem change across the entire planet? Not in the form of Green House Gasses. I think Global Warming is a natural phenomenon.
Does that mean we can continue to be wasteful, use unrenewable fuel sources? Does that mean we can continue to pollute, loot, and plunder the Earth? No. We should be more responsible and find cleaner pollution free fuel sources. We need transportation, and Gasoline vehicles and other oil dependant modes of transportation are archaic outdated systems. We can find more efficient, and less pollution emitting ways to power our homes and cars. This fight is purely political. There is no religion in the whole we should no longer support Oil based fuel sources. If this was any thing to do with religion Kay would agree that Oil-based fuel alternatives should be explored. Basically this is a Republican vs. Democrat political thing. Also Notice most Republican Politicians backgrounds. Dick Cheney President of Haliburton (One of the major Oil Drilling Companies in America.) Sarah Palin and her work on the  Alaska Oil and Gas Conservation Commission. I am all for using Natural Gas which is a reusable resource that is gained from waste. It can be used to safely power vehicles (Proven in Western PA. Where Natural Gas Conversion Kits can be found and is used a lot.), as well as a fuel source to generate power. Nuclear Reactors are safer then they were 30 years ago, we now have ways to reuse the nuclear waste instead of just dumping it somewhere. All of these things would curb or even cut our dependency on Oil. But Republicans do not want that, because most would lose a lot of money if they did. Which makes them all Hypocrites, considering they make millions some even billions off Oil. Yet they act like they are not looking out for their own pockets, when Democrats do things that would benefit them financially. One group would like to profit off destroying our environment using petroleum based products and other pollution causing forms of transportation. The other group would like to profit by pushing products that do not harm the environment as much, using alternative fuels for transportation and power. Both groups want all the wealth for themselves. Neither can be trusted because they both try to discredit each other by using illegal means, such as hacking a Secured Network Infrastructure. (Both under US and Interpol jurisdictions. The person if caught is looking for a sentence of up to 10 years and another 10 year prison sentence in the country that Secured Network Infrastructure is based in.) Let’s stick to the facts, pollution has a negative effect on the ecosystems of which we are dependent for food. As well as air quality (see smog indexes in major cities with more buildings than trees). I mean so what pollution may not be causing this climate shift, but at the same time it isn’t slowing it down but speeding it up. People need to wake up and see that someone will make money either way.  I would just rather breathe cleaner air, eat seafood without worrying about the poisons in it, drink water out of my tap not in a bottle. To me Republicans just don’t want to do that, the generations that are behind mine always said the future generations can handle it. We keep saying this, my generation IS the future generation (Late 70’s early 80’s birth generation) We need to start tackling these problems now, because if we do not resources will dwindle and there will be wars for them..It will destroy the human race, there will be no future generations at that point.

2 Responses to “Growing low-oxygen zones in oceans worry scientists”

  1. hmmm, I wonder if similar pressures brought fish out to start crawling and to become reptiles then mammals then human.


  2. dorian said

    hello sabio! feasible. here’s another thought: how about if now we will start to see the reverse adaptation? human-mammal-reptile-fish?


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