http://blog.cleantechies.com/2010/03/29/ocean-oxygen-catastrophic-change/
Lower Ocean Oxygen Levels Predict Catastrophic Change
Published on March 29th, 2010 by Celsias
Posted in Climate Change & Carbon Emissions, Pollution, Water Resources
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There is a cascade failure going on in the world’s oceans that promises nothing but trouble in the future, and the problem stems in part from agricultural practices developed over the last half-decade aimed at growing more food on the same amount of land to feed rising populations.
A cascade failure is the progressive collapse of an integral system. Many scientists also call them negative feedback loops, in that unfortunate situations reinforce one another, precipitating eventual and sometimes complete failure.
The agricultural practices relate to “factory farming,” in which farmers grow crops using more and more chemical fertilizers, specifically nitrogen and phosphorus, which are the first two ingredients (chemical symbols N and P) listed on any container or bag of fertilizer. The last is potassium, or K.
But farmers aren’t the only culprits. Lawn enthusiasts add to the problem with their massive applications of fertilizer designed to maintain a species of plant that doesn’t provide either food or habitat, and is grown merely to add prestige. And groundskeepers at parks and large corporate headquarters are equally guilty. In fact, a whole generation needs to rethink its addiction to lawns.
Whoever is guilty of applying the fertilizer, these megadoses are eventually washed off the fields and lawns and into waterways. From there, they migrate to the nearest large bodies of water, where they spark such tremendous and unnatural growth in aquatic plants that the result is eutrophication , or lack of oxygen in the water as bacteria act to reduce the sheer mass of dying organic matter.
One of these aquatic growths is algae, or phytoplankton. Moderate algal growth can produce higher fish yields and actually benefit lakes and oceans, but over-stimulation leads to a whole host of problems whose integral relationship to one another threatens not only aquatic but human life.
A classic example would be the Baltic Sea, where phytoplankton are raging out of control. The Baltic Sea is, as a result, home to seven out of ten of the world’s largest “dead zones,” aquatic areas where nothing survives.
One of the other three is the Gulf of Mexico, where a 2008 dead zone the size of Massachusetts is expected to grow in future years thanks to the U.S. government’s biofuel mandate. Most of the crops for biofuel are grown along the Mississippi River, which drains directly into this dead zone.
In the Baltic, as elsewhere, overfishing has exacerbated the problem. Fish feed on smaller aquatic organisms, which themselves feed on the algae. Take the fish out of the equation, and the balance is lost. It’s very much like removing the wolves that keep down the deer population in order to protect the sheep, and it doesn’t work in the ocean any better than it works on land.
Once the algal blooms begin to thrive, they block sunlight to deeper water and begin to kill off seaweeds and other aquatic plants which are home to fish species. The dying plants then consume more oxygen as bacteria consume them. And, as the seaweeds die, the few remaining fish and shellfish species move away, deprived of habitat.
This is a classic example of a negative feedback loop, and it is reinforced by every meal of fish, every instance of Scotts lawn fertilizer, and every ear of corn grown with a little help from Cargill or Dow, to name just two multinational fertilizer manufacturers.
Another example is occurring in the Pacific Northwest , along the West Coast of the United States, where — in Washington State, Oregon, and even Northern California — piles of Dungeness crab shells on the ocean floor mark areas of severe eutrophication well within sight of land.
Elsewhere along the Pacific shoreline, bird deaths – ranging from pelicans to sea ducks – predict a failure in the natural world that can’t help but reverberate among the planet’s prime predator, man.
These areas of eutrophication have always been present, but their spread – from one or two areas to miles of coastal waters – indicates a larger problem that is likely about to overwhelm not only the fishing industry and tourism but the existence of oceans as living entities.
As Oregon State University ocean sciences professor Jack Barth notes, the once-scarce areas of low oxygen have become the “new normal”, with old areas repeating and new areas cropping up every year. In many of these areas, oxygen levels are 30 percent lower than they were a mere half-decade ago.
Not all algal blooms are harmful or noxious, of course. But those which occur in response to eutrophication do seem to be, and these – known as HABs, or harmful algal blooms – include pseudo-nitzschia producing algae, which deliver a neurotoxin called domoic acid that can kill humans, birds and aquatic mammals that eat the affected shellfish; golden algae, which under certain conditions produce toxins that cause massive fish and bivalve (clams, mussels, oysters) kills; brown tides, which are not toxic in themselves but create aquatic conditions that can kill fish larvae; red tides, which produce brevetoxins that can affect breathing and sometimes trigger fatal, respiratory illnesses in humans; and blue-green algae, or cyanobacteria, which can form dense colonies that cause water to smell and become toxic to fish, pets and humans.
This last, which has spread from Texas to Minnesota, has led to livestock deaths in the former. In the latter, where having a lake home is a sign of prestige, many homeowners have been forced to sell at a loss to get away from once-pristine lakes so smelly and toxic that dozens of pet dogs have been killed drinking the water.
Lower oxygen levels in oceans are very attractive to one species; jellyfish, and these odd creatures with their many tentacles and poisonous sting thrive under such conditions. In fact, jellyfish have few predators except man, and those few (tuna, sharks, swordfish, a carnivorous coral , one species of Pacific salmon and the leatherback turtle) are all at great risk of extinction because of eutrophication and its related conditions, pollution, overfishing and climate change.
As one of the most prolific species in the ocean, and certainly one with a long history (the species has been around since the Cambrian), jellyfish will probably take over the oceans if things continue as they have been going since the 1960s. This is good news for the Japanese, Chinese and other Oriental cultures who regard the slimy beast as a delicacy.
For the rest of us, jellyfish are an acquired taste, and one we had better acquire if we want to keep eating seafood. Either that, or we can support legislation that, in the U.S. at least, promises some relief through research, monitoring and rule-making regarding the Great Lakes and both coasts.
Article by Jeanne Roberts appearing courtesy Celsias.
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This article seems to contradict the NASA finding that Phytoplankton population is decreasing.
www.gsfc.nasa.gov/topstory/20020801plankton2.html
It also contradicts the old paper of 1958 by Prof Ryther that Diatom blooms cause high Dissolved Oxygen level.
http://www.jstor.org/stable/1539030
The truth is perhaps that Diatoms blooms have decreased and other algal blooms have increased. No one seems to be monitoring this change.
Usually Chlorophyll 'a' is measured, however, Chlorophyll a is present in all types of algae, so it is not an effective means to identify useful vs harmful algae.
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