Our oceans are in dire shape- and without them all life is screwed

Global warming has often been discussed with regard to its effects for life on land: increased temperatures and heat waves, increased weather extremes, less but more intense rainfall, drought and forest fires.

Water, however, remains less considered. Even discussions of floods or rising sea levels, which focus on water, study mainly their consequences for land inhabitants.

Yet oceans, it is well known, cover three quarters of the earth's surface. And oceans have absorbed about a quarter of all carbon dioxide (CO2) emissions, one of four main greenhouse gases causing global warming. This absorption of CO2 is integrally related to the three major factors impacting the oceans: global warming, ocean acidification and decreasing amounts of oxygen. As a result, the current situation of the oceans is dire. And its impact will be severe not only for marine life but also for all life -- plant, animal and human -- on land.

Ocean Acidification

Carbon dioxide (CO2) exists naturally in the air. But through the use of fossil fuels, in particular coal and oil, the amount of CO2 in the air has increased exponentially since the Industrial Revolution began.

As the oceans absorb carbon from the air, their chemistry changes. This process is known as ocean acidification, and it has brutal consequences for marine and land life.

Oceanographers estimate that before the use of fossil fuels, the ocean's PH balance, which measures its acidity, had been relatively stable for the past 20 million years. During the last great extinction of marine life, which occurred 55 million years ago, 50 percent of some groups of deep sea animals were wiped out.

But the current levels of carbon being absorbed by the oceans is far higher than the levels being absorbed then.

A United Nations Environment Program (UNEP) report released in 2010 on the "Environmental Consquences of Ocean Acidification" and based on studies conducted over the past two decades off the coast of Hawai'i has confirmed that the increased CO2 concentration levels in the ocean mirror the increased CO2 levels in the atmosphere.

Ocean Acidification and Phytoplankton

Already the increased levels of ocean acidification have led to a loss of phytoplankton and of coral reefs. And losses of phytoplankton and of coral reefs have a ripple effect.

First, much marine life relies on them for nourishment. Flounder, haddock, pollock, salmon and shrimp all eat phytoplankton. Humans eat many of these fish. Krill eat phytoplankton and whales eat krill. So a decrease in one threatens the liveilhood of the other.

Second, phytoplankton also absorbs carbon dioxide. Phytoplankton floats along the ocean's surface absorbing CO2 as land plants do in photosynthesis. As the CO2 is absorbed, the plant dies and sinks to the ocean floor, releasing CO2 along the way. Cold water can hold higher levels of CO2 than warmer water, so most of the CO2 released, which turns water acidic, is to be found along the ocean floor. But this acidic water does not stay at the ocean's floor. During an upswell, it rises to the surface and even the shore. Its acidity is deadly for the shells of marine life, such as shrimps, clams and oysters.

If the smallest part of the food chain is affected by ocean acidification, it ripples all the way up the food chain, making the largest part of the food chain vulnerable.

"Since the time before the industrial revolution," says the National Resource Defense Council's Lisa Suatoni, "ocean acidity has increased 30 percent."

And the bad news does not end there: According to oceanographers, the water rising from the ocean's depths holds CO2 that has accumulated over the past decades. Thus, in coming years, the increased levels of CO2 absorbed by the oceans will re-emerge as increased ocean acidification reaching the shores. Higher levels of cean acidification have already led to tremendous problems for the oyster industry. In the summer of 2007 oyster harvests began to plummet in the Pacific Northwest. The situation was extreme. The oyster hatcheries were keen to find the culprit, which turned out to be ocean acidification.

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