Water And Oceanography

Measuring the Health of the Worlds Oceans

Lee Norris's image for:
"Measuring the Health of the Worlds Oceans"
Image by: 

Co2 gas from human activity is lowering the pH of sea water and threatening to cause a major die off of marine life in the oceans. This is a potential ecological disaster of mega proportions.

Why are the ocean's pH level important? In the 1950s, the majority of the scientific community believed that knowledge of man made CO2 levels were not worthy of the money spent on research. The common scientific wisdom was that human made CO2 would be taken up by plants or would get mixed into the oceans and cause no harm. Today it is understood that CO2 levels are remaining in the atmosphere for a longer time. Also, human generated CO2 levels are affecting the oceans as well. Over the next century, the changes caused by rising CO2 levels in the ocean could be critical to our survival.

Today, some think that the term "ocean acidity" is over reactionary and a misleading term. In fact ocean pH levels are dropping, but the pH level is never expected to fall below the neutral state and into the acidic range. It is argued that a better term should be ocean pH neutralization. Others like the term ocean acidity, because in fact it is reactionary. They believe that the public needs to be concerned because with the lowering of pH, a great urgency does in fact exist. The fact is that no one knows what wound happen. Through studies of evidence and models, they can only predict what might happen. Some of the things that might occur are frightening.

If you remember high school chemistry, pH is a measurement of the balance between acidic and alkaline. pH is measured from 1 to 14. Number 1 being extremely acidic and number 14 being extremely Alkaline. The number 7 is in the middle and neutral.

CO2 obeys Henry's law for gases. This law states that the concentration of dissolved gas in a solution is directly proportional to the partial pressure of the gas above the solution. Another words, an increased concentration of CO2 in the atmosphere directly leads to an increase in the amount of CO2 in solution in the ocean.

Calcifying organisms such as snails and crabs depend on pH ranges staying in the alkaline or they cannot maintain their shell structure. calcium carbonate is removed from sea water through the process of acidification, Calcium carbonate tends to dissolve in the deep ocean due to the effect of pressure and raise the CO2 concentration and lowering pH levels even more. Any rise in the amount of CO2 is a lowering of pH. PH measurements have been recorded all over the earth and the worlds oceans are well mixed and the pH is fairly constant all over the earths oceans.

Today, the pH of sea water is at an average of 8.17. In the year 1750 at the beginning of the industrial revolution, the pH level was at an average of 8.25. Co2 gas today is 30% more abundant that in 1750#. To the casual observer, this drop might not seem like much. Through out geologic history, pH has dropped further due to volcanism. Marine organisms had survived in those times when the ocean's pH levels were much lower than today. In the past, pH drops had occurred over eons and the CO2 levels had time to mix with deep sea water. Today, the increases in acidity are much faster and most of the drop in pH is occurring in the upper layers of the ocean. It must be noted that the upper zones of the oceans are where the greatest percentage of marine life is found.

The level of past amounts of CO2 dissolved in sea water is known from ice core samples that trapped gas levels as far back as 800,000 years. Scientists know that About 1/3 of the CO2 created by human activity enters the oceans. Scientist know that this CO2 in coming from human sources because CO2 from the burning of Fossil fuels contains little or no radio active carbon or carbon 14.

On an evolutionary time scale, human activity is causing a very sudden drop in pH levels. Marine organisms that grow shells may not have enough time to adapt. The two and a half centuries since the beginning of the industrial revolution is short when compared to the eons of evolutionary time. Over the next century, at our present rate of greenhouse gas production, ocean pH levels are expected to drop even further. At our present rate of fossil fuel consumption and projected future consumption rates, ocean pH is expected to drop into the 7.78 to 7.67 range.

All living things live in a narrow pH range. Most fish thrive in a pH range of between 8.0 to 8.5. Plankton, the largest sink of CO2 gas on earth. In fact, marine biologists are concerned that the pH levels in the ocean could drop to the point where plankton growth is inhibited. Plankton draws as much CO2 out of the oceans and atmosphere as all the land pants do#. This could further accelerate the effects of global warming and ocean acidity. Lowering pH could have other effect such as the extinction of many species such as coral. Some scientist believe that coral reefs are doomed anyway due to predicted higher temperatures. If life in the oceans are lost, what are the chances of our survival?

The acidity of sea water is a measure of the concentration of negatively charged hydrogen ions. The more negatively charged ions in a solution, the lower the pH and the higher the acidity. When CO2 combines with sea water, it forms a weak solution of carbonic acid. This acid is the chemical species that releases the negatively charged hydrogen ion. Calcium Carbonate is the material that coral and mollusks use to make their shells and other body structures. Those shells do not form readily in low pH waters.

Proposed solutions to ocean acidity and global warming.

There are studies and proposals to avoid an ecological catastrophe. The problem is, what is the correct action to take? Acidification is a human problem and correct decisions must be made or the oceans as we know them could be lost to us.

There is a movement to fertilize the oceans with iron. Iron causes the plankton to grow by encouraging photosynthesis. The theory is that the iron fixation rate is a ratio of 1:300,000. In other words, for every ton of iron spread in the ocean, 300,000 tons of CO2 would sink to the deep ocean floor. The theory is that the plankton would absorb CO2 dies and sink to the bottom of the ocean. The CO2 is stored there until ocean currents bring it to the surface again.

Cargo vessels would periodically dump iron into the ocean on their routine voyages. Industries that produce green house gases would buy carbon credits and fund the endeavor and receive carbon credits. An experimental project is already underway to study the effects of this proposal. 3000,000 tons of CO2 gone from the environment might seem like a lot, but in reality, that amount is a drop in the bucket when compared to the billions of tons of CO2 that enter the atmosphere and the oceans due to human emissions. No one really knows what the effects of causing massive plankton blooms would be on different ecosystems in the ocean. Some scientists have theorized that the CO2 would only be released again after the plankton dies.

About 1/3 of U.S. CO2 emissions comes from electrical generating and coal fired plants. A process called accelerated weathering of limestone scrubs CO2 from the exhaust of generators and deposits it in a soluble compound. Acid water is corrosive to limestone. Dissolution of limestone by carbonated water generates soluble bicarbonate ions. This is the same process by which rain water erodes limestone cliffs, caves and sinkholes only it is a much faster process. It is then deposited deep in oceans.

There is a plan to combat acidification from volcanic activity by treating sea water. This would be done by modifying the chemical composition of the sea water by treatment plants near volcanoes and coast lines. A number of industrial processes can remove acid from sea water including those processes used in the manufacture of vitamins and chlorine. CO2 is scrubbed out with silicates. The acid is naturalized forming bicarbonate, the most plentiful form of carbon in the oceans. The electricity to run these treatment plants would be made from geothermal power in the volcanoes. There is expected to be side effects to the local environment from the discharge of high alkaline water. This discharge could cause a dead zone by killing off local marine life for hundreds of meters from the point of discharge. It would be possible to remix sea water with the discharge and lower it to a safer range of pH. This type of treatment would be a very costly to construct and operate. At the same time, no one is sure what the real benefits would be.

No one knows what the effects are of elevated CO2 levels in the deep ocean environment . The study of deep oceans is relatively new. Deep ocean fish and other marine animals probably already exist in a high CO2 environment. The effects of elevating this concentration still further could be disastrous to deep ocean populations causing dead zones. The spread of deep ocean sea life is sparse and some species will have a hard time finding mates. More studies need to be done.

More about this author: Lee Norris

From Around the Web