Rise in ocean acidic levels

Global warming is one of the hottest topics in the world today. It has been identified as the reason for many of the environmental problems affecting the world. We have already featured some of these issues associated with global warming. Today, we focus on ocean acidification, another result of global warming.

Carbon dioxide, the principle greenhouse gas, increases the acidity level of the ocean. Nearly 50 per cent of all carbon dioxide produced through fossil fuel burning by vehicles and factories in the past 200 years, has ended up in the oceans due to the 'cleansing' action of wind and rain.

This has resulted in the acidity levels of the ocean increasing by 30 per cent, and in the decades ahead, it will create new risks for coral, zooplankton and other creatures that help support North Pacific fisheries, according to researchers.

Ocean acidification is the name given to the ongoing decrease in the pH (a measure of the acidity or alkalinity of

 a liquid) level of the Earth's oceans, caused by their absorption of carbon dioxide from the atmosphere.

Between 1751 and 1994, surface ocean pH is estimated to have decreased from 8.179 to 8.104. The oceans' natural alkalinity pH is about 8.2. When the acidity level rises, the pH value goes down.

The cause of this acidification is the ocean's absorption of carbon dioxide which has been produced by fossil-fuel combustion (burning). Currently, this is about two billion tons of the gas each year. As this gas dissolves, it sets off a chemical reaction that produces carbonic acid, which in high-enough concentrations, can erode the protective shells and other structures of some sea creatures.

The North Pacific Ocean has some of the most acidic waters, having absorbed more carbon dioxide than tropical oceans. The North Pacific appears to be more acidic because it is colder than tropical oceans, which enables it to absorb more carbon, and because it has older, more carbon-rich water than the North Atlantic.

In some areas of the North Pacific, at depths ranging from about 300 to more than 1,000 feet, researchers have already detected a kind of saturation (full) point where acidity causes shells to disintegrate (dissolve) faster than they can grow.

This contrasts to the North Atlantic, where the saturation point typically is at depths that exceed 7,500 feet.

By the end of the century, these North Pacific saturation zones expect to expand and extend into much shallower waters. Researchers are also starting to understand the expanding saturation zones' possible effects on sea life.

There are 200 species of coccolithophores and phytoplankton, which play an important role in the food chain. So far, only six of those species are exposed to the higher acid levels of the saturation zone. They showed noticeably different responses that ranged from no effect to a 66 per cent decline in the process that builds shells.

Another important question that would arise is the fate of corals. In tropical areas, researchers expect major reefs to reach a kind of end around 2060. By then, coral organisms may not be able to adapt fast enough, and reef systems will either crash or be seriously degraded.

It will also affect the deep-sea corals of the North Pacific, which are vital habitat for rockfish, cod and many other commercially important fish species. These soft corals are found at much shallower depths than the cold water hard corals of the North Atlantic that form vast reefs.

Some researchers imagine that the differences may reflect the greater natural acidity of the older North Pacific waters, which has limited the kinds of coral that could evolve.

However, at what point would these soft corals suffer from ocean acidity?

The oceans cover over two thirds of the planet's surface and provide both livelihood and sustenance for much of the world's population.

Therefore, all living beings will experience the effects of ocean acidification. It is time to think again and start to live environmentally friendly.

Compiled by Janani Amarasekara

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Fact File

* Ocean acidification is the name given to the ongoing decrease in the pH(a measure of the acidity or alkalinity of a liquid) of the Earth's oceans

* It is caused by their uptake of carbon dioxide from the atmosphere.

* Between 1751 and 1994 surface ocean pH is estimated to have decreased from approximately 8.179 to 8.104 (a change of -0.075)

* Since the industrial revolution began, ocean pH has dropped by approximately 0.1 units.

* Dissolving CO2 in seawater also increases the hydrogen ion (H+) concentration in the ocean, and thus decreases ocean pH.

* The use of the term "ocean acidification" to describe this process was introduced by two scientists named Caldeira and Wickett (2003).

Time			pH		pH change

Pre-industrial (1700s)	8.179		 0.000
Present-day 		8.104		-0.075
2050 (2×CO2 = 560 ppm)	7.949		-0.230
2100			7.824		-0.355