Tuesday, 22 April 2014 09:47





When carbon dioxide (CO2) is absorbed by seawater, chemical reactions occur that reduce seawater pH, carbonate ion concentration, and saturation states of biologically important calcium carbonate minerals. These chemical reactions are termed "ocean acidification". Calcium carbonate minerals are the building blocks for the skeletons and shells of many marine organisms. But excessive carbon in the atmosphere from the burning of fossil fuels over the last two centuries has caused increased acidity in the oceans, which is threatening ecosystems, sea creatures and their food supplies.

These rising levels of acidity, along with the effects of global warming, could affect the ability of the oceans to absorb greenhouse gases.  Since the beginning of the Industrial Revolution, the pH of surface ocean waters has fallen by 0.1 pH units.

Ocean acidification is expected to impact ocean species to varying degrees.Photosynthetic algae and seagrasses may benefit from higher CO2 conditions in the ocean, as they require CO2 to live just like plants on land. On the other hand, studies have shown that a more acidic environment has a dramatic effect on some calcifying species, including oysters, clams, sea urchins, shallow water corals, deep sea corals, and calcareous plankton.

Impacts of ocean acidification

a) On living organisms

The pteropod, or “sea butterfly”, is a tiny sea creature about the size of a small pea. Pteropods are eaten by organisms ranging in size from tiny krill to whales and are a major food source for North Pacific juvenile salmon. Pteropod’s shell when placed in sea water with low pH the shell slowly dissolves after 45 days

In recent years, there have been near total failures of developing oysters in both aquaculture facilities and natural ecosystems on the West Coast. These larval oyster failures appear to be correlated with naturally occurring upwelling events that bring low pH waters under-saturated in aragonite as well as other water quality changes to nearshore environments. Lower pH values occur naturally on the West Coast during upwelling events, but recent observations indicate that anthropogenic CO2 is contributing to seasonal undersaturation.

Many marine organisms that produce calcium carbonate shells or skeletons are negatively impacted by increasing CO2 levels and decreasing pH in seawater. For example, increasing ocean acidification has been shown to significantly reduce the ability of reef-building corals to produce their skeletons.

b) On coastal communities and economies

Coastal tourism generates billions of dollars in revenue each year for local communities through recreational fishing, diving and boating. Coastal tourism activities support local businesses, such as hotels, restaurants and shops. As in Goa over 90% of new economic development is dependent on coastal tourism. Healthy coral reefs generate tourist money and provide protection for coastal infrastructure (hotels, resorts, etc.) from storm surge and other natural phenomena. The coral ecosystems that underpin these commercial activities are highly threatened by ocean acidification because their calcium carbonate structures will experience high erosion rates.


Last Updated on Wednesday, 23 April 2014 07:11