Introduction to Ocean Acidification

http://www.eschooltoday.com/ocean-acidification/what-is-ocean-acidification.html

Ocean acidification is one of the top environmental issues today. It is simply a term that means the oceans are becoming more acidic. This trend is pretty worrying to environmental scientists, as they have studied this to know that almost all ecosystems (particularly those of the upper oceans) will be affected in one way or the other.

What is ocean acidification?
It is the changes in the chemical make-up of all the waters in the oceans, as well as its temperature, resulting from excess carbon dioxide in the atmosphere. The changes involve the lowering of the pH of the water.

To understand this better, we need to first understand what pH is, together with atmospheric Carbon Dioxide.

What is pH of water?
pH of water is the measure of how acidic or basic water is. The scale is from 0 to 14, and 7 is the neutral point (pure water). If the pH is closer to 0, that water is more acidic. If it is closer to 14, the more basic it is.

“During the last 20 years, it has been established that the pH of the world’s oceans is decreasing as a result of anthropogenic carbon dioxide emissions to the atmosphere.” *1

Lower pH seas and oceans are known to cause major problems for marine organisms and ecosystems.

Carbon Dioxide (CO2)
The atmosphere is made up of air, and air is composed of gases including: Oxygen 21%, Nitrogen 78%, Argon 0.9% and Carbon Dioxide
(CO2) 0.04%. These gases occur naturally in the atmosphere. However, the concentrations of atmospheric CO2 in the atmosphere have increased a lot since the industrial revolution. Humans are burning a lot more fossil fuels than ever before. Fossil fuels are the main source of CO2 . It is known that the Amazon, together with other major forests covers are large absorbers of CO2 from the atmosphere, but in fact, the Oceans, is the largest carbon sinks on the planet.

What is causing the ocean’s acidification?

Ocean waters are constantly reacting with environmental gasses. In particular, the oceans absorb up to half of the carbon dioxide in the atmosphere. They play a key role in the carbon cycle too, by acting as a carbon sink (store).

In this case, the upper level or layer of the ocean or seawater (H2O) absorbs CO2, forming Carbonic acid. The chemical symbol for carbonic acid is H2CO3.

Here is the chemical equation:
H2O+CO2=H2CO3

The result of this reaction increases Hydrogen ions in the water, and reduces carbonate ions. The reaction also leads to a reduction of the pH by about 0.1 units. Remember that the lower the pH, the more acidic the water is.

Note that the margin may look small, but the effect on living organisms depending on carbonate ions is very significant.

“The IPCC forecasts that ocean pH will fall by “between 0.14 and 0.35 units over the 21st Century, adding to the present decrease of 0.1 units since pre-industrial times” *1

Water pH levels are not consistent across the globe. Some places such as the eastern Pacific have lower pH, whiles the artic ocean area has a higher pH.

The above conditions are normal, but unfortunately, the earth has seen an increase in Anthropogenic CO2 concentrations since the industrial revolution. (Anthropogenic CO2  is the portion of atmospheric CO2 resulting from human activities such as burning fossil fuels) As a result, more CO2 is absorbed by ocean water, as the equilibrium point has changed a bit.

 

How does Ocean Acidification impact us?

The oceans provide extraordinary ecosystem services to societies, food, regulation services (carbon absorption), cultural and recreation as well as nutrient recycling.

Below are some ways that ocean acidification impacts us:

Marine Calcifiers:
Some marine ecosystems, particularly those that use Calcium Carbonate to build their shells (such as coral and oyster reefs) could change with increasing ocean acidity. These species are called calcifiers.

“In a future ocean hat continues to absorb excess CO2 from industrial emissions, deforestation, and other human activities, sensitive species could lose their protective shells and eventually die out, while other species that build stronger shells could become dominant.”Source:Ocean acidification: A risky shell game, 6 OCEANUS MAGAZINE Vol. 48, No. 1, 2010 www.whoi.edu/oceanus

Shellfish and reef-forming corals are all at risk from the slightest drop in pH.Less survival of these species mean less or diminishing coral reef systems. More importantly, these form the habitats of many algae and phytoplankton, which form the basis of all marine ecosystems.

Biogeochemical cycles:
The oceans play a massive role in the carbon cycle, by absorbing CO2  from the upper layers and transporting them to the ocean beds for storage. This is possible by phytoplankton absorbing the CO2 and sunlight to produce O2 and Carbohydrates. This is called the ‘biological carbon pump’. The efficiency of the pump depends on the amount of CO2 absorbed and the calcium carbonate that are produced. Acidic waters reduces the biological component that absorbs the CO2, thereby reducing the oceans capacity to perform its role as a carbon sink.

Shell marine animals (Pteropods):
Acidic oceans may be corrosive to shell animals in the ocean. It is known that shells of some small marine snails in the southern ocean around the Antartica are already dissolving, potentially altering the food webs of that region. Source: Ocean Acidification, Summary for Policymakers,
Third Symposium on the Ocean in a High-CO2 World. UNESCO

Economic Losses:
Molluscs and Oyster larvae are among the species that have been extensively studied under ocean acidification. It is estimated that by 2100, losses due to declines in mollusk production from ocean acidification may be around $130 billion USD. Note that the cultural, spiritual and educational value of the awesome coral reef systems may all be affected, including the shifts that will occur if the acidification continues.
Ocean Acidification.Summary for Policymakers. Third Symposium on the Ocean in a High-CO2 World, Page 10 http://unesdoc.unesco.org/images/0022/002247/224724E.pdf

 

How can ocean acidification be reduced?

“The severity of future changes in ocean conditions will depend largely on the choices we make regarding energy use in the upcoming years and decades”

There is always something one can do to minimize the impact of a problem, as long as the issue is well understood and the causes are clear. Ocean acidification, like global warming, is one that has clear causes: excessive anthropogenic CO2. We already know where the CO2 comes from, so how about enforcing the solutions below?

Cut Carbon Dioxide emissions:

Humans are deeply involved with using energy from fossil fuels. Transport, industry and homes all use fossil fuels. Now is time to switch to clean energy (or renewable energy). In recent time, the consumption of renewables are growing and huge resources are being invested into it — but we need to do more, as it is the only way to reduce the in the atmosphere.

Move subsides on Fossil Fuels to Renewables:
Governments must encourage the growth of the green sector and make fossil fuels less attractive. Green energy is not cheap, but ultimately, it will pay off and become worthwhile.

Ocean management:
Because species and ecosystems are already vulnerable and endangered in many waters, protected areas, laws and policies that aim to protect those species must be set up and enforced. There must be hefty fines and consequences to those who break the law by going after endangered species. This way, the health of marine biodiversity will be improved, and biological factors that aid absorption will be less affected. Sustainable fishing must be enforced to reduce by-catch, overfishing and destructive fishing practices.

Education and information:
When people are aware of things happening in their environment, they are more likely to respond positively to rules, regulation and policies that aim to correct things we do wrongly. Individuals must find and share information from reliable sources. Leaders must invest in education and providing information on these environmental issues, and get everyone to be part of the solution.

 

Here are some interesting facts and figures…

How fast is ocean chemistry changing?
Since the Industrial Revolution, the world’s oceans have become 30 percent more acidic, on average. Scientists predict the acidity of our oceans could double or triple by the end of the century compared to preindustrial times. Natural Resources Defense Council., Gulf of Maine, Ocean Acidification: http://www.nrdc.org/oceans/acidification/files/ocean-acidification-maine.pdf

Source: Ocean Acidification. Summary for Policymakers. UNESCO

Coral Reefs
One of the greatest impacts of Ocean Acidification is on reef building corals, which are known as a ‘framework species’. Without corals, reefs cannot exist. Ocean Acidification is already slowing their growth rates. Left unchecked they will soon stop growing and erode away. The Great Barrier Reef generates over 6.5 billion dollars in tourism revenue and 63,000 jobs. Source: Ocean Acidification – The other CO2 challenge., http://oceanacidification.net/

Finfish

Finshish includes all fish types that we eat outside of shellfish. They include herrings, sardines, anchovies, tuna, cod, flounder and many others. Finfish are very important because apart from their membership in marine food chains for top predators, they are also a source of food for humans and offer many more economic benefits. Ocean acidification will make these vulnerable as their habitats will change. It can also affect their behavior, fitness and larval survival.

Carbon dioxide from fossil fuels
Each year industrial processes and combustion of fossil fuels release over six billion metric tons of carbon into the atmosphere each year.* Two major issues are related to this: Global Warming (because of CO2’s greenhouse effect) and Ocean Acidification. Together, they form the biggest environmental threat in mordern time.
Source: http://timeforchange.org/ocean-acidification-effect-of-global-warming