Ocean acidification
Assumption
The main assumption made in this study is that the results of
reviewed studies, which were done on small case studies, could be applied to
the real situation happening on our oceans.
Introduction
Ocean acidification refers to an ongoing reduction of pH measured
on the surface of the ocean. This is
caused by anthropogenic intake of carbon dioxide which is derived from the
atmosphere. It is has been recorded that over the years, the amount of carbon
dioxide has decreased from 8.179 to 8.104 between 11751 and 1994. Research shows that increased emission of carbon dioxide into the
atmosphere has led to increased rate of ocean acidification. It has been shown
that ocean acidification is a growing major problem which will have negative
effects on the balance of the carbon cycles.
Ocean acidification is also a challenge facing the marine world. Recent
research release in Copenhagen shows that the seas are absorbing carbon dioxide
at unprecedented rate posing major challenge to marine life. Since the start of
industrial revolution, scientists estimate that there has been an increase of
about 30 in
ocean acidification.
Therefore ocean acidification is a major problem facing the world that
need to be tackled by decreasing emission of carbon dioxide.
How is carbon maintained in the atmosphere
In order to understand ocean acidification, it is important to
understand how carbon dioxide is maintained in the atmosphere. Like other major
gases, carbon dioxide is maintained in the atmosphere through the carbon
cycle. This cycle describes how carbon
dioxide is generated and used in atmosphere. Carbon cycle ensures that there is a flux of
carbon dioxide between biosphere, lithosphere and the atmosphere. However,
increase human activities which emit carbon dioxide like use of fossil fuel
have led to new flux of carbon dioxide. While some of the carbon dioxide has
been taken up by terrestrial plants and oceans, there is a substantial amount
that remains in the atmosphere
There is organic and inorganic carbon cycle. Comparing the two, the organic cycle is
relevant in ocean acidification since it takes into consideration the different
forms of carbon dioxide that is existent in the atmosphere today.
Ocean acidification
Ocean acidification can be described as the process through which
carbon dioxide get dissolved into the ocean.
Carbon is a soluble gas and when it comes into contact with water, it is
dissolved. When carbon dioxide is dissolved in water, it reacts forming a
balance of ionic and non-ionic compounds which include.
Dissolved free carbon dioxide
Carbonic acid
Bicarbonate
Carbonate
The ratio of these by-products varies greatly depending on a
number of factors like water temperature and alkalinity. Once dissolved in
water, carbon dioxide increased the amount of hydrogen ion concentration (H).
The increase of pCO2 in the surface of the ocean comes with different effects
on the seawater carbon system (Sabine, 2004).
It leads to reduction in the pH, decreased availability of carbonate
(CO32-) ions and in addition, it lowers the saturation of major shell forming
mineral which means it will have an impact on the life of most marine animals
that live in shells, as can be illustrated in the following chemical reaction
(Kolbert, 2006)
CO2 CO32- H2O
2HCO3-
Therefore, the term ocean acidification can be understood in terms
of pH changes. It refers to the reduction in pH and it does not simply imply
that the ocean surface pH water comes below the neutral (7.0) level.
The additional carbon dioxide which is not absorbed by the sea or
through the terrestrial plants is already having an impact on the world. It has been shown to affect the carbonate
chemistry by reducing ions, aragonite, and calcite, which are used by most
marine organism to make their external skeletons and shells. This implies that
if the current trend in emission is maintained or increased, our oceans will
become more acidic by the end of the century and this could decrease the pH
of seawater by more than 0.34 units
compared to the pre-industrial levels. This change
in ocean chemistry has been scientifically proved and its effects are well
known.
Is there scientific evidence to prove ocean acidification
There is well documented scientific evidence that shows that ocean
acidification is taking effects on our
oceans. Historical science evidence shows that a study of carbon dioxide that
has been preserved in ice shows that before the industrial revolution, the
oceans had a pH of 8.2. However, since the industrial revolution, the level of
oceanic pH has dropped by more than 0.1 units. Although this may
be perceived to be insignificant, scientific evidence shows that the level of
acidity has increase by a value of 30. This trend is like to grow considered
the current standards where the ocean is absorbing about 2.2 million tons of
carbon dioxide every day, implying that
unless stern measures are taken, our oceans will become more acidic and marine
life will be endangered.
It is estimated that if nothing is done to mitigate the current
situation, there will be further ocean acidification and the pH will drop by
further 0.3 to 0.5 units by the time the world ushers 2100. Since the ocean will continue to absorb more
anthropogenic carbon dioxide, there is a possible that the marine life will have
changed drastically and marine ecosystem will be severely affected. The future
ocean pH will depend on the mitigation strategy that will be taken by the
society to curb emission of carbon dioxide into the atmosphere or the rate at
which the world will increase the number of terrestrial plants to capture
carbon dioxide in the atmosphere.
Impacts of ocean acidification
It is postulated that the current rate of ocean acidification will
have an impact on the oceans in different ways. One way in which it affects
marine life is through calcification. This implies that change in ocean
chemistry has a direct and indirect impact on the marine habitats through
calcification process. Calcification is an important process for marine animals
as it enables them to make their out skeleton and shells through calcium
bicarbonate. This process is important
for biological survival of most marine organisms and if affected, their life
will also be directly affected. Calcification process mainly involves
precipitation of dissolved calcium ions to form a solid calcium-carbonate
structure like coccoliths.
Once they are formed, these structures are chemically soluble and can be
dissolved unless the surrounding sea water is saturated with carbonate ions. Calcium carbonate occurs as aragonite and
calcite. Comparing the two, aragonite is more soluble. This implies that marine
organism which product aragonite as their skeleton and cells are more
vulnerable to dissolution if there is an increase in ocean acidity compared to
those that produce calcite. Increase in
carbon dioxide result to lower pH and this decrease the saturation of calcium
carbonate compounds. This raises the saturation horizons to the sea surface.
It is believed that through interfering with calcification
process, ocean acidification will have an impact on the marine ecosystem. It
will lead to destruction of important food chain which involves both autrophs
and heterotrophs in organism like coccoilthophooers, corals, foraminifera,
molluscs, crustaceans, and many others. Research has already found out that the above
mentioned marine organism experienced reduced calcification and dissolution
when they are exposed to higher levels of carbon dioxide.
Apart from problems associated with calcification, it is also
estimated that animal will also suffer from other reproductive and
physiological effects. For example, they are likely to suffer from carbon
dioxide induced acidification in their body fluids or hypercapnia. They are also likely to suffer indirectly through food inadequacies due
to destabilization of the food chain. In addition, this may also force come of
the marine organism to relocated to
other areas due to decrease in
food resources and deterioration of conditions in the environment and this will
have a direct impact on survival of other animals.
Ocean acidification may also have other impacts which are not
related to marine life. It will decrease burial of carbonate sediments for a
number of centuries and in some cases it will lead to dissolution of existing
carbonate sediments.
This will have an effect in that more carbon dioxide may leave the
atmosphere and enter into the ocean.
Conclusion
Ocean acidification is a process that leads to increased
deposition of carbon dioxide into the seawater. Carbon dioxide is maintained by
the atmosphere by the carbon cycle where excess carbon is absorbed by the
terrestrial plants and the sea. Human activities have increased carbon dioxide
in the atmosphere and this has led to increased deposition carbon dioxide into
the ocean reducing the pH and increased acidity. This has affected the
calcification process which is important for marine animals. Therefore ocean
acidification is a major problem facing the world that need to be tackled by
decreasing emission of carbon dioxide.
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