By Paul Kimanzi

Ocean Acidification is an unfamiliar term to many people outside the scientific community. This term has received very little attention despite its potential to wipe out all species in the ocean and heavily impact on our food security. Ironically, most of the activities carried out by humans on this planet are heavily contributing to this phenomenon.  

A pollution expert Dr Eric Okuku explains ocean acidification is a sister of climate change because it is caused by the same pollutant as that causing the latter, which is anthropogenic carbon dioxide in the environment.

When the excess carbon dioxide (CO2) in the atmosphere gets dissolved in water it forms carbonic acid, making the water more acidic and lowering its pH. Dr. Okuku says the situation has adverse effects on marine ecosystems.

Dr Eric Okuku (in checked shirt), WIOMSA President Dr Jacqueline Uku (far left), WIOMSA Vice President Dr Mathias Igulu (right), Sweden based Ocean Acidification Expert Prof. Sam Dupont (2nd right) and Mr. Samuel Mwangi (3rd right) discuss marine issues on October 21, 2019, in Mombasa.   

‘Ideally, the water should be slightly neutral or basic, but with the increasing amount of CO2 to the environment, the water becomes more acidic, hence lowering the pH of the sea water. With the low pH, we have organisms that require carbonates to build their shells such as coral reefs and molluscs. Such organisms lack the building material; that is the carbonate that they require to build their shells,’ explains Dr Okuku.

What is pH?

Ocean acidification is usually expressed in terms of the pH of seawater.  pH is a measure of acidity or alkalinity. A pH below 7 is considered acidic, and a pH greater than 7 is considered alkaline, or basic.

Averagely, the pH of ocean water is currently 8.1.  The pH scale is logarithmic, so a one point change on the scale means a tenfold change in concentration.

The pollution experts says that climate change and ocean acidification are purely human-induced phenomenon which have adverse effect on marine ecosystem.

What happens to marine organisms?

‘We expect the larvae to have a bit of abnormality in the development. If they can’t build their shells, they are left at the mercy of the environment,’ adds the pollution expert.

According to Dr Okuku, the shells exposed to such unfavourable condition may easily dissolve, leaving the organisms defenselessly exposed because they cannot survive without the shells.

Sweden based Ocean Acidification Expert Prof Sam Dupont takes regional marine researchers through laboratory experimental set up on ocean acidification from the scratch to results approach  

According to information published on Earth Eclipse website, the site that runs environmental articles, oceans require a particular level of pH to maintain the natural biochemistry needed to allow a healthy ecosystem to remain intact for the species living in the water. When oceans absorb high levels of carbon dioxide, the acidity levels raise and the natural order of the ocean becomes compromised.

Calcium carbonate minerals are building blocks for skeletons and shells of marine organisms.

Basically, there are two main causes of atmospheric CO2; fossil fuel emissions and deforestation.

Fossil fuel emissions are basically the gases or emissions spewed out of vehicles, power plants, factories that are burning fossil fuels such as coal, oil and gas and airplanes emissions.  Fossil fuel consumption has increased exponentially since the industrial revolution, to bring about many issues related to climate change, such as ocean acidification.

On the other hand, deforestation is a two-fold matter. Burning down forests emits a lot of carbon dioxide into the atmosphere which is similar to burning fossil fuels.  Forests are critical marine ecosystem especially the mangroves which are regarded as carbon sinks because they take in a lot of carbon. Deforestation does not only create more CO2 in the atmosphere, but it also destroys part of the very things that help absorb it.

Marine species have found themselves at the receiving end of the human activities. Such activities do not only threaten their existence but also threaten the food security for humans.

Dr. Okuku continues that for an organism to survive, it has to do a number of things. ‘Noting that these organisms cannot calsify because the carbon is less, so they have to keep on producing much more shells to avoid losing their shells meaning the rate of production must be higher and that will require more energy. The implication is that the energy that should contribute in the growth and in building the defence immune system of these organisms, it will be invested in the production of shells,’ continues Dr Okuku.

WIOMSA President Dr Jacqueline Uku shares her contribution on marine science with regional marine scientists during ocean acidification training held in Mombasa in October 2019

Still  when the environmental pH goes down, the pH of internal body fluids of marine species also go down. These organisms have optimum levels of pH where their bodies can function. For them to survive they need energy to maintain their pH figures of their internal fluid at the level where it should be, a scenario Dr Okuku calls ‘lose-game situation’.

According to a study conducted by Nature Geoscience indicates that the oceans are now acidifying 10 times faster today than 55 million years ago when a mass extinction of marine species occurred. This study looked back over 300 million and found that “the unprecedented rapidity of CO2 release currently taking place” has put marine life at risk in a frighteningly unique way.

Information published on the US National Ocean Service website indicates that the changes in ocean chemistry can affect the behavior of non-calcifying organisms as well. Certain fish’s ability to detect predators is decreased in more acidic waters. When these organisms are at risk, the entire food web may also be at risk.

The information further states ocean acidification is affecting the entire world’s oceans, including coastal estuaries and waterways. Many economies are dependent on fish and shellfish and people worldwide rely on food from the ocean as their primary source of protein.

Winners and losers of ocean acidification

When ocean acidification happens, there are winners and losers.

All organisms that require carbonates to build their shells will definitely lose. Scientists believe seagrass and seaweed might benefit from excess acid in the ocean. However, Dr Okuku says it is something that is currently being determined by research.

Climate scientist Dr Janice Lough from the Australian Institute of Marine Sciences echoes Dr Okuku’s position but adds that ‘although there are a few winners as you get higher CO2 there are many more losers.’