The World’s Oceans are a sink for CO₂, with various factors affecting carbon uptake including wind, sea surface temperature, and biota. Since the industrial revolution anthropogenic emissions of CO₂ have increased, this has led to an increase in CO₂ in the oceans. So far around 500 billion tons, approximately one third of CO₂ emitted, has been absorbed by the oceans (NRDC, 2009). Have you ever considered how much CO2 your lifestyle creates or thought about trying to reduce it? The rise in CO₂ in seawater has already increased the acidity of the by 0.1 pH units since the industrial revolution, and pH could by the end of this century decrease by a further 0.3-0.4 pH units. Increased CO₂ in seawater leads to the formation of carbonic acid which causes ocean acidification. The oceans act as a buffering system taking up excess amounts of CO₂ which control the pH of seawater by a series of reactions (IPCC, 2007):

                        CO₂ + H₂O —>  H₂CO₃ —> H⁺ + HCO₃^- —> 2H⁺ + CO₃^2-                               

Carbon dioxide + Water —> Carbonic acid —> Bicarbonate —> carbonate

Over the time the amount of CO₂ in the oceans with increase the chemical reactions taking place with the ocean. Just looking at the reaction above would imply that the amount of carbonate within the ocean would increase however this will not be the case. In fact the carbonate reacts with the seawater to produce more bicarbonate, as is shown in the equation below:

               CO₂ + H₂O + CO₃^{2- —>} HCO₃^- + H⁺ +CO₃^{2- —>} 2HCO₃^-

Carbon dioxide + Water + Carbonate —> Bicarbonate + Carbonate —> Bicarbonate

The amount of carbonate is in oceans will decrease but the amount of bicarbonate found will increase. The reduction in carbonate affects key calcifying organisms, such as coral and plankton which use calcium carbonate to form their hard shells and skeletons (Iglesias-Rodriguez et al. 2008).  These key organisms form the base of marine food webs, any change in the species has the potential to impact entire ecosystems (NOAA, 2008). This study examines the socio-economic effects that ocean acidification could bring.

The impact of reduced carbonate and pH will travel through the marine environment. Some types of plankton may be unable to maintain their hard exterior, meaning a decrease in the numbers within their species group. The expected loss of plankton will impact the commercial and local fisheries that rely on plankton as a food source for the majority of marine life. Commercial fisheries are a multi-billion dollar business; in excess of $60 billion per year is spent of fish and shellfish (NOAA, 2008). Fishing provides the livelihoods for over 500 million people, with 90% of these living in developing countries and supporting entire communities (UN, 2009). Global fisheries are generally located in zones of upwelling water. Here nutrients are brought to the surface, bringing large concentrations of plankton, and therefore attracting schools of fish feeding. These areas are particularly vulnerable to ocean acidification, as lower pH water will be brought to the surface from upwelling deep water (Turley and Williamson, 2011). Fish is an important source of protein for around 1 billion people. As the population of the world increases, if the fisheries fail it could greatly affect global food security (UN, 2009).

The reduction of calcium carbonate and increase in oceanic acidity will lead to a decrease in coral reef formation and diminished resiliency to coral bleaching, a term which describes the death of a the symbiotic bacteria that live within the coral themselves. Many ecosystem services are provided to us through coral reefs. Corals are an important ground for fisheries, they provide shellfish, reef fish, and act as a nursery for commercial fish (European Science Foundation, 2009). Furthermore coral reefs protect coastal communities from events such as storm surges and hurricanes, if natural shoreline protection was compensated more expensive man made sea defences would be needed to replace the natural protection (NERC, 2009).

In some countries corals bring an important source of income, through tourism and cultural heritage, corals in the Great Barrier Reef are showing a recent decline in calcification (UN, 2009).  The Great Barrier Reef Marine Park Authority (2009) estimated that the reef contributed to 8.6% of Australia’s Gross Domestic Product (GDP) for 2006-07, this is a highly significant portion for one tourism attraction.

Acidification could also lead to more rapid climate change, as it slows down the oceanic carbon pump, reducing the oceans ability to absorb additional CO₂. This will lead to an increase in costs to cap the CO₂ in the atmosphere (European Science Foundation, 2009).  Hood et al. (2009) have attempted to quantify the ecosystems service of carbon uptake by the oceans using the current price of carbon credits. They claimed that the oceanic uptake of CO₂ was equal to an annual subsidy of 0.1-1% of the Gross World Product or $40-400 US billion.

Areas most affected by ocean acidification will be small island developing states, developing countries and coastal regions as they rely on services provided by marine ecosystems the most for their livelihoods (UN, 2009). The reduction in CO₃^2- brought about by increased anthropogenic CO₂ in the atmosphere will affect marine life, but to what extent is largely unknown as there is a scarcity of relevant data which inhibits the assessment of the possible impacts. Future research should focus on the possible reductions of ocean acidification and areas where the impacts are likely to be the greatest both for the human population and environment. Moreover the cumulative impacts of various environmental problems need to be predicted and mitigation options explored, such as rising sea levels, temperature combined with the possible effects of ocean acidification.

If this issue has got you thinking about what you could change about your lifestyle to become a little more environmentally friendly, why not take a look at Energy Saving Warehouse’s range of products to help you do just that?

References

European Science Foundation (2009) Impacts of Ocean Acidification. Science Briefing Policy. No: 37. France.

GBRMPA (2009). Research Publication No. 98: Economic Contribution of the Great Barrier Reef Marine Park, 2006-07. G.B.R.M.P. Authority. Queensland, Great Barrier Reef Marine Park Authority: 19-21

Hood M. et al. (2009) Ocean Acidification: A summery for policy makers from the second symposium on the ocean in a high- CO₂ world. The Second Symposium.

Iglesias-Rodriguez, D. M. (2008) Phytoplankton calcification in a high-CO₂ world. Science. Vol: 320, 336-340.

IPCC (2007) Climate Change 2007: Working group I: The Physical Science Basis. Chapter 10.4 Changes Associated with Biogeochemical Feedbacks and Ocean Acidification.

NOAA (2008) Ocean Acidification. State of the Science Fact Sheet. National Oceanic and Atmospheric Administration. US Department of Commerce.

NRDC (2009) Ocean Acidification: The other CO₂ problem. Natural Resources Defense Council.

Turley and Williamson (2011) Socio-Economic Aspects of Ocean Acidification. Report for UNFCCC Subsidiary Body for Scientific and Technological Advice. Bonn, Germany.

UN (2009) Ocean Acidification: A hidden risk for Sustainable Development. UN-DESA Division for Sustainable Development. Copenhagen Policy Brief No 1.

The implications and impacts from ever increasing greenhouse gases emitted into our atmosphere are profound.  It is the responsibility of scientists and policy makers to find methods of reducing these emissions and increasing the worlds carbon sinks. The oceans are one of the largest natural carbon sinks in the world, absorbing around 30-50% of anthropogenic emissions per year. With this in mind, scientists have come up with a way of potentially enhancing the amount of carbon that can be sequestered by the ocean by using iron to increase the amount of photosynthesis that occurs in surface waters. This method is known as iron fertilisation.

What is the Iron Fertilisation hypothesis?

Some areas of the world oceans are known to be rich in nutrients but have very little growth. In the late 1980’s Scientist John Martin claimed that iron was a limiting factor in growth in these areas and by adding iron he could stimulate phytoplankton growth in surface oceanic layers (Buesseler et al. 2003). Phytoplankton use carbon dioxide during the process of photosynthesis, therefore, by adding iron to oceanic waters and increasing the phytoplankton growth, this would also increase the amount of CO₂ absorbed through the oceans.

What evidence supports the hypothesis?

John Martin needed to prove that iron was a limiting factor in phytoplankton growth. He studied the depth profile of iron throughout the oceans and found that iron acted in the same way as nitrogen and phosphorus, both micronutrients. It has a high surface depletion, indicating that something is taking it out of the surface waters; furthermore iron is regenerated at depth due to bacterial decomposition. This signifies that iron is a micronutrient and can be a limiting factor from growth.

Twelve oceanic iron experiments were carried out to test whether iron enrichment would increase primary productivity in areas of high nutrients but low productivity (Boyd et al. 2007). Buesseler and Boyd (2003) studied three experiments all with locations in the southern ocean. They stated that all of the experiments produced noticeable increases in biomass and associated decreases in dissolved inorganic carbon and macronutrients. Powell (2008) also reported that all 12 experiments reported up to a 15 fold increase in chlorophyll content in the surface of the oceans.

The 12 experiments verify that iron enrichment does enhance primary productivity in high nutrient but low chlorophyll areas of the oceans and therefore iron has a fundamental role in photosynthesis.

However, very little work has been carried out to test whether the amount of carbon taken up in the surface waters during these experiments has been transported down throughout the water column, and sequestered into the seafloor or deep layers of the ocean. If this process is not completed then the carbon will re-emerge later in a different location.

What are the impacts of iron fertilisation?

Iron fertilisation is a popular notion in carbon sequestration as it has been portrayed as a cheap, fast and easy way to mitigate climate change. However uncertainties and doubts regarding this method of geo-engineering have increased dramatically since John Martin first came up with concept.

So far only 12 small scale experiments and computer models have been used to predict the impacts and benefits of large scale long term iron fertilisation. While this is a fairly risk free process of assessing the costs and benefits of this method of carbon sequestration, it by no means can replicate the effects of a large scale experiment.

Creating large scale phytoplankton blooms could change the balance of the oceans food chains and could increase the number of large predators including fish, jellyfish and algae concentrations. The increase in fish and commercially available food could lead to an increase in the world’s fisheries. However some phytoplankton blooms are toxic and could therefore be harmful to the whole food chain, including human consumption.

The fertilisation of the oceans could cause deficits in oxygen or nutrient in far removed areas of the ocean, due to the oceanic circuits. Areas that have been enriched with iron months or even years previously will be lacking in nutrients as they will have already been consumed.

The UN Convention on Biodiversity states that precautionary action must always apply in the face of uncertain consequences. This applies to iron fertilisation experiments in the oceans, and it is now forbidden for any iron enrichment to take place within a countries coastal waters. Furthermore the London Protocol against marine pollution could also apply to the input of dissolved iron as the consequences of this are still mostly unknown.

According to Boyd (2008) the costs of iron fertilisation have been severally underestimated. The amount of carbon that can be absorbed by iron fertilisation in the long run has greatly decreased over the past 20 years by 5-20%. Especially when compared to the amount of fossil fuel emissions that are emitted into our atmosphere, iron fertilisation alone, can be considered to make little difference to the greenhouse gas effect.

Conclusion

Iron fertilisation is an interesting concept of geo-engineering and is successful at drawing carbon out of the atmosphere in short periods of time. However the impacts of large scale experiments, or even the commercialisation of iron enrichment to reduce the effects of climate change, are largely unknown and high in risks. It is unlikely that iron fertilisation will ever occur to the scale that will achieve significant impacts in aiding the efforts to reduce the amount of greenhouse gases in the atmosphere. However, every little does help in terms of reducing these gases, especially carbon dioxide so why not have a look at our tool to help you consider your footprint?

References

Buesseler, K. et al. (2008) Ocean Iron Fertilisation –Moving Forward in a Sea of Uncertainty. Science Vol: 319. P: 162

Powell, H. (2008) Will Ocean Fertilisation Work? Oceanus Magazine. Vol: 46. P: 10-13

Boyd, P. (2008) Implications of large scale Iron fertilisation of the Oceans. Marine Ecology Progress series. Vol: 364. P: 213-218.