Reducing our CO2 emissions is the only possible response to ocean acidification

© UNESCO. Interview with Kirsten Isensee, marine biologist specialized in ocean carbon.

While the Global Ocean Acidification Observing Network meets in Geneva on 16 January, Kirsten Isensee, a marine biologist specialized in ocean carbon currently working for the Intergovernmental Oceanographic Commission of UNESCO, spoke of  the threats posed by ocean acidification and explained the role of the Network.

The Network, which was created in 2012, aims to bring together scientists from as many countries as possible – 28 to date – to pool reliable and comparable data allowing them to assess the extent of ocean acidification and its impact worldwide. The objective is to build a global database and, using this data, provide future projections.

Is enough data available?
Ocean acidification is a complex phenomenon and it is difficult to observe. Isolating this phenomenon from other factors affecting the ocean is challenging. Moreover, it takes time to observe developments that impact ecosystems. Taking into account the generation spans of the different species, it can take months or years to observe the impact of acidification and the degree to which species adapt to their changing environment. Most of the research conducted today is short term and lab based. This is not enough. We need to conduct research in the sea to further our knowledge but the high costs involved make this difficult.

Compared with preindustrial levels shown here, the projected increase in ocean acidity is about 170% by 2100 if high CO2 emissions continue (RCP* 8.5).

How big a threat does ocean acidification pose to the environment?
The acidity of the ocean has increased by 26% since the beginning of the industrial era, because part of the carbon dioxide released into the atmosphere is absorbed by the ocean, triggering chemical reactions that reduce seawater pH. This process is known as acidification, also called the "other CO2 problem" in reference to rising water temperatures. As acidity increases, the ocean’s ability to absorb CO2 decreases. The fast pace of acidification is also an issue, as it is very difficult for species to adapt within such a short period of time. The phenomenon has a negative impact on coral reefs and shellfish, as their calcium carbonate shells are harder to produce and maintain in an increasingly acidic environment.

Economic impacts have already been observed; for example the higher mortality rate of oyster larvae in hatcheries on the west coast of the United States is reducing their productivity. Keep in mind that acidification takes its toll on the ocean as a whole, even in areas with little or no direct anthropogenic influence such as the Arctic. This is further proof that all parts of the ocean are connected and form a global system.

© NOAA
The Limacina helicina pictured here is a victim of ocean acidification. Its normally-protective shell is so thin and fragile, it is transparent.

Is there enough awareness of this issue, and is it being addressed properly?
It is starting to receive some attention, at least from the scientific community. In 2004, when the first “Ocean in a High CO2 World” symposium was held in Paris, the subject was was little known. This is no longer the case. The first symposium gathered 120 participants. The latest symposium, in Monterey (United States) in 2012, brought together 530 experts and scientists. We can also measure the development of this field of research through the increasing number of publications and events focusing on acidification. Another notable indicator is that acidification is mentioned in the final outcome document of the 2012 United Nations Conference on Sustainable Development (Rio+20), which was not the case earlier.

Is it possible to mitigate ocean acidification?
There is only one way: reduce our CO2 emissions. But it is possible to promote ecosystem resilience locally by acting on other stressors affecting the ocean, by creating marine protected areas and implementing a sustainable management of coastal areas.

What is the role of the Intergovernmental Oceanographic Commission of UNESCO?
The IOC has always been a pioneer in identifying threats to the ocean. Ocean acidification is a relatively new field of study, and the IOC has been at its forefront since the very beginning. The Commission is participating in several international initiatives such as the Ocean Acidification International Coordination Centre and the Global Ocean Observing System (GOOS). It is well placed to bring together scientists and policy makers. It also seeks to involve developing countries, which are not the largest emitters of CO2, because the ocean concerns us all.

Interview by Agnès Bardon, UNESCO Media Services

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This map shows the “saturation state” for the mineral form of calcium carbonate called aragonite. Coral growth benefits from Ω≥3. By 2100, computer model projections show that Ω will be less than 3 in surface waters around tropical reefs if CO2 emissions continue on the current trajectory.

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