Press release

Get ready for Ocean Acidification – Nature-Comment by AWI-scientist and Swedish colleague

[27. June 2013] 

Bremerhaven, 27 June 2013. AWI-scientist Prof. Dr. Hans-Otto Pörtner and his colleague Dr. Sam Dupont (University of Gothenborg, Kristineberg, Sweden) publish in the current issue of the journal nature the article: “Get ready for ocean acidification“. They summarize the current status of knowledge and demonstrate needs for action. Their appeal: more interdisciplinary research has appeared necessary.

It is indeed important to understand the immediate responses of single species to more acidic waters. “More particularly, efforts should be targeted towards improving our knowledge of overarching principles, such as shifts in biogeochemical processes like nitrogen fixation, or the interactions between distantly related organisms such as animals, plants and bacteria“, says Hans-Otto Pörtner, head of the section Integrated Physiology at the Alfred Wegener Institute, Helmholtz-Centre for Polar and Marine Research. The two researchers also give recommendations for action: “On the short term we can buy some time by reducing other pressures decreasing ecosystem resilience such as over-fishing, eutrophication or pollution. Ultimately, however, only the reduction of CO2 levels in the atmosphere, best through reductions in CO2 emissions, will alleviate the long-term challenges of global ocean acidification“, Pörtner says.

Background Ocean Acidification:

Every year they absorb more than 25 per cent of the carbon dioxide, which is produced by burning fossil raw materials. Since the start of the industrial revolution, the oceans have absorbed around one half of this greenhouse gas. But even the expansive oceans cannot absorb unlimited quantities of carbon without this having consequences. In the same way as all gases, carbon dioxide dissolves in water and unlike most gases it also reacts with it to produce carbonic acid. The more carbon dioxide penetrates into the oceans, the more carbonic acid is created. This process impacts the chemistry of the seawater and reduces its pH value.

Above all organisms with lime shells and skeletons such as corals, crustaceans, and mussels will suffer from increasing ocean acidification. From a certain pH value not only the building material is absent, the calcification process itself becomes increasingly more difficult and the lime shells even start to dissolve. How ocean acidification impacts individual organisms has far reaching consequences for the entire ecosystem: starting from the food chain through to the carbon content in the atmosphere. Calcifying algae, for example, build biomass by photosynthesis. But they also store carbon in the lime scales of their housing. When they die, they drop to the bottom of the ocean. The heavy lime material acts as ballast and permits the transportation of more carbon to great depths. A part of the carbon reaches the ocean bed and forms lime deposits over geological periods such as the chalk cliffs of Rügen. However, if the ocean acidification attacks the lime housing of the algae, the ballast effect is reduced and the carbon storage function of the oceans weakened.

More highly developed sea inhabitants such as fish also react to lower pH values. The acidic water influences their development primarily in the first stages of life, i.e. when the fish in the egg and as larva have not yet developed any mechanism to protect them from ocean acidification.

More information and additional images can be found in our focus on Ocean Acidification.


Information for editors:

Your contact persons at the AWI is Professor Dr Hans-Otto Pörtner (phone +49 471- -1307; e-mail: Your contact person in the department of communications and media relations is Dr Folke Mehrtens (phone +49 471 4831-2007; e-mail:

The Alfred Wegener Institute conducts research in the Arctic and Antarctic and in the high and mid-latitude oceans.  The Institute coordinates German polar research and provides important infrastructure such as the research icebreaker Polarstern and stations in the Arctic and Antarctic to the international scientific world. The Alfred Wegener Institute is one of the 18 research centres of the Helmholtz Association, the largest scientific organisation in Germany.



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Das Alfred-Wegener-Institut forscht in den Polarregionen und Ozeanen der mittleren und hohen Breiten. Als eines von 19 Forschungszentren der Helmholtz-Gemeinschaft koordiniert es Deutschlands Polarforschung und stellt Schiffe wie den Forschungseisbrecher Polarstern und Stationen für die internationale Wissenschaft zur Verfügung.