What is it?
Prior to the Industrial Revolution, atmospheric carbon dioxide (CO2) was 280 ppm (parts per million). Burning fossil fuels has increased atmospheric CO2 until today it’s 417 ppm and rising. In fact, we’ve produced twice as much CO2 than what the atmosphere has absorbed. Land plants and trees have absorbded around 25%, while the ocean has absorbed another 25%. And that’s changed the chemistry of the ocean.
Why is it a problem?
Marine animals such as the plankton at the base of the food chain, such as the sea butterflies in the image and video on this page, and other creatures like shellfish and crustaceans (including krill), need biogenic calcium carbonate (CACO3) to built shells and exoskeletons. While some of the CO2 absorbed by the ocean stays as dissolved gas, most combines with water (H2O) to produce H2CO3, or carbonic acid, causing the oceans to become more acidic and reducing the availability of CACO3.
This has two key impacts : (1) less CACO3. means zooplankton can’t develop during their planktonic phase and (2) more acidic water dissolves shells and corals. There are other, unexpected impacts on marine life as well.
Colder waters hold more CO2 than warm waters, meaning the sub-Antarctic and Antarctic regions are affected faster than in warmer regions. As these areas act as nurseries for creatures at the bottom of the oceanic food web, the entire oceanic ecosystem is now threatened.
Ocean acidification is happening today faster than at any time in the last 300 million years, making it unlikely that marine organisms will be able to adapt before becoming extinct.
Why is it a problem for braided river birds?
- Short to mid-term – reduced availability of winter food for migratory river birds that depend on hapua, estuaries, and oceans
- Long-term – the absence of winter food for migratory river birds
Research and references
- 2019: Comeau et al; Resistance to ocean acidification in coral reef taxa is not gained by acclimatization. Nature Climate Change 9, 477–483
- 2019: Schlunegger et al: Emergence of anthropogenic signals in the ocean carbon cycle Nature Climate Change 9, 719–725
- 2018: Ocean acidification in the IPCC Special Report: Global Warming of 1.5°C
- 2018: Riebessell et al; Toxic algal bloom induced by ocean acidification disrupts the pelagic food web; Nature Climate Change 8, 1082–1086
- 2019: Beaugrand; Prediction of unprecedented biological shifts in the global ocean. Nature Climate Change 9, 237-243
- 2016: NIWA; Investigation ocean acidification
- 2012: Bednarsek et al: Extensive dissolution of live pteropods in the Southern Ocean; Nature Geoscience 5, 881–885
- 2012: Doney et al; Climate change impacts on marine ecosystems PubMed (PMID:22457967) (open access)
- 2009: Doore et al; Physical and biochemical modulations of oceanic acidification in the central North Pacific;
- 2003: Caldeira & Wickett; Anthropogenic carbon and ocean pH; Nature 425, 365
- Science Learning Hub NZ: Ocean dissolved gases
- Otago University: Ocean Acidification Research Theme
- Smithsonian Institute: Impacts of acidification on shellfish
- NOAA: Ocean-Atmosphere CO2 Exchange
- BIOACID: Biological Impacts of Ocean Acidification
- See also Climate change/references (this website)