Sea butterlfies dissolving image: David Littschwager/NOAA
Changing the chemistry of the ocean
“Plankton are responsible for at least half of the oceans’ CO2 uptake, so they help to regulate climate.” – NIWA
All animals including humans need biogenic calcium carbonate (CACO3). We use it to grow bones and teeth, fingernails, muscles (including our heart) and our nervous system. On the land, we get CACO3 from calcium-rich foods.
In the ocean everything from fish, crustaceans, kina, shellfish like mussels, oysters and paua, sea butterflies to the tiny coccolithophores that form the base of the food chain need CACO3 to built shells and exoskeletons, muscles and nervous systems (Video 2). The oceans have absorbed around 50% of the excess CO2 we have emitted into the atmosphere. While some of that CO2 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 marine creatures to absorb CACO3 (Figs. 2 & 3) This has several impacts:
- Zooplankton can’t develop properly during their embryonic and planktonic phases
- Acidic water dissolves shells and corals and can make adults prone to disease
- Fish are becoming less fearful of predators and can’t navigate as well (possible issues with nervous systems), reducing the changes of juvenile fish reaching adulthood.
- The muscles of mussels and other shellfish such as oysters and paua are not as strong. This makes it harder for them to hold tight against waves and rough seas (storms)
- It also makes free-swimming oceanic creatures from algae to fish, harder to swim.
- With less carbon able to be taken up by marine organisms, less carbon can be stored at the bottom of the ocean when they die, ie, this nature carbon sink may be reduced (see the carbon cycle).
“Ocean acidification is changing the productivity and composition of phytoplankton communities at the base of the aquatic food web. Now a study shows that acidification impairs the swimming ability of flagellated microalgae, suggesting that their capacity to survive is threatened in a high CO2 world.” – Jolanda Verspagen, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam
“We found that living in an acidic environment makes small reef fish become attracted to the smell of their potential predators. Their sense of smell was acutely affected in CO2 rich waters in ways that gravely threaten their survival.” – Alistair Cheal, Australian Institute of Marine Science