Climate change impacts on ocean acidification

Key points

Ocean acidification is the process of oceans becoming more acidic, making it hard for some marine life to thrive.
Increasing carbon dioxide levels in the atmosphere – mainly caused by burning fossil fuels – is driving ocean acidification. This is because oceans absorb carbon dioxide from the atmosphere, which makes them acidify.
Ocean acidification affects ecosystems, the natural food chain, our food supply, our economy, and tourism and recreation.
Reducing carbon dioxide emissions is the best way to prevent further ocean acidification. Managing and reducing other pressures on ecosystems can also help them to cope with ocean acidification.

Impacts of ocean acidification in NSW

Ocean acidification is a chemical reaction where sea water absorbs carbon dioxide from the atmosphere. Once dissolved, the carbon dioxide reacts with seawater. The excess carbon dioxide currently in our atmosphere has meant that absorption has increased. This lowers the pH, making the water more acidic.

Marine species can cope with short-term variations to ocean pH. However, ocean acidification is ongoing, which may reduce the ability of some organisms to adapt.

For example, ocean acidification reduces the concentration of carbonate in sea water. Marine organisms – such as coral, shellfish, and some plankton – use carbonate to build their shells. Less carbonate in the water makes it harder for marine organisms to form their shells and skeletons. Existing shells may also start to dissolve.

Ocean acidification will affect estuarine and coastal ecosystems of NSW in different ways. This is because other factors such as ocean upwelling, salinity and heat have varying impacts on ocean chemistry. Also, different plants and animals have different capacities to adapt. So the impacts of ocean acidification are not the same for all regions and all plants and animals.

For example, some algae and seagrass may benefit from higher carbon dioxide concentrations, as this may increase their photosynthetic and growth rates. But this growth may compromise the ability of other organisims to thrive.

Food chain

Ocean acidification could affect the natural food chain. For example, populations of species such as baleen whales and birds that feed on calcifying organisms would decrease. It could also result in fewer predators at the top of the food chain, such as dolphins and seals.

Economy and food supply

Ocean acidification could disrupt NSW's marine and estuarine ecosystems. This would affect fisheries and aquaculture, and reduce the availability of seafood.

Marine life in NSW at risk include:

oysters
mussels
abalone
squid

These make up a large proportion of the seafood industry.

Ocean acidification may make coral reefs slower to recover from coral bleaching. This will negatively affect tourism and recreational diving.

How ocean acidification is affected by climate change in NSW

The oceans naturally absorb carbon dioxide, but the increased amount of carbon dioxide in the atmosphere means that oceans absorb too much. Since the Industrial Revolution in the early 1800s, the oceans have absorbed about one-third of the carbon dioxide that humans have released into the atmosphere. This has increased ocean acidification by nearly 30%, which is about 10 times faster than any other time in the past 50 million years.

If carbon dioxide emissions continue at the current rate, the surface ocean pH could change from the current 8.1 to 7.7 in the next 100 years. This means the oceans will become more acidic.

The impacts of ocean acidification are amplified in coastal marine habitats. Runoff from acid sulfate soils can decrease the pH of nearshore ocean water. Sea level rise and flooding – driven by climate change – worsens the impacts of coastal acidification.

Adapting to ocean acidification in NSW

Reducing carbon dioxide emissions is the best way to prevent further ocean acidification.

We can help organisms and environments cope with increasing ocean acidification. Managing the marine estate and catchment can reduce other pressures, such as acid sulfate soil run-off, turbidity and pollution.

Marine Estate Management Authority

The Marine Estate Management Authority (MEMA) is managing the NSW marine estate as one continuous system.

By focusing on improving water quality and delivering effective governance, NSW can reduce the pressure on marine organisms and ecosystems . This will help the marine environment cope with acidification.

The NSW Marine Estate Management Strategy 2018–2028 Initiative 3 ‘Planning for climate change’ aims to address climate change impacts in adaptation planning, strategies and decision making. This initiative includes:

researching how we can help oceans to build capacity to deal with rising pH
helping coastal and marine managers and communities to access new research findings.

Coastal management program

Coastal management programs (CMPs) set the long-term strategy for coordinating coastal management, with a focus on achieving the objectives of the Coastal Management Act 2016 (NSW).

CMPs identify coastal management issues and the actions required to address these issues.