Ocean Acidification refers to the ongoing and worsening decrease in the pH (an indicator of acidity in substances) of the Earths’ ocean water.
The pH level of the ocean has been falling since the beginning of the Industrial Revolution. In fact, the logarithmic pH scale shows that the pH level has fallen 0.1 pH units over that time period. While this may not seem like much, it is a 30% increase in ocean acidity.
For this reason, ocean acidification is sometimes called “climate change’s equally evil twin.”
Since the beginning of the industrial era, the ocean has absorbed 525 billion tons of CO2, around 22 million tons a day. This absorption process is largely facilitated by the ocean’s role as a carbon sink and the biological carbon pump mechanism. The ocean’s surface layers absorb CO2 from the atmosphere, where it is then used by phytoplankton during photosynthesis. The biological carbon pump involves these microscopic plants converting CO2 into organic carbon, some of which sinks to deeper ocean layers as part of dead organisms or fecal pellets. This deep-sea deposition of carbon is crucial, as it prevents the rapid re-release of CO2 back into the atmosphere, thereby mitigating the greenhouse effect and helping to regulate Earth’s climate and slow down the global warming of the planet.
However, this comes at a weighty cost to the balance of ocean ecosystems. These changes have been occurring so quickly, “faster than any known change in ocean chemistry in the last 50 million years.” This means that organisms have not had time to keep up. They haven’t been able to adapt to the increased acidity and decreased pH that makes up their habitats.
Ocean acidification and global warming are different problems but are closely linked because they share the same root cause—human emissions of carbon dioxide.
The pH Scale Explained
The pH scale ranges from 0 to 14, with the mid-point, 7, being neutral. Numbers higher than seven are considered “basic” or alkaline, while numbers lower than seven are “acidic.” When the pH number goes down, the acidity goes up. More hydrogen ions means higher acidity and a lower pH.
Today, the ocean’s average pH is around 8.1, which is basic. Scientists estimate that by the end of the 21st century, the ocean could have a pH level of 7.8.
What Causes Ocean Acidification?
Ocean acidification is caused by the decrease in the pH level of the ocean. This is set in motion during the biological carbon pump when the ocean absorbs more CO2 than it can process and because of the dissolution of shallow carbonate sediments in the ocean. It is just one of the many ways that climate change is affecting our oceans today.
The change in acidity is caused due to chemical reactions following the absorption of carbon dioxide that increase the acidity of the water. The majority of this change can be set at the feet of humankind, the burning of fossil fuels, and changes in land use.
The ocean is responsible for absorbing 30 percent of the CO2 released into the atmosphere, so when that amount increases, so too does the percentage that the oceans take in. The seawater takes in the CO2, and subsequent chemical reactions occur that result in more hydrogen ions. This increase means that the seawater’s acidity rises, and carbonate ions decrease.
Effects of Ocean Acidification
Scientists know that over time the pH levels of the oceans are going to decrease further, leading to an overall increase in ocean acidification. Some estimates suggest that by the end of the century, acid levels could be 150 percent higher.
This would lead to an ocean pH level that hasn’t existed for more than 20 million years. When it did, the ocean was several degrees warmer and in the middle of a major extinction event. Ocean acidification is leading to the destruction of important calcium carbonate minerals that many sea creatures need to build their skeletons and shells.
Impact on Marine Life
- Increased ocean acidity impairs fish’s ability to detect predators and affects larval clownfish’s habitat selection, destabilizing marine food webs.
- Alters nutrient cycles and availability, potentially shifting food chain dynamics.
- Disrupts sensory systems of marine organisms, affecting natural behaviors such as mating and foraging.
- Dissolves calcium carbonate structures, undermining the structural integrity and biodiversity of marine ecosystems.
There are wide-ranging implications in regard to the increasing acidity levels of the ocean over time. One of the most prominent is the impact on biological organisms. There are some plants, such as algae and seagrass, that might benefit from the change, but others, including oysters, clams, and corals, would be negatively impacted by increasing CO2 levels. So far, increasing carbon has proven to decrease corals’ ability to produce their skeletons, and for marine organisms to build and maintain their shells. It also compromises fertility in the ocean and impacts the coral’s ability to recover from a variety of disturbances.
In fact, by 2080 the ocean will be so acidic that coral reefs will disappear more quickly than they’re able to rebuild. Beyond lost biodiversity, acidification will affect fisheries and aquaculture, threatening food security for millions of people, as well as tourism and other sea-related economies.
In regards to shellfish, scientists have noted larval oyster failures that are connected to increases in the pH level of the ocean. The oyster industry is incredibly important, but only one of many ocean-based industries that would be disrupted by further rises in acidification. Another interesting study was done on pteropods, also known as the “sea butterfly.” This very small sea creature’s shell was determined to dissolve in low pH level waters over a period of 45 days.
These changes also have an impact on leading marine animals as well, such as fish, which suffer from a decreased ability to detect predators in more acidic waters. Other studies have shown that larval clownfish struggle to find suitable habitats in more acidic waters. As a crucial part of the food chain, the entire marine ecosystem falls into danger.
Broader Economic Impact
- Disrupts commercial shellfish industries, affecting oysters, clams, and scallops.
- Threatens the survival and economic viability of coral reef ecosystems, crucial for tourism.
- Impacts fisheries by altering fish populations and behaviors, affecting food supply chains.
- Raises costs and reduces efficiency in aquaculture due to the need for mitigation strategies.
- Affects local economies dependent on marine biodiversity for livelihoods, such as fishing communities.
When the ocean’s ecosystem is threatened, so too are the livelihoods of millions of people who depend on the ocean for their own substance and for their employment. Coast estuaries and waterways are affected as well, meaning that as the problem increases, it’s going to be harder and harder to avoid. Incredibly important parts of the fishing industry are in danger, such as the American lobster, scallops, and red king crab.
What Solutions Are There to Stop Ocean Acidification?
Ocean acidification is just one of the many negative impacts of the global climate crisis. It, like the broader warming of the planet and the melting of glaciers, is the fault of humans-created fossil fuels. Anything that humanity does to stop or mitigate climate change will be a beneficial step towards ocean conservation.
Luckily, an increased focus on this problem by groups such as NOAA’s Ocean Acidification Program is forging relationships between scientists, the public, and governmental officials in order to monitor the changes in ocean chemistry. Now that the impacts of ocean acidification are being closely monitored, so it is more likely that enough can be done in time to stop a total collapse of marine ecosystems. NOAA notes that it is impossible at this time, due to the early stages of their research, to truly know what exactly ocean acidification is going to result in.
NOAA encourages educators to include lessons on ocean acidification alongside this about the food web and the broader interconnectivity of ocean, and the world, ecosystems.
Ocean Insights: Hear From Our Experts
By Rida Nasir
Researcher and Conservationist, with an MSc in Environmental Science
Ever since the atmospheric carbon dioxide has increased by 40%, it has resulted in a 25% rise in ocean acidity. On one hand where the carbon dioxide in the atmosphere being absorbed by the ocean is beneficial, at the same time, it will lower the ocean's water pH level to such a level that it will no longer sustain life, balance the ecosystem, or support the economy. In my opinion, to stop this from happening we need to tackle the root cause - the emissions of carbon dioxide in the atmosphere. To reach 350 parts per million, which is what the level of atmospheric carbon dioxide was in 1988, humans would need to remove more than 500 billion tons of carbon from the atmosphere. To “turn back the clock” on climate change, we would need to capture today’s emissions plus an enormous backlog - the alarming situation is that it's nearly impossible to meet our climate goals at the current pace of carbon dioxide production.
FAQs
How does ocean acidification differ regionally?
Ocean acidification levels can vary regionally due to factors such as upwelling, river runoff, and varying atmospheric CO2 levels. Areas with heavy industrial activity or significant riverine input might experience more rapid changes in ocean chemistry.
Are there any successful mitigation strategies being tested to address ocean acidification locally?
Local mitigation strategies, like seagrass restoration and kelp farming, have shown promise in buffering pH levels by absorbing CO2 in coastal areas. These strategies also enhance habitat complexity and biodiversity, providing additional ecological benefits.
What technologies are being developed to monitor ocean acidification?
Advances in sensor technology and remote monitoring are allowing scientists to track pH changes more accurately in real-time. Autonomous underwater vehicles (AUVs) and buoy-based sensors are increasingly used to gather pH data from remote and vast ocean areas.
