Ocean acidification

Definition

Ocean acidification is the process by which the pH levels of the ocean decrease due to the absorption of excess carbon dioxide (CO2) from the atmosphere. This phenomenon impacts marine ecosystems, particularly organisms that rely on calcium carbonate for their shells and skeletons, and is intricately linked to various biogeochemical cycles, the carbon cycle, and climate change dynamics.

5 Must Know Facts For Your Next Test

1. Ocean acidification is driven primarily by increased atmospheric CO2 from human activities such as fossil fuel combustion and deforestation.
2. As CO2 dissolves in seawater, it reacts to form carbonic acid, leading to a decrease in pH levels, which can affect marine life, particularly calcifying organisms like corals and mollusks.
3. The current rate of ocean acidification is estimated to be occurring at least 100 times faster than historical natural events, threatening biodiversity in marine ecosystems.
4. Impacts of ocean acidification include disrupted food webs, weakened coral reefs, and altered behaviors in fish species, potentially affecting fisheries and coastal economies.
5. Mitigating ocean acidification requires global efforts to reduce CO2 emissions and enhance carbon sequestration practices to protect marine environments.

Review Questions

• How does ocean acidification affect marine organisms that rely on calcium carbonate?
  • Ocean acidification lowers the pH of seawater, which decreases the availability of carbonate ions necessary for organisms like corals and shellfish to form their calcium carbonate structures. As these organisms struggle to maintain their shells and skeletons, it can lead to weaker growth and increased mortality rates. This disruption not only impacts individual species but also threatens entire marine ecosystems that depend on these calcifying organisms.
• Discuss the role of human activities in exacerbating ocean acidification and its broader implications for marine biogeochemical cycles.
  • Human activities, particularly the burning of fossil fuels and land-use changes, have significantly increased atmospheric CO2 concentrations. As the oceans absorb this excess CO2, they undergo chemical changes that lower pH levels. This shift disrupts marine biogeochemical cycles, affecting nutrient availability and overall ocean health. The resulting changes can ripple through food webs and impact ecosystem services that humans rely on, such as fisheries and coastal protection.
• Evaluate the potential long-term consequences of ocean acidification on global fisheries and food security.
  • Long-term consequences of ocean acidification could severely threaten global fisheries by impacting fish populations that rely on healthy coral reefs and other habitats affected by changing water chemistry. As important species decline or alter their behaviors in response to lower pH levels, it could lead to reduced fish stocks available for consumption. This would not only affect local communities dependent on fishing for their livelihoods but also have broader implications for global food security as seafood remains a critical protein source for billions of people worldwide.

Related terms

pH:

A scale used to specify the acidity or basicity of an aqueous solution, where lower values indicate higher acidity.

calcium carbonate: A chemical compound (CaCO3) that is crucial for marine organisms like corals and shellfish, which use it to build their shells and skeletons.

carbon sequestration:

The process of capturing and storing atmospheric carbon dioxide to mitigate climate change, often involving natural systems like forests or oceans.