Which organisms are primarily threatened by ocean acidification?

Ocean acidification poses a significant threat primarily to organisms like oysters and corals. This process occurs when excess carbon dioxide (CO2) is absorbed by ocean water, leading to a decrease in pH levels and making the water more acidic.

Oysters are especially vulnerable because they rely on calcium carbonate to form their shells. Acidic waters can reduce the availability of carbonate ions, which are essential for shell formation, making it more difficult for oysters to build and maintain their shells. This not only affects individual oysters but can also have broader implications for entire ecosystems, as they play a crucial role in marine habitats.

Corals face similar challenges. They also depend on calcium carbonate to build their skeletons. Ocean acidification can weaken coral structures, making them more susceptible to erosion and other stressors, such as temperature changes and pollution. Healthy coral reefs are vital for the biodiversity of marine life, providing shelter and nourishment for numerous marine species.

While other organisms such as plankton and fish species are impacted by ocean acidification as well, the direct effects on the calcifying organisms like oysters and corals are particularly significant and well-documented. Therefore, the correct answer highlighting the primary threat from ocean acidification is indeed oysters and corals.