Ocean Chemistry Along the Oregon Coast
The waters off Oregon’s coast are among the most productive in the world, supporting rich marine ecosystems, thriving fisheries, and abundant wildlife. Scientists are also observing changes in ocean chemistry that can affect marine life and coastal communities. Two of the most important changes being studied are ocean acidification and hypoxia, or low-oxygen conditions.
Oregon’s Dynamic Ocean
Every spring and summer, strong north winds drive a natural process called upwelling. During upwelling, cold, nutrient-rich water rises from the deep ocean to the surface. These nutrients fuel the growth of plankton, which form the foundation of Oregon’s marine food web.
Upwelling is one of the reasons Oregon’s coastal waters support healthy populations of fish, seabirds, marine mammals, and the many species found in our rocky shore habitats. However, the same ocean conditions that make our coast so productive can also make it more vulnerable to ocean acidification and low-oxygen events.
Ocean Chemistry: Ocean Acidification and Low Oxygen Waters
The ocean is constantly changing, and scientists are observing shifts in ocean chemistry that can affect marine life and coastal ecosystems. Two important changes being studied along the Oregon coast are ocean acidification and hypoxia (low oxygen conditions).
What is Ocean Acidification?
Ocean acidification occurs when carbon dioxide (CO₂) from the atmosphere is absorbed by seawater. This changes the chemistry of the water and gradually lowers its pH, making it slightly more acidic.
Along the Oregon coast, naturally deep ocean water already contains higher levels of carbon dioxide. When this water is brought to the surface during upwelling, coastal waters can become more acidic than in many other parts of the world. Scientists are studying how these conditions affect marine species and ecosystems.
Source: usa.oceana.org
The ocean naturally absorbs carbon dioxide, helping regulate Earth’s climate. As carbon dioxide levels in the atmosphere have increased over time, the amount absorbed by the ocean has also increased. Although the change in ocean pH is relatively small, even small changes can affect marine organisms that are sensitive to water chemistry.
How Does Ocean Acidification Affect Marine Life?
Many marine animals, including oysters, clams, mussels, snails, and some tiny plankton, build shells or skeletons from calcium carbonate. More acidic water can make it harder for these organisms to build and maintain strong shells. Low-oxygen events can also affect bottom-dwelling species such as Dungeness crab and other animals that live near the seafloor.
Scientists have found that some shell-forming species may grow more slowly, develop weaker shells, or require more energy to support normal growth and development. Because these species are important food sources for other animals, changes at the base of the food web can affect the broader ecosystem.
In Oregon, oyster hatcheries were among the first to observe the effects of changing ocean chemistry on developing shellfish larvae. Their experiences helped draw attention to ocean acidification and sparked additional research along the West Coast.
What is Hypoxia?
Hypoxia occurs when oxygen levels in the water become too low to support many forms of marine life. Along the Pacific Northwest coast, ocean currents, seasonal upwelling, water temperature, and nutrient inputs can all influence when and where hypoxic conditions develop. In estuaries, river mouths, and other areas influenced by freshwater runoff, nutrient inputs can also contribute to algal blooms that may lead to low-oxygen conditions.
Along the Oregon coast, seasonal upwelling can sometimes bring naturally low-oxygen water onto the continental shelf. In some years, oxygen levels can drop enough to stress marine organisms or cause fish, crabs, and other animals to move away from affected areas.
Scientists have documented periodic low-oxygen events along the Pacific Northwest coast since the early 2000s. In severe cases, large numbers of bottom-dwelling organisms have been affected.
Why Does This Matter to Us at Otter Rock Marine Reserve?
The Otter Rock Marine Reserve and Marine Garden protect a diverse community of marine life, including mussels, sea stars, anemones, crabs, fish, and many other species that depend on healthy ocean conditions.
Researchers continue to study how changing ocean chemistry may affect Oregon’s nearshore habitats and the species that live there. Conditions vary from place to place and from year to year, making long-term monitoring especially important.
By learning about ocean acidification and hypoxia, visitors can better understand the challenges facing Oregon’s marine ecosystems and the value of scientific research, monitoring, and conservation efforts along our coast.
Research and Monitoring
Scientists throughout Oregon are working to better understand ocean acidification and hypoxia. Researchers from Oregon State University and members of the Oregon Ocean Acidification and Hypoxia Council monitor ocean conditions and study how marine species respond to changing environments.
By tracking changes in water chemistry and oxygen levels, scientists can improve our understanding of these processes and help coastal communities prepare for future changes.