West Coast National Parks Work with NOAA to Better Understand Ocean Acidification in the Rocky Intertidal and Beyond

Rocky intertidal creatures with hard shells or exoskeletons, like these from Cabrillo National Monument, are among the many marine organisms that will be directly challenged by increasing ocean acidification (OA). Overall, the ocean has become 30% more acidic over the last 200 years, but not all parts of the ocean are being impacted equally. This summer, NPS and NOAA scientists are sampling OA up and down the West Coast and learn where the risks to marine life are greatest.

Michael Ready

On the surface, the Pacific Ocean might look like one big, homogeneous body of water. In fact, ocean conditions vary in all kinds of ways. Sea surface temperature, for example, is usually different in different places. In the same place, it often varies at different times of year or from one year to the next. The same is true of ocean chemistry, including ocean acidification (OA).

What is ocean acidification?

The ocean naturally absorbs over a quarter of the carbon dioxide (CO2) in the atmosphere. So as a result of rising atmospheric CO2 concentrations from burning fossil fuels, levels of CO2 in the ocean are also increasing. When CO2 enters the ocean it reacts with sea water and forms carbonic acid (H2Co3). Carbonic acid is a weak acid which separates or dissociates into a hydrogen ion (H+) and a bicarbonate ion (HCO3-). As more hydrogen ions are formed from this reaction, the pH of the ocean is decreasing, meaning it is becoming more acidic. This is called ocean acidification (OA).

Over the last 200 years, the ocean has become 30% more acidic. The last time it was this acidic was over 300 million years ago. This is presenting new challenges for marine life, and especially for organisms with hard shells and skeletons like oysters, mussels, crabs, and corals.

Learn more about OA and how it impacts marine life in national parks.

Seven West Coast national parks are teaming up with the 2021 National Oceanic And Atmospheric Administration (NOAA) West Coast Ocean Acidification (WCOA) Cruise to check several OA indicators up and down the coast. The NOAA research cruise vessel is the Ronald H. Brown.

Image courtesy of Wes Struble/NOAA

Like sea temperature rise, OA is a huge threat to marine life. But for now, it is harder to track remotely on a large scale. So this summer, seven West Coast national parks are teaming up with the 2021 National Oceanic And Atmospheric Administration (NOAA) West Coast Ocean Acidification (WCOA) Cruise. They’ll collect water samples in-person to check several OA indicators. Their data will help paint the most detailed picture yet of OA conditions up and down the coast, from parks’ rocky intertidal zones to dozens of miles offshore.

The National Park Service (NPS) and NOAA tested a similar collaboration for the first time during NOAA’s 2016 WCOA Cruise. As scientists aboard the NOAA ship collected water samples offshore of Cabrillo National Monument and Olympic National Park, scientists at the parks collected samples from their intertidal zones. This time, scientists at Cabrillo National Monument, Channel Islands National Park, Olympic National Park, Point Reyes National Seashore, Golden Gate National Recreation Area, Redwood National Park, and Lewis and Clark National Historical Park will participate.

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The 2021 WCOA cruise will head from north to south. Along the way, it will pause to travel along over a dozen established transects perpendicular to the coast. That will allow the scientists on board NOAA’s Ronald H. Brown research vessel to collect water samples at different depths and distances from shore. Olympic will be the first park site it reaches in late June. When it gets there, the scientists at Olympic will have their sampling gear ready to go. Coordinating the timing of the sampling means the samples can be used to help decipher the spatial patterns of OA from the very edge of the shore, out to the sea.

NPS scientists with a freshly collected water sample from the Cabrillo's rocky intertidal zone in 2016. This year, scientists from seven parks will collect water samples from their rocky intertidal zones as scientists with the 2021 NOAA WCOA cruise collect samples offshore of their respective parks.

NPS / Alex Warneke

Other important patterns could emerge as well. That’s because the scientists will be collecting data on other potential stressors like temperature and dissolved oxygen levels in addition to ocean pH. Abnormally high temperatures or low oxygen could worsen the negative effects of OA on marine life. Thus, the scientists will be on the lookout for patterns of overlap between more acidic conditions and those other stressors. They’ll even be able to see how some marine life is responding to different combinations of stressors by checking for tiny sea snails called pteropods in their water samples. The abundance, diversity, and shell-condition of these creatures could all hold new clues about impacts to marine life more broadly.

For the NPS, the collaboration’s findings may help answer key questions like, “Which parks’ intertidal communities are at greatest risk from OA?” In addition, the participating national parks are part of an extensive network of rocky intertidal monitoring sites from Alaska to Mexico. Their OA sampling will provide a valuable link between the broader West Coast OA and long-term rocky intertidal data sets.

Rocky intertidal monitoring in Olympic National Park. The national parks participating in OA sampling are also part of a network of rocky intertidal monitoring sites stretching from Alaska to Mexico. The sampling will serve as a link between the broader West Coast OA and rocky intertidal data sets.

NPS

Of course, the West Coast is not the only place where OA is a concern for parks. It’s also not the only region where NOAA and NPS will be working together this year. Stay tuned for more information about upcoming OA cruises collaborating with parks along the Gulf of Alaska, Gulf Coast, and East Coast.