On the Edge: The Curious Lives of Intertidal Organisms and How We Monitor Them (U.S. National Park Service) (2024)

The rocky intertidal zone is resilient, but it is also delicately balanced. As we have just learned, changes in a single population could have major consequences on the food web. This is one of the reasons why it is important to monitor populations within the intertidal zone. A current example is sea star wasting disease, which has caused the ochre sea star to suffer major die offs since 2013. As a top predator in the intertidal food web, the ochre sea star is a keystone species. Keystone species have a disproportionate effect on their ecosystems relative to their population size. A major decline in sea stars could have a ripple effect on other populations. Monitoring offers an opportunity not only to track disease progress, but to monitor population decline and recovery among both sea stars and the many organisms they interact with.

In the Redwood National and State Parks (Del Norte County, Calif.), the Klamath Inventory and Monitoring Network has collaborated with University of California­–Santa Cruz scientists to routinely monitor three rocky intertidal communities since 2004: Enderts Beach, Damnation Creek, and False Klamath Cove. These three sites are also part of the Multi-Agency Rocky Intertidal Network (MARINe), a coastwide monitoring program that includes several national parks as well as local and state governments, universities, and private organizations.

You may find yourself wondering: What do researchers look for? How do they collect data? Upon arriving at a site, researchers note the time of day, weather, tide level, presence of debris, and the count of birds, marine mammals, and humans. After their initial observations, researchers have two goals: assess the site’s biodiversity, and check in on the target species. At all the participating MARINe sites from California to Alaska, there is a list of core species that researchers may encounter at a site. These species are chosen using a set list of criteria. Researchers then select target species from that list based on their presence and abundance at a specific site. Each population is monitored using long-term, fixed plots. A fixed plot does not move, even if the species living in it move. Many of the target species are sessile, or sedentary, so their fixed plots are relatively small. Mobile organisms have larger fixed plots to accommodate their daily movement. At the three sites in Redwood National and State Parks, the target species are:

If a target species population changes, an invasive species arrives, or a disease starts appearing, researchers make sure to keep an eye on it. Between 2004 and 2018 at these three sites, some changes occurred, but there have been no major changes in community structure. For example, sometimes a storm event will remove all or part of a mussel bed, so the mussel population may decline. But over time, those mussels return, and the population recovers. Population recovery suggests that a community is stable. The Klamath Network regularly reports on intertidal community conditions at these sites.

The constantly changing conditions of the rocky intertidal zone characterize it as a disturbed ecosystem. Some aquatic and terrestrial ecosystems are disturbed primarily by human activity, but the rocky intertidal zone in Redwood National and State Parks is different. The natural disturbance of changing tides plays a much bigger role in shaping this ecosystem. Unfortunately, many rocky intertidal zones suffer from human impacts too. Sea-level rise and warming waters caused by climate change threaten all marine communities, as does pollution (especially plastic and oil). Intertidal zones can also be degraded by overuse. Because of the unique organisms that live there, tidepools are a popular destination for visitors, and not everyone is well-educated on how to visit without harming organisms. Human impacts, large and small scale, can upset the delicate balance in this incredible ecosystem. This is not to say that people shouldn’t visit! We just need to tread lightly and treat the intertidal zone with respect.

Let’s return to your trip. Perhaps you found a sea star, a bed of mussels, and an anemone. Perhaps a shore bird landed nearby and flew off with a crab in its beak. Whatever you saw, hopefully you have a better understanding for this incredible place, and hopefully you are curious to learn more. When the tide begins to come in again, you retreat onto the sand and watch as this magic little world disappears under the water. It is hidden for now, but it will be back tomorrow. Will you?

Visit the Redwood National and State Parks website for more information on getting to Enderts Beach, Damnation Creek, and False Klamath Cove, ocean safety, and responsible tide-pooling.

Explore the MARINe website to learn more about target species, monitoring protocols, and the participating sites along the coast.

Learn more about the Klamath Network rocky intertidal monitoring program.

Article by Natalie DiNenno, Southern Oregon University science writing intern for the Klamath Network, as part of the Fall-Winter 2022 Klamath Kaleidoscope newsletter.