Rocky Intertidal Communities Monitoring

Sea anemone surrounded by several purple urchins in a tidepool
Sea anemone and purple urchins in a Santa Cruz Island tidepool.

NPS / Jessica Weinberg McClosky

Why We Care

Some of the best examples of rocky intertidal habitat in southern California occur at parks in the Mediterranean Coast Network. The rocky intertidal zone is an area between marine and terrestrial habitats where organisms living within this zone are well adapted to alternating exposures to both the air and sea. The "undisturbed tidepools" are unique features specifically mentioned in the enabling legislation establishing Channel Islands National Park.

Despite the intertidal community's resistance to the drying sun and pounding surf, it is vulnerable to impacts caused by humans. The diversity of species offers visitors a chance to experience a relatively pristine intertidal marine community. Cabrillo National Monument in San Diego hosts tens of thousands of visitors to the tidepools each year. However, visitors can cause damage through trampling, rock turning, or removal of organisms. Pollution is also a major threat to intertidal organisms, being particularly vulnerable to major oil spills.

Because the rocky intertidal community is a major significant ecosystem on the islands and is susceptible to human-caused disturbances, Channel Islands National Park began long-term monitoring of the rocky intertidal zone in 1982 and Cabrillo National Monument began monitoring in 1990.

How We Monitor

Park researchers monitor twenty-one sites on five islands twice each year at Channel Islands National Park.

  • Fixed photoplots and point-intercept transects are used to monitor the percent cover of core species.
  • Circular plots and timed searches are used to collect information on size distribution and relative abundance of owl limpets, black abalone and ochre sea stars.
  • Data are submitted to the Multi-Agency Rocky Intertidal Network (MARINe), a regional consortium of government and non-government entities established to standardize the collection of rocky intertidal data throughout the Pacific coast
Park staff person pointing something out in a rocky intertidal monitoring plot
Monitoring a rocky intertidal plot at Cabrillo National Monument.


Cluster of at least four large black abalone in a rock crevice
Black abalone are a rocky intertidal monitoring focal species. Monitoring helped shed light on their dramatic population decline, and informed actions such as the closure of the black abalone fishery in southern California. Black abalone were federally listed as endangered in 2009.

NPS / Steve Whitaker

Our Goals

  • Determine the long-term trends in percent cover of thirteen key sessile organisms in the rocky intertidal ecosystem.
  • Determine population dynamics of black abalone (Haliotis cracherodii), owl limpets (Lottia gigantean), and ochre sea stars (Pisaster ochraceus)

Why It Matters for Park Managers

  • Results from monitoring are used to improve our understanding of rocky intertidal zone ecosystems, identify seasonal patterns to inform management decisions concerning visitor use, identify marine ecosystem issues (i.e. disease, effects of climate change, fishery impacts), and inform regional assessments of sensitive species status.
  • Monitoring has confirmed depletion of several marine populations and supported management actions including the closure of black abalone fishery in southern California.
  • Monitoring showed the dramatic effects El Niño could have on ochre sea stars and mussels (Mytilus californianus).

For More Information

Download 1-2 page PDFs about the Mediterannean Coast Network's monitoring programs.

Source: Data Store Saved Search 3548. To search for additional information, visit the Data Store.

The Mediterranean Coast Network documents its findings in reports published in the NPS Natural Resource Publication Series.

Source: Data Store Saved Search 1510. To search for additional information, visit the Data Store.

Protocols describe in detail the procedures used to collect, manage, analyze and report monitoring data. They follow strict guidelines for content and format, and are reviewed and revised by subject-matter experts in each field.

Source: Data Store Saved Search 1522. To search for additional information, visit the Data Store.

Last updated: September 24, 2021