Before the Tide Comes Back: Monitoring Rocky Shores at Golden Gate and Point Reyes

The intertidal zone is the strip of shore between the highest and lowest tides — sea floor for part of the day, open air for the rest. The San Francisco Bay Area Inventory and Monitoring Network of the National Park Service monitors five rocky intertidal sites along the coast, at Golden Gate National Recreation Area and Point Reyes National Seashore. In June 2022, a science communication intern went along.

Racing the tide

The crews start before dawn. To reach one Golden Gate site, the team eased down a short but very steep slope with their gear at six in the morning, having woken at four. The early start is the point: surveys are timed to the year's lowest tides, which expose the most shore. These extreme tides are driven largely by the gravitational pull of the full moon, and their timing varies.

Four hours later, the spot where the intern had been standing was under water deeper than her head.

What lives there

Life on rocky shores is hard — pounding waves, beating sun — and the species there are specialists:

• crabs, sunning their colorful claws;
• ochre sea stars, including a young one wedged in a crevice;
• anemones from smaller than a quarter to bigger than a hand — some of the large ones reportedly more than 60 years old;
• mussels, barnacles and algae.

How the monitoring works

The team worked fast, each person knowing their role, to finish before the tide returned:

Members of this team helped develop the monitoring protocol themselves.

Why it matters

Surveying year after year tracks changes in species diversity, distribution and abundance, and helps researchers understand the effects of disease, oil spills, climate change and ocean acidification.

Visit, or learn more

• Rocky intertidal monitoring · Pacific Coast Science and Learning Center · Multi-Agency Rocky Intertidal Network (MARINe)
• Tidepooling at Point Reyes · NOAA tide predictions

Sources

Based on "A Zone of Its Own - Adventures in Rocky Intertidal Monitoring," by Mosaics in Science intern Jailyn Hoskins, San Francisco Bay Area Network Science Communication Team, National Park Service, Golden Gate National Recreation Area and Point Reyes National Seashore; a work of the United States government in the public domain. Its photographs, credited jointly to the National Park Service, Environment for the Americas and the intern, are not reproduced; rewritten in hubnx's own words.