Lessons Learned from a Spring in the Intertidal Zone

Photographs by Andy Meislin

The intertidal zone is filled with all kinds of creatures. From anemones to mussels, limpets to sea stars, a wide range of organisms call the rocky shores home. This spring, undergraduate students dotted the shores while taking a field course on intertidal research. As a sophomore interested in marine biology but with very little experience exploring tide pools, the class was an introduction to all things fieldwork and an opportunity to literally get my feet wet. Throughout the quarter learning from Professors Jim Watanabe and Mark Denny along with TA Rachel Crane, we became more familiar with the creatures in the intertidal zone and developed independent research projects testing how they survive.

Neap tides are sleep tides.

Our class was scheduled every Tuesday and Thursday morning, but ocean tides don’t follow typical college schedules. Instead, the tides fluctuate in week-long periods, creating larger tidal ranges (and lower tides) twice a month during full and new moons. To put it simply, these “spring tides” occur when the Earth is aligned with both the sun and the moon. The gravitational pull of the sun and moon causes the ocean to bulge more than usual and create higher high tides and lower low tides. When the sun and moon are at right angles to each other (during the first and third quarter moon), the Earth experiences more moderate “neap tides.”  

From an intertidal research perspective, early morning “spring tides” were the prime time to head out. We would bundle up and hike down to the rocky shores at sunrise, taking advantage of the lowest tide of the day. We scampered around the boulders, peering into crevices to look for cool creatures and taking measurements about the environment. Every other week during the moderate “neap tides,” we slept through sunrise and instead attended lectures about the intertidal zone and the types of organisms that live in and around it. 


Taking measurements takes technique.

Something that became clear in the first few weeks of the course is that intertidal fieldwork is more than just getting soaked to the gills by waves while looking at cool organisms. Developing research questions and collecting data takes skill. Even seemingly simple measurements like height or surface area have standardized methods. Early in the quarter, we had a class on how to measure things and collect data in the intertidal zone. These methods ranged from traditional to wacky. Some, like temperature and height, used instruments such as thermocouple thermometers and optical surveying stations. Others got pretty creative. Do you want to know how to capture the surface area of a limpet? Cover it with aluminum foil! Want to keep track of snails? Find some brightly-colored “snail” polish and paint them!

Along with covering marine organisms with colorful nail polish, we learned how to ask questions in ways that could lead to answers. Closely observing patterns of adaptation and competition in the rocky intertidal can help reveal gaps in knowledge and potential research questions to explore. Some questions may not have clear answers, or the answers may be too complex for us to understand, but asking them in the right way may bring us closer to understanding how organisms survive and interact with one another.


Fieldwork is a team sport.

After learning how to ask research questions and how to collect data, we chose independent projects to work on throughout the rest of the quarter. My project explored the relationship of shell condition to the internal temperature of owl limpets. We observed some owl limpets with algae on their shells and some with other smaller limpets on their shells. Still other owl limpets had either both algae and limpet “riders” or a completely clean shell. That observation raised a number of questions. Is the owl limpet impacted by what’s on its shell? If it is impacted, how might that change how the owl limpet lives?

Two other students, Niza Contreras and Osanna Drake, also explored owl limpets. Together, we created a fieldwork team along with Mark and Rachel. The three of us would hike down to owl limpet walls with instruments (and datasheets!) and measure body and air temperature, limpet size and orientation and the condition of the limpet shell. By using walkie-talkies, we communicated with either Mark or Rachel to get height measurements of the limpets on the rock. Some of the best moments came when we got into a data collecting rhythm. Breaking up tasks among the group made taking measurements more efficient and allowed us to accomplish more during a single low tide.

Teamwork extended beyond the rocky intertidal. Throughout the quarter, we bounced ideas off of one another to gain a greater understanding of our research questions. Particularly for questions that don’t have a simple answer, getting second, third and fourth opinions about how ecosystems work can really help to shape our answers. Seeing the group aspect of research in action showed me another way that scientific work can be done. We learned a lot from each other by pooling our abilities, and that helped each of us succeed individually.


Nature is variable.

One of the main takeaways from the course was Jim’s common phrase: “Nature is variable.” The question of the impact of algae on owl limpet shells takes place mainly in the snapshot of spring. By summer, the algae burns off and would no longer have any impact on limpet internal temperature. The experience of a limpet in the rocky intertidal may change over the course of the year, and our questions might have been different had the class been taught in another season. Still, asking questions is important. The intertidal zone fluctuates and changes, but those changes are not just noise to ignore. Instead, learning how they shape ecosystems gives us a peak into the lives of organisms that call the rocky intertidal home.