A classroom at the edge of the Sea of Cortez

One of the educational highlights of my life occurred during my senior year (late 1998) as an undergraduate at UC Santa Cruz. I enrolled in a wonderful quarter-long intensive course in marine ecology. The plan was to spend the first 5 weeks in Santa Cruz and the last five in the upper Gulf of California in northern Mexico. By this point in my education, I had been able to take a number of excellent courses in marine sciences – invertebrate zoology, marine botany – and I was ready to apply to graduate school. I didn’t know initially if I’d get into the class (an interview was required), but I had taken scientific diving the previous academic year so that I would be able to dive as part of the experience if I made it into the course.

I was reminded of this trip this part fall as I attended the annual Western Society of Naturalists meeting in Seaside, California. Per tradition, a naturalist of the year award is given at the meeting to a prominent ecologist or naturalist. This past year, it was given to Peter Raimondi and his long-time colleague at Santa Cruz, Mark Carr. Pete was one of the instructors for our class to the Gulf. In fact, our group of 20 or so eager undergraduates was the first cohort of the marine ecology field course that has since become an important part of the marine ecology curriculum on the Santa Cruz campus. From Pete’s remarks at the meeting, I learned that the inspiration for the course came from an earlier Santa Cruz course taught by the naturalist Ken Norris. In fact, Dr. Norris’s work led to the creation of the UC Natural Reserve System, a collection of research reserves throughout the state that sample the diversity of California’s ecosystems.

A unique aspect of the marine ecology field course – and a logistically challenging one to be sure – was the opportunity to dive in the subtropical waters of the Gulf of California. I logged about 9 dives during our stay in Mexico. The warmer diving in northern Mexico was a welcome change from the cold waters around Monterey where I had previously done all of my diving.



CEDO in Puerto Penasco, Sonora, MX.

Once we arrived in Mexico, we were required to participate in group research projects to get our feet wet in marine research, so to speak. My main project was conducted with a fellow student Derek Smith. Together we investigated whether shading impacted the abundance of zooxanthellae in a colonial anthozoan, Palythoa ignota. Zooxanthellae are symbiotic dinoflagellates that provide food for coral polyps. The idea was hatched at our first stop in Mexico, the Intercultural Center for the Study of Deserts and Oceans (CEDO) in Puerto Peñasco. If memory serves me correctly, we had had a hard time deciding on a project to conduct, but got a burst of inspiration (or some helpful prodding from course instructors) shortly before we were scheduled to leave for our next site farther south. With time running short, we had to quickly assemble some field gear and get out to the rocky intertidal to deploy the experiment.

The plan for the experiment was simple: we would construct cages with mesh coverings and cement these to the rocky substrate over colonies of Palythoa to reduce the amount of ambient light reaching the anthozoans. Palythoa isn’t a high intertidal species, so we needed a low tide to access the site and it happened that our window of opportunity occurred in the dark. With lamps and some assistance from other students, we went about the messy business of removing organisms from the rocks in order to secure our cages to the benthos. The experiment was set and we’d be back to Puerto Peñasco towards the end of our stay in Mexico to collect the data.


Left: A small colony of Palythoa polyps. Right: Our experimental manipulation
 of light level at the subtidal site. The cage in the middle is the classic cage control.

About a week later we found ourselves at Guyamas along the central coast of the Sea of Cortez.  Here, Palythoa only grew subtidally. We selected a second site to conduct a repeat experiment that was accessible only after a decent boat ride to a place removed from the city. We again placed our cages into colonies of Palythoa. Though our sites were admittedly very shallow, at least one of us needed to dive to make the clearings on the substrate, cement the cages to the rock, and later sample the animal tissue to count zooxanthellae cells.

We stayed in Guyamas for a week to ten days, and sampled the cnidarian tissues before leaving to count the density of zooxanthellae. Derek committed the needed manpower, doing all of the microscope work. As it turns out, we were fortunate to have conducted this repeat experiment. Once we returned to Puerto Peñasco for the second time, regrettably many of our cages in the intertidal had been lost. There were not enough surviving cages to really test our shading effects on cell counts.

My experiences in the outdoors classroom of Mexico were notable in several ways. To begin with, my work with Palythoa was the first manipulative experiment I had ever conducted. Manipulative experiments are the bread and butter of experimental ecology, the most conclusive way to infer causal mechanisms about ecological processes. During the course I was also exposed to new habitats and new organisms in northern Mexico. I saw my first mangroves, for instance. I also had a chance to conduct science in teams. The course was a wonderful opportunity to make some great friends. (Oh, and did I mention that real Mexican tortillas are amazing!?)

The value of field research for biologists can’t be overstated. To get it early in one’s career and in large doses is a blessing. While science inevitably involves background research in libraries, time pouring over data and statistics, and digestion of theory (and I enjoy each of these in respectable quantities), none of these other activities can compensate for observation and experimentation in the field. Natural history is not just a quaint discipline of the 1800s, it is the foundation of meaningful ecology. It is integral to the generation of hypotheses and the interpretation of the relevance of experimental results. It also goes beyond the role of science as a human endeavor– it connects us to our immeasurably rich natural heritage.


An urchin - one of my better underwater shots in Mexico.

Sunset at Punta Ingacio at Bahia Kino along the Gulf coast.

Incredible plants: the sea palm

The sea palm, a rocky intertidal kelp found along western North American shores is one of the most distinctive seaweeds in the world. In shape it is remarkably similar to terrestrial palm trees; it has a knobby holdfast for firm attachment to the rocks, an elastic stipe for flexibility, and a tuft of drooping rugose blades at the top. The species name is Postelsia palmaeformis and it was first described by western science in 1852 based on collections made during a Russian expedition to western North America in 1839 (Abbott and Hollenberg 1976).

 

Individual sea palm (left) and grove (middle) at Carmel, Monterey Co, CA. Close-up of the holdfast on a plant at Gleason Beach, Sonoma County, CA. (right).

Postelsia is distributed on rocky shores from central California to British Columbia. It occurs at about the middle intertidal zone, so only a moderately low tide is necessary to see it exposed. However, it is not among the safer seaweeds to hunt for along the coast since it grows on highly-wave exposed shores where it is beaten by the surf. Research by Paul Dayton and Robert Paine in Washington State has shown that this wave energy is necessary for persistence of this annual species in the rocky intertidal (Dayton 1973, Paine 1988). Sufficient wave action removes carpets of sessile mussels, giving the sea-palm bare space to colonize. Or, in some cases, juvenile palms settle on mussels or algae and eventually cause both species to get removed by waves from the rock and open more space – a sort of suicide for the good of the species (Dayton 1973). Without the assistance of physical disturbance, mussels would dominate the rocks leaving no space for Postelsia.



A grove of Postelsia at Glass Beach in Mendocino County, CA takes an incoming wave.



Newly recruited sporophytes, Gleason
Beach, Sonoma Co., CA.

Sea-palms occur in gregarious patches because their spores typically only disperse short distances (Dayton 1973). Perhaps during rising tides, spores drip from the hanging fronds of the plant onto adjacent rocks and settle rapidly (Paine 1988). There they germinate into a microscopic stage of the kelp life cycle known as the gametophyte. Sperm from male gametophytes fertilize eggs attached to female gametophytes, and there start a new generation of adult plants (the sporophytes).



Sampling some "sea crunchies"
(dried sea palm blades) made by a
company in northern California.

Like some other seaweeds, Postelsia is edible. Seaweeds tend to be rich in minerals like iodine, but they may also have high levels of more toxic metals, so they should probably be eaten only in moderation.










References
Abbott, I.A. and G.J. Hollenberg. 1976. Marine Algae of California. Stanford University Press, Stanford, CA.
Dayton, P.K. 1973. Dispersion, dispersal, and persistence of the annual intertidal alga, Postelsia palmaeformis Ruprecht. Ecology 54:433-438.
Paine, R.T. 1988. Habitat suitability and local population persistence of the sea palm Postelsia palmaeformis. Ecology 69:1787-1794.

Shasta!

I went to northern California this week for a retreat of sorts and didn’t plan to have a nature adventure. However, by northern California the sun had burned away the dreariness of the Northwest and there was a beautiful crisp blue winter sky … and Mt Shasta! This majestic mountain, full of bright white snow loomed in a cloudless sky. I’ve passed Mt Shasta many times and long been impressed at it’s stature – a mountain over 14,000 feet and the second tallest peak in California, only a bit behind Mt. Whitney. It is almost the southern-most of the Cascades, the volcanic range of the western US.

I briefly explored the juniper-covered slopes on the northern side of the mountain, including Pluto’s Cave, a wide-mouthed, dank depression set in the volcanic landscape. The junipers were not really shrubs, but more like full fledged trees. They dominate an interesting landscape in this part of northern California, dry habitat that is a little western finger of the Great Basin (Baldwin et al. 2012). I didn’t take a close look at the trees, but based on their height and the bluish berry-like cones I observed on one tree, at least some may have been Juniperus occidentalis, one of 5 species of junipers in California (Baldwin et al. 2012). As I continued south in the late afternoon, the valley darkened but Shasta kept glowing, the pure white of the mountain turning to a golden pink.

Reference:
Baldwin et al. 201.2 The Jepson Manual. Vascular Plants of California. University of California Press.