Stinkin’ Seaweed Supports Students

by Megan Dethier, Alex Lowe, David Duggins

This is a story about a wonderful synergy between college students, life at marine labs, and research opportunities. Students at many stages in their careers come from all over the world to UW's Friday Harbor Labs, to take courses, work as an assistant for a scientist, or take part in the National Science Foundation (NSF) Research Experience for Undergraduates (REU) program. The students work as apprentices, guided by an instructor or mentor on individual research projects. The projects can range from studies directly related to research conducted by resident scientists at the Labs, to ideas inspired by students' own coursework or observations of nature. Because the time for these projects is usually a short 8-10 weeks, most constitute a “pilot study” where an experimental protocol is tested so that the scientist can follow up on the student’s work in a more rigorous fashion in the future.

Fig. 1: Wendel Raymond contemplates the enormity of a wrack pile on a coastal Washington beach. Photo credit: Annie Thomson.

Sometimes, however, the pieces fall together well enough to make the project publishable in peer-reviewed scientific journals. This happened with an effort within our research group to study how kelp tissues change as they die and begin to rot. While this may seem like an odd thing to care about, detached and degrading kelp blades are actually a very important part of nearshore food webs in many cold-water ecosystems. Kelps grow large and fast, but then either die seasonally (some kelps are annuals, like some garden plants) or eventually get torn from the rock by storms or strong tides, or have their stalks chewed away by sea urchins. This means that there is a lot of kelp mass that wafts around in local currents and eventually gets washed up on beaches and becomes “stinkin’ seaweed” (Fig. 1), or sinks into deep water. All this biomass is a very large potential food source.

Living kelps differ in their food quality, especially because some have anti-grazer chemicals that make them bitter and indigestible to animals like urchins - some of the most common subtidal kelps in San Juan County are like this. We wondered if rotting kelp - colonized by bacteria and with its tissue becoming softer - might be a better food source than live kelp, and if this might depend on the kelp species in question. The changes to rotting kelp might make it a great food source to animals that wouldn’t eat it otherwise.

Fig. 2: Students harvest sea urchin gonads (the orange colored material) for testing. Laura Watson, pictured here, was a high school intern who went on to attend Caltech.
Photo credit: Megan Dethier.

Over the course of two years, various members of our research group worked with 6 different undergraduates - 2 REU students, 3 spring-course students, and 1 fall-course student - to do projects that examined various facets of this question. These relationships benefitted the undergrads, as well as the technicians and graduate students who gained experience teaching, mentoring, and managing research. The problem-solving skills learned on both sides of the student-mentor relationship prove invaluable inside and outside of science, and require tools and techniques that can’t be purchased from or found on Wikipedia.

The students contributed many pieces to a larger nearshore food web study through their projects. One student project looked at whether small crustaceans prefer to eat fresh or rotting pieces of two different kelp species; another looked at how the caloric contents of kelps change as they rot; yet another looked at how well populations of copepods multiply when fed fresh or rotting kelp, and more students looked at how well newly-hatched isopods and adult urchins grow on these different diets. When we combined these studies with others from FHL scientists and graduate students, we found that together they told a coherent story about the fate of the kelp we see growing along the shore in the San Juan Islands. The nasty-chemistry kelp rots very slowly - probably because of the anti-grazer chemicals, which also tend to be anti-bacterial - but with most of the parameters we measured, the kelp gradually became better food as it rotted (Fig. 2). In contrast, the common Bull Kelp - a favorite among local kelp-consumers because it has very few of the anti-grazer chemicals - rots much faster and generally becomes a less preferred and less valuable food source as the process occurs (Fig. 3). We know little about the particular organisms (bacteria, fungi, etc.) that cause seaweeds to rot, but now we know that this process may be very important in terms of its effects on the food value of all the kelp biomass that washes onto the beach or sinks into deep water.

Fig. 3: Blades of Bull Kelp (Nereocystis luetkeana) as driftweed. Photo credit: Alex Lowe.

Because these diverse results were generally consistent, and because the issue of the fate of seaweed biomass is extremely important for deep-water ecosystems, our manuscript is now published in an excellent marine ecological journal (Journal of Experimental Marine Biology and Ecology vol. 460, p. 72-79). For most of the 6 undergraduate student authors, this was their first publication and they are thrilled to see their names in print! Such a concrete sign of their progress as a scientist is a significant boost to getting into graduate school or getting a job in a scientific field. In fact, of the manuscript authors: Alex Lowe is now a Ph.D. student in UW Biology, and this fall Wendel Raymond is entering graduate school at University of Alaska Fairbanks - Juneau and Morgan Eisenlord is starting in Cornell University's graduate program. And of course, the P.I. ‘grownups’ are happy about the publication too!

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