divers ready on the bow
Getting ready to do science underwater – photo by P. Kitaeff

West Coast Laboratory and Field Research

My field research at Friday Harbor Labs during summer 2021 and 2022 was supported by a Bates College Faculty Development grant ($7,500); my research in 2019 and 2020 was also supported by a Bates College Faculty Development Grant ($9,482), an additional Bates research grant ($3,000), and a Friday Harbor Labs Dudley Fellowship ($1,500).

p.producta on bottom
Kelp crab on benthic kelp – photo by M. Dittrich

Effects of an invasive seaweed (Sargassum muticum) on nearshore subtidal habitats in the Salish Sea

We are beginning to explore the effects of invasive wireweed (Sargassum muticum) on nearshore habitats through a combination of field habitat surveys to map annual distribution and abundance, laboratory feeding experiments to assess native herbivory preferences, and sample collection (via snorkel) to quantify changes in C:N and chemical defenses across the growing season.

Long-term monitoring of intertidal seaweed communities at Cattle Point

In the early 1970s, the marine algae class at Friday Harbor Labs established semi-permanent, marked transects that span a range of wave exposure levels and substrate types on the south end of San Juan Island. With many collaborators, I have collected data at these same transects (using the methods established in the 1970s) since the summer of 2012. We hope to use these data to assess whether intertidal seaweed communities have changed over the past 40 years and how much communities vary from year to year. Many students, from high school to graduate level, have successfully employed their real-world seaweed ID skills and contributed greatly to this project!


Counting crabs and kelp (snorkeling for science)

Since 2019, I have collaborated with students (including snorkelers in the FHL marine subtidal ecology courses in 2021 and 2022) and colleagues to collect data about bull kelp abundance/density (0.5 m^2 quadrats) as well as kelp crab abundance and distribution at three sites on San Juan Island: Cattle Point, Deadman’s Bay, and Eagle Cove.IMG_2314

Laboratory feeding experiments

My collaborators and I continue to collect data to further elucidate ecologically-relevant feeding preferences of the Northern Kelp crab (Pugettia producta) and the graceful kelp crab (P. gracilis) AND sea urchins (genus Strongylocentrotus), including:

  • effect of encrusting bryozoans on the growth and feeding behavior of green urchins – with Demi Carballosa
  • effect of temperature on kelp crab (genus Pugettia) feeding rates and preference – with Cara Womacks, Katrina Johnson, Shelby Fox, Natalie Meenan, and Sasha Seroy
  • preference for vegetative vs. reproductive bull kelp (Nereocystis luetkeana) – with Muriel Dittrich, REU, Friday Harbor Labs and University of Alaska Southeast
  • feeding preferences on native and non-native brown algae in the Salish Sea – with Katrina Johnson, Bates College
  • feeding preference of sea urchins (Mesocentrotus, Strongylocentrotus) on native and non-native seaweeds in the Salish Sea – with James Calhoon, Bates College
  • preference for different ages (juvenile, adult) and structures (blade, stipe) of bull kelp (Nereocystis luetkeana) – with Bryce O’Brien, Bates College
  • preference for wireweed (Sargassum muticum) in the absence of morphology, using artificial food (a.k.a. “macroalgal jell-o”) – with Declan Farr, REU, Friday Harbor Labs and University of Southern California
  • analysis of gut contents of field-collected Northern and graceful kelp crabs (genus Pugettia) around the Salish Sea – with Kasey Cordova (REU) and Dr. Megan Dethier, Friday Harbor Labs

Underwater science and interactions between native, annual and non-native, perennial seaweeds

We transplanted bull kelp (N. luetkeana) and wireweed (S. muticum) onto concrete blocks and deployed them in the nearshore subtidal (~3 m depth) to assess whether non-native wireweed competes with native, annual bull kelp.

“Kelp-on-blocks” setup, summer 2020

I established new subtidal 2×2 meter plots near Point Caution, San Juan Island in summer 2019 to quantify what juvenile bull kelp compete for: space or light. The four treatments are: cleared and unshaded, cleared and shaded, cleared and partially shaded, and uncleared and unshaded. We found that light is the most important factor structuring where new bull kelp sporophytes begin to grow.

My collaborators and I are also interested in understanding variation in wireweed (Sargassum muticum) distribution and abundance from year to year, as well as the level to which local consumers (like the Northern Kelp crab) use this invasive seaweed as a habitat or food source. We tagged and measured S. muticum in spring and summer 2019 and also completed surveys to count kelp crab abundance – this work will continue into 2021 and beyond.

East Coast Field Research

Maine Coast

While at Bates College, I have worked with students in two courses to establish permanent intertidal transects at three sites around the Gulf of Maine in collaboration with the Northeastern Coastal Stations Alliance (NeCSA). These three sites are located on the Phippsburg and Harpswell Peninsulas and vary in substrate, wave exposure, and level of human impact. This work is especially timely because the Gulf of Maine is currently changing rapidly in terms of temperature, pH, and salinity.

My Bates thesis students and I  investigated how sessile species diversity and the presence of more resilient species changes between sites and seasons. We also recently deployed a temperature sensor at one of our sites.

In the future, we hope to combine our data with data from NeCSA partners to help provide a broader view of how intertidal regions around the Gulf of Maine are changing.

Past Research

Clam Crushing

I worked with Dr. Megan Dethier and her lab group at Friday Harbor Labs to quantify shore crab (Hemigrapsus sp.) feeding preferences for juvenile clams across a range of sizes. Our aim was to calculate feeding rates and determine preferences using laboratory experiments. It is possible that very small crabs, usually not considered to be significant predators, may be responsible for very high field mortality of newly settled clam spat before the baby bivalves achieve a size refuge. We utilized microscopy and imaging software for morphological measurements, such as dactyl length of shore crab claws. We used a Materials Testing System (MTS) to compare the force required to crush the shell of different types of juvenile clams, including softshell (Mya), Manila (Venerupis), and the invasive Varnish (Nuttallia) clams, across an ontogenetic range of sizes. Going forward, we will investigate the force produced by shore crab claws across a range of sizes and how that relates to ability to crush clam species of interest. This is especially valuable information for shellfish growers who seek to protect their “crop” from predators.

Kelp Pulling

In collaboration with Dr. Stephanie Crofts (University of Illinois – Urbana-Champaign), I am conducting ongoing research on material properties of juvenile bull kelp. We have shown that morphology is an important determinant of where juvenile bull kelp fail under tension and that some of the material properties of juvenile bull kelp vary. These factors indicate that drag, which is a major factor influencing mature bull kelp, may be less of a constraint for small individuals of this annual species. Our future work will assess how damage from common kelp consumers (gastropods, crustaceans, echinoderms) changes the force required to cause juvenile bull kelp stipes to fail. We also aim to compare the breaking force required in juveniles of other kelp species with different morphology and life history patterns.


I collaborated with Dr. Chelsea Wood and her lab group in the School of Aquatic and Fisheries Sciences at the University of Washington to look at parasite prevalence across trophic levels using published papers that quantify the abundance of these parasitic nematodes.

Crab Claw Morphology and Feeding Preferences

I worked on crab claw morphology and feeding preferences with two collaborators (Dr. Stephanie Crofts and Dr. Marianne Porter, Florida Atlantic University) as well as several undergraduate students at UW/FHL and FAU who have assisted in data collection and photo analysis. Crustaceans, such as the Northern Kelp Crab (Pugettia producta), are found in kelp bed food webs but feeding patterns and trophic impacts can be challenging to quantify in the field. Some crab species, such as Dungeness (Metacarcinus magister) are defined as specialized shell-crushers, while many other crabs are thought of as generalist detritivores. A better understanding of how morphology relates to feeding choices will facilitate interpretation of changing trophic relationships between invasive and native species and as species’ ranges expand as a result of global changes in the ocean.

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