I have a special place in my heart for seaweeds – one of the first family photos presaging my life as a marine biologist shows me eating seaweed in Maine at the age of 2.  Robin’s photos in the essay below illustrate why as an adult I still appreciate seaweeds; they are so lovely and diverse in shape and color, even the non-edible ones!  They also can be a window into some of the complexities of how climate change is interacting with marine ecology.  Robin’s work shows that some species are likely to be more resilient to warming – both gradual slow warming and short-term heat waves – than others.  And she also shows how science at FHL managed to go on during the pandemic, even though plans had to shift.  We greatly appreciate this kind of flexibility and persistence!

Studying Seaweed in a Changing World

by Robin J. Fales

Robin is a Doctoral Candidate at the University of Washington in the Department of Biology and Friday Harbor Labs in the Carrington Lab.  She is originally from Southern California where she earned her B.S. in Ecology and Evolutionary Biology from University of California Irvine and a M.S. in Biology in the Coastal Ecology Lab at Cal Poly Pomona.  She moved to Washington to pursue a PhD in 2019 and started working at the Labs during 2020.  Her work at FHL has been supported by the FHL Research Fellowship Endowment Fund, North West Climate Adaptation Science Center (NW CASC) Fellowship, Robert T. Paine Experimental & Field Ecology Fellowship, Frederic H. & Kirstin C. Nichols Endowed Graduate Fellowship, Phycological Society of America Grant in Aid of Research, Richard R. and Megumi F. Strathmann Endowed Fellowship, and the Suzanne Ragen FHL Endowed Scholarship.

You might be surprised by how much seaweed is in our lives, from nori in sushi to cosmetics to fertilizer.  My favorite culinary use of seaweed is in ice cream (in the form of carrageenan) as a thickening agent.  My parents have joked that must be the reason that I love seaweed, since the dessert has been a lifelong favorite.

I study brown seaweeds that create habitat for other species — a seaweed canopy is a fantastic place for invertebrates and fishes to hide!  Specifically, I studied rockweeds for my masters, which are a group of brown seaweeds that live in the mid and high intertidal zones.  My masters work (Fales and Smith 2022) revealed long-term declines and local extinctions of a species of rockweed which provides important habitat where few other canopy forming seaweeds can live.  Due to the nature of the survey work and long-term studies that I performed (not experimental manipulations), the reason why these declines and local extinctions happened remains a mystery.  Therefore, I became motivated to ask more mechanistic questions about seaweed ecology and climate change during my PhD.  Working in Emily Carrington’s lab, I have learned new skills and techniques in eco-physiology (the response of an organism to environmental conditions) which allows me to seek answers to questions like “why have seaweeds declined?” or “which temperatures are most stressful?”

The Labs have been very influential on my journey to becoming a kelp eco-physiologist, especially since the world shut down during the first year of my PhD due to the pandemic.  In spring of 2020, I isolated at FHL and TAed the only virtual marine biology laboratory course.  I was proud of our efforts to bring FHL to students who could not attend in person, and being there allowed me to dive head-first into the natural history of the San Juans (Figure 1).  I was excited to learn to identify the species that flourish in the cold waters of Washington, many of which are not present in California.  Learning kelps was no small task because we have 22 (!) species in the Salish Sea, 17 of which were new to me.  That quiet first field season at FHL strongly shaped my research questions and scientific future.

Overall, my dissertation examines the response of habitat-forming kelp species to warming and other stressors, to inform conservation and management.  My initial plan to study bull kelp was delayed by the pandemic since I could not be trained on boats in 2020, so I pivoted to working on the intertidal kelp, sea cabbage (Hedophyllum sessile).  I found the daytime timing of the tides on San Juan Island extremely interesting because low tides along the rest of the west coast occur at earlier hours in the summer.  For example, low tides are around 3 a.m. in southern California in summer.  Even though the San Juans have moderate air temperatures, the timing of our low tides makes the region a thermal hot spot.  Therefore, I examined the response of sea cabbage to aerial heatwaves that coincide with low tide, like the 2021 PNW heat dome (Figure 2).  While the heat dome was an unfortunate event that caused mass mortality of intertidal organisms (Raymond et al. 2022), I was fortunate to be able to use it as a natural experiment.  I found very high survival of sea cabbage following the heat dome and propose that the strange cabbage-like morphology shades and protects the growing region which allows the kelp to recover after large amounts of bleaching, a form of irreversible tissue damage (see Figure 2b).

My goal of working on bull kelp eventually came to fruition through an exciting partnership and actionable science project with the Washington Department of Natural Resources.  This work focused on understanding differences in adult bull kelp’s response to warming across the Salish Sea.  I spent late spring/early summer this year traveling across the state of Washington sampling 8 kelp forests (Figure 3).  I selected sites to utilize the natural gradient of temperature across the Salish Sea to test whether populations responded differently to warm temperatures.  After collecting small pieces of kelp blades, I brought them back to the laboratory and incubated them at temperatures from 9 to 24°C (48 to 75°F) for 24 hours and then measured physiological rates of growth, photosynthesis, and respiration, as well as PAM fluorometry (a measure that assesses light harvesting efficiency in the chloroplast).  Together these metrics allow us to understand how the kelp is functioning across temperatures.  Ultimately, we found that all populations performed poorly above 21°C (70°F) indicating that this species is at risk due to warming temperatures, especially in hot regions like southern Puget Sound and the Strait of Georgia.  I am proud that this research is being used to support bull kelp conservation and management in Washington.

I hope that my current and future research will continue to help shape the future of kelp management and conservation.  In addition to seaweed science, I also love seaweed photography.  Below I share some examples of beautiful seaweeds from San Juan Island (Figure 4).

Please feel free to reach out to Robin by email at rjfales@uw.edu or Twitter (@intertidalecol) if you have any questions about this work.  Or see more of Robin’s seaweed photos on Instagram (@intertidalecologist).

References

Calloway et al.  2020.  Puget Sound kelp conservation and recovery plan.  Prepared for NOAA-NMFS, Seattle, WA.  https://nwstraits.org/our-work/kelp/

Fales and Smith 2022.  Long-term change in a high-intertidal rockweed (Pelvetiopsis californica) and community-level consequences.  Marine Biology.  doi: 10.1007/s00227-022-04022-1

Raymond et al.  2022.  Assessment of the impacts of an unprecedented heatwave on intertidal shellfish of the Salish Sea.  Ecology.  doi: 10.1002/ecy.3798

Weigel, Brooke.  Helping the kelp: Effects of ocean warming on bull kelp forests.  FHL Tide Bite.

White et al.  2023.  The unprecedented Pacific Northwest heat-wave of June 2021.  Nature Communications.  doi: 10.1038/s41467-023-36289-3