If Seaweed Could Talk

Renowned phycologist and marine ecologist Susan Brawley discovered that even the simplest organisms can teach us profound lessons.

By Olivia Milloway and Catherine Schmitt

Older woman in green hip boots speaking to a younger woman holding a pad, pen, and cellphone. They're outside on a rocky, algae-covered stretch of coastline with the ocean behind them.
Brawley (left) talks to author Olivia Milloway about changes along the shoreline of Schoodic Point.

Image © Schoodic Institute / Catherine Schmitt

It was a cold, cloudy afternoon in the middle of December 2021, and the tide had ebbed from Schoodic Point’s hard granite rocks. Against a neutral palette of stone and sea, the withdrawing surf exposed a kaleidoscope of jewel tones: deep red seaweeds, brown strands of rockweed, green sea lettuce, and hard pink skeletons of coralline algae. “The rocky shores of Acadia National Park harbor a thriving community of marine algae,” said Susan Brawley, as she carefully cut pieces of seaweed from the rocks. “That can tell us something about the past and future of life on Earth.”

“The rocky shores of Acadia National Park harbor a thriving community of marine algae that can tell us something about the past and future of life on Earth.”

Continuing a century-long legacy of intertidal research along these shores, much of it by women, Brawley has visited this portion of Acadia National Park since 1989. That’s when she left Vanderbilt University for the University of Maine, and Schoodic Point became her field station. At that time, she likely had no idea that her work in the park would result in dozens of scientific papers, involve hundreds of students, bring her fame in phycology (the study of algae), and connect fellow marine scientists all over the world with Acadia National Park.

Patch of exposed intertidal seaweeds and algae in a patchwork of smooth and shaggy textures, and jewel tone shades of green, red, and pink.
Many different kinds of macroalgae grow in Acadia's intertidal zone.

Image © Schoodic Institute / Catherine Schmitt

In those early days, Brawley collected material to study algal reproduction in wave-tossed environments. Then she moved on to cellular structure and DNA. She considered things like whether waves dilute sperm and eggs before fertilization occurs, how some algae tolerate freezing and heat stress, and the genetic code of one species of red algae, Porphyra umbilicalis. Surprising as it may seem, the answers to questions like these give clues to how life evolved on Earth and what the future holds.

Woman in green hip boots and a warm coat standing in a tidepool, backlit by early morning sunlight. She's just scooped something out with both hands. Water is dripping down from her hands forms concentric circles across the surface of the tidepool.
Brawley scoops water from a tide pool to examine small swimming animals known as amphipods, which feed on certain kinds of algae.

Image © Schoodic Institute / Catherine Schmitt

Porphyra umbilicalis, also known as purple laver, is related to the fossil alga, Bangiomorpha, one of the oldest fossils on Earth and the first organism known to reproduce through sex. “In their long history on Earth, these algae have survived mass extinctions but lost some of the cellular pathways and motor proteins that most organisms—including humans—retained,” said Brawley. “Yet still they thrive. This is an environmental testimonial to adaptation.” To know something about how ancient life developed and persisted enriches our own life in the present. It provides perspective on our place in a vast and still mysterious universe.

Humans have a microbiome too, and just as for humans, these tiny organisms are vital to the proper growth and development of their algal host.

Most recently, Brawley is studying the makeup of the algal microbiome—its personal collection of bacteria—on both sides of the Atlantic Ocean. Humans have a microbiome too, and just as for humans, these tiny organisms are vital to the proper growth and development of their algal host. Brawley’s results showed that the microbiomes of Fucus vesiculosus (also known as bladderwrack) on both shores of the Atlantic resemble each other at similar latitudes but vary from northern to southern latitudes.

This geographic pattern is likely an adaptation as the species contracted and expanded its range in response to past glacial cycles and recent environmental conditions. Experimental transplants of Fucus at Schoodic Point showed that algal microbiomes are also likely influenced by environmental stress—the degree to which they are exposed by the tides. In a time of rapid and significant climate change, large-scale shifts in the microbiome under stress could affect the host organism in ways that might serve as a warning to humankind. As author Ed Yong wrote, we “contain multitudes.” Thinking of each of us as a living community rather than a single entity might help with our own tolerance to stress and adaptation to change.

Close-up of mounds of green-brown algae, some of it glowing in the early morning sun rising over the evergreen trees out of focus in the distance. Lens flares arc across the image
Late afternoon sunlight filters through fronds of Fucus vesiculosus on the Schoodic Point shoreline. Algae like this have produced half of the oxygen in Earth's atmosphere and form the base of many marine food webs.

Image © Schoodic Institute / Catherine Schmitt

“No Algae, No Living Earth”

When Brawley was twelve years old, she left her home in Charlotte, North Carolina, for a three-day field trip to the Duke Marine Laboratory led by Harold Humm. She remembers every moment, including collecting her first specimen of Fucus, and shortly afterwards—before entering high school—she started working in Humm’s laboratory.

The disappearance of an organism that, with other algae, has produced half of the oxygen in the atmosphere is concerning.

The Fucus that Brawley collected on southeastern U.S. shores more than fifty years ago is now gone. Shifting microbiomes could be one reason why. The disappearance of an organism that, with other algae, has produced half of the oxygen in the atmosphere, setting the stage for evolution of other organisms, is concerning. Fucus and other algae are also the base of many marine food webs and create habitat. As Brawley put it, “No algae, no living Earth as we know it.”

“The microbiome is absolutely required for normal growth, [so] anything that disturbs that microbiome, such as warming waters or hotter air exposures at low tide, could do it,” said Brawley. “These are very deep relationships that have evolved over tens of thousands of years or more. It makes me feel terrible. Climate change and the dastardly things that are happening, it’s really personal.”

Changing Patterns

When extreme low tides arrived again at Schoodic Point in November 2022, Brawley met her field crew in a parking lot near the shore. As crew members organized their gear, she told them about the motor proteins and cytoskeletons of seaweed. The team, a group of early career ecologists, was excited about an afternoon of collecting specimens. Once at the site, just off the road to Schoodic Point, Brawley immediately noticed that rocks along the shoreline were in different locations, moved by waves during a recent storm. “It wasn’t like this in September,” she said as she scanned the water’s edge.

The team scrambled over the barnacled rocks and through slippery brown algae, heading toward the red algae of the lower intertidal. At this point in the twelve-foot tidal range, the entire lower shore was exposed, tinted pink by coralline algae. According to Brawley, this pink alga now dominates the lower intertidal at Schoodic Point.

The pink alga is Corallina officinalis, and it has increased at the expense of Chondrus crispus (Irish Moss) and Fucus distichus (related to bladderwrack). Brawley connects the changes to rising seas and subsequently wetter conditions in the lower intertidal zone. It could also be a result of overfishing of sea urchins in the 1990s. Sea urchins scrape surfaces to feed on algae, so they can prevent the thick developments of C. officinalis that are now found at Schoodic Point. She speculated that without urchins grazing the rocks and ledges, the Corallina spread.

Three younger women stand on a pink and red algae-covered rocky shelf, around an older woman, who is holding up a small piece of algae in one hand and pointing at part of it with the other.
Brawley (second from right) explains the biology of algae to Schoodic Institute staff.

Image © Schoodic Institute / Catherine Schmitt

Corallina is calcified, and regardless of how and why it has increased its hold on the lower intertidal zone recently, it now forms a turf-like armor that seems to exclude other algae,” said Brawley. “Because Corallina is usually common in the shallow subtidal, and not dominant in the lower intertidal, rising seas are likely at work. There’s just enough sea level rise to affect the lower shore; higher areas of the lower intertidal zone now look more like areas of the shallow subtidal zone I once saw in the same places.” But Brawley emphasized she needed to test those assumptions through field experiments.

Adam Kozlowski, a biologist with the National Park Service’s Inventory and Monitoring Program, has seen similar shifts. Kozlowski employs permanent plots and transects that he returns to year after year. He is part of a team that includes Jessica Muhlin, a former student of Brawley’s, now a professor at Maine Maritime Academy. After seven years of monitoring, the team has started to see subtidal species in the lowest reaches of the intertidal zone.

Brawley’s extensive research on how algae reproduce may help land managers restore coastal ecosystems.

“Long term data sets and research like Susan Brawley’s [are] invaluable for understanding the nature, pace, and trajectory of change in ecosystems,” said Acadia National Park Resource Management Program Manager Rebecca Cole-Will. Cole-Will thinks Brawley’s work will help managers address “the fundamental and existential question” of how to manage for climate change. Marine algae and other intertidal organisms such as blue mussels and periwinkles support fishing livelihoods, and harvesters may need new and adjusted access to the shore as sea level rises and populations shift. Other tidal areas may need extra protection if certain species become threatened or endangered. And Brawley’s extensive research on how algae reproduce may help land managers restore coastal ecosystems.

A Teaching Touchstone

Down on the shore, Brawley took only a few individual blades of seaweed from each rock or pool, to minimize disturbance. “Normally when I’m here,” she said, “I have a very specific objective to accomplish between tides.” On that day, she was collecting pieces of purple laver for laboratory experiments. But her goal was to teach, too.

Brawley calls Schoodic Point a “touchstone,” the place where she and her students have maintained multiple research projects in all seasons. “Schoodic Point is a dynamic ecosystem and a breathtaking place to do science,” Muhlin said. “I feel so incredibly fortunate that my graduate work with Susan…allowed me to professionally connect with Acadia National Park. I…learned so much about the life between the tides at Schoodic.”

Figure in a dark jacket nearly blends in to the landscape of algae-covered boulders. Beyond there is a strip of dry, barren boulders backed by towering conifers. The clouds streaking the sky are glowing in shades of yellow and orange as the sun sets.
Brawley collecting samples of Porphyra umbilicalis from Schoodic Point.

Image © Schoodic Institute / Catherine Schmitt

There are few scientists with thirty-plus years of research in a national park. Brawley’s observations are what we gain from this kind of long-term relationship.

There are few scientists with thirty-plus years of research in a national park. Brawley’s observations are what we gain from this kind of long-term relationship. Cole-Will said these insights are something “only a person with an intimate, sustained and passionate connection to the landscape would see.”

To tour the tide pools of Acadia with Brawley is to explore the logic of taxonomy’s founding father Carl Linnaeus, the evolution of life on Earth, and the wisdom of Isabella Abbott and other titans of twentieth century phycology. To the unaccustomed, such information can be baffling yet enlightening. The team of early-career ecologists in the field with her that day learned how much they didn’t know about patterns shaped by tides and waves, seasons and weather, and, lately, an overheating planet.

As Brawley and the field crew made their way down to the Great Pool, a tide pool whose unusual depths harbor subtidal seaweeds that need the security of a constant blanket of water, she noted that—like elsewhere along the shore—the pool was covered with a shag carpet of Corallina. The Fucus and kelps she once collected there were gone. These changes are a sign of things happening at Schoodic Point, profound things we know about only because of the work of Brawley and her team.

About the authors
Headshot of a woman with brown hair and a gray t-shirt outside on a sunny day.

Olivia Milloway is a former recipient of the Cathy and Jim Gero Acadia Early Career Fellowship in science communication at Schoodic Institute at Acadia National Park. She is currently a Fulbright student grantee studying marine biology at the Smithsonian Tropical Research Institute in Panama. Image used with author's permission.

Woman with long red hair, wearing a blue jacket and a green shirts stands in front of a forest

Catherine Schmitt is a science communication specialist with Schoodic Institute at Acadia National Park. Image courtesy of Linda Moses.

Acadia National Park

Last updated: March 13, 2024