The Bucket Ecologist

Biology Professor Maria Rosa uses economical and sustainable techniques to restore aquatic habitats from Conn’s campus to Colombia.

By Melissa Babcock Johnson and Amy Martin

t’s a cool morning in early April and the rain is coming in spurts. Just down the road from the heart of Connecticut College’s campus, Assistant Professor of Biology Maria Rosa and two of her research assistants—Sasha Jansujwicz ’27, a biology and environmental studies double major from Bangor, Maine, and Sophie Moniz ’25, a biology major from Alexandria, Virginia—are decked out in tan waders and brown rubber boots. Their first destination is Mamacoke Cove, a designated natural area within Conn’s Arboretum on the banks of the Thames River.

After a short walk across a natural bridge that sports a spine of train tracks, Rosa, a prolific young researcher who joined Conn’s faculty in 2018, opens her neon yellow Seahorse-brand protective equipment case and removes two Bluetooth sensors that measure the water’s conductivity, pressure, salinity, temperature and level. She is focused and eager, declaring, “We’re going to get really good long-term data inside this cove.”

One instrument will log each six-hour tidal cycle in 15-minute increments. If Rosa wanted to, she could leave it running for 14 years, she says. She ties it to a buoy, explaining the process to Jansujwicz and Moniz, who hang on her every word.

While Rosa is almost knee-deep in the brackish pond, she moves a rock and spots a clam underneath. She exclaims with delight and then apologizes to the clam for disturbing it. “This is complete speculation, but it could be part of a Native American clam garden based on what I’ve seen and heard about them,” she says. “It matches.”

Once the instruments are up and running in South Cove, it’s time to cross the tracks and trek over to the cordgrass-covered Mamacoke Island to assess the situation on the coastline. With today’s weather, the scene feels and looks like an English moor. Rosa pulls out a clipboard topped with a map of the marsh. The map is marked with the locations of about 30 pins originally placed in the 1950s by noted botanist and wetlands expert William Niering, the late Lucretia L. Allyn Professor Emeritus of Botany at Conn. Rosa and her students will reference Niering’s data and that of Jean C. Tempel ’65 Professor Emeritus of Botany Scott Warren, who retired in 2007.

“The pins have been in the same location for decades and are about 15 meters apart,” Rosa says. “We go in and measure elevation to see if there are any changes in the marsh and try to use that to estimate marsh height. This is how we knew before that the marsh was keeping up with sea level rise. But over the last couple of years, it hasn’t.”

Professor Maria Rosa, center, works with student researchers on the docks at the Kohn Waterfront to monitor the progress of 3D printed biodegradable plates serving as artificial aquatic habitats in the Thames River. Photos by Sean D. Elliot

On average, the numbers have been falling, indicating that the sediment is shrinking. “Basically, the edges of the marsh are in trouble,” she says as she points to areas where the shoreline is collapsing into the water. “Slumping like this is indicative that the marsh is degrading.”

Nearly all of Rosa’s research involves Conn students as active participants through classwork, summer science research programs or as research assistants; some have even traveled with her to research locations in the Caribbean and South America. She employs methods that are accessible and easy for budding scientists to learn; she sometimes refers to her work as “Bucket Ecology” because “we are literally working with buckets.” Today, Moniz and Jansujwicz will help her repeat one of Warren’s data collection techniques from 1994 by measuring the distance between various pins and the marsh’s edge. Rosa will also compare today’s numbers to her own data from a year ago.

This early spring session provides only a tiny glimpse of the ongoing, in-depth research Rosa has been conducting at the Mamacoke Island habitat for the past seven years. She’s not just tracking the marsh’s decline—she’s trying to reverse it, with help from the Audubon Society and the National Fish and Wildlife Foundation. Last fall, these organizations awarded Rosa a total of nearly $5 million to study and restore the area.

The Mamacoke project is one of many for Rosa, who specializes in marine biology and ecology and works to develop new techniques to restore natural ecosystems and protect vulnerable shorelines—right on campus and around the world.

Reefs are essential to marine ecosystems, but humans have destroyed so much natural habitat.

— Professor Maria Rosa

Print the Reef

In the summer of 2022—with the future of marine habitats and coral reefs around the world at stake—Rosa’s excitement was palpable as two student researchers stood on Conn’s rowing dock at the Kohn Waterfront and fished a PVC pipe tree out the Thames River. It was adorned with 12 small, 3D printed biodegradable plates, and, to Rosa’s delight, each was teeming with life.

Rosa lay down on the dock to get a closer look, her voice rising as she began to describe what she was seeing to her colleague, Associate Professor of Biology Taegan McMahon, and the half dozen student researchers gathered around.

“So many barnacles! Scallops! Look at that, that’s a sea snail … There’s the tiniest crab you ever saw!”

Rosa, who was named an emerging scholar by Diverse: Issues in Higher Education in 2020, had teamed up with McMahon, a conservation disease ecologist who also works with 3D printers, to look into the possibility of 3D printing biodegradable artificial aquatic habitats.

“Reefs are essential to marine ecosystems, but humans have destroyed so much natural habitat that there is nowhere for small marine invertebrates like coral and shellfish to settle,” Rosa explains.

Essentially, if the organisms have nothing to stick to, they can’t grow. Scientists have been working to create artificial habitats, but so far, the materials have been too expensive, create environmental problems of their own, or just don’t work well.

“Those little guys love plastic—throw a buoy into the ocean and it will soon be filled with barnacles—but we don’t want to introduce more non-biodegradable plastic,” Rosa says. “They don’t seem to like wood. We had had some success with 3D printed ceramic panels, but they cost anywhere from $50 to $200 each to make and are expensive to ship because they’re so heavy, so it becomes too costly to use on a large scale.”

So Rosa and McMahon decided to try some significantly less expensive plant-based biodegradable materials—one soy-based, one corn-based and one made from wood pulp. A $30 spool of material yielded approximately 30 of the 4x4-inch ridged panels. After McMahon’s student researchers confirmed the material would not harm the aquatic organisms they hoped would settle on the plates, there was one thing left to do: put them in the water to see if anything stuck.

“It worked beyond our wildest dreams,” Rosa says. “Within just one week, we had a whole variety of species settled on the plates. Even the wood pulp, which surprised me, since they don’t generally like wood.”

The team tested the plates in the Thames River for six weeks and conducted a detailed analysis. That research, which indicates the new panels attract marine life as effectively or better than PVC panels, was published in the July 2024 issue of the Journal of Experimental Marine Biology and Ecology in an article coauthored by Rosa, McMahon, Grace Robinson ’24, Mitchell Lockwood ’23, Nicolette Scola ’24, Tristan Ene and Gerard D. Gadigian.

“By using biodegradable materials and customizable 3D printing, we can create artificial reefs that better mimic natural conditions and accelerate ecosystem recovery,” Rosa says.

Rosa is now deploying pilot studies at other locations, including the Long Island Sound, the British Virgin Islands and Oceanarios Marine Park in Colombia. If those experiments go as well, the inexpensive 3D printed biodegradable plates could support large-scale reef restoration projects and become the new standard for artificial aquatic habitats across the world.

In 2023, Rosa secured another $177,000 in grants to add 80 more reef balls to Conn’s Thames River waterfront.

On the Ball

Rosa’s earlier reef work took a different shape. Back in 2021, she led a team of students and volunteers in the construction of reef balls, hemispheric concrete artificial reefs that turned Conn’s riverfront into a sustainable aquatic habitat and living laboratory. Called Camels Reef, the pilot project initially protected 35 linear feet of shoreline.

In addition to serving as a habitat for local fish, crabs and other marine life, the reef balls help rebuild the shoreline by minimizing erosion, promoting plant growth and creating a barrier that protects Conn’s rowing and sailing docks.

The technology, pioneered by the founders of the nonprofit Reef Ball Foundation, is relatively simple. A marine-friendly, pH-balanced microsilica concrete is poured into a fiberglass mold outfitted with inflatable buoys and tetherballs to create a hollowed center and voids for water and marine life to pass through. Sand is used to create a natural floor, and sugar water is sprayed on the mold, buoys and balls to give the concrete a rough texture ideal for barnacles.

The process can be completed anywhere and, depending on the size of the mold, the resulting reef balls can vary from one to eight feet in diameter and weigh anywhere from 30 to 8,000 pounds. Once placed in the water, the reef balls mimic natural reefs in nearly every way.

To pilot the project at Conn, Rosa secured a $10,000 donation from country superstar Kenny Chesney’s No Shoes Reefs initiative and its partner, the Reef Ball Foundation, which has placed over a million reef balls in more than 80 countries since its founding in 1997.

Along with Jason Krumholz, the foundation’s scientific coordinator, Rosa and her team of students built approximately 30 reef balls and placed them in the river. Many of the students wrote their names in the concrete.

The reef balls serve as a living classroom and provide a site for snorkeling and diving and other independent investigations. In 2023, Rosa secured another $177,000 in grants to add 80 more reef balls to Conn’s Thames River waterfront and significantly expand the protected area to more than 1,200 square feet, with the balls built “breakwater style” about 200 feet parallel to the shore.

The grants included $86,311.94 from the National Fish and Wildlife Foundation’s Long Island Sound Futures Fund; $50,000 from the Louise H. and David S. Ingalls Foundation, facilitated by foundation president Barbara “Bobbie” Brown ’76; $21,000 from the Bennack-Polan Foundation, facilitated by foundation vice president Mary Lake Polan ’65 P’02 ’10; and $20,000 from 11th Hour Racing.

“It’s amazing to see how quickly the environment is transforming,” Rosa says. “We have a restored waterfront and a great habitat for research, and it’s right here on our campus.”

We have a restored waterfront and a great habitat for research, and it’s right here on our campus.

— Professor Maria Rosa

Restore and Return

Rosa is hoping for similar results on Mamacoke Island. The generous funding she’s secured will support assessments and data gathering by her team, as well as the project’s design, permitting, construction, and ongoing maintenance, monitoring and conservation.

The Audubon CT In Lieu Fee (ILF) Grant Program awarded an initial installment of $590,249 out of $3.3 million earmarked for the project. Future installments will be disbursed as the project reaches various milestones. The ILF grant includes a $100,000 long-term management endowment to be managed by the Arboretum that will be established and funded at the beginning of the five-year regulatory monitoring and maintenance period. The second grant is for $1.5 million and will come from the National Fish and Wildlife Foundation with support from the National Oceanic and Atmospheric Administration.

“Right now, we’re focused on determining the status of the marsh and then making a plan to preserve what’s left of it,” Rosa says. “A lot of great data has been collected by previous professors over the past 30 or 40 years, but there are still a lot of gaps—and we were unable to get out there the last few years because it was so flooded.”

Rosa is determined to discover exactly what’s behind the erosion. It could be the loss of plants or animals, she says, or even the repeated pounding against the shoreline of waves made larger and stronger by floods and sea level rise due to climate change.

She first grew concerned in 2021 when she observed the flooding and documented a complete loss of marsh mussels due to what biologists call recruitment failure. Other experts she contacted suggested it was simply the end of the Metonic cycle, and therefore just an aberration. But in 2022 and 2023, the marsh flooded again. “At what point does a blip become the new normal?” she muses.

The grants, Rosa hopes, will allow her and her students to carefully rebuild.

“With conservation, we have an imperative to keep the site as close to natural as possible and natively source everything. We would build up the marsh sill, bring in the sediment and create an environment for the marsh to grow back,” she explains. “Once the habitat is restored, there is the possibility of a natural recruitment of mussels. They need that intertidal marsh to grow, and that’s all gone. The habitat must be restored before the biodiversity can return.”

We’re going to get really good long-term data inside this cove.

— Professor Maria Rosa