BY: Lisa d. Mickey
She readily admits that Ruppia maritima – also known as wigeon grass – might look like a “wimpy looking plant” to some.
But to Dr. Hyun Jung (“J”) Cho, professor in Bethune-Cookman University’s Department of Integrated Environmental Science, Ruppia is an underappreciated aquatic superstar when it comes to restoration.
Along with many other scientists, Cho is deeply involved in trying to regrow lost seagrass in the imperiled Indian River Lagoon (IRL). Her B-CU program currently is working in partnership with Riverside Conservancy and is focused on regrowing and restoring seagrass. The University and Conservancy collaborate on projects such as restoring aquatic habitats and providing research and field experience for students.
The IRL’s progressive decline of estuarine seagrass -- due to water-quality issues over the last decade -- fell under intense national scrutiny in 2021 when more than 1,100 manatees starved to death. The loss of such charismatic animals, which rely on seagrass as a primary food source, underscored the urgency for seagrass restoration while also eliciting public outcry.
But as focus on the IRL’s water issues and seagrass loss has intensified, Cho has steadily engaged with an unheralded seagrass species with which she has worked for many years in Mississippi and Louisiana before arriving in Florida in 2011.
“Ruppia maritima is not as abundant or as majestic looking as Thalassia testudinum [also known as turtlegrass], but when you have to rebuild, you must follow ecological succession – [the sequence of] what’s going to happen in nature,” said Cho.
“This is more of a pioneer species – the first to colonize – and it can grow in a bare habitat where you start with something small that will grow fast and produce a lot of seeds,” she added.
And then you allow nature to go to work.
Without competition from other species, Ruppia typically takes hold first and is followed by other more herbaceous plants later. What starts out small and sometimes barely visible can become taller and more prolific.
“You don’t try to initially restore the plants that are more of the climax species [that arrive later in the succession of plant colonization],” said Cho. “In restoration, we try to make the process happen in a shorter time period -- within one or two years -- but we still have to follow the course of nature.”
With Ruppia, Cho has learned that this seagrass engineers its habitat to make the area more favorable for other species of grasses to colonize and grow. Once other species colonize, Ruppia “acts like a fringe species,” she said, yielding the area to other plants moving into that space.
The beauty of Ruppia is that it can coexist with other plants. Cho described it as having “very flexible characteristics” when compared to other seagrass species, allowing it to tolerate salinity levels ranging from 5 ppt to 40 ppt. [Note: For comparison, the salinity of the ocean is approximately 35 parts (grams) of salt per thousand parts (grams) of water (ppt). In other words, ocean salinity = 35 ppt = 1 gram of salt dissolved in 1000 grams of water = 1 gram of salt dissolved in one liter of water.]
Called a “cosmopolitan species,” Ruppia’s range spans from Asia to Australia to North America and it can grow in tropical, subtropical, temperate, and even in northern climates.
And the fact that Ruppia flowers and produces seeds also makes it highly desirable by scientists working with the species.
“Even if the grass seemingly disappears, once you have seeds, it will come back as an annual plant next year,” Cho said. “And because ducks and waterfowl are attracted to this plant and ingest it, they become the dispersal agents to spread the grass.”
Cho, her B-CU graduate students, and Riverside Conservancy staff are currently growing Ruppia in a mosquito impoundment – a man-made channel -- located in Brevard County’s Merritt Island National Wildlife Refuge. The researchers also have more control over the seagrass growing within an impoundment than they would have in the open estuary.
“We needed to grow this grass where the water is exchanged between the lagoon and the impoundment and is affected by the tides or [the managed] culverts,” said Cho.
Another key aspect of Cho’s restoration project to regrow seagrass is using “buffer habitat,” such as areas around salt marshes, wetlands and mangrove trees. She and her B-CU students used small sprigs of Ruppia provided by an aquatic nursery, which they planted in February 2022, but Cho’s research in the IRL began in 2013, as a continuation of her research that started in the waters around the Gulf of Mexico following Hurricane Katrina.
“When you try to restore something, you don’t just look at the problem,” Cho explained. “You have to work with the environment first – the buffer, the ecosystem. You have to think about the surroundings that will buffer the problem and reduce the impacts in your system.”
Cho hopes the continued growth of Ruppia in the IRL can ultimately help usher in additional seagrass. The plants not only stabilize the lagoon and provide food and habitat for fish, animals and many other species, but seagrass also helps absorb excessive nutrients in the lagoon’s water column.
And while helping to lower the IRL’s nutrient load, Cho notes that Ruppia can help keep the lagoon’s water clear, potentially preventing harmful algae to bloom and take over.
“If we have healthy seagrass, algae cannot outcompete it,” she said. “Algae doesn’t have roots, so it depends only on the nutrients in the water column, while seagrass gets nutrients both from the water column and from the sediment.”
The goal is to establish the native Ruppia in the mosquito impoundment and to monitor the restored impoundment to assess it as a viable nursery site and source for IRL seagrass recolonization.
She also hopes to develop and “share protocol and strategy” toward future IRL seagrass restoration with Ruppia specifically in an impoundment environment.
“I’ve studied Ruppia for a long time,” Cho added. “As a scientist, I want to know more about this species. I see growing this plant as my lifetime goal.”
Cho receives funding for her Ruppia project from the Indian River Lagoon National Estuary Program and the Florida Fish & Wildlife Conservation Commission.