Two divers from the US Environmental Protection Agency hovered over a stretch of debris in the Delaware River on a recent July morning near Camden, New Jersey. They were relocating Vallisneria americana, or wild celery grass, a species vital to the water quality environment with less than two feet of visibility in the turbulent estuary. One diver captured a shaky clip of the thin, ribbon-like blades bending with the current while holding a GoPro camera and a headlamp.
Anthony Lara, the experiential programs supervisor at the Center for Aquatic Sciences at Adventure Aquarium in Camden, watched the divers’ bubbles rise from the EPA’s boat. Anthony had cared for these plants in tanks for months, growing them from winter buds to mature grasses that were about 24 inches long.
He admitted that releasing the grasses into the wild, where they might be pushed aside by a rival plant or eaten by a duck, was “a little nerve-wracking.” But life is like that.
The Delaware, Hudson, and Chesapeake watersheds’ Upstream Alliance, a nonprofit organization that promotes public access, clean water, and coastal resiliency, oversaw this project’s inaugural planting. The alliance is aiming to repopulate parts of the estuary with wild celery grass, a plant essential to freshwater ecosystems. They are doing this in partnership with the Center for Aquatic Sciences and with assistance from the EPA’s Mid-Atlantic team and the National Fish and Wildlife Foundation. It’s one of the newest projects to bring back plants and animals in order to improve the water quality of the Delaware River, which provides drinking water to about 15 million people.
These programs are being implemented all around the United States, where urban rivers are still making a comeback and exhibiting more signs of life 50 years after the Clean Water Act was passed. Water is frequently unavailable to the communities that live nearby, and ecosystems continue to struggle. Scientists, nonprofit groups, academic institutions, and government agencies are studying bivalves (like oysters and mussels) and aquatic plants more and more as a way to help nature rebuild fragile ecosystems, make them more resilient, and improve water quality.
by bringing suspended particles to the surface and enhancing water clarity, bivalves and aquatic vegetation. Additionally, they have a remarkable ability to cycle nutrients by both consuming them as food and increasing their accessibility to other organisms. Numerous small fish, crabs, and other bottom-dwellers find food and a home in thriving underwater plant meadows, which also serve as carbon sinks. Healthy bivalve beds produce structures that stabilize silt and serve as a base for benthic habitats.
Danielle Kreeger, research director at the Partnership for the Delaware Estuary, which is driving a freshwater mussel hatchery in southwest Philadelphia, asks, “Why not use the functional advantage of plants and animals that are inherently robust and rebuild them?” Then you get advantages in terms of water quality, fish and wildlife habitat, erosion reduction, and improved public access.
Since 2010, the Billion Oyster Project, which is located 100 miles north of Philadelphia, has been working to restore the bivalves in New York Harbor, enlisting the help of more than 10,000 volunteers and 6,000 students. In Belfast Lough in Northern Ireland, where they were previously thought to have been extinct for a century, oyster nurseries are being established. Additionally, 25,000 mussels were released into local rivers from a hatchery 30 miles west of Chicago, increasing the populations of popular freshwater mussel species.
Projects to restore underwater vegetation have been ongoing for years in the Chesapeake Bay, Tampa Bay, and more recently in California, where seagrass species are experiencing a significant loss. (For instance, in the last 15 years, Morro Bay has lost more than 90% of its eelgrass beds.) The California Ocean Protection Council’s 2020 Strategic Plan to Protect California’s Coast and Ocean wants to keep the current 15,000 acres of seagrass beds and grow 1,000 more acres by 2025.
According to scientists, the most important step in enhancing water quality, according to scientists, is to continue implementing techniques to stop contaminants from entering our waterways, particularly excess nutrients from sewage and fertilizers. For example, scientists say that the slight increase in plants in the Chesapeake Bay, which happened after decades of planting aquatic plants, is mostly due to nature resetting itself after nutrient pollution went down.
Additionally, any human involvement in a complex ecosystem presents a number of fascinating questions, such as how to maintain enough genetic diversity and keep an eye on competition for resources and food. According to scientists, they frequently learn as they go.
Nevertheless, reintroducing bivalves and aquatic plants in locations where the natural environment is improving can build a solid foundation for entire ecosystems. Restoration efforts connect people to local rivers and educate them about the ecosystems on which we depend for survival. They are an active kind of stewardship.
The size of the wild celery grass beds in the Delaware Estuary was a bit of a mystery until five years ago. Since the estuary is heavily sedimented and agitated by the tides, many experts believed the water quality was unsuitable and the plants couldn’t be seen in overhead photographs.
A 27-mile section of the Delaware River from Palmyra, New Jersey, past Camden and Philadelphia, to Chester, Pennsylvania, was discovered to have the plant growing when EPA researchers began surveying by boat to look for submerged vegetation in 2017. The Delaware River Basin Commission has labeled only that portion of the river as dangerous for “primary contact recreation,” including jet skiing, kayaking, and swimming.
According to Kelly Somers, senior watershed coordinator for the EPA’s Mid-Atlantic area, seeing healthy grass beds was thrilling because the plant is a good indicator of the quality of the water. According to founder and president Don Baugh, the EPA’s data, which is available via online maps, has proven particularly beneficial for the restoration efforts of the Upstream Alliance because most of the research on wild celery grass comes from other regions, primarily the Chesapeake Bay. Wild celery and other water plants have been brought back to life for more than 30 years now.
Mike Naylor, an aquatic biologist at the Maryland Department of Natural Resources, is one of the Chesapeake’s foremost authorities. In the 1990s, he used Chesapeake Bay photos from the National Archives to determine how bay grass beds were in the 1930s and 1950s. When he combined his findings with those from the Virginia Institute of Marine Science, he found that the underwater plants in the bay grew well for at least 200,000 acres during those decades before shrinking to about 38,000 acres by 1984.
When I spoke with Naylor in the middle of July, he had just returned from a harvesting trip with volunteers from the ShoreRivers organization. They had collected enough redhead grass (Potamogeton perfoliatus) to fill the back bed of a pickup truck, which will yield a few gallons of seeds for replanting, according to Naylor.
Scientists on the Chesapeake Bay have recently moved from transplanting adult plants to direct seeding, which requires significantly fewer resources and is far less time-consuming. According to Naylor, three individuals can disperse tens of acres of seeds in a single day.
The effectiveness of restoration efforts could be greatly increased by using more effective methods in conjunction with site selection that is guided by accumulated data on plant requirements. Scientists agree, though, that natural repopulation caused by better water quality is the main reason for the small growth of seagrass over the past 30 years.
Cassie Gurbisz, an assistant professor in the environmental studies program at St. Mary’s College in Maryland, says that nutrient load reductions have led to a large recovery of aquatic plants in the Chesapeake Bay.
The major threats to water quality are excess nutrients, primarily nitrogen and phosphorus from sewage and agricultural runoff. And bivalves can contribute to solving the situation. The Billion Oyster Project is investigating how oysters influence and are influenced by water quality. The project has recovered oysters at 15 reef sites. By 2035, the project will have restored 1 billion oysters to New York Harbor.
The cleaning properties of the marine ribbed mussel were investigated in a 2017 pilot project in the Bronx River Estuary. According to studies, 138 pounds of nitrogen could be stored in the tissues and shells of 337,000 adult ribbed mussels floating in the estuary over the course of six months. A single mussel may filter up to 20 gallons of water per day while it feeds. They do this by absorbing extra nitrogen into their shells and tissues and burying it as waste in the sediment. Because they are so sensitive to bad water quality, species of freshwater mussels are among the most endangered animals.
According to Kreeger of the Partnership for the Delaware Estuary, which has studied freshwater mussels in the area for 15 years, “in some watersheds, the causes of why they went away are still there, so they’re not really yet restorable.” The causes include problems related to climate change, such as rising waters and increasing stormwater runoff; habitat degradation brought on by dredging or filling; sedimentation or siltation from runoff; and others.
According to Kreeger, in many places, the habitat is stable enough and the water quality has improved enough to allow for rebuilding. The teaching and hatchery facility that the cooperation wants to build would be able to make 500,000 native mussels every year.
In response to the worry that releasing a lot of hatchery-raised mussels would reduce genetic diversity and spread illnesses in the wild, Kreeger says the hatchery team is working on biosecurity and genetic preservation strategies.
Kentaro Inoue, research biologist at the Daniel P. Haerther Center for Conservation and Research at the Shedd Aquarium in Chicago, says that projects like propagation or restoration should preserve the genetic diversity and makeup of the current population without interfering with natural or evolutionary processes. He is working with the hatchery of the Urban Stream Research Center, which has put about 25,000 mussels into waterways in the Chicago area, to look at DNA samples from restoration sites.
The main problem is that many animals that are reproduced share the exact same maternal DNA. (Only four mother mussels produced the initial 24,000 juveniles that the hatchery released.) By marking their mussels, the center hopes to allay some of these worries by preventing the reproduction of creatures with the same genetics in a later season. Even so, Inoue says, “We need to do more monitoring after we release young fish raised in hatcheries into the wild.”
Despite these worries, experts agree that restoring bivalve and aquatic plant ecosystems is a key strategy for maintaining improved water quality. “We’re restoring nature’s capacity to keep itself clean,” says Kreeger.
