Scientists intentionally harm marsh in bid to save it
Pouring tons of chemical fertilizer into a pristine creek to study pollution may sound like weird science to some, but such research on the Ipswich-Rowley border is shedding light on overdevelopment in coastal areas.
Potassium nitrate is being distributed over 24 acres of the Great Marsh to simulate nutrients released from lawn fertilizer, faulty septic systems, and municipal wastewater treatment plants. The aim is to assess how those nutrients impact plants and animals living in the marsh, according to Linda Deegan, a senior scientist with the Marine Biological Laboratory at Woods Hole Oceanographic Institution. However, as early results from the experiment start to roll in, it's shedding light on development issues that could have national impact.
"This is the only place in the world that this research is being done; it has a lot of implications," Deegan said. "Not just for the Great Marsh, but in estuaries across the world. It can help us make important decisions regarding the practical implications of things like sewage treatment plants."
For the past four years, a water tank the size of a compact car has been set up each spring on a small patch of salt grass on a Great Marsh creek feeding into the Rowley River. It's filled with a potassium nitrate solution that is released into the water on the incoming tide through tubes running from the bottom of the tank.
The enriched tidewater then washes onto the salt marsh grasses, fertilizing them. The amount of fertilizer being released equals the nutrients that would be discharged from 1,000 homes, Deegan said.
On a trip out to the site recently, the treated marsh looked much like its surroundings. But subtle differences are starting to show up, Deegan said. The fertilized areas attract more shore birds and the marsh grasses there tend to grow faster and taller, but with poorer root development.
Of greater concern is a mat-like growth of algae that appears to have doubled in density since the experiment started, Deegan said. Such growth is linked to decreases in an important marsh minnow called the killifish. That loss ripples up the food chain, affecting shrimp, sand worms, and possibly other species dearer to human interests, she said.
"Striped bass use the salt marsh as a primary nursery," she said. "If the primary nursery isn't producing the right foods at the right time, you are not going to have as many striped bass."
Other results could surface at the Great Marsh experimental station as the impact from this very gradual study starts to take a toll, Deegan said. However, she's sure the work will not cause any long-term damage to the 20,000-acre salt marsh when work wraps ups five years from now.
"Salt marsh systems take centuries to build," Deegan said. "I don't think we're doing more harm than good here. If we ever get to that point, we'll stop what we're doing."
Local officials and environmental groups applauded the effort.
The Ipswich River Watershed Association and the Parker River Clean Water Association both said the research findings could guide future development in the prized real estate along the Great Marsh and the rivers that feed it. They also expressed confidence in Woods Hole's history of research.
"We're delighted that a world-class research institute is doing direct watershed research here in our watershed," said watershed association director Kerry Mackin. "To have the actual research in our watershed is incredibly valuable to us. In the big picture, it's extremely valuable in managing the watershed here."
Conservation officials in Rowley and Ipswich also endorsed the work. Both towns had to sign off for Deegan to get necessary state permits, and both believe the findings could benefit them greatly.
"It helps us get a picture of what's going on in the salt marsh," said Rowley conservation agent Brent Baeslack. "This work could tell us how development might impact shellfishing. It makes the protection of the marsh a little more immediate when you've got families here that have been shellfishing in that marsh for generations."
For Ipswich, the research hits a little closer to home. Ipswich's wastewater treatment plant discharges into the Great Marsh and the town has already discussed with the state some options for cleaning up that problem.
Knowing exactly what the plant may be doing to the marsh will help with future discussions, conservation agent David Pancoast said. "I know that the study was undertaken at least in part to advise the town about the potential impact of nutrient loading" from the plant," he said. "It's clearly information that the town of Ipswich needs."
The $3 million, nationally funded study is entering its fifth year. It has involved some 40 different researchers and assistants from universities and colleges in Maine, Louisiana, and Vermont as well as a few students selected from The Governor's Academy in Byfield each year.
There's still a lot to be learned from the Great Marsh work, Deegan said. "Nobody knows how salt marshes are affected by nutrient loading," she said. "But we are learning things here that we couldn't have learned in any other way."
