Can a floating island in the Charles River rescue its water quality?

BOSTON — Since early in the summer of 2020, a man-made island has been floating right in the middle of the Charles River.

It’s part of a science experiment focused on curtailing harmful algae blooms.

The small island, which sits in the shadow of the Longfellow Bridge, is designed to replicate a local wetland.

It’s about 700 square feet, the size of a typical one-bedroom apartment. It has 3,000 plants, representing about two dozen species native to New England, covering the structure, which is comprised of 24 interlocking pieces.

“The floating wetland is an experiment,” explained Laura Jasinski, Executive Director of the Charles River Conservancy. “It’s a pilot program to study how adding good ecology back to the river could make the Charles more adaptable and fight the algae blooms.”

Algae blooms are harmful to people because they release toxins which can cause skin irritations or more serious problems if ingested. Pets can also suffer health problems when exposed.

The Charles River Conservancy is focused on getting the water quality in the river to the point that people can regularly swim in it.

Jasinski said great strides have been made over the last 30 years.

“The EPA has a grading system for the river. In 1990, we were at a D, almost a failing grade. As early as 2017, we were at an A-,” she said.

Paul McDougall grew up in Cambridge and remembers swimming and skating on the Charles River.

“You go back the 50s and 60s, you had a lot of industry going on," he explained. "Of course, back then that’s where they dumped all their excess chemicals and things.”

Those days may be long gone, but the algae blooms are now becoming more frequent, due to increasing water temperatures and storm runoff.

The floating wetland is a novel experiment, looking at a new way to control the algae, according to Max Rome, a PH.D. student at Northeastern University. He says the natural food chain has broken down over the years which has allowed the algae to flourish.

Today, a natural predator for the algae has a hard time thriving in the Charles River basin.

Rome is testing whether this floating wetland gives these organisms, known as zoo plankton, a better chance at surviving.

When the island was built last spring, it was designed to be porous, allowing the roots of the plants to dangle in the water, providing a habitat for the zoo plankton.

“Some people who study these algal blooms kind of consider these algal blooms and this type of water pollution to be the biggest water quality issue in the world right now,” said Rome. “This type of solution is super applicable to any urban water body, any developed water body, where re-establishing wetlands is difficult.”

The experiment in the Charles River will last two years.

Jasinski hopes it will ultimately make her dream of a swim-able Charles River a reality.

“It’s really exciting to think about what a fully usable Charles River could be for Boston and Cambridge," she said. "A lot of people have to go to a public pool or drive a significant distance to get to a beach or a natural body of water.”

Algae blooms are popping up in other parts of the state. For example, some of Cape Cod’s freshwater ponds have been repeatedly closed due to algae blooms.

Swimming area proposed on Charles

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