Near Dover, MA, reeds grow out of sandbars along the Charles River where sediment has built up over time. Wetland vegetation offers a diverse habitat for microorganisms to thrive and pathways for nutrients like nitrogen, which in excess quantities can pollute the water, to exit the river.

Yet in the Charles’s lower basin, an area that extends from the Watertown Dam to Boston Harbor, that natural process is completely absent. Here, large rocks, granite retaining walls, and the Esplanade’s manicured lawns contain the river, limiting habitat diversity for microorganisms and contributing to nutrient pollution.

Engineer Max Rome estimates that, in the steady climb toward total ecological restoration, the Charles is “90% of the way there,” but there is still more to be done.

Rome, a stormwater program manager at the Charles River Watershed Association, investigated ways of reintroducing vegetation to the river and came across “one simple way to take a granite wall and turn it into something that’s very alive”: Rafts carrying wetland plants rooted entirely in the water column.

“All of the nutrients that they need to grow, they're pulling right out of the water. So, the same things that are pollution to the Charles River — excess nitrogen, excess phosphorus — those things are actually sustaining the growth of these wetland plants,” Rome said in an interview with The Scope. “The roots that are going down to the water are creating a kind of complex habitat as a substrate for microorganisms and tiny animals to survive in ways that would be difficult for them to survive elsewhere in the river.”
These symbiotic platforms are called "floating wetlands." Rome sat down with The Scope’s audio editor Rebeca Pereira to talk about them and the future of the Charles River.

This episode was produced and edited by Rebeca Pereira.

Music from Alec Cowan, Tim Kahn, MattJ99, Logic Moon, and EminYILDIRIM through freesound.org.

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