By Matt Berg
THE BOSTON GLOBE
In the latest effort to rid the Charles River of its notoriously “dirty water,” conservationists launched an artificial island full of native plants Tuesday afternoon to study whether it could reduce harmful algae blooms.
Members of the Charles River Conservancy, a group that has worked to maintain the river and its parks for decades, have visions of people swimming in the water on a sweltering summer day, or fishing with friends. They dream of restoring the river to pre-development days.
“So many people still think of it as ‘that dirty water,’ and we’ve made a lot of progress,” said Laura Jasinski, executive director of the Charles River Conservancy. “But we still have new challenges.”
Over the course of two years, scientists will study the effect the 700-square-foot floating wetland has on the river’s water quality. The island, home to 15 native wetland species, was launched near the Longfellow Bridge by the mouth of the Broad Canal Tuesday afternoon.
After collecting water samples from North Point Park along the Charles in years past, “we learned that bacteria levels were at a level where you could swim the vast majority of time in summer, but the problem is with algae blooms” in the late summer, Jasinski said.
The algae bloom predicament “is getting worse, and that’s what’s most concerning,” she said. “They’re hard to predict.”
Algae blooms are overgrowths of algae that can produce dangerous toxins. Nutrients in runoff from surrounding impermeable surfaces, such as pavement and roads, combined with high temperatures in the summer, cause the blooms to peak in July and August, Jasinski said.
The theory is that the island could create a home base for tiny organisms that eat the algae.
“What we’re going to study is how it creates a habitat for zooplankton, the natural predator of algae,” she said.
“While development along the Charles has fundamentally changed the river’s ecology, there are lessons we can learn from its original state,” Max Rome, a doctoral student in engineering at Northeastern University who is working on the project, said in a statement.
If researchers discover a noticeable difference in water quality, several islands may be launched in years to come. It’s hard to say what that might look like, but Jasinski imagines one possibility: an area surrounded by islands, allowing for especially clean water and a designated swimming area.
Along with other data collected from the island, “We would like to understand the effect of proximity of the islands. Could you surround a swimming area with these? How many would there need to be?” Jasinski said.
Although it can technically support the weight of humans, the island is not open to the public, she said. Those who want to get a close look can do so from kayaks or the bridge.
She invited people curious about conservation efforts to take a look at resources on the organization’s website.
“We want to engage people in understanding the river,” Jasinski said. “It’s complicated to understand all of the water science, but we want to make it more accessible to people.”