College of Arts & Sciences

arts&sciences

The Mighty Mucus of the Rowley River

A sticky polymer produced by tiny algae could be crucial in the fight to preserve the New England coastline.

By Andrew Thurston

The recent recipient of a 2012 Sloan Research Fellowship for outstanding achievement in ocean sciences, earth scientist Robinson “Wally” Fulweiler ­studies the tidal flats on the ­northern Massachusetts coast. Photo by Melody Komyerov

Come in closer. turn your eyes from the sweeping beauty of the New England tidal flat, from its rushing grasses, wading heron, and stooping clammers. We’re looking deep into the muddy silt for a sticky mucus of microscopic particles that researchers believe is binding this precariously beautiful vista together.

The minute workings of nature on the tidal flat of the Rowley River, near upscale Newburyport on the northern Massachusetts coast, could hold the key to understanding how humans impact coastal environments—and the climate in general. In a two-year National Science Foundation-funded project, Robinson “Wally” Fulweiler, assistant professor of earth sciences and biology, is studying tiny algae—and the mucus they generate—on which so many tidal flats depend.

Nature’s Glue

The term “mucus” perhaps doesn’t do the extra-polymer secretion justice. As sediment washes in and out of flats, says Fulweiler, the secretion—produced by microphytobenthos, algae and bacteria living on the surface of sediment—helps it stay in place. “We think there are major benefits of having tidal flats,” she adds. “They help salt marshes maintain themselves and salt marshes are really, really important for stopping erosion and storm surges, mitigating nutrient pollution, and serving as nursery habitats. Tidal flats also help process nutrients, so they’re like a filter—the estuaries’ first line of defense.”

When people live near tidal flats, which they often do, a lot of defending is needed. Levels of nutrients like nitrogen and phosphorous, by-products of lawn fertilizer and human waste, can reach excessive levels and be especially damaging to fragile marine areas. To test the potential human impact on the microphytobenthos, Fulweiler and a team of students increased the supply of nutrient-rich river water to six 1-meter-square sections of the Rowley River flat (six others were left as control plots). With core samples taken, Fulweiler is now back in the lab using a nutrient auto analyzer and a mass spectrometer to assess the effect of additional nutrients on the extra-polymer secretion—the mucus: “It will tell us how sticky it was, about its ability to help grow and even maintain the tidal flat,” says Fulweiler, an associate director of the BU Marine Program. “One of my students, Amanda Vieillard (CAS’11, GRS’14), is going to be looking at how adding the nutrients changed that—and by how much.”

Fulweiler frequently has students working with her in the lab and in the field. She estimates around eight undergraduates participate in her research each semester, while five graduate students are currently working with her for the duration of their degree programs. As well as looking at mucus stickiness, they’re also helping her test the latest samples to determine the tidal flat’s denitrification capacity, an essential part of the planet’s nitrogen cycle. “Denitrification is a bacterial process that removes nitrogen from the system; essentially, it acts as a natural nitrogen filter,” explains Fulweiler.

Human Impact

Although the goal for this project is to find the best way to preserve delicate tidal flats, it fits into a broader purpose: “We’re interested in how humans impact coastal systems,” says Fulweiler, whose upcoming research will take her to the continental shelf to study biogeochemical changes in the ocean. “There are two different scales at which humans can do that: there’s the local scale, where you come in and change the land use or dump pollutants, and then there’s the larger-scale impact of climate change—warming temperatures, acidification, that sort of thing.”

She expects to find that by reducing the number of nutrients that slip into the water table, we’ll help the magical mucus flourish, allowing us all plenty of time to take in the rest of the captivating view it supports.