River plants may play major role in health of ocean coas...( Recent research at MITs Department o...)

Recent research at MITs Department of Civil and Environmental Engineering suggests how aquatic plants in rivers and streams may play a major role in the health of large areas of ocean coastal waters.

This work, which appeared in the Dec. 25 issue of the Journal of Fluid Mechanics (JFM), describes the physics of water flow around aquatic plants and demonstrates the importance of basic research to environmental engineering. This new understanding can be used to guide restoration work in rivers, wetlands and coastal zones by helping ecologists determine the vegetation patch length and planting density necessary to damp storm surge, lower nutrient levels, or promote sediment accumulation and make the new patch stable against erosion.

Professor Heidi Nepf is principle investigator on the research. Brian White, a former graduate student at MIT who is now an assistant professor at the University of North Carolina, is co-author with Nepf of the JFM paper. Marco Ghisalberti, a postdoctoral associate at the University of Western Australia, worked with Nepf on some aspects of this research when he was an MIT graduate student. This work was supported by grants from the National Science Foundation.

Traditionally people have removed vegetation growing along rivers to speed the passage of waters and prevent flooding. But in recent years that practice has changed. Ecologists now advocate replanting, because vegetation provides important habitat. In addition, aquatic plants and the microbial populations they support remove excess nutrients from the water. The removal of too many plants contributes to nutrient overload in rivers, which can subsequently lead to coastal dead zonesoxygen-deprived areas of coastal water where nothing can survive. One well-documented dead zone in the Gulf of Mexico, fed by nutrient pollution from the Mississippi River, grows to be as large as the state of New Jersey every summer.

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