WASHINGTON, Sept. 7 (UPI) -- A ten-fold increase in native aquatic vegetation in the Potomac River in Washington shows it is responding to restoration efforts, scientists say.

Decreasing nutrients from agricultural runoff and an improvement in water clarity have increased the abundance and diversity of submerged aquatic vegetation, or SAV, a U.S. Geological Survey report says.

"Improvements to plant communities living at the bottom of the river have occurred nearly in lock step with decreases in nutrients and sediment in the water and incremental reductions in nitrogen effluent entering the river from the wastewater treatment plant for the Washington, DC area," USGS scientist Nancy Rybicki says.

SAV are critical to the ecosystem in the Chesapeake Bay and its tributaries. They provide oxygen, food, and shelter so that invertebrates, fish, crabs and waterfowl can survive.

Since 1990, the area covered by native SAV has increased ten-fold, the diversity of plant species has increased, and the proportion of exotic species to native species has declined as nutrients have declined, the USGS report says.