Submerged Aquatic Vegetation (SAV) in the Chesapeake Bay dropped by 30 percent from 2002 to 2003, according to a report synthesizing the annual aerial SAV survey data collected by the Virginia Institute of Marine Science. Released on May 18 by the Chesapeake Bay Program, the report calls this the largest single-year decline in SAV since 1984.

The marked decline of Bay grasses in 2003 is linked to near-record rainfalls during last spring and summer that washed colossal amounts of nutrients and sediment from the land into the Bay, according to the report. Increased water turbidity, when combined with cloudy, sunlight-poor days, hampered the grasses' growth.

Bay grasses are critical players in the Chesapeake Bay ecosystem. They oxygenate estuarine waters and provide food, shelter and nursery areas for juvenile striped bass and crabs. They also act to reduce pollution by absorbing nutrients and trapping sediments.

Since the 1960s Bay grasses have seen a steady decline due to poor water quality and enhanced growth of epiphytes - which foul underwater plants. Scientists and regional partnerships have been working hard to reverse the trend through directed restoration efforts. In the past 15 years, there has been some re-growth of SAV in the Bay, but at least in brackish areas, recovery has been limited to one species commonly known as widgeon grass, explains ecologist Michael Kemp of Horn Point Laboratory.

"Thirty years ago, in this same region, there were six or seven species that were pretty abundant. As a community, it was much more robust. Now the system is much more vulnerable to variation in climate - like what occurred in 2003," he says.

Kemp is not surprised that a single year with extremely high levels of precipitation caused such a striking decline in SAV. "It's a reminder that the plants disappeared originally because of poor water quality. And this underlying problem has not improved," he says.

- Erica Goldman

SAV Weblinks

• Chesapeake Bay Program
  http://www.chesapeakebay.net/baygras.htm
• Virginia Institute of Marine Science
  http://www.vims.edu/bio/sav/
• Maryland Department of Natural Resources
  http://www.dnr.state.md.us/bay/sav/index.html
• NOAA Chesapeake Bay
  http://noaa.chesapeakebay.net/sav.htm
• US Fish and Wildlife Service Chesapeake Bay Office
  http://www.fws.gov/r5cbfo/CBSAV.HTM
• Maryland Marine Notes:
  Restoring Bay Grasses to the Chesapeake: A Long Way Back
  http://www.mdsg.umd.edu/MarineNotes/May-Aug00/index.html

This page was last modified June 08, 2004

h/V03N1/side7.html