Coverage of Bay Grasses

Bay Grasses (Submerged Aquatic Vegetation)

Bay Grass Coverage and Habitat Status

The abundance of bay grass in Chesapeake Bay has fluctuated greatly since the Virginia Institute of Marine Science (VIMS) started mapping the resource in 1984. The following is a bulleted timeline of events that have affected the growth of bay grasses over the last century.

  • Eelgrass, the most widely distributed species in the bay, was nearly decimated by “wasting disease” in the early 1930’s.
  • Despite significant increases in bay grass numbers by the 1940’s, introduction of exotic species such as water chestnut and Eurasian watermilfoil displaced many native bay grasses.
  • Mute swans reproduced rapidly and began feeding on bay grasses after their introduction in 1962.
  • Tropical Storm Agnes (1972) caused widespread damage to bay grass beds.
  • Large scale declines in submerged aquatic vegetation in the late 60’s and early 70's due to increases in nutrients and sediments to the bay.
  • Tracking of bay grass populations by scientists began in 1978.
  • VIMS started mapping bay grasses with aerial photography in 1984.
  • In 2002, bay grasses reached record high numbers with an estimated 85,252 acres of SAV mapped bay-wide.
  • Hurricane Irene and Tropical Storm Lee (2011) significantly reduced underwater grasses in the upper part of the bay.
  • In 2015, VIMS mapped the most underwater grass ever recorded since the survey began. 91,621 acres of grass were mapped throughout the Bay, with an increase in all four salinity zones since 2014.
  • Underwater grasses reached 53,277 acres in Maryland’s portion of the Chesapeake Bay in 2015, the highest abundance ever recorded by the aerial survey.


Bay Grass Coverage Data

Submerged Aquatic Vegetation Area in the Chesapeake Bay Chart 

Maryland's Bay Grass Coverage Chart 

NOTE: Scales on above graphs are different

View Maryland’s Tributary Specific Bay Grass Coverage and Habitat Status (1984-2015)

View Baywide Yearly SAV Monitoring Project Reports at Virginia Institute of Marine Science