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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 timeline of events that have affected the growth of bay grasses over the last century:

1930s Eelgrass, the most widely distributed species in the bay, was nearly decimated by “wasting disease” in the early 1930s.
1940s Despite significant increases in bay grass numbers by the 1940s, introduction of exotic species such as water chestnut and Eurasian watermilfoil displaced many native bay grasses.
1962 Mute swans reproduced rapidly and began feeding on bay grasses after their introduction in 1962.
late 60s-early 70s Large scale declines in submerged aquatic vegetation in the late 60s and early 70s due to increases in nutrients and sediments to the bay.
1972 Tropical Storm Agnes (1972) caused widespread damage to bay grass beds.
1978 Tracking of bay grass populations by scientists began in 1978.
1984 VIMS started mapping bay grasses with aerial photography in 1984.
2002 In 2002, bay grasses reached record high numbers with an estimated 85,252 acres of SAV mapped Chesapeake Bay-wide.
2011 Hurricane Irene and Tropical Storm Lee (2011) significantly reduced underwater grasses in the upper part of the bay.
2015 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.
2016 In 2016, underwater grasses increased for the fourth straight year in the state's portion of the Chesapeake Bay, reaching a record of 59,277 acres.
2017 Underwater grasses reached 62,357 acres in Maryland's portion of the Chesapeake Bay in 2017, surpassing the 57,000 acre target and achieving a new record for the third consecutive year.
2018 Maryland experienced record high rainfall and stream flows into the Chesapeake Bay in 2018 and 2019. This led to higher levels of nutrient and sediment pollution, poorer water clarity and record low salinities in many of Maryland’s waterways. Because of these reduced habitat conditions, underwater grass abundance declined in 2018 and again in 2019 to 39,151 acres.
2021 Maryland’s waterways experienced a slight (13%) increase of SAV between 2021 and 2022. 39,760 acres of SAV were mapped in Maryland’s waterways in 2022.

MDs Bay Grass Coverage Chart

View Maryland's Tributary-Specific Bay Grass Coverage and Habitat Status

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

Click here to view the most recent Baywide SAV Monitoring Report.

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