Access Our Results

Researchers at the Virginia Institute of Marine Science have been using aerial photography and ground surveys to monitor the distribution, extent, density, and species-composition of seagrass beds in Chesapeake Bay annually since 1978 (with hiatuses in 1982-84 and 1987 due to funding gaps). State and federal resource managers use data from VIMS' seagrass monitoring program as an indicator of water quality and ecosystem health, and to track progress toward the Chesapeake Bay Program's baywide restoration goal of 185,000 seagrass acres.

VIMS and the CBP have used a number of different spatial units to collect, analyze, and present seagrass data:

Baywide Total
Baywide Total

VIMS’ Seagrass Monitoring Program keeps track of annual changes in the Bay's total seagrass coverage as a means of gauging progress toward the Chesapeake Bay Program's long-term restoration goal of 185,000 acres, with interim targets of 90,000 acres by 2017 and 130,000 acres by 2025. VIMS reports its seagrass coverage data in hectares, the metric equivalent of an acre. One hectare contains about 2.47 acres.

By Segments

Since it was established in 1983 to restore Bay health, the Chesapeake Bay Program has used various forms of a segmentation scheme to better collect, analyze, and present environmental data. The Bay Program currently defines 93 segments within the Bay and its tributaries, each delineating an area with similar salinity, water depth, marine life, and circulation patterns. Where possible, these segments are bounded by prominent geographic features such as points, islands, or stream mouths; and contain one or more stations to monitor water quality. In 2003, these segments were further modified to better reflect political boundaries. VIMS’ Seagrass Monitoring Program uses the CBP segments as one way to organize its observations and analysis.

By Map Quadrangles

The Seagrass Monitoring Program at VIMS uses the boundaries of the U.S. Geological Survey's 7.5-minute topographic maps (also known as quadrangles or quads) as another way to organize its seagrass observations and analysis. These maps are drawn at a scale of 1:24,000; each portrays an area of about 50-60 square miles depending on latitude. VIMS reports seagrass coverage within 259 7.5-minute quad maps along the shoreline of Chesapeake Bay and its tributaries, and Virginia's Eastern Shore.

By Salinity Zone

In 2013, the Chesapeake Bay Program and researchers at VIMS began to categorize seagrass abundance in Chesapeake Bay using 4 different salinity zones, which encompass underwater grass communities that respond similarly to storms, drought, and other growing conditions. This makes it easier for scientists to connect changes in grass communities with changes in growing conditions through time. Marine scientists measure salinity in parts per thousand, or ppt, with full seawater at about 35 ppt. The 4 salinity zones used to categorize seagrass coverage in Chesapeake Bay are:

  • Tidal Fresh (no salt, < 0.5 ppt)
  • Oligohaline (slightly salty, 0.5-5 ppt)
  • Mesohaline (moderately salty, 5-18 ppt)
  • Polyhaline (very salty, 18-25 ppt)
By State

VIMS tracks the abundance of underwater grasses as an indicator of Bay health for the Chesapeake Bay Program, a federal-state partnership established in 1983 to monitor and restore the Bay ecosystem. Organizing seagrass coverage by segments within a state helps local resource managers monitor their specific seagrass restoration goals. We provide data for 4 of the 7 jurisdictions that participate in the Bay Program: Delaware, Maryland, New York, Pennsylvania, Virginia, W. Virginia, and Washington, D.C.)

By Geographic Zone

The VIMS Seagrass Monitoring Program began tracking the abundance of underwater bay grasses in 1978, and initially segmented their data by 4 broad geographic zones.. In the interest of long-term consistency, we still make our data available using these categorizations. The 4 geographic zones, based broadly on north to south and east to west divisions, are: Upper Bay, Middle Bay, Lower Bay, and Coastal Bays.

You can access, organize, and compare the data for these units via

We also compile and present our seagrass monitoring data in a series of annual reports.