EarthWorks Geospatial Catalog


Seagrass beds are critical wetlands components of shallow coastal ecosystems throughout the state. Seagrass beds provide food and cover for a great variety of commercially and recreationally important fauna and their prey. The leaf canopy of the seagrass bed calms the water, filters suspended matter and together with extensive roots and rhizomes, stabilizes sediment. Eelgrass and other seagrasses are often referred to as "Submerged Aquatic Vegetation" or SAV. This distinguishes them from algae, which are not classified as "plants" by biologists (rather they are often placed in the kingdom protista), and distinguishes them from the "emergent" saltwater plants found in salt marshes. In addition to the term SAV, some coastal managers use the term SRV or submerged rooted vegetation. This term probably arose to avoid confusion because non-scientists considered both seagrasses and algae as "plants" or "vegetation," and did not realize the term SAV excluded algae. (refer to The DEP Eelgrass layer, produced from data collected in 2001, is the second statewide mapping of the eelgrass resources along the coast. The data were compiled from similar methodologies as the earlier 1995 dataset. A similar third iteration of this statewide mapping is planned for the 2006-07 seasons. Eelgrass, Zostera marina, is the most common seagrass present on the Massachusetts coastline. The other species found in embayments of the Massachusetts coast is Ruppia maritima, widgeon grass, is present in areas of less salinity along the Cape Cod and Buzzards Bay coast. The layer is named EELGRASS_POLY. With the February 2006 update, which added the 2001 data, the EGRASVPT_PT layer of field verified points was discontinued. CZM changed the name of these data from "DEP Eelgrass" to "Eelgrass." To allow for consistent evaluation and comparison of a variety of datasets with distinct spatial resolutions, accuracies, and other characteristics, the Massachusetts ocean management planning area was partitioned into 250 x 250-meter grid cells, each with a unique ID. These data were converted to the planning area grid by extracting all of the cells in which the data layer occurred. The data were then dissolved into one feature.
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