Submerged aquatic vegetation (SAV) is a diverse assembly of rooted macrophytes found in shoal areas of Chesapeake Bay, from its mouth to the headwaters of its tributaries. It historically contributed to the high primary and secondary productivity of Chesapeake Bay (Kemp, et al., 1984). The dramatic baywide decline of all SAV species in the late 1960s and 1970s (Orth and Moore, 1983) was correlated with increasing nutrient and sediment inputs from development of the surrounding watershed (Kemp et al., 1983). This situation galvanized diverse groups into formulating a policy and implementation plan that would ensure the future of SAV in Chesapeake Bay.

The 1987 Chesapeake Bay Agreement, signed by the governors of Pennsylvania, Maryland, and Virginia; the mayor of the District of Columbia; the chair of the Chesapeake Bay Commission; and the administrator of the U.S. Environmental Protection Agency, set as a major commitment the "need to determine the essential elements of habitat quality and environmental quality necessary to support living resources and to see that these conditions are attained and maintained" (Chesapeake Executive Council, 1987). The Submerged Aquatic Vegetation Policy for the Chesapeake Bay and Tidal Tributaries (Chesapeake Executive Council, 1989) and the Implementation Plan for the Submerged Aquatic Vegetation Policy (Chesapeake Executive Council, 1990) were developed to guide managers and scientists in areas of SAV assessment, protection, education, and research. The 1992 amendments to the 1987 Chesapeake Bay Agreement state that "distribution and abundance of SAV as documented by baywide and other aerial surveys will be used as an initial measure of progress in the restoration of living resources and water quality" (Chesapeake Executive Council, 1992). The strong link between water quality and SAV distribution and abundance (Batiuk et al., 1992; Dennison et al., 1993) supports the concept that SAV is a good barometer of Chesapeake Bay health (Orth and Moore, 1988).

The annual survey is a critical tool for evaluating progress towards the new SAV restoration goals in the Chesapeake 2000 Agreement.   In 2003, the CBP adopted the Strategy to Accelerate the Protection and Restoration of SAV in Chesapeake Bay including a new baywide restoration goal of 185,000 acres by 2010.  Progress towards these long-term goals can only be evaluated in the context of detailed inter-annual changes in SAV distribution.

The term "submerged aquatic vegetation" is used for both marine angiosperms (the so-called true seagrasses) and freshwater macrophytes that have colonized Chesapeake Bay and its tributaries. SAV encompasses twenty-three taxa from twelve vascular macrophyte families and three taxa from one freshwater macrophytic algal family, the Characeae, but excludes all other algae (See SAV Classification). Seventeen species of SAV exclusive of the algae are commonly found in Chesapeake Bay and its tidal tributaries.

Zostera marina (eelgrass) is dominant in the lower reaches of the bay. Myriophyllum spicatum (Eurasian watermilfoil),Stuckenia pectinata (sago pondweed), Potamogeton perfoliatus (redhead grass), Zannichellia palustris (horned pondweed), Vallisneria americana (wild celery), Elodea canadensis (common elodea), Heteranthera dubia (water stargrass), Ceratophyllum demersum (coontail) Najas guadalupensis (southern naiad) Najas minor, Najas gracillima,  and Najas sp. are less tolerant of high salinities and are found in the middle and upper reaches of the bay ( Stevenson and Confer, 1978; Orth et al., 1979; Orth and Moore, 1981, 1984). Ruppia maritima (widgeon grass) is tolerant of a wide range of salinities and is found from the Chesapeake Bay mouth north to the Susquehanna Flats.

Approximately nine other species are found only occasionally. When present, they occur principally in the middle and upper reaches of Chesapeake Bay and in the tidal rivers (See SAV Classification). Of all species of SAV, the most abundant are Z. marina, R. maritima, V. americana, H. verticillata, P. perfoliatus, Stuckenia pectinata (P. pectinatus), and M. spicatum.

Zostera marina and R. maritima are the dominant SAV species found in the Delmarva Peninsula coastal bays.