The term "submerged aquatic vegetation" (SAV) for the purpose of this report encompasses twenty taxa from ten vascular macrophyte families and three taxa from one freshwater macrophytic algal family, the Characeae. SAV excludes all other algae, both benthic and planktonic, which occur in Chesapeake Bay and its tributaries (Appendix A). Although these other algae do constitute a portion of the SAV biomass in Chesapeake Bay and its tributaries (Humm, 1979), this study did not attempt to identify, delineate, or discuss the algal component of the vegetation nor its relative importance in the flora, except for the Characeae. This is the case, for example, with the benthic marine algae, including many macrophytes, which sometimes co-occur in the same beds as vascular plants, even as epiphytes on vascular plants.
Ten species of submerged aquatic vegetation are commonly found in the Chesapeake Bay and its tributaries. Zostera marina (eelgrass) is dominant in the lower reaches of the bay. Myriophyllum spicatum (Eurasian watermilfoil), Potamogeton pectinatus (sago pondweed), Potamogeton perfoliatus (redhead grass), Zannichellia palustris (horned pondweed), Vallisneria americana (wild celery), Elodea canadensis (common elodea), Ceratophyllum demersum (coontail), and Najas guadalupensis (southern naiad) 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, 1983). Ruppia maritima (widgeon grass) is tolerant of a wide range of salinities and is found from the bay mouth to the Susquehanna Flats. Approximately 13 other species are only occasionally found. When present, these species occur primarily in the middle and upper reaches of the bay and the tidal rivers (Appendix A). Hydrilla verticillata (hydrilla), a recently introduced species, presently dominates SAV beds in the tidal freshwater reaches of the Potomac River. It was also reported again in 1994, in the Susquehanna River and Flats, where its growth was not as widespread as in the Potomac River (Kollar, pers. comm.).
Zostera marina and R. maritima are the species reported from Chincoteague Bay.