The term "submerged aquatic vegetation" (SAV) for the purpose of this
report encompasses twenty-three taxa from twelve vascular macrophyte families
and three taxa from one freshwater macrophytic algal family, the Characeae.
The term "SAV" in this report excludes all other algae, both benthic and
planktonic, which occur in Chesapeake Bay, its tributaries, and the Delmarva
Peninsula coastal bays. Although these other algae species
constitute a portion of the SAV biomass in this region (Humm, 1979),
this survey did not attempt to identify, delineate, or discuss the algal
component of the vegetation nor its relative importance in the flora. The
aerial survey cannot differentiate epiphytic algae on submersed vascular
plants or differentiate many benthic marine algae species, including many
macrophytes, which can co-occur in the same SAV beds.
Seventeen species of submerged aquatic vegetation are commonly found in
Chesapeake Bay and its tributaries. Zostera marina (eelgrass), the
only "true" seagrass species, can tolerate salinities as low as 10 ppt, and
is dominant in the lower reaches of the bay. Myriophyllum spicatum
(Eurasian watermilfoil), Stuckenia pectinata (sago pondweed),
Potamogeton perfoliatus (redhead grass), Potamogeton crispus
(Curly pondweed), Potamogeton pusillus (Slender pondweed), Zannichellia palustris
(horned pondweed), Vallisneria americana (wild celery), Elodea
canadensis (common elodea), Ceratophyllum demersum (coontail),
Hydrilla verticillata (hydrilla), Heteranthera dubia (water
stargrass), Najas guadalupensis (southern naiad), Najas minor, Najas
gracillima, and Najas sp. are freshwater
species, some of which have the capacity to tolerate some level of salt, 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; Moore et al., 2000). Ruppia maritima
(widgeon grass) is tolerant of a wide range of salinities and is found
from the bay mouth to the Susquehanna Flats. Approximately 9 other species are
only occasionally found. When present, these less common species occur primarily
in the middle and upper reaches of the bay and the tidal rivers. 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.
key to Chesapeake Bay SAV is available from the Maryland Department of
Natural Resources web page.