Shallow Water Habitats

Submerged aquatic vegetation or “SAV” are non-flowering or flowering plants that grow completely underwater.  In the Chesapeake Bay region, the term “SAV” is usually used to refer to various rooted aquatic angiosperms or “underwater grasses” found growing in shallow littoral areas ranging from high salinity regions to freshwater tidal environments.  Approximately 20 species are commonly found throughout the Chesapeake Bay and eastern shore coastal bays. Individual species are distributed based on their tolerances to environmental conditions including: salinity, light, temperature, nutrient levels, sediment type, and physical setting. 

Beds of SAV are important habitats in the Chesapeake Bay region as both marine and freshwater SAV communities have been found to provide habitat, protection, nursery areas, and other functions for economically valuable fishery species; are primary sources of food for waterfowl; serve as indicators of local water quality conditions; affect key benthic processes; and decrease the potential for shoreline erosion by dampening nearshore waves and water flow.

SAV have declined from historical abundances. There are a number of factors that can affect SAV abundance.  The most important factor is water quality, especially as it affects the light available to the SAV leaf surface for photosynthesis.  Both excess nutrient and suspended sediments reduce light by direct shading or promoting the growth phytoplankton or other algae.  Herbicide toxicity can have local effects.  Fishing, aquaculture and recreational boating practices can also affect SAV beds both directly through the use of the gear and placement of aquaculture structures and propeller scars from vessels attempting to traverse shallow areas.

Recruitment and growth of SAV can also occur as habitat conditions improve. In some cases the re-growth may be a result of the explosive growth of non-native species, especially in tidal freshwater and low salinity areas. 

Because of the importance of SAV to the bay ecosystem and the widespread and extensive declines that been observed, restoration of SAV by plantings of shoots or seeds, has been an important component of shallow water habitat management.  And, due to the direct links between SAV and water quality there has been a focus on restoring water quality to levels that will enhance natural recovery.