Submerged aquatic vegetation or SAV are important components of shallow water areas of the York River estuary. The plants that comprise these communities are distributed in shallow water areas (<2m) along the estuary from polyhaline to freshwater areas according to their individual salinity tolerances. Eelgrass (Zostera marina) is the only true seagrass and is found only in the lower York River where salinities average above 20 psu. It is a cool water species that decreases in abundance in the summer due to high water temperatures. SAV in this region have declined precipitously from historical abundances due to excessive levels of turbidity and nutrients. Infection of a marine slime mould-like protist, Labyrinthula zosterae, also impacted this species in the 1930s, nearly decimating it from this area. Widgeon grass (Ruppia maritima) co-occurs with eelgrass but can also grow in low salinity areas. Pondweeds (Potamogeton) and many other SAV species grow in both low salinity and freshwater areas. Macroalgae or “seaweeds” are currently a minor component of SAV in the York River system. Several algal genera common in the area include: Agardhiella, Ulva, Enteromorpha and Chara. While there has been a great deal learned through research and monitoring relative to SAV communities in the Chesapeake Bay, in general, and the York River, in particular, more efforts are needed to advance SAV protection and restoration to achieve the SAV restoration goals. Research efforts are needed to further understand the relationships between environmental conditions and SAV response and the interactions between of various stressors on SAV. Other areas for further research focus include investigations of the relationships between natural and restored SAV growth, survival and bed persistence and biological stresses including herbivory or secondary physical disturbance through foraging, bioturbation or other activities. One important need is to quantify the short and long term relationships between SAV decline and recovery and climatic factors such as storms, droughts, and temperature extremes that may be influenced by climate change.

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