Maritime seepage wetlands known as Sea-Level Fens are confined to a few sites with an unusual combination of environmental conditions for this region. They occur very locally along the Atlantic Coast from Virginia to Massachusetts, and possibly New Hampshire. Only four occurrences are known in Virginia, all of them on the Eastern Shore (Accomack County). Habitats are situated just above normal highest tide levels, at the bases of slopes where abundant groundwater discharges along the upper edges of estuarine bays. The constant influx of fresh groundwater dilutes the impact of occasional salinity inputs from storm tides and spray. The hydrology of these sites is best characterized as saturated, although shallow standing water and small, muck-filled pools are locally present at all sites. Soils are organic and nutrient-poor.
The vegetation exhibits characteristics of both inland seepage bogs and tidal oligohaline marshes. Stands are generally a physiognomic mosaic of open woodland, scrub, and herbaceous patches. Woody species include red maple (Acer rubrum), blackgum (Nyssa sylvatica), sweetbay magnolia (Magnolia virginiana), and wax myrtle (Morella cerifera). Characteristic herbs include twig-rush (Cladium mariscoides), beaked spikerush (Eleocharis rostellata), northern white beaksedge (Rhynchospora alba), feather-bristled beaksedge (Rhynchospora oligantha), water sundew (Drosera intermedia), ten-angled pipewort (Eriocaulon decangulare var. decangulare), coinleaf (Centella erecta), brown-fruited rush (Juncus pelocarpus), and bladderworts (Utricularia spp.). These communities are extremely rare and local throughout their known range along the Atlantic Coast from New Jersey to Virginia. Many state-rare plants are associated with the Virginia occurrences. Chronic sea-level rise, with associated intrusions of tidal flooding and salinity, comprises a serious threat to the long-term viability of all sea-level fens.
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|A Sea-Level Fen occupying a distinct zone of freshwater seepage between an upland slope and salt marsh near Gargathy Bay, Accomack County. Abundant plants here include twig-rush (Cladium mariscoides), beaked spikerush (Eleocharis rostellata), northern white beaksedge (Rhynchospora alba), and ten-angled pipewort (Eriocaulon decangulare var. decangulare). Photo: Irvine Wilson / © DCR Natural Heritage.|
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