F. Wetland Classification and Characterization:

The tidal wetlands along the lower Connecticut River are exemplary and yet representative examples of the variation in the types of tidal wetlands found along most of the larger estuaries in the northeastern United States. Tidal inundation is the common factor shared by salt, brackish, and freshwater tidal marshes, with dissimilarity in major floristic elements and physiognomy correlated to variations in salinity and duration of flooding. The classification established by the National Wetlands Inventory is used here to provide a general characterization of the wetlands in the project area. Three systems of wetlands are present in this area: namely, the Estuarine, Riverine, and Palustrine. A general description of the floristic and vegetational variation that can be observed in these marshes is presented below and is based upon a synthesis of information contained in Barrett (1989), Hotchkiss (1947), Metzler and Rozsa (1982, 1986), and Nichols (1920).

Estuarine System: The Estuarine System embraces those tidal waters with a salinity greater than 0.5 ppt and less than 30 ppt. Surface water salinities are the most important determinant of wetland vegetation, because these are the waters that will actually flood the marsh surface. Since plants are most actively growing during the late spring and summer months, the salinity conditions at that time of year are of the greatest importance to determining the characteristics of the vegetation. The estuarine system in the lower Connecticut River extends from the mouth of the river north to, and including, Great Meadows in Essex, a distance of approximately 13 kilometers (8 miles). Estuarine marshes in the lower Connecticut River system include both salt and brackish tidal marshes, described below.

Salt Marshes: Salt marshes are those tidal wetlands with a soil salinity greater than 18 ppt and, thus, attain their optimal development in the project area in proximity to the chief source of salt water, Long Island Sound. At the beginning of the growing season, there is little or no detectable salt water in the surface waters of the river. By late July and early August, surface waters with a salinity greater than 18 ppt penetrate as far north as the railroad bridge in Old Lyme/Old Saybrook, a distance of approximately 8 kilometers (5 miles). However, throughout much of Great Island soil salinities are still below 18 ppt, except for the extreme southern portion. Here, in a very narrow zone, salt marshes occur.

As is typical of most salt marshes along the shoreline of Long Island Sound, the dominant vegetation zone is the high marsh, characterized by black grass (Juncus gerardii), salt-meadow cord-grass (Spartina patens), and spike grass (Distichlis spicata). The vegetation here often forms a mosaic rather than a distinct zone. Other plant associates include seaside goldenrod (Solidago sempervirens), perennial salt marsh aster (Aster tenuifolius), salt marsh aster (Aster subulatus), and spearscale (Atriplex patula var. hastata). Also found on the high marsh are pannes, or shallow depressions, containing glasswort (Salicornia europaea), stunted smooth cordgrass (Spartina alterniflora), sea lavender (Limonium nashii), seaside plantain (Plantago oliganthos), sea blite (Sueda maritima), and arrow-grass (Triglochin maritimum). The low marsh zone exists as a narrow band along the waterward edge of the marsh, including creeks and ditches. Smooth cordgrass typically forms a monoculture here.

Submerged aquatic vegetation beds composed of a sparse cover of eelgrass (Zostera marina) occur in the shallow subtidal waters of South Cove and near the lower portion of Great Island.

Brackish Marshes: The second type of tidal wetlands in the estuarine system is that occupying the mesohaline and oligohaline portions of the river from Great Island to Great Meadows. There is a gradual but progressive change in physiognomy (life form or structure) in the vegetation from short brackish meadows at the downstream end of the mesohaline zone to tall common reed (Phragmites australis) at the upstream end of the oligohaline zone.

The primary vegetational community in areas such as Great and Upper Islands and Ragged Rock Creek is the brackish meadow. Dominant plants include salt-meadow cordgrass and black grass, and this vegetation differs little in appearance from that of the high salt marshes. Certain salt marsh associates are even more abundant here, however, such as seaside goldenrod and arrow-grass. Saltwort and sea lavender are less abundant in the brackish meadow than in the high salt marshes. As the soil salinity diminishes, the above-named grasses and rushes give way to other graminoids, especially bentgrass (Agrostis stolonifera var. palustris) and the spike rushes (Eleocharis palustris and E. rostellata). Other common associates include straw sedge (Carex straminea), red fescue (Festuca rubra), mock bishop-weed (Ptiliminum capillaceum), New York aster (Aster novi-belgii), salt marsh fleabane (Pluchea purpurascens), silverweed (Potentilla anserina), common threesquare (Scirpus pungens) and Olney threesquare (S. americanus).

Smooth cordgrass is the characteristic plant of the low marsh zone in brackish marshes. In contrast to this zone in the salt marsh, a distinctive understory vegetation is present and composed of one or more of some of the following: dwarf spike rush (Eleocharis parvula), the diminutive umbellifer lilaeopsis (Lilaeopsis chinensis), and, less commonly, mudwort (Limosella subulata) and pygmy-weed (Crassula aquatica). All of these except for dwarf spike rush are state-listed species of special concern.

Several species of bulrushes and threesquare sedges form a very distinctive community type in the brackish marshes. These are all clonal or colony-forming species, and individual colonies may cover up to five acres. Common threesquare occurs throughout the brackish marsh complex and Olney threesquare is found only at lower salinity sites. The three bulrushes in this community type are short bayonet grass (Scirpus paludosus var. atlanticus), tall saltmarsh bulrush (S. cylindricus) and robust bulrush (S. robustus); the first two are state-listed species of special concern (see Appendix D). S. robustus is chiefly a species of mesohaline waters and is replaced by S. cylindricus in fresher, oligohaline waters. While S. robustus usually occurs as monospecific stands, colonies of S. cylindricus generally contain a number of associates such as dotted smartweed (Polygonum punctatum), showy bur-marigold (Bidens laevis), rush (Juncus acumunatus), water parsnip (Sium suave), and softstem-bulrush (Scirpus validus).

From Upper Island to Great Meadows, the vegetation is predominantly brackish reed. The dominant species here is narrow-leaved cattail (Typha angustifolia) which often forms extensive monospecific colonies. The average height of this cattail is 1.6 meters (5 feet). Other reed species that may form extensive colonies here include robust bulrush, common threesquare, common reed, and rose mallow (Hibiscus palustris). In brackish meadows, colonies of reed vegetation may occur throughout. Likewise, in reed dominated areas, pockets of brackish meadow vegetation occur throughout. As in the salt and brackish marshes, the low marsh zone in the reed communities principally supports smooth cordgrass.

At Great Meadows, there is a unique tall reed vegetational community dominated by the hybrid cattail (Typha x glauca) on the high marsh. This cattail can grow to heights of 2.5-3.3 meters (8-10 feet). Common reed and rose mallow are often codominants, and the former may occur in dense, monospecific stands. Associates include marsh fern (Thelypteris palustris), spike rush (Eleocharis smallii), arrow arum (Peltandra virginica), purple loosestrife (Lythrum salicaria), bur-marigold (Bidens cernua), mermaid weed (Proserpinaca palustris), and dotted smartweed. In the drier upland borders, freshwater cordgrass (Spartina pectinata) and switch grass (Panicum virgatum) are often dominant plants. The low marsh zone along North Cove is composed principally of common threesquare, and associates include salt marsh hemp (Amaranthus cannabinus), dotted smartweed, and sweet flag (Acorus calamus).

On muddy intertidal flats, the vegetation is often sparse and composed of a variety of herbs. These include dwarf spike rush and several state-listed species of special concern, including lilaeopsis, tidal arrow-head (Sagittaria spatulata), mudwort, and Hudson arrowhead (Sagittaria subulata). The last species is more prevalent on freshwater tidal mudflats.

In the protected subtidal waters and tidal creeks of the brackish marsh system, a distinctive community of submerged aquatic vegetation develops. The primary species here are horned pondweed (Zannichellia palustris var. major), Sago pondweed (Potamogeton pectinatus), pondweed (Potamogeton richardsonii), redhead-grass (Potamogeton perfoliatus), red pondweed (Potamogeton alpinus), tape-grass or wild celery (Vallisneria americana), widgeon grass (Ruppia maritima), and water-weed (Elodea nuttallii).

Riverine System: As defined by the National Wetlands Inventory, the riverine system includes those freshwater wetlands and deepwaters contained within the river channel and composed of nonpersistent vegetation, as contrasted with the palustrine wetlands described below which contain persistent vegetation. In the project area, this system lies principally between Great Meadows and the northern boundary. The dominant plants are nonpersistent emergent herbaceous plants, and include wild rice (Zizania aquatica), pickerelweed (Pontederia cordata), common threesquare, softstem-bulrush, bullhead-lily (Nuphar variegatum), and arrow-arum intermixed with arrowheads (Sagittaria spp.), bur-marigolds (Bidens spp.), and other low-growing species which occur in the low marsh zone. Pure and mixed stands of wild rice generally characterize the majority of riverine tidal marshes in the project area (Metzler and Rozsa, 1982), although nearly pure stands of common threesquare and arrowheads, or both, are common along the exposed shore of the river. Associates include Hudson arrowhead, common arrowhead (Sagittaria latifolia), common threesquare, water purslane (Ludwigia palustris), false pimpernel (Lindernia dubia), and golden club (Orontium aquaticum), the last of which is a state-listed species of special concern.

Palustrine System: These are wetlands of freshwater environments, both tidal and nontidal, which support persistent vegetation and occur primarily above the mean high tide mark. Several vegetation types of palustrine tidal emergent wetlands are present in the project area, and are especially well-developed and rich in species diversity. The first is the Acorus community-type of the mid-tidal marsh with sweet flag, three-way sedge (Dulichium arundinacium), and reed canary-grass (Phalaris arundinaceum). Associates include tussock sedge (Carex stricta), water horsetail (Equisetum fluviatile), yellow iris (Iris pseudacorus), purple loosestrife, spotted jewelweed (Impatiens capensis), common bur-marigold (Bidens frondosa), water smartweed (Polyganum amphibium), bur-reed (Sparganium eurycarpum), swamp dock (Rumex verticillata), and rice cutgrass (Leersia oryzoides).

In the Peltandra community-type, in addition to arrow-arum, a number of species may dominate including common cattail (Typha latifolia), river bulrush (Scirpus fluviatilis), and common reed. This type occurs on regularly flooded marshes, and community associates include sedges, rice cutgrass, common bur-marigold, and blue flag (Iris versicolor).

The Onoclea community-type of the high marsh is the most floristically diverse of the freshwater wetland community types. Characteristic and often dominant plants include sensitive fern (Onoclea sensibilis), common cattail, and river bulrush. Associates include marsh fern (Thelypteris palustris), ground-nut (Apios americana), clearweed (Pilea pumila), cut-leaved water-horehound (Lycopus americana), arrow-leaved tearthumb (Polygonum sagittatum), spotted Joe-Pye-weed (Eupatorium maculatum), marsh bellflower (Campanula aparinoides), and tall meadow-rue (Thalictrum polygamum).

In the subtidal areas, there are nearly twenty species of aquatic vascular plants (see Table 2) that occur in the submerged aquatic vegetation beds in the project area waters. The most common species are tape-grass, pondweed (Potamogeton spp.), coontail (Ceratophyllum demersum), and water-weed. The core site waterbodies containing the greatest diversity of submerged aquatic vascular plant species are Hamburg Cove, Selden Cove, and Salmon River.

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