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Estuarine Systems

General Description and Location Estuaries form one of the predominant landscapes of the coastal zone. They consist of interconnected networks of intertidal marshland with tidal channels of various sizes branching throughout, generally interfacing with marine or Atlantic Ocean waters via deep channels through sounds and bays or through smaller inlets. Following are the generally recognized vegetative and geophysical components of estuaries and their interrelationships:

  • Salt Marsh. Intertidal marshlands in estuarine (salinity ranges 15 to ~40 ppt) areas that are variously flooded and dewatered by tidal forces, with influence from lunar cycles, wind, rainfall and river discharge, particularly within or near river deltas. Smooth cordgrass (Spartina alterniflora) is the dominant plant.

  • Black Needlerush Marsh. The portion of highest elevation salt marsh dominated by black needlerush (Juncus roemerianus), which often occurs in dense stands. This habitat is usually near uplands.

  • Salt Flat. Sparsely vegetated, hypersaline (greater than 40 ppt salinity) and exposed flats of sand and/or mud. Typical plants include glassworts (Salicornia spp.) and saltwort (Batis maritima).

  • Salt-Shrub Thicket. Bands or patches of usually low, dense shrubs that typically interface high salt marsh and uplands. Characteristic plants include sea ox-eye (Borrichia frutescens), marsh elder (Iva frutescens) and groundsel tree (Baccharis halimifolia).

  • High Marsh Pool. Poorly drained pools in high salt marsh, often near uplands. Salinity is highly variable depending on frequency and timing of tidal input and rainfall. Both soils and water may become hypersaline (greater than 40 ppt salinity).

  • Estuarine Intertidal Flat. Mud and sand flats in estuarine systems that have little or no vegetation and are dewatered on ebb tide and submerged during high tides. Mud and sand flats may occur between marshlands and channels and creeks or may be interspersed within marshlands.

  • Estuarine Intertidal Sandbar. Sandbars in estuarine systems that are partially exposed during part of most tide cycles and river stages but are typically submerged during high tide.

  • Estuarine Tidal Channels and Creeks. Tidal estuarine waterways of variable depth and with currents generated by riverine and/or tidal flows.

  • Estuarine Subtidal/Submerged Flat. Mud and sand flats with little or no vegetation that are inundated during all or part of each tidal cycle. Submerged flats include sand and/or mud bottom areas outside of channels and creeks and usually lie between channel habitats and tidal marshlands.

  • Oyster Reef. Bars or reefs primarily composed of live and dead eastern oyster (Crasostrea virginica). Oyster reefs can be either intertidal or subtidal and are usually in flats between tidal channels and salt marsh. Reefs may occur in flats within expanses of salt marsh.

Associated Species

Highest Priority: High Priority: Moderate Priority

Louisiana (Tri-colored) Heron, Black Rail, Black Skimmer Mink, Diamondback Terrapin, Black-bellied Plover, Bottlenose Dolphin : Greater Scaup

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