Table 1. Continued. 



System and Subsystem 8 



Riverine 



Lacustrine 



TI 



LP 



UP 



IN 



LM 



LT 



Palustrine 



X 

 X 

 X 

 X 

 X 



a ST = Subtidal, IT = Intertidal, TI = Tidal, LP = Lower Perennial, UP = Upper Perennial, IN = Intermittent, LM = Limnetic, 

 LT = Littoral. 



mangle) and eastern oysters (Crassostrea virginica), are 

 also included in the Estuarine System. 3 



Limits. The Estuarine System extends (1) upstream and 

 landward to where ocean-derived salts measure less than 

 0.5°/oo during the period of average annual low flow; (2) 

 to an imaginary line closing the mouth of a river, bay, or 

 sound; and (3) to the seaward limit of wetland emergents, 

 shrubs, or trees where they are not included in (2). The 

 Estuarine System also includes offshore areas of contin- 

 uously diluted sea water. 



Description. The Estuarine System includes both es- 

 tuaries and lagoons. It is more strongly influenced by its 

 association with land than is the Marine System. In terms 

 of wave action, estuaries are generally considered to be 

 low-energy systems (Chapman 1977:2). 



Estuarine water regimes and water chemistry are 

 affected by one or more of the following forces: oceanic 

 tides, precipitation, freshwater runoff from land areas, 

 evaporation, and wind. Estuarine salinities range from 

 hyperhaline to oligohaline (Table 2). The salinity may be 

 variable, as in hyperhaline lagoons (e.g., Laguna Madre, 

 Texas) and most brackish estuaries (e.g., Chesapeake Bay, 

 Virginia-Maryland); or it may be relatively stable, as in 

 sheltered euhaline embayments (e.g., Chincoteague Bay, 

 Maryland) or brackish embayments with partly obstructed 

 access or small tidal range (e.g., Pamlico Sound, North 

 Carolina). (For an extended discussion of estuaries and 

 lagoons see Lauff 1967.) 



Subsystems. 

 Subtidal.—The substrate is continuously submerged. 

 Inter tidal.— The substrate is exposed and flooded by 

 tides; includes the associated splash zone. 



3 The Coastal Zone Management Act of 1972 defines an estuary 

 as "that part of a river or stream or other body of water having 

 unimpaired connection with the open sea, where the sea-water 

 is measurably diluted with freshwater derived from land 

 drainage." The Act further states that "the term includes estuary- 

 type areas of the Great Lakes." However, in the present system 

 we do not consider areas of the Great Lakes as Estuarine. 



Classes. Rock Bottom, Unconsolidated Bottom, Aquatic 

 Bed, Reef, Streambed, Rocky Shore, Unconsolidated 

 Shore, Emergent Wetland, Scrub-Shrub Wetland, and 

 Forested Wetland. 



Riverine System 



Definition. The Riverine System (Fig. 4) includes all 

 wetlands and deepwater habitats contained within a chan- 

 nel, with two exceptions: (1) wetlands dominated by trees, 

 shrubs, persistent emergents, emergent mosses, or 

 lichens, and (2) habitats with water containing ocean- 

 derived salts in excess of 0.5'Voo. A channel is "an open 

 conduit either naturally or artificially created which 

 periodically or continuously contains moving water, or 

 which forms a connecting link between two bodies of 

 standing water" (Langbein and Iseri 1960:5). 



Limits. The Riverine System is bounded on the land- 

 ward side by upland, by the channel bank (including 

 natural and man-made levees), or by wetland dominated 

 by trees, shrubs, persistent emergents, emergent mosses, 

 or lichens. In braided streams, the system is bounded by 

 the banks forming the outer limits of the depression within 

 which the braiding occurs. 



The Riverine System terminates at the downstream end 

 where the concentration of ocean-derived salts in the 

 water exceeds 0.5°/oo during the period of annual average 

 low flow, or where the channel enters a lake. It terminates 

 at the upstream end where tributary streams originate, 

 or where the channel leaves a lake. Springs discharging 

 into a channel are considered part of the Riverine System. 



Description. Water is usually, but not always, flowing 

 in the Riverine System. Upland islands or Palustrine wet- 

 lands may occur in the channel, but they are not included 

 in the Riverine System. Palustrine Moss-Lichen Wet- 

 lands, Emergent Wetlands, Scrub-Shrub Wetlands, and 

 Forested Wetlands may occur adjacent to the Riverine 

 System, often on a floodplain. Many biologists have sug- 

 gested that all the wetlands occurring on the river flood- 

 plain should be a part of the Riverine System because they 



