20 



systems (Hutchinson 1975). Though less abundant 

 than lichens, aquatic liverworts such as Marsupella 

 emarginata var. aquatica or mosses such as Fissidens 

 julianus are found on the rocky shores of lakes and 

 rivers. If aquatic liverworts or mosses cover 30% or 

 more of the substrate, they should be placed in the 

 class Aquatic Bed. Other examples of Rocky Shore 

 dominance types are the caddisfly Hydropsyche and 

 the fingernail clam Pisidium. 



Unconsolidated Shore 



Definition. The class Unconsolidated Shore includes 

 all wetland habitats having three characteristics: (1) 

 unconsolidated substrates with less than 75% areal 

 cover of stones, boulders, or bedrock; (2) less than 30% 

 areal cover of vegetation other than pioneering plants; 

 and (3) any of the following water regimes: irregularly 

 exposed, regularly flooded, irregularly flooded, season- 

 ally flooded, temporarily flooded, intermittently 

 flooded, saturated, or artificially flooded. Intermittent 

 or intertidal channels of the Riverine System or inter- 

 tidal channels of the Estuarine System are classified 

 as Streambed. 



Description. Unconsolidated Shores are charac- 

 terized by substrates lacking vegetation except for 

 pioneering plants that become established during brief 

 periods when growing conditions are favorable. 

 Erosion and deposition by waves and currents produce 

 a number of landforms such as beaches, bars, and 

 flats, all of which are included in this class. Uncon- 

 solidated Shores are found adjacent to Unconsolidated 

 Bottoms in all systems; in the Palustrine and Lacus- 

 trine systems, the class may occupy the entire basin. 

 As in Unconsolidated Bottoms, the particle size of the 

 substrate and the water regime are the important 

 factors determining the types of plant and animal com- 

 munities present. Different substrates usually support 

 characteristic invertebrate fauna. Faunal distribution 

 is controlled by waves, currents, interstitial moisture, 

 salinity, and grain size (Hedgpeth 1957; Ranwell 1972; 

 Riedl and McMahan 1974). 



Subclasses and Dominance Types. 

 Cobble-Gravel— The unconsolidated particles 

 smaller than stones are predominantly cobble and 

 gravel that have been transported away from Cob- 

 ble-Gravel shores by waves and currents. Shell 

 fragments, sand, and silt often fill the spaces between 

 the larger particles. Stones and boulders may be found 

 scattered on some Cobble-Gravel shores. In areas of 

 strong wave and current action these shores take the 

 form of beaches or bars, but occasionally they form 

 extensive flats. Examples of dominance types in the 

 Marine and Estuarine systems are: the acorn barnacle 

 Balanus, the limpet Patella, the periwinkle Littorina, 

 the rock shell Thais, the mussels Mytilus and Modio- 

 lus, and the Venus clam Saxidomus. In the Lacustrine, 



Palustrine, and Riverine systems examples of domi- 

 nance types are the freshwater mollusk Elliptio, the 

 snails Lymnaea and Physa, the toad bug Gelastocoris, 

 the leech Erpodella, and the springtaiMgrem'a. 



Sand.— The unconsolidated particles smaller than 

 stones are predominantly sand which may be either 

 calcareous or terrigenous in origin. They are promi- 

 nent features of the Marine, Estuarine, Riverine, and 

 Lacustrine systems where the substrate material is 

 exposed to the sorting and washing action of waves. 

 Examples of dominance types in the Marine and 

 Estuarine systems are the wedge shell Donax, the soft- 

 shell clam Mya, the quahog Mercenaria, the olive shell 

 Oliva, the blood worm Euzonus, the beach hopper 

 Orchestia, the pismo clam Tivela stultorum, the mole 

 crab Emerita, and the lugworm Arenicola. Examples 

 of dominance types in the Riverine, Lacustrine, and 

 Palustrine systems are the copepods Paras tenocaris 

 and Phvllognathopus; the oligochaete worm Pristina; 

 the freshwater mollusks Anodonta and Elliptio; and 

 the fingernail clams Pisidium and Sphaerium. 



Mud.— The unconsolidated particles smaller than 

 stones are predominantly silt and clay. Anaerobic 

 conditions often exist below the surface. Mud shores 

 have a higher organic content than cobble-gravel or 

 sand shores. They are typically found in areas of minor 

 wave action. They tend to have little slope and are fre- 

 quently called flats. Mud Shores support diverse popu- 

 lations of tube-dwelling and burrowing invertebrates 

 that include worms, clams, and crustaceans (Gray 

 1974). They are commonly colonized by algae and 

 diatoms which may form a crust or mat. 



Irregularly flooded Mud Shores in the Estuarine 

 System have been called salt flats, pans, or pannes. 

 They are typically high in salinity and are usually sur- 

 rounded by, or lie on the landward side of, Emergent 

 Wetland (Martin et al. 1953, Type 15). In many arid 

 areas, Palustrine and Lacustrine Mud Shores are 

 crusted or saturated with salt. Martin et al. (1953) 

 called these habitats inland saline flats (Type 9); they 

 are also called alkali flats, salt flats, and salt pans. 

 Mud Shores may also result from removal of vege- 

 tation by man, animals, or fire, or from the discharge 

 of thermal waters or pollutants. 



Examples of dominance types in the Marine and 

 Estuarine systems include the fiddler crab Uca, the 

 ghost shrimp Callianassa, the mud snails Nassarius 

 and Macoma, the clam worm Nereis, the sea anemone 

 Cerianthus, and the sea cucumber Thyone. In the 

 Lacustrine, Palustrine, and Riverine systems, 

 examples of dominance types are the fingernail clam 

 Pisidium, the snails Aplexa and Lymnaea, the crayfish 

 Procambarus, the harpacticoid copepods Cantho- 

 camptus and Bryocamptus, the fingernail clam 

 Sphaerium, the freshwater mollusk Elliptio, the shore 

 bug Saldula, the isopod Asellus, the crayfish Cam- 

 barus, and the mayfly Tortopus. 



Organic— The unconsolidated material smaller 



