Estuarine, intertidal, mixed fine, lagoon, eulittoral

Lagoons are formed when longshore water-borne sediments are deposited to form a spit closing off (partially or totally) an embayment.  Open lagoons are regularly flushed by freshwater and tidal action through a channel, while enclosed ones have no permanent channel and rarely flush.  The latter are usually filled gradually by salt marsh vegetation.  Some lagoons drain completely at low tide, while others retain water because of a sill in the channel. Water in the lagoon evaporates, concentrating salts. Interstitial salinities can reach as much as 80 ppt, but are more commonly in the euhaline range. Toward the landward end of these lagoons, the salinity can grade to < 0.5 ppt if there is freshwater influence.  Productivity is high because of marsh vegetation, eelgrass, microalgae, and terrestrial input. Shorebirds, waterfowl, river otters, and hawks all use these habitats.  Tidal creeks draining lagoons tend to contain mixed-coarse substrata and are occupied by a unique set of plants and animals using this high-flow, variable-salinity habitat.  Probably the inhabitants of each lagoon creek are different, although all will contain filter feeders, epifaunal and infaunal.  Few surveys of benthic organisms in lagoons were found.