Natural Community Systems -- Photo Guide

Sparsely vegetated intertidal system

sparsely vegetated intertidal system at Great Bay National Wildlife Refuge (photo by Ben Kimball for the NH Natural Heritage Bureau)
Sparsely vegetated intertidal system at Great Bay National Wildlife Refuge 
(photo by Ben Kimball)


DescriptionThis system consists of intertidal areas with sparse vascular vegetation.  It includes partially protected intertidal shores along rivers and other embayments; coastal shoreline strand/swales on coarse to fine mineral sediments; intertidal rocky shores on rocky or cobbly materials; and intertidal mudflats on broad to narrow, nearly flat extents of sand, mud, and silt.  Vascular plant cover is sparse to generally no more than 25%.

Coastal shoreline strand/swales are flooded less than daily and are often characterized by plant stems and other detritus washed in on the higher tides and covering much of the substrate surface.  These upper intertidal areas form either large patches or narrow strands along protected low-energy shorelines and are important habitat for various arthropods, shore birds, and other animals. 

Intertidal rocky shores are on open stretches of estuarine rivers and streams or quiet, partially enclosed shores.  They are flooded daily by tides.  Macroalgae are often common on bedrock and rubble including Ascophyllum nodosum on larger outcrops and Fucus vesiculosus on less stable strata.  Rocky shores may form large patches or narrow strands below the upper intertidal shoreline and are important habitat for various arthropods, predatory fish, wading birds, mud snails, and other animals.

Intertidal flats are gently sloping, sparsely vegetated areas between salt or brackish marshes landward and subtidal communities seaward (including tidal creek channels).  They form in depositional environments protected from high-energy wave action along the coast behind rocky spits, barrier beaches, and sand bars or along bays and rivers.  These flats have a great diversity of taxonomic groups and constituent species represented, including benthic diatoms and microalgae (important contributors to the estuarine primary productivity), invertebrates (including polychaete worms and mollusks), and Arthropods (green crabs, rock crabs, flat-clawed hermit crabs, and horseshoe crabs).  During the diurnal (twice daily) tidal flooding several species of fish and other aquatic species feed on the benthos and epibenthic algae.  This community also provides important foraging habitat for shorebirds and other animals when the intertidal flat is exposed.  The diverse variety of primary foods (microalgae, phytoplankton, and detritus) available to consumers supports the high productivity found on intertidal flats.  Macroalgae is typically uncommon across the exposed substrate.

Diagnostic natural communities:

      • Coastal shoreline strand/swale (S2)

      • Intertidal rocky shore (S3)

      • Intertidal flat (S3)

Landscape settings: partially protected, intertidal coastal embayments

Soils: fine to coarse mineral and rocky substrates; moderately to strongly minerotrophic

Spatial pattern: large patch, extensive narrow-linear to extensive fringes; 101,000+ m long lengths of shoreline; uniform or narrow zonation parallel to shore

Physiognomy: sparsely vegetated

Distribution: restricted to the Great Bay estuarine complex, tidal coastal rivers, and other tidal embayments

Characteristic species:

Coastal shoreline strand/swales
   Spergularia marina (seabeach sand-spurrey)
   Salicornia europaea (common glasswort)
   Suaeda linearis (southern sea-blite)
   Limonium carolinianum (sea lavendar)
   Puccinellia maritima (seaside alkali-grass)

Associated systems:  This system occurs between salt marsh systemsbrackish tidal riverbank marsh systems or upland communities landward and subtidal systems seaward.

sparsely vegtated intertidal system at Great Bay (photo by Ben Kimball for the NH Natural Heritage Bureau)
sparsely vegetated intertidal system at Great Bay (photo by Ben Kimball)

sparsely vegetated intertidal system at Adams Point (photo by Ben Kimball)
sparsely vegetated intertidal system
at Adams Point (photo by Ben Kimball)

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