Salt Marshes

  • Found on low-energy coastlines/sheltered shorelines, often behind a spit/bar so near estuaries and harbours usually
  • High oxygen content
  • High nutrient availability
  • Light
  • Cleaning action of tides
  • Can be affected by various factors: weather/climate, tides, wave type, sea level, human actions, river regime, sediment supply

Salt marsh succession

  • Each community improves conditions for next
  • Rainwater leeches salt from soil
  • Plants try out the marsh through transpiration
  • Plants contribute organic matter
  • Up the marsh: improved soil fertility, reduced salinity, reduced sea water flooding


  • In sheltered areas
  • Low lying areas of shore submerged at high tide
  • Composed of silt and clay
  • Eelgrass, algae, pioneer species (halophytes), mixture of fine silts

Lower marsh

  • Cordgrass
  • Halophytes like spartina and glasswort
  • Covered by most tides, especially high tide

Upper marsh

  • Sea lavender
  • Sea aster
  • Rushes/reeds
  • Only covered by the highest spring tides

Carr woodland

  • Oaks and shrubs
  • Alder, willow, sallow
  • Succession stage between swamp and forest


  • Agriculture
  • Land reclamation
  • Sea defences
  • Industry like power stations and oil refineries
  • Clay extraction
  • Leisure
  • Dredging
  • Alien species
  • Sea level rise
  • Storms
  • Climate changes


  • Spit protection – sea defences
  • Managed retreat
  • Grazing management
  • Avoiding disturbances
  • Not interfering with tidal patterns
  • Salt marshes can be given special status like SSSI or Wetlands RAMSAR site

Keyhaven Salt Marsh:

  • Western Solent, Southern Hampshire
  • Behind Hurst Castle Spit, south coast of England – provides sheltered environment behind
  • Home to oystercatcher, peewit, common blue butterfly, wold spider
  • Human uses: boating, yacht club, cattle farming, birdwatching
  • Threats: groyne construction (starved spit), sea level rise (1989 storm pushed shingle onto marsh, causing damage), grazing animals
  • Spit recession – shingle pushed back onto marsh – marsh subsided under weight – spit has also been breached during storms
  • It is an SSSI and Wetlands RAMSAR site – gives it protection so damage is not done to other species
  • Armoured blocks and beach nourishment added to spit in 1996 – 550m of rock armour, spit nourished with 300,000m3 of shingle
  • Shoreline management plan 1998 – options for protecting marsh – noted that the spit and marsh are not independent of each other