- 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
Mudflats
- 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
Threats:
- Agriculture
- Land reclamation
- Sea defences
- Industry like power stations and oil refineries
- Clay extraction
- Leisure
- Dredging
- Alien species
- Sea level rise
- Storms
- Climate changes
Management:
- 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