Estuarine Mudflats

• Location of Morecambe Bay

  It is in the North-west of England and is the confluence of four principal estuaries, the Leven, Kent, Lune and Wyre.

  Collectively these form the largest single area of continuous intertidal mudflats in the UK.
• What is the Spring Tidal range of Morecambe Bay

  9m
• What plants and organisms are present in Morecambe Bay?

  The estuaries support dense invertebrate communities. Extensive glasswort are present in the Lune estuary, contrasting with the fringing saltmarshes and more open intertidal flats of the Leven and Kent estuaries.
• What is a tidal mudflat / saltmarsh?

  If there is sheltered water in river estuaries or behind splits, silt and mud will be deposited as the saltwater flows into the estuary bringing fine sediments which meets the equally slow moving river which is also carrying its own load of fine silts and clays. As the two flows meet fine particles settle by the process of flocculation. This creates a zone called an intertidal mudflat.
• Algae, see rush and glasswort

  A few plants such as algae can tolerate this lengthy submergence and the high levels of salinity. 

  These small saline tolerant plants are able to trap mud around them increasing the height of the mud, creating a surface that remains exposed for increasingly longer periods between tides. 
• Sward Zone

  • The landward side of the intertidal mudflat is marked by a small cliff above which is the sward zone. This zone may only be covered by the sea for less than 1 hour in each 12 hour tidal cycle. 
  • In the sward zone sea water may collect in hollows which become increasingly saline as water evaporates. These hollows often enlarge into saltpans which are devoid of vegetation for algae and the occasional halophyte 
  • As the tide retreats water drains into creeks which are then eroded rapidly
  • The upper sward zone may only be inundated by the highest spring tides. 
• Examples of halophytes

  Sea rush and glasswort.
• Mudflats

  Mudflats are low-lying areas of the shore found in estuaries or behind spits, submerged at high tide, and made of silt and clay. They form where the slow-moving freshwater from rivers meets the incoming seawater at high tide. This interaction brings fine sediments, and through flocculation, the particles clump together and settle. When the tide recedes, the mudflats are exposed, revealing a smooth surface with signs of tidal action. They can cover vast areas, sometimes spanning tens of square kilometers.
• Saltmarsh 1. Formation of a mudflat

  • In areas of low energy (often behind a spit or bar)
  • sediment accumulates, sticks together, and builds up to form mudflats
• Saltmarsh 2. Low Marsh

  • Pioneer plants colonise area
  • Cordgrass - have long roots to trad sediments, encourage deposition and stabalise the mudflat
• Saltmarsh 3. High Marsh

  • Conditions less harsh, mud level rises
  • Rain washes out salt
  • Decomposition of plants increases soil fertility
• Saltmarsh 4. Uplands

  • rarely submerged
  • characterised by oak trees and shrubs
• 4 marks - Development of a Saltmarsh

  • Salt marshes tend to develop in sheltered estuaries behind spits
  • Silt is deposited by the river which gradually builds up to form an intertidal mud flat
  • The mud flat continues to build and rise above sea level with the addition of further silt
  • Vegetation which is highly adapted to environment colonises the mud which itself traps further sediment