Mudflats

Estuarine mudflats, Shoeburyness © Claudia Watts

Introduction

Mudflats are created by the deposition of fine silts and clays in sheltered low energy coastal environments such as estuaries, where they may form the largest part of the intertidal area. Mudflats play an important role in coastal defence, dissipating wave energy. They also have a high biological productivity with abundant invertebrates such as ragworms, lugworms, sandhoppers, cockles and Hydrobia snails that provide food for internationally important populations of migrant and wintering birds. Mudflats are also important fish nurseries for species such as plaice.

Threats

• Land reclamation

  Common periwinkle (Littorina littorea) © Claudia Watts

• Barrage schemes
  Creation of enclosed bays for amenity or perceived aesthetic reasons destroys mudflats and the associated wildlife interest
• Sea level rise
  As sea levels rise, sea defences prevent compensating landward migration of high water mark, thus squeezing out intertidal flats. There may be insufficient mobile sediment to adjust to new tidal levels in some cases; in other circumstances erosion of mud flats may reduce their extent and quality
• Dredging for navigation
  This has a negative impact on sediment supply and the sediment biota
• Pollution
  Industrial and agricultural run-off or polluted storm-water discharge, including eutrophic river water, can create abiotic areas or encourage the growth of algal mats that will adversely affect invertebrate communities
• Bait digging
• Invasion by hybrid cord-grass Spartina anglica
  This has spread along coasts and vegetated some upper-shore mudflat areas, disrupting the ecology.

Juvenile Common shore crab (Carcinus maenas) © Claudia Watts

Habitat management

Ensure that natural tidal movements are not impeded and that there is continued presence of brackish pools, ditches and muddy creeks.

Coastal defences should not interfere with existing patterns of movement of sediments and it should be appreciated that extensive defence work on soft maritime cliffs and slopes some distance up-current from mudflats may have an adverse effect.

Rare and scarce terrestrial invertebrates associated with mudflats:

Centipedes (Chilopoda)
Schendyla peyerimhoffi		Nb
Geophilus fucorum		Nb
True bugs (Hemiptera-Heteroptera)
Saldula setulosa		RDB2
Flies (Diptera)
Snail-killing flies, picture-wing flies, grass flies and allies (Acalyptrata)
Parydroptera discomyzina	(Ephydridae)	RDB2
Leptocera varicornis	(Sphaeroceridae)	N
Beetles (Coleoptera)
Rove beetles and allies (Staphylinidae / Scydmaenidae / Silphidae)
Bledius diota		RDBK
Bledius furcatus		RDB1
Carpelimus schneideri		RDB1
Arena tabida		RDBK
Bledius tricornis		Nb
Diglotta sinuaticollis (D. submarina)		N
Bledius limicola		Local
Bledius spectabilis		Local
Bledius subniger		Local
Bledius unicornis		Local

This habitat is essentially a marine one and as such is not fully covered by the Buglife Habitat management handbooks, which deal with terrestrial invertebrate groups. Little information is therefore available to offer management advice for this Priority Habitat.

For more detailed habitat management advice, Buglife has produced a series of handbooks on 32 BAP priority habitats, written by leading national experts. For further details please contact Buglife on 01733 201 210 or info@buglife.org.uk

The ‘Managing Priority Habitats for Invertebrates’ series has been funded by the Department for Environment, Food and Rural Affairs as a resource for land managers and advisors. Details of Defra's schemes can be found at www.defra.gov.uk/erdp/schemes/es/default.htm

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