Bodies of saline water partially separated from the sea and retaining some brackish, saline or hyper-saline water at low tide.
Four types occur in Suffolk: 1. Small rivers that have been ponded back by shingled bars and are occasionally over-topped by the sea; 2. Pools enclosed within a shingle beach; 3. Shallow pools on clay trapped behind ridges of shingle fed by percolating sea water; 4. Bodies of water behind sea walls fed by both rainwater and percolating sea water, sea spray or sluices.
Importance for wildlife
Saline lagoons occur in a range of dynamic conditions giving rise to varied forms and salinity. They support a range of salt-tolerant species including: Starlet Sea Anemone Nematostella vectensis, Mud snails Hydrobia sp. and H. neglecta, Lagoon Cockle Cerastoderma glaucum, Lagoon Sand Shrimp Gammarus insensibilis and Avocet Recurvirostra avosetta. They are part of a complex mosaic of coastal habitats, including vegetated shingle, saltmarsh and coastal and floodplain grazing marsh.
Important associated species
- Black-tailed Godwit Limosa limosa (winter feeding)
- Avocet Recurvirostra avosetta
- Herrring Gull Larus argentatus subsp. argenteus
- Starlet Sea-anemone Nematostella vectensis
- Lagoon Sand Shrimp Gammarus insensibilis
- Fancy-legged Fly Campsicnemus magius (bare banks)
- Bearded Stonewort Chara canescens
*Suffolk Priority species
**Priority - Research Only. Common and widespread, but rapidly declining
Factors affecting habitat in Suffolk
- Sea level rise occurring too fast for coastal habitat formation to keep pace with.
- Bar-built sedimentary barriers moving naturally landwards over time, leading to the broads being filled in by sediments.
- Pollution causing nutrient enrichment, which can have major detrimental effects.
- Coastal defence works preventing sediments moving along the shore and leading to the loss of coastal structures where many coastal lagoons are located.
- Encroachment by common reed (Phragmites australis).
- Damage to lagoons by removal of material or during maintenance of coastal defence structures
Habitat management advice
- Maintain water quality: Water pollution is likely to affect all elements of the special fauna.
- Minimise human disturbance: Poorly managed physical disturbance can have a detrimental effect on bird populations.
- Maintain structural diversity: Convoluted margins, shallow areas and islands add variety and also help to disrupt turbulent mixing induced by wind.
- Encroachment from the lagoon edge of beds of Phragmites or Sea club-rush (Bolboschoenus maritimus) may significantly affect the extent and structural quality of the lagoonal habitat, but sometimes a limited amount of vegetation encroachment may be acceptable. For example, reeds can provide sheltered habitat for the Starlet sea-anemone (Nematostella vectensis) and a substratum for bryozoan colonies.
- Maintain the margins: It is the margins of saline lagoons that are of importance to many invertebrates. The management of the surrounding habitat is therefore as important to these groups as the lagoon itself.
Vision for Suffolk
- Improve knowledge of extent and quality of saline lagoons.
- Maintain the existing extent of saline lagoons to ensure no net loss.
- Re-create lowland saline lagoons as opportunities arise.
- Encourage the restoration and improvement of degraded saline lagoons.
Where to find further information
- Buglife – advice on managing BAP habitats
- Buglife – Notable invertebrates (pdf)
- JNCC – Habitat Description (pdf)
- MAGIC website – interactive mapping information including designations
- Making Space for Nature, a Review of England’s Wildlife Sites and Ecological Network 16 Sep 2010. Chaired by Professor Sir John Lawton CBE FRS. Defra website (pdf)
- Natural Environment White Paper June 2011 – The Natural Choice: securing the value of nature (pdf)
- Benacre broad by Emma Aldous
- Starlet sea-anemone by Smithsonian Environmental Research Center
- Redshank by Edwyn Anderton (Flickr)
- Small Phoenix by Paul Kitchener (Flickr)