Area: 748.11 hectares.
The overall site is comprised of coastal brackish / saline lagoons covering 65% of the area, sand and shingle shores (including dune systems) 29.3%, permanent saline / brackish marshes 2.3%, tidal flats 1.9% and salt marshes 1.5%
Soil and geology:
The basic components of the site are shingle, peat, nutrient-rich, sedimentary, clay, mud, sand, gravel, pebble, chert/flint.
Containing lowland, coastal, sub-tidal rock (including rocky reefs), shingle bar, barrier beach, subtidal sediments (including sandbank/mudbank), intertidal sediments (including sandflat/mudflat), open coast (including bay), enclosed coast (including embayment), lago.
The site includes the whole of the Fleet lagoon and the adjacent Chesil Bank. The Fleet is the largest and best example of a barrier-built saline lagoon in the UK and Chesil is one of the three major shingle structures in the UK. The salinity gradient, peculiar hydrographic regime and varied substrates, together with associated reedbed and intertidal habitats and the relative lack of pollution in comparison to most other lagoons, have resulted in the Fleet becoming extraordinarily rich in wildlife. Outstanding communities of aquatic plants and animals are present, supporting large numbers of wildfowl and waders. Chesil Bank is of great significance to the study of coastal geomorphology and supports nationally important populations of shingle plants and invertebrates. It is also an important breeding site for seabirds, being the breeding site for the largest populations of little tern and ringed plover in south-west Britain.
On the landward, more stable side of Chesil Bank, large, internationally and nationally important populations of shingle plants occur including an almost continuous belt of shrubby seablite alongside the Fleet lagoon. The plant life includes no fewer than 150 species of algae and the lagoon is best known for the most extensive mixed populations of eelgrass and tasselweeds in Britain. The Fleet also supports distinct and highly unusual mollusc associations and other notable invertebrates. It is an important breeding area for fish and is a bass nursery. In all, 23 species of fish have been recorded. Other habitats which are integral components of the site include saltmarsh, reedbeds, grassland and scrub.
Special Protection Area (SPA).
The Fleet is a special protection area because of the brent goose Branta Bernicia, with an overwintering population of c.3,182.
Criteria for its selection as a Ramsar site.
1. The Fleet is an outstanding example of rare lagoon habitat and is the largest of its kind in the UK. In Europe lagoons are classified as a priority habitat by the EC Habitats and Species Directive. The site also supports rare saltmarsh habitats.
2. The Fleet supports 15 specialist lagoonal species – more than any other UK site – and five nationally scarce wetland plants as well as ten nationally scarce wetland animals. Chesil Bank is one of the most important UK sites for shingle habitats and species.
3. The site is the largest barrier-built saline lagoon in the UK, and has the greatest diversity of habitats and of biota.
4. The site is important for a number of species at a critical stage in their life cycle including post-larval and juvenile bass Dicentrarchus labrax, acting as an important nursery for this and other species.
Species/populations occurring at levels of international importance, qualifying the area as a RAMSAR site.
Species with peak counts in winter:
Dark-bellied brent goose, Branta bernicla 1,460 individuals, representing an average of B. bernicla, 1.4% of the GB population (5 year peak mean 1998/9-2002/3)
Species/populations identified subsequent to designation for possible future consideration.
Species with peak counts in winter:
Mute swan , Cygnus olor, Britain 1,169 individuals, representing an average of 3.1% of the population (5 year peak mean 1998/9-2002/3).
Noteworthy flora
Nationally important species occurring on the site.
Foxtail stonewort Lamprothamnium papulosum (Nationally Rare)
Ruppia spiralis (Nationally Scarce)
Zostera spp. (Nationally Scarce)
Noteworthy fauna
Birds
Species currently occurring at levels of national importance: Species regularly supported during the breeding season:
Little tern, Sterna albifrons albifrons, W Europe 81 apparently occupied nests, representing an average of 4.1% of the GB population (Seabird 2000 Census)
Species with peak counts in spring/autumn:
Common greenshank, Tringa nebularia, Europe/W Africa 6 individuals, representing an average of 1% of the GB population (5 year peak mean 1998/9- 2002/3)
Species with peak counts in winter:
Little egret, Egretta garzetta, West Mediterranean 24 individuals, representing an average of 1.4% of the GB population (5 year peak mean 1998/9- 2002/3)
Common pochard, Aythya ferina, NE and NW Europe 659 individuals, representing an average of 1.1% of the GB population (5 year peak mean 1998/9- 2002/3)
Red-breasted merganser, Mergus serrator, NW and C Europe 270 individuals, representing an average of 2.7% of the GB population (5 year peak mean 1998/9- 2002/3)
Common coot, Fulica atra atra, NW Europe 2139 individuals, representing an average of 1.2% of the GB population (5 year peak mean 1998/9- 2002/3)
Species Information
Nationally important species occurring on the site.
Fish.
Bass Dicentrarchus labrax
Invertebrates.
Lagoon sand worm Armandia cirrhosa (RDS insufficient info.)
Lagoon sand shrimp Gammarus insensibilis (RDS Rare)
Starlet sea anemone Nematostella vectensis (RDS Rare)
Lagoon snail Paludinella littorina (RDS Rare)
Scaly cricket Pseudomogoplistes squamiger (RDS endangered)
Lagoon sea slug Tenellia adspersa (RDS insufficient info.)