The recent acquisition of Dingle Marshes, a collaborative effort by SWT, RSBP and English Nature, makes this an appropriate time to feature Saline Lagoons. The new reserve was bought at a cost of £850,000 with the assistance of the National Heritage Lottery Fund, and includes coastal and flood plain grazing marsh and reedbed as well as 21 lagoons with estuarine sedimentary fauna. Members who read their copy of Suffolk Natural History (SNS Transactions Vol 35) over the Christmas break, will recall that it included an article on saline lagoons with coloured illustrations of some of the rare estuarine fauna that can benefit from conservation measures. The Lagoon sand shrimp and the Spire snail are two of these, but the standard bearer BAP species amongst this group is the Starlet sea anemone.
| Saline Lagoons |
| Starlet sea anemone |
| Bright wave moth |
The Bright wave, another rare inhabitant of sandy shingle beaches, was the target of a 1999 field meeting at Thorpeness, and several separate visits by members of the Suffolk Moth Group. It seems likely that this National BAP species may have abandoned its Suffolk localities, as it has not been positively identified here for some years.
Brackish lagoons are composed of a range of dynamic environmental conditions which make them particularly challenging habitats for colonisation by aquatic species. Coastal lagoons in Suffolk have varied forms and salinity and they support an unusual fauna and flora, including some national rarities.
1 Definition
Lagoons are essentially bodies of saline water, natural or artificial, partially separated from the adjacent sea. They retain a proportion of their sea water at low tide and may develop as brackish, full saline or hyper-saline water bodies.
In Suffolk there are four types of brackish lagoon: firstly, small rivers that have been ponded back by shingle bars over which the sea occasionally transgresses (for example Benacre, Easton and Covehithe Broads); secondly, pools enclosed and isolated within a shingle beach (such as at Shingle Street); thirdly, shallow pools on clay (often former grazing marshes) trapped behind ridges of shingle eg. behind the Walberawick / Dunwich shingle ridge; and fourthly, brackish bodies behind sea walls fed by percolation, sea spray or sluices (lagoons on Havergate Island). Both the latter two formations are fed by rain water and percolating sea water through the shingle and tend to be very saline.
There are 26 species of flora and fauna that are indicative of brackish lagoons. Of these 14 are present, or have been recorded, in the brackish lagoons of Suffolk. Of particular note are the Starlet sea anemone Nematostella vectensis, which occurs in very high densities (up to 10 000 individuals / m2, the snails Hydrobia ventrosa and H. neglecta, the lagoon cockle, Cerastoderma glaucum and the crustacean Gammarus insensibilis.
2 Current status
2.1 Local
All of the fifteen brackish lagoons (individual lagoons or groups) in Suffolk have been designated as SSSIs (44 hectares) or CWSs (16 hectares). Suffolk contains about 8% of the national resource.
2.2 Natural Areas
Suffolk Coast and Heaths, Suffolk Coast Maritime.
3 Current factors affecting the habitat in Suffolk
The processes which lead to the natural development of some types of lagoons are generally inhibited by human coastal activities. It is probable that the formation of new lagoons will not keep pace with the process of lagoon loss. Current factors affecting this habitat in Suffolk include:
The lagoons behind them will eventually be filled as bar sediments approach the shore.
4 Current action
4.1 Legal status
In Great Britain 10 species of invertebrate and plant associated with lagoons are protected under the Wildlife and Countryside Act 1981. Of these the Starlet sea anemone Nematostella vectensis, the crustacean Gammarus insensibilis and the polychaete worm Alkmaria romijni occur in Suffolk.
4.2 Management research and guidance
A shoreline management plan for the Suffolk coast has been produced by Suffolk Coastal District Council, Waveney District Council and the Environment Agency. The plan identifies key lagoons and promotes policies relevant to their management. The overall policy of the SMP is to allow the natural operation of coastal processes where this does not have economic or human interest consequences. At Benacre, Covehithe and Easton broads, implementation of this policy will result in loss of land, including the existing saline lagoons, over the next 75 years. It is not economically or environmentally desirable to provide defences along this section
of coast, although the SMP promotes some management work to slow down the rate of coastal retreat. The need to create saline lagoon habitat to compensate for losses due to coastal erosion is recognised in the SMP. This is an issue which may be addressed through UK Government compliance with the Habitats Directive. Already, the National Trust is involved with lagoon creation at Orford Ness and by the end of 1998 will have created l.9 ha of new lagoon.
5 Action plan objectives and targets
1 Maintain the existing area, number and distribution of lagoons on the Suffolk coast.
2 Create a further 5-10 ha of saline lagoon habitat by the year 2010 to maintain existing resource and to compensate for potential habitat loss through coastal erosion.
This species occurs along the Atlantic and Pacific coasts of North America but otherwise is only known from England in Europe. It is usually found buried upright in soft muds at the edges of creeks in saltmarshes and in brackish pools, sometimes attached to sea grasses or algae. It feeds on small invertebrates associated with mudflats.
1 Current status
1.1 National
The Starlet sea anemone occurs in only a few coastal lagoons in the southern counties of England and along the East Anglian coast. It may also occur in some brackish ponds and ditches.
The species is listed as vulnerable by IUCN/WCMC and rare on the GB Red List.
1.2 Local
This species is present in the complex of lagoons at Shingle Street and Orfordness, and a recent survey revealed its existence in three of the lagoons. Several specimens have been recently recorded (1997) from lagoons on Havergate Island and from Benacre and Covehithe Broads. It also occurs in very high densities (up to 10 000 per m2) in some of the shore pools behind the shingle barrier at Dunwich. This species has been found in mud samples from the mudflats on the northern side of the Stour Estuary. This is a very atypical habitat, but potentially it may occur elsewhere within the Stour estuary and possibly in other estuaries where conditions are suitable.
1.3 Natural Areas
Suffolk Coast Maritime.
1.4 Protection
It is protected under Schedule 5 of the Wildlife and Countryside Act 1981.
2 Current factors causing loss or decline
Loss and damage to lagoons and other sheltered brackish water habitats caused through coastal erosion, pollution, drainage and other activities. .
3 Current action
Saline lagoons are a priority habitat under the EC Habitats Directive. Two sites in Suffolk, Benacre-Easton Bavents SSSl and Orfordness (part of the Alde-Ore Estuary SSSl), have been designated Special Areas of Conservation for their saline lagoons.
4 Action plan objectives and targets
1 Maintain and protect viable populations at all known localities in the county for this species.
2 Assess the status of this species in the Stour Estuary and brackish ponds and ditches in the vicinity of known populations.
3 If feasible, introduce to one new site by the year 2005
This moth has a bright orange ground colour and flies from late June to early August and overwinters as a larva. It inhabits coastal sandhills and sandy shingle beaches and rests during the day amongst small bushes or low herbage.
1 Current status
1.1 National
The moth occurs on only three areas of coast in Great Britain; in Kent (from Walmer to Sandwich), near St Osyth, Essex and in Suffolk. It is believed to be declining at two of these. The species is listed as rare on the GB Red List, but may be regarded as vulnerable.
1.2 Local
The moth is known to occur on a 3 km stretch of coast from Thorpeness to Aldeburgh. This land is managed as a Local Nature Reserve (with a management agreement with RSPB) and a Suffolk Wildlife Trust Reserve. The moth was recorded in 1982 by B. Elliot & B. Skinner). Little is known about its ecology. 
1.3 Natural Areas
Suffolk Coast Maritime.
1.4 Protection
None.
2 Current factors causing loss or decline.
Recreational pressure on upper beaches.
3 Current action
Survey work was undertaken in 1997 through English Nature's Species Recovery Programme, but without success.
4 Action plan objectives and targets
1 Identify the status and precise habitat requirements of this species in Suffolk.
2 Maintain or restore a viable population within the currently or previously occupied areas..
