The brackish lagoons of Kings Marsh on Orford Ness

Lagoons on Kings Marsh Orford Ness

Orford Ness contains one of the largest areas of unimproved brackish marsh in Suffolk. Brackish lagoons are an important habitat because they support a small but significant group of unusual plants and animals, as a result of the fluctuating salt content of the water.

The original lagoons

Coastal brackish lagoons are listed as a priority habitat in Annex 1 of the EC Habitats Directive (92/43/EEC) and are a key habitat within the UK and Suffolk Biodiversity Action Plans (BAPs).

In a national context the Alde-Ore complex, of which Orford Ness is part, is one of the richest sites for brackish lagoons. These lagoons (pools with a mix of fresh and salt water) in Kings Marsh are mostly man-made structures. They were originally 'borrow pits' formed when clay was 'borrowed' for use in the construction and repair of the river walls.

Only very few species can tolerate the changing salt levels in these lagoons, and we have some nationally very rare species, such as the starlet sea anemone (Nematostella vectensis), a species within the UK BAP. The importance of this habitat is one reason why Orford Ness was designated as a Special Area for Conservation under European Union Directives.

New lagoons

In order to protect against the loss of this brackish water coastal lagoon habitat to actions of the sea, two new lagoons were constructed in Kings Marsh during 1998.

The new lagoons, lying adjacent to a clay defence wall, were created under an EU LIFE Nature project and also fulfilled part of the proposal to increase the area of these lagoons under the Suffolk BAP.

The new lagoons complement the existing ones and help to ensure the continuation of this important habitat and the species that need it, such as the starlet sea anemone (Nematostella vectensis). They also provide a great environment for water-based invertebrates such as shrimp, which are an excellent food source for breeding avocet, redshank, oystercatcher and migratory waders.

In 2011 further work was done as part of the third EU-funded LIFE project on the Ness. Two new brackish lagoons were created in the Kings Marsh. The northernmost lagoon also links to Stony Ditch through an inlet sluice, and via a water control point to the network of creeks and ditches that control water levels within the marsh. By carefully using the sluice and controls, water levels can be better managed within the Kings Marsh, particularly to encourage avocet, common tern and other nesting birds to use the islands in the lagoons.