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Bird's nest stonewort

What action is going on for this species?

The following will give you information on what work has been taking place through the Species Action Framework:

Species background

Bird's nest stonewort (Tolypella nidifica) is a brown-green charophyte (a type of alga), which grows to 20-30cm high on sandy substrates in brackish waters.

Why is this on the Species Action List?

Bird's nest stonewort meets criterion 1a of the Species Action Framework, as a species for conservation action.

It has declined substantially in the last 25 years and presently is known in the UK from only two sites, both in Scotland. 

There is reasonable knowledge to identify actions to benefit the species.  Other brackish water charophyte species would benefit from any habitat and water quality improvements e.g. the rare foxtail stonewort, and action could raise broader awareness of the conservation issues for charophytes and other aquatic macrophytes.

Bird's nest stonewort is a UKBAP Priority Species and is included on the Scottish Biodiversity List.

Habitat, distribution and abundance

Bird's nest stonewort grows in saline lagoons and other brackish water bodies.  In recent years it has only been recorded on North Uist in Loch an Duin and Loch an t-Struith Mhoir.  Historical records for this species exist for Norfolk, Suffolk, Shetland and Orkney (Loch of Stenness and Loch of Boardhouse).

More widely it is associated with the northern coasts of Europe including the Baltic, the North Sea and northern Norway.

General ecology

Stoneworts are associated with clear waters, containing low to moderate levels of nutrients, and are often early colonizers of new or disturbed habitats.  The term 'stonewort' refers to the fact that calcium compounds are deposited on the external surfaces of the plant, although in bird's nest stonewort this is less pronounced.  Bird's nest stonewort may tolerate salinities of 2 to 18 ppt (parts per thousand), values of 15 ppt being thought to be optimal.  Although similar in form to vascular plants, stoneworts are a group of algae, which consist of extremely large cells.  They have rhizoids, rather than roots, and as they have no vascular system, they are directly dependent on the water column for nutrients.  Reproduction is by spore production. Spores of the stonewort are believed to remain viable for many years.

History of decline, contributory factors and current threats

In Orkney the bird's nest stonewort has not been recorded in Loch of Stenness, a saline lagoon, since 1994; and it was last found in Loch of Boardhouse in 1923. Bird's nest stonewort remains in the the North Uist lochs, Loch an Duin and Loch an Struth Mhor. Pressures on stoneworts include changes in salinity, eutrophication and species succession.

The 'Species Lead' at Scottish Natural Heritage

Stewart.Angus@snh.gov.uk   Tel 01463 725000