North Merseyside Biodiversity Action Plan: Stonewort

By | August 8, 2008
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1 Current status
1.1 National
Stoneworts are large algae mostly associated with freshwater bodies ranging in size
from deep lakes and canals to small ephemeral ponds. Most species require
calcareous, low-nutrient conditions. They are, therefore, fairly restricted in
distribution, being largely confined to high water quality habitats on sand, peat or clay
Lesser Bearded Stonewort was until recently classified as Near Threatened, occurring
at only 30-35 British sites. However, information gathered as a result of the national
action plan indicates that it is more widespread than previously thought and it is no
longer classified as a Priority Species. Opposite and Clustered Stoneworts are also
Nationally Scarce, occurring in fewer than 100 10km squares in Britain.

1.2 Local
In North Merseyside stoneworts are only known to occur on the Sefton Coast. Five
species have been recorded in recent years: Lesser Bearded Stonewort Chara curta,
Opposite Stonewort Chara contraria, Bristly Stonewort Chara hispida, Common
Stonewort Chara vulgaris and Clustered Stonewort Tolypella glomerata.
Translucent Stonewort Nitella translucens was recorded in the Leeds-Liverpool Canal
in Litherland in 1977. There are local historic records of Smooth Stonewort Nitella
flexilis and Delicate Stonewort Chara virgata, the latter at Otterspool Park, Liverpool,
but it is not known if any of these still occur.
Recent surveys have only been carried out on three to four sites: Ainsdale Sand Dunes
NNR, parts of the Ainsdale & Birkdale Hills LNR, Altcar Rifle Ranges and Seaforth
NR. It is therefore impossible to be precise about the distribution of these species.
Unidentified stoneworts have been recently found in two ponds on Formby Hall Golf
Most known sites are in dune pools and slacks, where several species often occur
together. These species can exist both as perennials and short-lived annuals and can
therefore survive in water bodies that dry out in summer. Clustered Stonewort thrives
only in such ephemeral pools.
Lesser Bearded Stonewort was first discovered on the Ainsdale NNR in 1978 in a
slack which had been created two years earlier. It is now known to occur in four
slacks, all of which are close to the original site.
Opposite, Common, Bristly and Clustered Stoneworts almost certainly have a more
widespread distribution.