Environmental Engineering Reference
In-Depth Information
ate habitat management, particularly the deepening of these temporary pools to create permanent ponds.
This has certainly happened on Cefn Bryn, as part of the otherwise pioneering Tir Cymen agri-environ-
ment scheme, and before this in the early 1990s the former Gower Countryside Service used volunteers
to deepen some of the water bodies near the summit of the common.
Plants recorded elsewhere as associated with ephemeral pools include pennyroyal Mentha pulegium
andtherareandthreatenedthree-lobedwatercrowfoot Ranunculustripartitus .Therearenorecentrecords
of pennyroyal, but it has been recorded in the past from several heathland areas in the peninsula and it
may still grow at some of the sites. Whether these historic records were associated with temporary pools
is not clear. Three-lobed crowfoot, on the other hand, which is at the limit of its British range in Gower,
certainly occurs in ditches and ponds near Rhossili and is disappearing as a result of changes in agricul-
ture and the loss of the habitats in which it grows.
Temporary pools on heathland in southern England often hold two of Britain's rarest crustaceans,
the fairy shrimp Cheirocephalus diaphanus and the triops Triops cancriformis . Both of these remarkable
crustaceans have highly specialised ecological requirements. The fairy shrimp, in particular, is an enig-
matic creature found in seasonal and temporary pools, puddles and wheel-ruts. The eggs persist in dry
mud after breeding pools dry up in summer and hatch after autumn rains replace the water. It is an ex-
tremely local species, but often abundant where it does occur. Given the similarity of habitats and climate
to the English sites, investigation of the Gower pools would be worthwhile.
OnRyersDowntherearefoursmallpools,thelargestofwhichcontainsthreelocallyimportantplants
- lesser marshwort, floating club-rush and marsh St John's-wort Hypericum eolodes - as well as a num-
ber of other aquatic plants. Spiked water-milfoil Myriophyllum spicatum is common in ponds and ditches
over much of the peninsula, but is replaced in western Gower by alternate water-milfoil, which prefers
acid water. Mare's-tail Hippuris vulgaris is a very local plant occurring in ponds and marshes. The pools
on Ryers Down are also important for invertebrates, particularly flies such as the rare predatory fly Do-
lichopus phaeopus , together with the equally rare beechafer, or bee beetle Trichius fasciatus , for which
this, together with Pengwern Common, is one of the few sites in southern Britain (Fig. 137). It is an ex-
tremelyhairybeetle,about14millimetreslong,withwasp-orbee-likeblackandorange-yellowmarkings
on its elytra; the thorax and abdomen are a light brown. The adults are seen from June to September and
visit flowers including thistles and thyme.
A farm pond at Horton is the only recorded breeding site in the Swansea area for great crested newt
Triturus cristatus , but it is likely that it occurs elsewhere in the peninsula. In contrast the palmate newt T.
helveticus , the smallest of the three newt species found in Britain, is abundant, being frequently found on
the commons, where it breeds in the small pools in the spring. The common newt T. vulgata also spends
much of its time on land, but between early spring and midsummer they can be found in shallow water at
the margins of ponds, pools and streams.
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