The Surrounding Sea - Gower - page 119

long-term impact of the dredging operations is difficult to determine, however. In 1996 a local dredging
company applied for permission to extract 200,000 tonnes per year from the Helwick Bank for a ten-year
period. This application represented both a continuation of existing practices and an increase in the sand
that might be removed. A five-year licence was granted in 1998 to extract 150,000 tonnes per annum
and in 2003 the company was granted a two-year extension to their licence. The extension permits the
company to extract up to 214,000 tonnes of sand at no more than 107,000 tonnes in a year. There is in-
tense local concern that the dredging might interrupt the movement and exchange of sediment between
the shoreline and the seabed and that the dredging might reduce the protection given to the shore by the
Helwick Bank.
Within Carmarthen Bay there are also several other smaller sandbanks in relatively shallow waters
that support a range of species (including bivalves, amphipods and worms), many of which spend most
of their time wholly or partly buried in the sediment. The Mixen Sands stretch westward from Mumbles
Head and are marked by a bell buoy, but there are no records of the species that may be found there. In
stormy weather, as with the Helwick, the sea can be seen breaking over the sandbank.
CARMARTHEN BAY
Carmarthen Bay contains a complex of unusually diverse marine habitats and associated species, includ-
ing habitats important for migratory fish and migratory and wintering bird species. There is a wide range
ofseabedtypes,includingmud,sandandrock,althoughfinesandcharacterisesthemajorityoftheseabed
from Caldey Island in the west to Worms Head in the east. The bay, with its adjacent estuaries, sandbanks
and extensive salt marshes, is one of the most varied stretches of coastline in the UK . It is designated as a
Special AreaofConservation underthe EC Habitats &Species Directive, andisaSpecial Protection Area
under the EC Directive on the Conservation of Wild Birds, mainly because of the numbers of common
scoter that occur here. In Britain this diving duck is considered a nationally threatened species because
of its small and declining breeding population. Despite an estimated 20,000 individuals overwintering in
Carmarthen Bay, by far the most significant British site for this species, there are only 200 pairs breeding
in Britain and Ireland. The scoter is unusual among ducks in that the male is almost black, with only an
orange-yellow patch on its bill. The female is dark brown with pale cheeks.
The bay encloses a wide range of rich and diverse marine habitats, species abundance and richness
being strongly influenced by the prevailing wave and tidal regimes, with the eastern side of the bay, par-
ticularly Rhossili Bay, being open to the full force of the prevailing southwesterly swell. Two very sim-
ilar animal communities have been identified in the bay, the first corresponding to areas where there are
stronger tidal flows, increasing wave height and correspondingly coarser, cleaner sediments with a gen-
erally low species diversity, and a second community with a high species diversity which is dominated
by deposit feeders. This second community can be divided again due to differences in abundance and di-
versity into two groups, one related to areas containing fine material and mud and one related to areas of
clean fine sand.
The larger fauna of the seabed typically consists of the deposit-feeding polychaete worms Spiophanes
bombyx, Magelona spp. and Spio spp., the amphipods Perioculodes longimanus , Pontocrates arenarius
and Bathyporeia spp.andthebivalves Mysella bidentata , Chamelea gallina and Fabulina fabula .Thelat-
ter species is an important food item for the common scoter. In areas of stronger tidal flows, increasing
wave height and correspondingly coarser and cleaner sediments, such as off Rhossili, sedentary animals
like the thin-shelled Fabulina fabula and the fragile tube-dwelling polychaete Spiophanes bombyx are
much reduced and instead Nereis cirrosa and the cumacean Pseudocuma longicornis are present. The cu-
macean, a minute bottom-living, somewhat scorpion-like crustacean, is an active burrower in the upper