Wembury bay

Lat/long Wembury bay
50 18.80N
50 18.90N
04 04.17W
04 06.20W
50 18.26N
50 18.57N
04 04.45W
04 06.22W

Location description (1957)
Wembury Bay. The rocky shores of this bay form one of the best collecting grounds on the open coast in south-west England, more particularly the two projecting rocky reefs known as Church Reef (near Wembury Church and Mill) and West Reef (at Wembury Point opposite the Mewstone). The reefs, composed of Lower Devonian slate, appear to represent a dissected and much eroded marine platforrn, formed at a period of higher sea level not later than the last interglacial period. The cliff at which this platform originally ended is indicated by the inland contours between Wembury Beach and Point. Much "head" has accumulated at the foot of, and outward from, the ancient cliff, covering the rock platform; and this deposit is at present being slowly eroded away, forming a low vertical cliff just above H.W.S. At the foot of this modern cliff a varying amount of beach material has accumulated, varying from flat stones to fine sand. Towards West Reef this beach forms a conspicuous band above mid-tide, and at intervals extends through gaps in the rock to below L.W.mark. Church Reef rises more continuously to the present H.W. region and ends abruptly about the point where the sea today has caught up with the ancient cliff. Eastward of this the steep rocky cliffs are a modern feature. The reefs are broken into an uneven series of ridges running at right angles to the south-easterly dip of the strata. The gullies between the ridges therefore run more or less parallel to the coast, especially in West Reef, and these offer the maximum protection from wave action. The protection afforded by the seaward ridge to such a gully is enhanced by the fact that, owing to the seaward dip of the strata, the lee side of the ridge is vertical or overhanging. Furthermore, on both reefs relatively high ridges occur on the outer seaward face giving extra protection to the ridges inside them. The laminated rocks provide ideal habitats for a diverse crevice fauna. In time they fall to pieces, breaking into flat slabs which have accumulated in some of the gullies and provide valuable cover for many forms which might not otherwise persist intertidally. Thus, although the bay as a whole is exposed to the full force of the Channel waves, with adverse effects on the fauna of the sand and gravel patches that occur at intervals between the two reefs, the reefs are able to harbour a great variety of intertidal and shallow-water organisms. West Reef has the advantage over Church Reef in occupying a larger area, in receiving additional protection from the Mewstone, in having perhaps the better exposures of friable rock and the greater accumulations of flat boulders, and in being altogether free from the clogging effects of periodic sand deposition (contrast, e.g. the reef at Portwrinkle in Cornwall). Many of these advantages are lost towards the western part of this reef, exposed to the south-west, where the fauna is more ordinary. Both reefs have a rich algal flora, at least from mid-tide downwards. The dominant fucoid species are luxuriant and a variety of other brown and red weeds colonize the pools and sheltered ledges. Above mid-tide, on Church Reef particularly, the lichen Pygmaea (=Lichina) pumila makes extensive dark patches on the otherwise bare seaward-dipping surfaces. A forest of Laminaria hyperborea (cloustoni) is evident at extreme L.W.S. especially on the Yealm side of Church Reef, and along the whole Wembury Bay shore of West Reef. One element of the intertidal fauna, nearly all small-sized forrns, uses the cover provided by these weeds. It has been studied, on Church Reef, by Colman (1940). For a given weight of weed the densest populations were found in Pygmaea, largely made up of Campecopea hirsuta and Lasaea rubra, but even the bases of Ascophyllum nodosum hold a surprising number. The variety increases down the shore and is greatest in Laminaria holdfasts. The fauna of tufted weeds in rock pools is rich, but awaits quantitative study. It includes the very local and peculiar amphipod Pereionotus testudo. Animals sessile on weeds include four species of lucernarnians, which occur in certain favourable sites on Chondrus, Halidrys, etc. The extensive fauna to be found on the underside of stones or sheltering beneath them, include the gymnoblast Myriothela cocksi, the echinoid Psammechinus miliaris, and the holothurian Cucumaria saxicola. The crustaceans Nebalia bipes and Apseudes species occur in suitable sites at West Reef. The more open fissures in the rocks provide cover for young lobsters, for several species of crabs and for littoral fish (rockIings, blennies, etc.). The larger crevices that occur between the lamina still in situ, workable with a crowbar, are tenanted by the gephyrean Thalassema neptuni, and the polychaetes Terebella lapidaria, Polycirrus caliendrum, Amphitrite gracilis, Eunice harassi, Lysidice ninetta, and Marphysa sanguinea; while the smaller crevices between the individual laminations possess a fauna of small but interesting species that persists, with varying composition to the highest tidal levels. This last fauna has been studied, mainly on Church Reef, by Morton (1954). It is remarkable for the admixture, with marine forms of species of air-breathing land groups. Thus, with the bivalve Lasaea rubra the gastropod Cingula cingillus, the isopod Gnathia oxyurea, the nemertean Prosorhochmrls claparedi, small marine polychaetes, etc., are found the pulmonates Otina otis and Leucophytia bidentata, the myriapod Scolioplanes maritimus, the hemipteran Aepophilus bonnairei, the beetles Micralymma marinum and Aepopsis robinii, the collembolan Anurida maritima, larvae of the flies Clunio marinus and Limonia unicolor, the pseudoscorpion Neobisium maritimum, and several mites (Acarina). At Wembury are two examples of freshwater streams flowing over the tidal zone. One issues below the old boat-house at Wembury Point and the other stream flows in the valley below the church. Stones lying in these streams intertidally provide cover for a few invertebrate species tolerant of irregular salinities. The church stream has long been known as a site for the archiannelid Protodrilus f!avocapitatus. An oligochaete, Enchytraeus pellucidus, also occurs, less erratically. In both streams the planarian Procerodes (=Gunda) ulvae, and the amphipod Marinogammarus pirloti are abundant, while M. stoerensis and the isopod Jaera albifrons are common at times. The two Marinogafflmarus species, Procerodes, and Protodrilus are all restricted to this type of habitat. Strong winds from the south-east dislodge quantities of laminarian and fucoid weed which accumulate along the high-water line. The biggest weed deposits are found near Wembury Point, whence loads are removed for manure. The weedy high-water drift provides a favourable breeding place for the kelp flies (Coelopidae) and their dipterous predators (chersodromine Empididae and Ceratinostoma ostiorum). Certain staphyline beetles and at least one oligochaete are also characteristic, but the fauna of this drift has not yet been fully studied. Flocks of turnstones (Arenaria interpres) and oyster-catchers (Haematopus ostralegus) regularly frequent the reefs as predators, some non-breeders remaining throughout the nesting season. They may be joined by parties of curlew and other waders, especially during autumn passage. Herons and solitary kingfishers fish in the pools and gullies during winter. Indeed the intertidal food supply on West Reef and that in the adjacent deposits of rotting weed have attracted a greater variety of bird life to Wembury Point than to any other part of the coast between the Start and Dodman.
Updated information No updated information
Species List >Cataphellia brodricii
Henricia oculata
Homarus gammarus
Psammechinus miliaris
Sabellaria alveolata