Breakwater
Lat/long
50 19.97N 50 20.06N	04 08.07W 04 09.57W
50 19.89N 50 19.96N	04 08.17W 04 09.47W

Location description (1957)

Apart from a line of granite blocks in the southern facing, the surface masonry and the great mass of the foundations consists of limestone, originally quarried at Oreston; and it is mainly this imported limestone rock that is exposed at low water. As on the Hoe foreshore, this rock is extensively bored by various organisms, to such an extent that considerable damage is done to the structure. The chief organisms involved are the boring sponge Clione celata and the abundant bivalve Hiatella striata. The first reduces the surface of the rock, to the depth of several millimetres, to a friable mass, the second bores tubular galleries into the pure rocks to the depth of a few centimetres, so dose together as to cause inevitable disintegration of the rock. In addition, rock-boring polychaetes are numerous, including the species Dodecaceria concharum, Polydora ciliata, P. hoplura, and Potamilla reniformis. Dodecaceria forms holes of oval or figure-of-eight section, which may penetrate for several inches into the heart of the stone; Polydora ciliata forms small U-shaped burrows, open at each end, whilst P. hoplura makes similar burrows of larger size. Another rock-borer is the mollusc Gastrochaena dubia. The top level of the breakwater is above H.W. springs, but is drenched by the waves of heavy seas. Faunistically it is notable for its population of Littorina neritoides which here grow to an unusual size. The platform and the seaward slope provide a habitat that can only be colonized by a few organisms that are especially tolerant of strong wave action, and these tend to cluster in hollows or clefts in the masonry. Patella vulgata, P. aspera, and Chthamalus stellatus are the chief sessile animals; Porphyra, Corallina, and limited patches of stunted fucoids are the chief algae, the first giving cover to the amphipod Hyale perieri. Towards low water the seaward face on the south side, where masses of stones and big moulded concrete blocks have been deposited to break the waves, bears a rich growth of brown and red weeds. The thick Enteromorpha patches on the blocks provide an ideal habitat for the marine chironomid Thalassomyia frauenfeldi. The distribution of some of the commoner species on the breakwater, and the effect of wave action on them, is discussed by Southward & Orton (1954).

Updated information

No updated information

Species List

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