The principles and aims of numerical taxonomy were clearly stated by Sokal & Sneath (1963) and their procedures have since been adopted by many botanists working with numerous different groups of plants. Marine algal taxonomists, however, seem largely to have ignored these developments although Whitton (1969) has recommended that numerical techniques should be employed to help solve outstanding problems in the taxonomy of the Cyanophyta.

Since its original isolation and description by Droop in 1953, ‘Monochrysis’ lutheri has proved to be one of the most valuable of cultured phytoflagellates. It has been used by many workers, too numerous to cite, in laboratory studies on phytoplankton growth kinetics, nutrition and biochemistry, and also in mariculture and animal feeding experiments, particularly experiments on the raising of crustacean and molluscan larval stages.

In a previous paper, (Shelton, 1974) it was shown that the antennules and some other appendages of certain field and laboratory populations of the brown shrimp, Crangon crangon (L.), may become colonized by a filamentous organism tentatively identified as a blue-green alga. Other workers (Johnson et al., 1971) have described similar growths on benthic Crustacea, fish eggs and algae (Bland & Brock, 1973) and have identified the epizooic organism as Leucothrix mucor Oersted (Harold & Stanier, 1955), a filamentous, heterotrophic bacterium, common in the intertidal zone.

The brown shrimp Crangon crangon (L.) is a burrowing caridean decapod, inhabiting sandy, sandy-mud and muddy substrata down to 90 m, but occurring mainly in shallow water and between tidemarks (Lloyd & Yonge, 1947; Allen, 1966b). The species also exhibits seasonal inshore and offshore migrations, reportedly in relation to salinity, temperature and availability of food (Ehrenbaum, 1890; Havinga, 1929, 1930; Meyer, 1935; Broekema, 1941, Academy Thesis, Groningen; Lloyd & Yonge, 1947; Allen, 1966a, b; Tiews, 1970). In addition Hartsuyker (1966) reported up and downshore migrations on each tidal rise and fall in the Wadden Sea. In contrast, Havinga (1929) stated that the species rests quietly buried in the substratum by day and feeds at night, and nocturnal emergence was confirmed by Lloyd & Yonge (1947) in aquarium observations. However the latter authors found no difference between field catches during day and night tides in the Bristol Channel and Severn Estuary. Tiews (1970) reported greatest activity at dusk and that C. crangon continued to swim during the night even after feeding. So far there is therefore evidence of nocturnal and tidal rhythms of emergence in C. crangon which deserves further experimental investigation.

A study of the intertidal macro-invertebrate fauna of south east England was carried out as part of the investigations funded by the Department of the Environment of the likely ecological implications of the Maplin development proposals. The main aim of this study was to determine the potential food resource the invertebrate populations represent for the large numbers of wading birds which overwinter in this region. This article will concern itself solely with aspects of the invertebrate populations, the relationships between the waders and their invertebrate food supply will be presented separately (Kay, Blindell & Goss-Custard, in prep.).

Abereiddy Quarry is shown in Plate I. It lies at 51° 56′N, 5°13′W (Ordnance Survey Reference SM 795315), 6 km northeast of St Davids in Pembrokeshire (Text fig. 1). The quarry, a disused slate working, is surrounded by high cliffs except to the west where there is a channel open to the sea. In 1902–3, operations ceased and the quarry began to fill with fresh water and sea spray. During 1932–3 the west wall was breached to allow access to the sea so that the basin could be used as a harbour. Abereiddy is now a deep, fully saline marine basin which, at low water, is 66 m across from north to south with a surface area of 0.356 ha and a maximum depth of 24 m. In this situation it has been possible to observe sublittoral rocky sea-bed communities in an extremely sheltered area through a summer thermocline and associated oxycline. Abereiddy Quarry has previously been investigated by Bailey, Nelson-Smith & Knight-Jones (1967), who published details of the vertical distribution of Spirorbis spp. The biology of serpulid worms in Abereiddy Quarry has been the subject of continuing investigations carried out from University College Swansea (E. W. Knight-Jones, personal communication).

Benthic faunal communities have usually been described from data collected during a single survey, and it has been assumed that most benthic communities are reasonably stable. However, in areas such as important fishing grounds or around effluent disposal areas where surveys have been repeated periodically, the results quite frequently show marked changes. These do not always correlate to annual breeding cycles but are more unpredictable and of a different period.

There is much variation in the form of colony assumed by the common hydroid Clava, and two forms were for long distinguished as separate species, a diffuse one found on stones and rocks in the lower part of the tidal zone and in shallow subtidal depths, with scattered polyps arising from an open hydrorhizal network of creeping stolons, and a clustered one, living on fucoid and other seaweeds in the tidal zone, with densely clustered polyps borne on a compact hydrorhizal base of very short anastomosing stolons. Johnston (1847) did not separate these forms and recognized one species only, named by priority Clava multicornis (Forskal, 1775). It was largely on the authoritative works of Hincks (1868) and Allman (1871–2) that the two forms became accepted as distinct species, the name Clava multicornis (Forskål) being adopted for the diffuse one (though Hincks admitted uncertainty in ascribing Forskål name to this) and Clava squamata (Müller, 1776) for the clustered one. More recently certain authors have considered them to be forms of one species, designated by priority Clava multicornis, but others have continued to treat them as separate species, and the question of their specific identity or distinctness cannot be said to have been resolved. Broch (1916, pp. 38–40), from a study of material from various localities, concluded that there are all transitional conditions between the two forms, rendering specific distinction impossible, and that they are evidently ecologically conditioned forms of one species. He did not, however, adduce any experimental or other evidence in support of his belief.

Parathemisto gaudichaudi (Guerin) exists in a range of morphological forms comprising the compressa extreme, in which the fifth pereopod (P5) is only slightly greater in length than the sixth pereopod (P6), the bispinosa extreme, in which P5 is about twice the length of P6, and a complete range of intermediate forms. Other features such as the shape of the carpus and merus of the third and fourth pereopods and the shape of the uropod peduncles also vary between the two extremes. In an earlier paper on the taxonomy of the genus (Sheader & Evans, 1974) it was noted that specimens of Parathemisto gaudichaudi kept in the laboratory could moult towards either of these extremes.

Cephalopod molluscs have attracted little attention as potential hosts for digenetic trematodes. Though none appears to serve as a first intermediate host, many do act as second intermediate, paratenic, or final hosts. Hence, they probably play a more important role in the life history and dissemination of Digenea in the marine environment than is generally recognized.

When the free-swimming larva of the polychaete tubeworm Spirorbis spirorbis settles permanently on a suitable substratum, it forms a thin, mucous, anchoring tube, which covers only the posterior half of the body. Within 3 h the worm has built a comparatively thick, calcareous tube onto the anterior end of the initial, mucous tube, which later becomes a compressed and folded remnant (Nott, 1973). The volume of calcareous material forming the tube cannot be stored within the body of the larva before settlement and must, therefore, be taken up rapidly from sea water or ingested material.

The known range of the northern rockling, Ciliata septentrionalis, extends from Iceland and northern Norway in the north to Plymouth in the south (Wheeler, 1965). This species has probably been confused with the five-bearded rockling, C. mustela (L.), in the past (Wheeler, 1969) and this together with the small size of the fish, enabling it to escape through the mesh of most trawls, may explain the paucity of records and knowledge of the species. Brook, (1885, 1888) described the egg and larval development of C. mustela but the egg and larva of C. septentrionalis have not been described. It is probable that the abundance of both these species can only be estimated by a combination of fecundity studies and egg and larval counts.

Although freshwater teleost cell and tissue culture is an established field, the in vitro maintenance and growth of marine or estuarine fish tissues and cells is less well reported (Wolf & Quimby, 1969). Small demersal gobiid teleosts of the genus Pomatoschistus Gill, 1864 are widely distributed and very abundant around the coast of Britain and play an extremely important role in estuarine and coastal ecosystems (Hartley, 1940; Miller, 1963, Ph.D. Thesis, University of Liverpool; Green, 1968). Excluding the in vitro maintenance of whole organs (e.g. Bonnin, 1971a, b and Doneen & Bern, 1974) the culture of cells or tissues from gobiids has not been reported.

The muscles of the paired fins of rays have long been known to possess large sensory endings of a special type, first described in Torpedo by Poloumordwinoff (1898) and Cavalie (1902), and subsequently re-examined by Barets (1956). They consist of many parallel beaded nerve fibres, derived from a large myelinated parent axon, lying between the muscle fibres of the fins. That they respond to stretch (as was inferred from their structure and position) was shown by Fessard & Sand (1937). Since these are the only sensory endings known in any fish which are stretch receptors lying amongst muscle fibres (neuromuscular spindles are absent from fishes), more information about their structure and relationships with the muscle fibres of the fins is desirable. In this note, we describe the ultra-structure of this simple type of stretch receptor, and the type of muscle fibre with which it is associated.

Like most heavy metals, cadmium is only found in minute amounts in natural sea water. Krauskopf (1956) stated that cadmium concentration of normal sea water ranges from 0.032 to 0.075 PPb (μg/l−1) while Goldberg (1965) gave a somewhat higher value of 0.11 ppb. Cadmium concentrations determined by Preston (1973) for the North-East Atlantic Ocean range from <0.01 to 0.41 ppb, and similar values have been found by Windom & Smith (1972) in the West- and Chester & Stoner (1974) in the South Atlantic Ocean (0.04–0.17 ppb).

Most work in tunicate heart physiology has been directed towards finding the actual physiological cause of heart reversal rather than the adaptive advantage of it to the animal (see reviews by Krijgsman, 1956; Kriebel, 1968; Goodbody, 1974). Krijgsman (1956) concludes: ‘We do not know whether there is any functional significance in the periodic reversal of beat. One can see no reason why a permanent one-way circulation should not be efficient. Presumably the cause of reversal is the periodic exhaustion of the pacemakers, which has no physiological significance.’ Because of the abundance of pacemaker systems in nature in which periodic exhaustion does not take place, this conclusion should be re-examined.

An important factor in the seasonal cycle of phytoplankton growth is the establishment and breakdown of the seasonal thermocline (Sverdrup, Johnson & Fleming, 1946). When surface heating is sufficient, more buoyancy is produced than can be dissipated by wind and tide. The stabilization of the water column allows the phytoplankton sufficient time in the surface layer to utilize the light energy for increased net production and the spring bloom is triggered. At the end of the summer period the erosion of the thermocline may result in an increase of nutrients in the upper layers. If production has become limited by surface depletion of nutrients during the summer, then the thermocline breakdown may result in an autumnal bloom particularly if a period of calm sunny weather follows. The importance of the thermocline development and season length is clearly illustrated in plankton studies of the North Atlantic, for example Robinson (1970).

The most comprehensive hydrographic work on the English Channel, even today, is that of Lumby (1935). Lumby used the surface observations of ships of opportunity (steamers on regular routes) that were gathered over a period of 25 years from 1903 to 1927. The number of observations gathered runs into tens of thousands and these were subdivided into convenient regions for the purpose of constructing an Atlas of sea surface temperature and salinity. The mean monthly values of temperature for each region from which the monthly contours were drawn can be considered as established to within ± 0.2 °C. Despite the fact that these data have been available for half a century no satisfactory explanation for these monthly temperature distributions has been offered. In this paper the role of horizontal turbulence in redistributing the net surface heating to produce these monthly temperature distributions is quantitatively examined.