Examination of the intertidal distributions of isozyme and pedal colour phenotypes of Actinia equina L. has shown that anemones displaying column coloration ranging from red to brown, are divisible into three, ecologically distinct forms in Britain, which we currently interpret as being morphs of a single species. These are termed the upper (U), mid (M) and lower (L) shore morphs, which are relatively most abundant on the upper mid, lower mid and low shores, respectively; not all morphs are represented on some shores. The U, M and L morphs may be separated on the basis of their hexokinase and malate dehydrogenase phenotypes. The U morph is homozygous slow and fast respectively, the L morph is slow and fast respectively whilst the M morph is heterozygous at both loci. Data on linkage of pedal disc colour and alleles at a tetrazolium oxidase locus, and of an association between alleles at the hexokinase locus and those at an esterase locus, are given.

Previous work has shown that three ecologically disinct morphs can be identified amongst beadlet anemones, Actinia equina L., ranging in column coloration from red to brown (Quicke, Donoghue & Brace, 1983; Quicke & Brace, 1984; Quicke et al. 1985). Each is adapted to a different inter-tidal range, and is characterized by a multi-locus gene complex, which includes loci encoding a number of metabolically important enzymes, pedal disc coloration and probably strength of pedal attachment. They have been named the upper (U), mid (M) and lower (L) shore morphs, and are relatively most abundant on the upper mid, lower mid and low shores respectively. Members of the U morph are typically homozygous slow and fast at a hexokinase locus and a malate dehydrogenase locus respectively, whereas those of the L morph are typically homozygous for the other allele at each of these loci; M morph individuals are heterozygous at both.

We have recently assessed phenotypic and genotypic diversity within an aggregation of the intertidal beadlet anemone, Actinia equina L., located at Burniston in N. Yorkshire, on the east coast of Britain (Quicke & Brace, 1983). The study was undertaken in order to provide information relating to the role of intraspecific aggression (Bonnin, 1964; Brace & Pavey, 1978; Brace, Pavey & Quicke, 1979) in modifying the spacing of individuals. Limited work on the genus Actinia (A. tenebrosa Farquhar) has already indicated that whilst genetically dissimilar anemones display aggression towards one another, auto-genotypic aggression is minimal (Ayre, 1982), as is also the case for the clonal anemone, Anthopleura elegantissima (Brandt) (Francis, 1973a,b,1976). We therefore anticipated that aggressive interactions would promote auto-genotypic clustering, initiated by the local settlement of the asexually produced, brooded young (Carter & Thorp, 1979; Gashout & Ormond, 1979; Orr, Thorpe & Carter, 1982), and that correspondingly, genetic diversity within aggregations of anemones would be low.

Culture of mussels, Mytilus edulis L. is a developing industry in Irish coastal waters. Settling larvae are collected on 10 m long ropes which are suspended from g.r.p. rafts at a density of five ropes per square metre or from paired long lines, buoyed by plastic floats, at a density of some four hundred ropes per hundred metres. Mussels are harvested after eighteen months when the ropes yield up to 5 kg live weight per metre or approximately 250 kg m−2. Commercial culture at this density clearly exerts a considerable effect on energy and nutrient flow in the coastal ecosystem. In order to quantify the role of cultured mussels we investigated the carbon and nitrogen budget for production rafts and long lines in Killary Harbour, a fjordic inlet on the Irish west coast (Rodhouse et al. 1984) and compared these with estimates for the wild population on the shore.

The oxygen-carrying capacity of the blood of decapod crustaceans fluctuates widely. Salinity stress results in doubling of haemocyanin concentration within 24–48 h in Carcinus maenas (Boone & Schoeffeniels, 1979) while in the lobster, Homarus gammarus respiratory pigment levels are very low prior to and following moulting (Spoek, 1974). In general, however, the most important factor regulating haemocyanin concentration is nutritional state. Following starvation low values are recorded (Wieser, 1965; Uglow, 1969; Djangmah, 1970) and there are concomitant reductions in ventilation, oxygen consumption and cardiac output (Ansell, 1973; Marsden, Newell & Ahsanullah, 1973; Wallace, 1973). The interrelationships between these events are poorly understood.

In previous papers (Broertjes, de Waard & Voogt, 1984a, b) we reported on the presence of vitellogenic substances in the starfish Asterias rubens and described their separation into three fractions, called 2, 3 and 4, which were isolated and purified. The interrelationship between these fractions was discussed and evidence was given that fractions 3 and 4 may be derived from fraction 2.

In recent years several workers have postulated the occurrence in a number of coastal animals of endogenous behaviour and physiological rhythms of semilunar periodicity (see Naylor, 1982). However, only a few of these long term rhythms have been demonstrated as free-running cyclical behaviour over long periods of time in constant conditions. For example, the supra-littoral amphipod Talitrus saltator (Montagu) has been shown to express semilunar variations in daily locomotor activity over three cycles of neap/spring tides during 46 days in constant conditions in the laboratory (Williams, 1979). In contrast, in the mid-shore sand-beach isopod E. pulchra (Leach) semilunar variations in swimming behaviour (Fish & Fish, 1972; Alheit & Naylor, 1976) and of respiration (Hastings, 1981a) have so far been demonstrated only in isopods collected at various stages of the neaps/springs cycle of tides and recorded for a few days in the laboratory. It, therefore, still remains to confirm unequivocally in Eurydice, and in many other forms, which appear to show semilunar periodicity, that such rhythmicity is expressed as a free-running rhythm over long periods of time in constant conditions.

The reproductive morphology and larval development in Spionidae has been dealt with extensively by Soderström (1920), Hannerz (1956), Orrhage (1964). Simon (1967), Blake (1969) and Rice (1980). The family shows a considerable variation in gamete morphology, modes of sperm transfer and types of larval development. One might also expect variability in features of the life history patterns, such as the life span, reproductive age, reproductive cycles and fecundity, both between and within species.

Previous population studies on spionids include the work on populations of Polydora ciliata (Johnston) (Dorsett, 1961); (Daro & Polk, 1973), on populations of Scolelepis squamata (Müller) (Joyner, 1962); (Richards, 1970), on a population of Scolecolepides viridis (Verrill) (George, 1966) and on a laboratory reared population of Malacoceros cf. fuliginosus (Guérin, 1973). The present paper is an attempt to analyse the patterns of life history as they appear in littoral populations of Spio martinensis Mesnil, Polydora ciliata (Johnston), Pygospio elegans Claparede and Malacoceros fuliginosus (Claparède) at localities in N. E. England. The main features considered here are the changes in the size (age) distributions, the annual cycles of reproduction, the output of offspring and population density changes.

The Spio species in the population at Black Middens, North Shields, which is referred to S. martinensis Mesnil (1896) in this paper, was previously referred to S. filicornis (Müller, 1776) by Brady (1943). This species is identical to Mesnil's species, both in morphology and with regard to known biological features, while S. filicornis differs from it morphologically and its distribution pattern (Hannerz, 1956; Rasmussen, 1973; Wolff, 1973, Gudmundsson, in preparation).

In marine crustaceans the polynuclear aromatic hydrocarbon benzo[a]pyrene undergoes changes mediated by benzo[a]pyrene mono-oxygenase (BPM), a cytochrome P-450 dependent enzyme system requiring molecular oxygen and NADPH as a cofactor: it has now been detected in several species (see O'Hara et al. 1982).

Coelomic fluid from the edible sea urchin Echinus esculentus (L.) has in vitro bactericidal activity against the marine pseudomonad, designated strain No. 111 (Wardlaw & Unkles, 1978). This particular bacterial strain was chosen because of its highly characteristic jet-black, agar-digesting colonies on marine agar plates which permitted it to be easily distinguishable from contaminants in bactericidal tests. Bactericidal activity is localised in the cellular components of the coelomic fluid, particularly in the red spherule cells (Messer & Wardlaw, 1980) and is demonstrable in almost all animals tested.

Sessile organisms capable of asexual reproduction may be expected to show much genetic differentiation among local populations: mating between distant individuals is unlikely and genetic drift will contribute to differentiation since habitats can be colonized by one or a few individuals. This study investigates genetic differentiation of populations of the sea anemone Metridium senile (L.) in Great Britain. Individuals of M. senile are sessile and reproduce both sexually, by free-spawning of gametes, and asexually, by regeneration of fragments torn from the pedal disc. Metridium senile is one of the most common and widespread of British sea anemones (Manuel, 1981); reports place it at an enormous number and variety of sites around Britian (unpublished results of surveys by the Underwater Conservation Society of the United Kingdom). The extensive geographic range and variability of the species have confounded attempts to determine the taxonomic status of the ecological and morphological forms, but make it an interesting system for genetic analysis.

Despite concern over declining catches of bass, Dicentrarchus labrax (L.), and disagreement over the cause, overfishing or erratic year classes (Kennedy & Fitzmaurice, 1972; Holden & Williams, 1974; Kelley, 1979), little is known of the early life history of this fish in the wild. Only occasional post-larvae have been recorded previously in young fish collections off Plymouth (Russell, 1935). These were caught between March and June, 2–24 km offshore and commonly below 20 m. The marine spawning grounds in the Plymouth area are unknown. Although Kennedy & Fitzmaurice (1968) found bass eggs at Splaugh Rock and Youghal Harbour on the south coast of Ireland and Barnabé (1978) observed spawning near the breakwater at Sète in the Gulf of Lions, bass eggs have not previously been found near Plymouth. Hartley (1940) recorded the growth and diet of bass in the Tamar Estuary. He noted that adults were very rare in the estuary which was used only as a nursery ground for this species.

Eggs of Dicentrarchus labrax (L.) have been collected from the mouth of rivers or inshore waters of salinity greater than 30 p.p.t. (Barnabé, 1978; Kennedy & Fitzmaurice, 1972). The main spawning period is between April and June (Kelley, 1979; Kennedy & Fitzmaurice, 1968), though ripe males have been reported as early as February and as late as mid-July (Kennedy & Fitzmaurice, 1972). The fertilised eggs 1·15—1·51 mm in diameter, are pelagic, take between two and five days to hatch and the prolarvae are 3·25—4·05 mm in length when they emerge (Barnabé, 1976; Bertolini, 1933, pp. 310–331; Lumare & Villani, 1973; Jackman, 1954). Postlarval stages have been recorded from the Bristol Channel in mid-June and mid-July (Russell, 1980) as well as off Plymouth between mid-March and mid-July (Russell, 1935, 1976; Russell & Demir, 1971). Although a few juveniles have been encountered, from the middle and lower reaches of estuaries, during their first summer (Kennedy & Fitzmaurice, 1972), it is not until the autumn/winter that relatively large numbers of o + bass have been reported from British estuaries (Claridge & Potter, 1983; Hardisty & Huggins, 1975; Hartley, 1940; Murie, 1903; Van den Broek, 1977; Wheeler, 1979). Juvenile bass have also been recorded from lagoons and coastal waters, during their first summer, indicating that these are important nursery areas (Arias, 1980; Barnabé, 1978; Chervinski & Lourie, 1972; Ferrari & Chieregato, 1981; Gandolfi, Rossi & Tongiorgi, 1981).

Cyathura is a genus of Anthurid isopods represented by some fourteen estuarine species around the world (Miller & Burbanck, 1961). They are unusual amongst the isopods in that the majority of individuals in a population show protogynous hermaphroditism, adults breeding as females in their first year, then changing to males over the following winter (Legrand & Juchault, 1963; Burbanck & Burbanck, 1974). The adults are tubicolous, virtually incapable of swimming, and have limited mobility, resulting in disjunct, stable populations, some of which, in the case of C. polita (Stimpson), are known to have maintained the same locations and densities over a period of 20 years (Burbanck & Burbanck, 1975). The embryos develop within a marsupium or brood pouch on the thoracic somites of the female, and are released as interstitial juveniles 1 mm or more in length. With populations averaging 200 to 400 individuals per square metre, these animals are convenient for autecological studies. Indeed, Burbanck & Burbanck (1979) considered that as hardy, euryokous animals, consistent in their tolerance to fluctuating environmental conditions, and convenient for study, Cyathura species are ideal ‘indicator organisms’ in estuaries.

The distribution patterns of many marine benthic invertebrates are not well known, and when records exist they are usually in the form of presence and absence data with little or no information on the relative density of populations from area to area.

The European sea-urchin, Echinus esculentus L., occurs from Finnmark in the north to the Canaries in the south. Around Britain, it is found from the Isle of Portland, English Channel, throughout most of the fully saline waters of the western and northern coasts, and in the North Sea as far south as Flamborough Head. Though it occurs between tide-marks in a few places, it is generally common from about 5 m depth below c.d. to about 100 m, though it is recorded from about 200 m depth (A. M. Clark, personal communication). It is a principal browser on the reefs on which it occurs, and feeds preferentially on kelp sporelings and other algae when it occurs in the photic zone, and on encrusting invertebrates and protochordates below the depth at which algae occur (De Ridder & Lawrence, 1982). E. esculentus is said to migrate inshore prior to spawning, and then retreat to deeper water in late spring (Elmhirst, 1922; Stott, 1931; personal observation), but a rigorous study of these apparent movements has yet to be undertaken. Echinoids fare better on a diet principally of algae than on one of animal material (Lawrence, 1975), so it might be assumed that the winter inshore migration could bring an urchin into a nutritionally richer area for the final developmental phase of gametogenesis.

The observed diminution in photosynthetic efficiency upon vitamin B12 limitation in Monochrysis indicates that nutrient limitation may profoundly influence the photosynthetic status of a natural population and must therefore be taken into account in productivity studies (Droop et al. 1982). It also suggests that photosynthetic efficiency could be used as a criterion between nutrient and light control of growth in natural populations. However, measurement of photosynthetic efficiency is cumbersome under field conditions and it would be advantageous if some other associated variable more quickly measured, such as, e.g. in vivo chlorophyll a fluorescence, could be used as a reliable indicator.

During a study of the reproductive cycle of a subtidal population of Chaetozone setosa Malmgren at an 80 m station off the Northumberland coast (Christie, 1981), the discovery of morphological and reproductive differences in an intertidal population lead to an extended comparative study of three Northumberland populations. The two additional populations chosen for comparison are situated at Low Newton by the Sea and Holy Island, Northumberland. All three populations are located within a maximum distance of 65 km from each other which makes these populations very close on a geographical scale.

Apart from isolated records of species of the genus Protankyra and a brief reference to a ‘Leptosynapta sp.’ from 1985 to 2360 m depth from the northern Bay of Biscay (Sibuet, 1977), the holothurian family Synaptidae is unknown in the deep sea. Yet this family of small, deposit-feeding forms are often numerous in soft sediments of shallow water. The present paper describes two previously unknown species of synaptid discovered from recent benthic sampling in the Rockall Trough (N.E. Atlantic). These species belong to the genus Labidoplax, four other species of which have been described from coastal areas in the north eastern Atlantic.

Symbiont-bearing solitary and colonial radiolaria occur abundantly in diverse water masses throughout the major oceans of the world, including oligotrophic surface water (e.g. Strelkov & Reshetnyak, 1971; Casey, 1971, 1977; Anderson, 1983; Swanberg, 1979, 1983). Studies of their nutrition (Anderson, 1978, 1983; Swanberg, 1983) suggest that the algal symbionts may serve a substantial role in sustaining host nutrition. Our studies on the role of symbiotic algae in radiolaria have shown that Amphidinium-type, dinoflagellate symbionts (Anderson, 1983, p. 118) associated with the solitary species, Thalassicolla nucleata, and a colonial form Collosphaera sp. contribute photosynthetically-derived carbon to the host. The amount assimilated by T. nucleata is proportional to the primary productivity of the symbionts (Anderson, Swanberg & Bennett, 1983 b). Little is known, however, about the effects of environmental variables such as light intensity and quality on the primary productivity of the symbionts and the kinds of photosynthetic products accumulated within the host cytoplasm.