The taxonomy of marine worms belonging to family Nereidae is still in an uncertain state. There are many species, like Nereis diversicolor Müller, N. japonica Izuka and N. limnicola Johnson, which are morphologically similar but have different reproductive habits. Clark (1977) reviewed many examples of reproductive isolation without morphological differentiation in polychaetes including members of the family Nereidae. He also stressed the need for detailed study in such polychaetes where taxonomic confusion exists.

Electrophoretic techniques have contributed a great deal in solving taxonomic problems (see Avise, 1975 and Burton, 1983). All electrophoretic methods have proved useful to varying degrees in characterizing specific organisms. In particular, acrylamide gel electrophoresis has seen extensive use because it has excellent resolving power (Brewer, 1970). Studies of the electrophoretic variation of nereid isozymes have not been reported, except by Jones (1970), who examined various polychaetous annelids for the presence of certain dehydrogenases. This present report contains preliminary observations concerning the applicability of isozyme electrophoresis to the study of nereid worms.

Spring and autumn phytoplankton blooms are characteristic of those temperate marine waters where thermal stratification occurs during the summer months (e.g. Raymont, 1976). However, in well-mixed coastal waters the phytoplankton production cycle may consist of a single peak of growth during the summer (Boalch, Harbour & Butler, 1978; Wafar, Le Carre & Birrien, 1983). In a recent paper, Brander & Dickson (1984) considered evidence from the Irish Sea continuous plankton recorder which reflects the phytoplankton growth cycle largely in the well-mixed areas of the sea. These data suggested a single late peak of production, in contrast to the bimodal blooms which are known to develop in the stratified areas of the Irish Sea (Burrows & Sharpies, 1973; Slinn, 1974). The purpose of the present work was to establish the production cycle for Belfast Lough, which lies adjacent to the North Channel, an area of strong tidal mixing which forms the northerly exit for water from the Irish Sea (Lee & Ramster, 1981; Howarth, 1984). There have been no previous measurements of primary production in Belfast Lough. There was considerable interest in this topic in the early years of this century when the Royal Commission on Sewage Treatment (1908) heard evidence that nutrient inputs from sewers into the lough resulted in excessive growth of the green alga Ulva, which caused a nuisance as it decayed around the shores. Although there have been no recent reports of this phenomenon, several sewage works continue to discharge partially treated effluent to the lough. An aim of this work was therefore to assess the role of anthropogenic nutrient inputs upon phytoplankton growth.

Studies of the dispersal behaviour of marine and estuarine benthic invertebrates have concentrated on the majority of species where the individuals disperse as a planktonic larva. The view that seems to be prevalent, summarised by Crisp (1974, 1976), is that larvae are an adaptation to allow species to colonise transient habitats and for species with adults of limited mobility to colonise distant habitats. The spreading of the species over wide areas has the advantages of reducing competition and facilitating greater genetic diversity, leaving the species more adaptable to subsequent environmental changes. These advantages are greater with longer distances travelled, and are an explanation for larvae spending up to several weeks drifting in the plankton, despite the acknowledged high mortality rates associated with the pelagic existence.

The paragnaths are soft outgrowths of the crustacean exoskeleton lying close to the mandibles on the aboral side. They are sometimes termed the metastoma, for instance in Pike (1947) in Galathea squamifera Leach, or the hypopharynx by Wägele (1987) in the isopod Antarcturus Schultz. It should be noted however that Manton (1964) stated that the crustacean paragnath was not the same structure as the insect hypopharynx.

The population dynamics of rock barnacles, Semibalanus balanoides (L.), residing in low and high intertidal zones are affected by conspicuously different factors. The barnacle population in the high intertidal zone tends to show longterm stability due to a low incidence of both predation and interspecific competition. Wave exposure, desiccation and intraspecific competition are more important factors affecting abundance and size distribution in this zone (Menge, 1976). In the low intertidal zone, barnacle predation by the dogwhelk, Nucella lapillus (L.) is intense (Menge, 1976) and both the adults and larvae are smaller than in the high intertidal zone (Barnes, 1953). The growth form of S. balanoides is density dependent with taller, more columnar individuals predominating at high densities and short conical barnacles at low densities. Lower fecundity of conical individuals may be due to lower internal shell volume compared with columnar forms (Wethey, 1984). Fecundity increases both with increasing age and base length (Arnold, 1977) and is positively density dependent (Wethey, 1984).

Prey populations, patterns of availability, and dispersion of prey can have farreaching effects on numbers and range-sizes of terrestrial Carnivora (Macdonald, 1983; Kruuk & Parish, 1982; Kruuk & Macdonald, 1985). These parameters may therefore also affect populations of otters Lutra lutra, living in the sea around Shetland, U.K., as well as populations of fish-eating birds there. This paper presents observations on fluctuations in numbers and activity of several species of demersal fish, over a 3½ year period, along a coast in Shetland. It aims to provide information on the distribution and availability of these species to some predators, especially to the otter, but also to the heron Ardea cinerea, the black guillemot Cepphus grylle and others.

When red blood cells are subjected to mechanical stresses, they change shape with very little resistance. Such deformability of erythrocytes plays a crucial role in their function and survival in the circulation since they must undergo large deformation whenever they pass through narrow capillary vessels. While this mechanical characteristic of erythrocytes has been attributed to their unique cellular structure, it has also been shown that considerable alterations in this property result from changes in cellular metabolism and in surrounding plasma physicochemistry (Weed, LaCelle & Merrill, 1969; Kikuchi & Koyama, 1984a, b). It might be supposed, therefore that red blood cell deformability would be modified, when animals are exposed to different environmental conditions, with significant effects on their acclimatization or survival under the varied conditions. However, little is known of this aspect of fish cardiovascular physiology.

The Pogonophora are tube-worms of predominantly deep sea distribution. They lack a functioning alimentary canal in the adult stage and are then dependent for nutrition on internal symbiotic chemosynthetic bacteria that occupy tissue derived from the larval endoderm (Southward, 1982, 1987, 1988; Southward & Southward, 1987; Southward et al. 1981). Of the two main subgroups, the small perviate Pogonophora are widely distributed in reducing sediments in the oceans, while the large vestimentiferan or obturate Pogonophora are restricted to hydrothermal vents or cold seeps. The small Pogonophora are often most abundant on steep slopes and in the Bay of Biscay Siboglinum atlanticum (Southward & Southward, 1958) can be a dominant element of the infauna of the sediments on the sides of canyons. This animal, like other small Pogonophora, lies buried in the sediment, in contrast to the vestimentifera which are attached to hard substrates. Until now there has been no fully quantitative information on the distribution of S. atlanticum and associated pogonophores of the Bay of Biscay. Dredges or trawls have been used for most previous sampling of pogonophores along the continental slope (Southward, 1979, 1985). Even the Plymouth-pattern deep-sea anchor dredge (Southward & Southward, 1963), which is designed to dig into the sediment immediately it is towed on the bottom, may drag for some distance through soft sediments before digging in, and then samples the upper few centimetres over a wider area than its mouth opening. During the last season of operation of R.R.S. ‘Frederick Russell’, before this vessel was disposed of by N.E.R.C., opportunity was taken to make a combined quantitative biological and chemical survey, using box-corers. The samples from the corers were large enough to allow the sample to be used for assessment of the population density of the pogonophores and analysis of sediment chemistry. Some inferences can now be drawn about the factors controlling pogonophore abundance.

The marine plankton contains an extremely diverse assemblage of ciliates which may be important in planktonic energy flow (e.g. see Burkill et al. 1987; Porter et al. 1985; Rassoulzadegan & Sheldon, 1986; Sherr & Sherr, 1987; Stoecker, Michaels & Davis, 1987; Verity, 1987). Many marine ciliates are delicate in nature and until recently have been poorly collected. Thus, they are often entirely missed in plankton sampling. During an investigation of the role of planktonic ciliates at the Isles of Shoals, Gulf of Maine (Montagnes & Lynn, 1988; Montagnes, Lynn, Roff & Taylor, 1988) samples were Bouin-fixed to preserve these delicate species. The ciliates were subsequently quantitatively protargol silver-stained to estimate species abundances and biomass (Montagnes & Lynn, 1987). This staining method, in addition to providing quantitative estimates of abundance and cell volume, gives invaluable taxonomic information by revealing cellular structures. Thus, it has been possible to compare the ciliates from the Gulf of Maine with described species.

The genus Ampelisca comprises more than 150 species and is one of the more important benthic genus of marine amphipods. New species are regularly added (Barnard & Agard 1986; Bellan-Santini & Marques, 1986; Goeke, 1987). Ampelisca are found from the intertidal zone to abyssal depths but most of them live on the continental shelf. In spite of many studies, it is often difficult to distinguish some species which are morphologically similar. In the last ten years, twenty-two species have been described from the north-eastern Atlantic (BellanSantini & Kaïm-Malka, 1977; Bellan-Santini & Dauvin, 1981, 1986; Dauvin & Bellan-Santini, 1982, 1985; Bellan-Santini & Marques, 1986). Materials come from MNHN of Paris collection, collected by Chevreux (1894–1924) (Dauvin & Bellan-Santini, 1985, 1986) and specimens collected during the last 25 years. All these new species are described from the Atlantic coast from northern Brittany to the Sahara and from the Mediterranean Sea.

Eupolymnia nebulosa (Montagu) is a tubicolous worm with its body divided into two regions: thorax with biramous segments and three pairs of gills; abdomen with numerous segments lacking notopodia. The head bears grooved foodgathering tentacles which are not retractile into the mouth. The worm, a typical deposit feeder, lives in mucous tubes encrusted with sand. Although the family Terebellidae is homogeneous in terms of body organization and feeding ecology, there is a remarkable heterogeneity of developmental pattern. In the genera Lanice and Loimia, the life-cycle involves two pelagic stages separated by a short benthic larval stage; in other genera the development is mixed or direct (Bhaud et al. 1987; Pechenik, 1979; Caswell, 1981). It is important to study the development of representatives of the family which may reveal the adaptive significance of the different modes of development or may yield information about evolutionary relationships within the family. In several previous papers larval development (Bhaud & Grémare, 1988 a, b) and reproductive biology (Bhaud et al. 1987) of E. nebulosa have been reported from the Mediterranean coast. The present article reports observations on juvenile growth and morphological organization in natural conditions. This is the first step to growth rate studies in terms of temperature and food supply (Bhaud, 1988).

Medusae are common constituents of the meso-and bathypelagic fauna. Small, transparent trachyline hydromedusae are usually most abundant, but the larger (2–10 cm diameter) pigmented coronate scyphomedusae are often collected in trawl nets (Thurston, 1977; Roe, James & Thurston, 1984; Larson, 1986) or observed from submersibles (Mackie & Mills, 1983; Mackie, 1985; Larson, Madin & Harbison, unpublished observations). Larger (30–70 cm) deep-sea semaeostome scyphomedusae are only infrequently collected in nets (Harbison, Smith & Backus, 1973; Larson, 1986), and would appear to be the rarest forms. For example, Thurston (1977) collected over 16000 midwater medusae in trawls yet he did not report taking a single mesopelagic semaeostome. However, recent investigations using submersibles have shown that these medusae are much more common than net hauls alone would suggest (Smith, 1982).

The distribution of dinoflagellate cysts in sediments is a subject of increasing interest. There have been several approaches, of which two are relevant to this investigation. The studies of palynologists who endeavour to relate the distribution of cyst assemblages to environmental factors (for example Reid, 1972; Wall et al. 1977; Harland, 1983) and the studies of phycologists, concerned with toxic dinoflagellate blooms, who concentrate on the distributions of cysts of bloom species (for example Anderson, Kulis et al. 1982; Thayer et al. 1983). Consequently an increasing amount of information on quantitative distribution of cysts has become available. In 1976 Dale reported the investigation of sediments from Trondheimsfjord, relating the abundance of cysts to the percentage abundance of finer sediment. Wall et al. (1977) provided a more comprehensive picture of this relationship showing that cyst density (numbers of cysts per gram dry weight of sediment) increased logarithmically with increased percentage of the silt plus clay mineral fraction to a level where this comprised 50–60% of the sediment, after this no further increase occurred.

Imposex, the development of a penis and vas deferens in the female (Smith, 1971) is known to occur in over 30 species of marine gastropods but, to date, in only one species has this syndrome been demonstrated to have a serious deleterious effect. This species is the dog-whelk, Nucella lapillus L. Both field and laboratory observations have provided conclusive evidence that imposex in N. lapillus is initiated by tributyltin (TBT), used as a biocide in antifouling paints, at concentrations in water of less than 1 ng Sn/1. This feature is manifest in the widespread occurrence of imposex even in areas far removed from centres of boating activity (see Bryan et al. 1986). Imposex appears to have little effect on the reproductive biology of N. lapillus until this syndrome is developed to its fullest extent when it sterilises the female because the pallial oviduct becomes occluded by vas deferens tissue thus preventing expulsion of the egg capsules (Gibbs & Bryan, 1986). Laboratory experiments have indicated that this condition, found in females close to harbours and marinas, may prevail after prolonged exposure during the first few years of life to TBT levels as low as 2 ng Sn/1 (Gibbs et al. 1987). Of six organotin compounds tested by Bryan, Gibbs & Burt (1988), tributyltin chloride proved the most effective in promoting imposex in N. lapillus.

Populations of the common dog-whelk Nucella lapillus (L.) are declining or have already disappeared at many sites on rocky shores around the United Kingdom (Bryan et al. 1986). There is conclusive evidence that this is caused mainly by tributyltin (TBT) compounds leached from ships' antifouling paints (Bryan et al. 1987). These compounds impose male sexual characters (or imposex) on female N. lapillus. Other stenoglossan gastropods including Nassarius obsoletus Say (Smith, 1981a) and Ocenebra erinacea (L.) (Féral & Gall, 1982) are similarly affected by TBT. The intensity of expression of imposex in N. lapillus can generally be related to the sea water concentration of TBT. The appearance of a small penis and the partial development of a vas deferens first occurs at TBT concentrations below 0.5 ng/1 (as tin), although reproduction appears to be unaffected at this level. At 1–2 ng Sn/1 penis size is markedly increased and in some females proliferation of vas deferens tissue overgrows the genital papilla, thus sterilizing the animal. At slightly higher concentrations virtually all females become sterilized and at around 10 ng Sn/1 oogenesis is suppressed and spermatogenesis initiated (Gibbs, Pascoe & Burt, 1988). Since development is direct and there is no planktonic stage, N. lapillus has a very limited capacity for dispersion: thus the sterilization of females heralds the almost certain decline of so affected populations (Gibbs & Bryan, 1986).