The phenomenon of acid secretion has arisen independently many times, for feeding, for penetrating calcareous material to make a shelter or to pursue prey, or for defence. This last category contains examples from many groups of marine organisms, in which acidic allomones may serve to deter fouling by epibionts or predation by teleost fish. Histochemical and histophysical methods have increased the precision with which acidic allomones can be identified within acid vacuoles, cells, glands, sacs or capsules. Acidic allomones are produced in pleurobranch molluscs by unicellular epidermal glands, by multicellular subepidermal sacs, or by an arborescent internal acid gland, connected to the buccal mass by a thick medio-dorsal duct. Some species have all three types. In the case of the epidermis, discharge is probably triggered directly by the trauma of attack by a predator (effectively, holocrine discharge), but the other types of gland are discharged by contraction of a strong muscle sheath, without tissue damage. Cypraeid molluscs have extensive, mobile mantle lobes which can ensheath the massive shell temporarily. The epidermal acid glands are orientated within the mantle so as to discharge away from the shell. The lamellariid and philinid molluscs have internal shells, well protected from chemical attack, and the multicellular, subepidermal acid glands are situated over all the surfaces of the body. In the tunicates investigated, both blood and tunic were neutral in Ciona intestinalis, but they were both acid (pH 1) in Ascidiella aspersa. In Ascidiella scabra and Ascidia mentula the blood was neutral, and the tunic alone was acid. The acid tunics contained abundant blind lacunae. It is unlikely that these acid-filled lacunae correspond to the blind-ending arterial ampullae described by other workers. Discharge is probably brought about directly through the trauma of attack. The perennial species of the alga Desmarestia, D. aculeata, exhibited a pH near to neutrality. Two annual species, D. dresnayi and D. ligulata, contained acid of pH 1–2, and showed strong precipitation of BaSO4 after BaCl2 treatment. Sections confirmed that the acid is normally held within the swollen parenchymatous cells which pack the sporophyte frond. The cuticle is comparatively thin in the acidic species. In conclusion, it is argued that acid secretion may be the allelochemical analogue of warning or aposematic coloration.

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).

Natural spawning of laboratory-held populations of Pholoe minuta occurred in synchrony with wild populations in Galway Bay. Larval development is described up to an age of 14 days using light and scanning electron microscopy. A pelagic planktotrophic larval phase (4-segment metatrochophores) was observed. Settled 3- and 4-chaetiger stages are described from meiofaunal benthic samples from the study area. A 3-week larval phase is indicated and the current findings are discussed in the light of existing literature on larval development in Pholoe minuta.

All groups of meso- and macro-zooplankton in the North Sea off Northumberland, at a depth of 53 m, were studied during a 15-year period (1969–83); copepod productivity was estimated from biomass and growth rates. Phytoplankton were seasonally bi-modal with peaks in April and August–October; copepods were uni-modal peaking in June–July. The predatory zooplankters: larval fish, decapods, ctenophores, medusae (the summer-autumn predators) peaked between May and September, while chaetognaths and euphausiids (the winter predators) peaked in December–January. Copepods and the summer-autumn predators were seasonally and inter-annually positively correlated, and declined in abundance from 1974 to 1980. Euphausiids and chaetognaths on the contrary increased in abundance during these years, and were seasonally and inter-annually negatively correlated to the copepods. The mean annual abundance of copepods was positively related to the previous winter's minimum, and inversely related to the abundance of chaetognaths and euphausiids. Annual copepod productivity averaged 1260 kJ m-2 year-1, and showed no relationship to other groups of plankton.

Surface fluorescence measurements in June in the Bay of Biscay showed little correlation with chlorophyll a measurements due to the presence of a marked diurnal fluorescence rhythm although satisfactory correlations have been obtained at other times of year in the same region (see Fig. 10 of Pingree et al. 1982). By contrast, the beam attenuation coefficient values showed a good correlation with the chlorophyll a measurements and can be used to map the sea surface distribution of chlorophyll a when the diurnal rhythm is present, particularly when the phytoplankton is dominated by a single species. This conclusion may be of considerable practical significance when contemplating synoptic surveys in such situations. As Prezlin & Ley (1980) have observed there is growing awareness that fluorescence per unit chlorophyll a is not a constant that can be used reliably in mixed phytoplankton biomass estimates based on in vivo chlorophyll a fluorescence, and the problem is clearly compounded if some species exhibit a marked diurnal fluorescence rhythm. Furthermore, the present observations support the caveats of Falkowski & Kiefer (1985), that in situ moored fluorometers, the use of air-borne laser-induced fluorescence, or satellite-received passive, solar-induced fluorescence, only measure fluorescence, not chlorophyll per se.

The fluorescence response near the shelf-break over a 24 h period following a drogued dahn buoy showed a variation of about a factor of 5 between the day and night fluorescence levels. Beam attenuation coefficient measurements and Coulter Counter analyses showed that these results could not be attributed to the migration of the phytoplankton.

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).

Two species of Lamippidae parasitic in Alcyonium digitatum (Octocorallia) are recorded from Wales and the French Channel coast: Enalcyonium forbesi and E. rubicundum. Both are redescribed. Animals recorded as ‘E. rubicundum’ from Banyuls (Mediterranean) proved to belong to an undescribed species, E. confusum n.sp. The family Lamippidae is divided into two subfamilies: Lamippinae and Linaresiinae.

The physiological rates of a normally omnivorous marine rotifer, Encentrum linnhei, were measured under the steady-state chemostat conditions in which the physiological state of the food-algae was kept constant whilst the rotifer growth rate was changed to preset levels. The specific clearance rate ranged between 50 and 100 μl/μg rotifer C/day (1.5–3.0 μ/rot/day) and varied hyperbolically with growth rate, a similar curve was obtained with the specific ingestion rate which varied between 1–2 μg C/μg rot C/day. A mean respiration rate of 0.45 μg C/μg rot C/day was obtained from oxygen consumption measurements. About 60‰ of ingested energy was found to be egested as paniculate matter and 9–4 °0 dissipated as heat, the latter comparing with a theoretical figure of 4–5‰.

From rates, transfer efficiencies were obtained giving a mean net growth efficiency (K2) of 38‰ and a mean overall growth efficiency (K1 of 15‰. A curvilinear increase of Kl with growth rate contrasts with linear and hyperbolic responses found with brachionid rotifers.

Twenty species, one of them represented by two ecologically different isolates, were grown at salinities from 0 to 60‰ at intervals of 5‰ or less. Growth was measured spectrophotometrically on a pigment extract, and formation of sexual organs was recorded. For each species the results are presented in a diagram, and compared with the salinity preference suggested by information in the literature and by the author's observations in nature.

Scale readings from 6269 bass caught in 1946–86 on various parts of the U.K. coast, with a few from the Channel Islands and France, have been analysed to determine U.K. growth patterns and assess the relative abundance of successive year-classes. In the U.K. growth was fastest on the south-east coast, slowest on the west coast. In the Channel Islands growth was initially slower than on the south-east coast but faster after maturity; though less fast than on the Biscay coast of France. Year-classes of exceptional abundance tended to grow more slowly than classes of normal abundance. There was evidence in each region of a slight long-term fall in growth rate. Best growth occurred in warm summers. The growth period commenced, and annulus formed, at dates ranging from early May for the youngest juveniles to mid July for adults; terminating in each case in October. Males grew rather more slowly than females and appeared less long-lived and less hardy, except on the south-east coast, where, exceptionally, samples were caught well offshore and included large, generally faster growing fish; this suggests a behavioural difference between the sexes rather than consistently slower growth in males. Explanations are offered for occasional fast growing fish, which occur mainly on the south-east coast and mainly with particular year-classes, notably 1966 and 1969. Problems of interpretation are considered and solutions offered.

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).