During the summer of 1990 the sublittoral communities on hard substrata were investigated at 32 localities off Orkney and St Abbs (Scotland). The environment in both places has an open coast character, with small seasonal fluctuations in temperature and salinity and a high transparency of the water. The major governing environmental factors are the available amount of daylight and the degree of exposure to water movement. For the photic zone two different communities, dominated by foliose algae, are described. Under exposed conditions a widespread community is found, dominated by red algae in the middle structural layer and characterized by a dense canopy of Laminaria hyperborea. Under more sheltered conditions a community occurs in which brown and green algae become more abundant in the middle structural layer, while the top layer is formed by Laminaria saccharina and Saccorhiza polyschides. In the aphotic zone, under exposed conditions, a community is found which consists of a number of variants, with a dominance of the suspension feeders Pomatoceros triqueter and Alcyonium digitatum or bryozoans and hydrozoans. These variants are found in different regions, depths and angles of inclination of the substrata. Comparable variants have also been found off Helgoland (German Bight). Under sheltered conditions the suspension feeders become of minor importance and the community is dominated by encrusting red algae. In a surge tunnel in the photic zone off St Abbs Head, a community dominated by Dendrodoa grossularia and Clathrina coriacea is present.

The hyperbenthic mysid, Boreomysis nobilis G.O. Sars, 1879 (Malacostraca: Peracarida), is reported from nine new locations around the island of Newfoundland in eastern Canada. It is commonest within and at the mouths of deep fjords and is less common or absent outside these fjords. Its absence from two bays where the depths, temperatures and salinities are all within the range inhabited by B. nobilis in other bays indicates that other factors are probably influencing local distribution patterns. The catch rates for B. nobilis are highest in the deep water within 150 m of the bottom. However, no differences were found in the vertical distribution of the different life-history stages of B. nobilis and no evidence was found for large-scale diel vertical migrations. Boreomysis nobilis was found to breed throughout the year, since all developmental stages were present on all sampling dates. However, there was a period of increased breeding activity in the late spring and early summer. An examination of the relationship between brood size, body volume of ovigerous females, and number of stage 1 larvae indicates that B. nobilis produced a smaller number of larger larvae than expected for epipelagic and coastal mysids

The life cycle, seasonal dynamics and production of two populations of Streblospio species (Annelida: Polychaeta), S. benedicti Webster, 1879, from muddy sediments of the Great Sippewissett Salt Marsh (southern New England, USA), and S. shrubsolii (Buchanan, 1890), from muddy areas of the Alfacs Bay (north-eastern Spain), were studied from November 1986 to September 1988. Both species have life-cycles shorter than one year. The American population showed a unimodal distribution most of the year while in the European population polymodal distributions were common. Average density of S. benedicti over the two-year period ranged from 24,086 to 677 individuals m−2 (annual average 4,554). The observed numbers of S. shrubsolii ranged from 65,668 to 2,579 individuals m−2 (average 35,311). The biomass of the American population ranged from 2·1 to 0·04g dry weight m−2 (average 0·5). The values obtained for the European population ranged from 5·9 to 0·1 g dry weight m−2 (average 4·1). Secondary production was higher in the European population (15·65 g dry weight m−2 y1) than in the American population (3·0 g dry weight m−2 y−1). Production to mean biomass ratios were 4·4 y−1 for S. shrubsolii and 5·4 y−1 for S. benedicti. Population densities are compared with previously published data for other Streblospio populations.

In order to elucidate the ecological significance of polychromatism in Idotea baltica (Crustacea: Isopoda), the distribution of the various phenotypes was studied for three consecutive years in a population from the Bay of Naples. The most abundant morphs were uniformis (males: 394%-100%; females: 24·6%-84·1%) and maculata (males: 0·59·8%; females: 0%·50%), their distribution varying throughout the year. The assessment of some biological characters (females size, fecundity and embryonic stages of development) did not show any differences accounting for preferential fitness of these phenotypes. Moreover, it was observed that phenotypic diversity in colour morphs followed seasonal changes in the substrate composition. In agreement with other investigators, it has been suggested that the camouflage function of polychromatism may have a fundamental role in the reduction of predation, and favour Idotea baltica colonizing a variety of changeable habitats.

Changes in the composition of the diet, foregut fullness, and the degree of digestion of ingested food were taken into account in determining diel feeding activity of the numerically dominant species of decapod crustaceans dwelling on the Catalan Sea Slope (western Mediterranean). Two 24-h periods were sampled at two different stations on the upper middle slope (between 400 and 710 m) using bottom trawls. Additional foregut fullness data for Aristeus antennatus and Acanthephyra eximia were recorded below 1000 m. The influence of the relatively shallow-living mesopelagic fauna (Pasiphaeidae, Sergestes arcticus, euphausiids, and fishes) over the 24-h cycle apparently had a large effect on the feeding activity rhythms in the deep-sea decapods studied. Species can be classified into two different groups according to their feeding patterns. Thus, species whose diet was based on pelagic prey (Plesionika edwardsi, Plesionika martia, and A. eximia) exhibited a feeding pattern conditioned to the availability of this type of prey. In contrast, in those species in which pelagic prey contributed only a small portion of the diet (A. antennatus, Plesionika acanthonotus, Polycheles typhlops, and Geryon longipes) no variations in the foregut fullness or in the percentage of undigested prey in foreguts during the diel feeding cycles were recorded. The decrease in the influence of the abundance of mesopelagic fauna with depth, with a commonly accepted boundary at around 1000 m would be responsible for the progressive flattening out of activity rhythms among the species dwelling on the lower slope. Foregut fullness values for certain species with broad depth distributions in the Catalan Sea (A. antennatus, A. eximia), would support this hypothesis.

Mussels were fed four concentrations of seston (between 0·99 and 10·3 mg total seston I−1), comprising three levels of organic content (71·9, 63·6 and 40·8%), made up from natural silt and two species of cultured phytoplankton. Two of the seston concentrations were below, and two above, the threshold at which pseudofaeces were produced. Measurements of physiological traits (filtration rates, pseudofaeces production, selection efficiency, absorption efficiency, absorption rates and rates of oxygen consumption) were made after 2 days and, for two of the seston concentrations, also after 12 days. When fed at a high concentration of seston of low organic content, the mussels increased their filtration rate, rejected a higher proportion of filtered material as pseudofaeces, and increased the efficiency with which filtered matter of higher organic content was selected for ingestion; this resulted in a constancy of the relationship between ingestion rate and the concentration of particulate organic matter, regardless of differences in seston organic content. Between 2 and 12 d, the mussels increased absorption rates for organics, primarily by increasing absorption efficiency, both for total organics and for the carbohydrate component of the diet. We suggest that these responses to changes in the food environment comprise physiological adjustments which result in higher net rates of absorption than would be predicted from considerations only of the organic/inorganic ratio of the suspended particles and assumptions of a non-compensating feeding behaviour.

Since 1980 many papers dealing wholly or partly with the genus Fenestrulina have been published, mainly by Anglo-Saxon and South American authors: e.g. Gordon (1984, 1989), Hayward (1980), Hayward & Ryland (1990), Hayward & Taylor (1984), Moyano (1985). These studies have increased the number of species of the genus known around the world. However, few authors have worked on the genus Fenestrulina in European seas, probably because it was assumed that this taxon was well known in these regions.

The Pycnogonida are a group regularly recorded in deep-sea benthic samples, although normally in low numbers. Most analyses from such surveys record new species, and many of these remain known only from a few specimens, often only the types. However, the amount of deep sea-bed sampled is necessarily proportionately so small that it may be argued that any species taken are probably common, owing to their having been sampled at all. It is evident from the gaps in the (often world-wide) distribution of these known species and their limited occurrence that deeper water pycnogonid faunas are still at best poorly known (q.v. Child, 1982).

The dry weight and organic carbon content of eggs and components of Clyde spring herring eggs were measured at intervals during their development. Comparison with previously published data suggests that an increase has occurred in the weight of these eggs over the past thirty years. It is clear that only a small proportion of the material deposited in the form of herring spawn actually remains attached to the substratum when the larvae hatch and so is available for potential integration into the benthic food web. This was confirmed by the determination at intervals over two years of the organic carbon content of the gravel sediments on spawning grounds of the Clyde spring herring. Although the deposition of herring spawn resulted in an immediate marked increase in the carbon content of the spawning ground sediments, carbon levels quickly returned to pre-spawning levels and there was no evidence of any permanent or long lasting increase. This held true when the spawn died and decayed in situ and even when it was mixed into the sediment by wave action. The rapid decrease in carbon levels is attributed to the strong water movements which frequently occur over the spawning grounds.

Epipelic diatoms represented the dominant microphy tobenthos on the intertidal mudflats of the Severn Estuary, south-western Britain. Algal biomass (measured as chlorophyll a concentration) varied over a seasonal cycle and was strongly correlated with sediment shear strength and critical shear stress and therefore with position on the shore. High levels of diatom biomass were positively correlated with the concentration of colloidal carbohydrate within the surface sediments. The critical shear strength for incipient erosion was significantly correlated with position on the shore (moisture content) and with both chlorophyll a and colloidal carbohydrate, the latter being the best biochemical predictor for the incipient erosion threshold. The range of stress required to cause incipient erosion varied from 1.0 to 8.0 N m-2, with the sediment increasing in resistance landwards. Two-way analysis of variance using both moisture content and colloidal carbohydrate as variables explained the stability of the sediment better than individual pair-wise comparisons.

A study of tributyltin (TBT) uptake, tissue distribution and breakdown in dog-whelks, Nucella lapillus, was carried out using 14C-labelled tributyltin chloride. The compound was introduced into animals by exposure to sea-water, from a diet of labelled mussels and by injection. Measurements of 14C were made on tissue extracts containing total 14C, TBT+DBT and TBT. Organs examined included digestive gland, kidney, mantle, foot, viscera, gonads and blood. Absorption of dissolved TBT occurred primarily via tissues associated with the mantle: autoradiographic evidence showed that of these the ctenidium (gill) and osphradium were probably most important. Of non-reproductive tissues, mantle displayed least evidence of TBT degradation whereas kidney and digestive gland contained lower proportions of 14C as TBT (~60%) than other tissues. By virtue of its more rapid response, initially at least, the kidney had a primary role in degrading dissolved TBT that reached the blood. Dog-whelks feeding on labelled Mytilus edulis absorbed organotins very efficiently via the digestive gland, which then played a major role in TBT breakdown. However, the capacity for degradation is not sufficient to prevent, TBT concentration factors of the order of 100,000 (dry tissue/water) being attained in N. lapillus. Autoradiography revealed surprisingly high grain-counts in nerves, which may be significant in view of evidence in the literature that neurohormones are intermediaries in the chain linking TBT with imposex.

Between 1984 and 1993, levels of imposex (the induction of male characters including a penis on females) were measured in gastropods Nassarius (Hinia) reticulatus (L.) at localities in south-west England. Since tributyltin (TBT) was thought to cause imposex, concentrations in tissues and sea-water were also determined. Measurements made prior to the restriction of TBT usage in 1987 showed that intensities of imposex were related to TBT levels in females. Tissue concentrations were also related to those of sea-water and concentration factors (dry tissue/water) were approximately 30,000 at 10 ng Sn I-1 and 75,000 at 1 ng Sn I-1. Penis development in females was initiated at about 1 ng Sn I-1 and in this respect JV. reticulatus appears less sensitive to TBT than the dog-whelk Nucella lapillus.

As result of the TBT restrictions, concentrations in sea-water and tissues at some of the more polluted sites decreased by factors of 5–10 times between 1987 and 1993. However, population imposex declined very slowly. This was attributed to the longevity of the snails, the slow decline of penis-length in older females and the limited recruitment of less-affected females.

It was concluded that N. reticulatus is a useful alternative to N. lapillus as an imposex-based TBT indicator at contaminated sites. However, when environmental TBT concentrations are declining fairly rapidly, analysis of N. reticulatus tissues provides a far better indication of change than measurements of population imposex.

The common whelk, Buccinum undatum L., was selected as a model host-parasite system in a seasonal study at an ‘accumulating’ sewage-sludge dump-site in the Firth of Clyde, Scotland, where marked spatial concentration gradients exist for a variety of trace contaminants in the sediments. A total of 2808 whelks was examined from seven sites over 18 months. The prevalence of larval digenean parasites increased significantly with distance from the dump site from approximately 2% on its periphery to 15.1% at a reference site 3 km from the centre. At a second reference site, 13 km from the dumping area, 19.7% of Buccinum were parasitized. The effects of site, season, sex and parasitism on growth and condition of Buccinum and exposure to sewage sludge on the age-prevalence relationship and host response to infection were examined. Age-frequency distributions of Buccinum were used to compare various sources of mortalities (natural, fishing, pollution and parasite-induced). Patterns in parasite prevalence recorded at the dump site were not correlated with any natural environmental or host-related factors that were examined. The gradient in parasitism in Buccinum is considered to result principally from the toxic effects of trace metals on the miracidium, reducing parasite transmission to the molluscan host. The Bucrinum-parasite system may therefore provide a sensitive and valuable biologically-based index of the dispersal of these contaminants around the sewage-sludge dump-site, and may have wider applications for marine environmental monitoring.

Samples of two loliginid squids Alloteuthis africana and A. subulata were collected from the continental shelf off the west Sahara in August-September 1987. Statoliths were taken from 124 specimens and processed using statolith ageing techniques. Statoliths of both species were very similar in shape. In the ground statolith, growth increments were examined and grouped into four growth zones distinguished mainly by the width of the increments. Age of adult mature males of both species did not exceed eight months, that of females six months. Alloteuthis africana grew faster than A. subulata in weight and, particularly, in length. At age 180 d the mantle of A. africana was twice as long and the body weight 1·2–1·5 times as large. Both species matured over a wide range of sizes and ages (from 120 to 180 d). The life span of A. africana and A. subulata hatching between January and May on the west Saharan shelf is about six months, much shorter than that of A. subulata in its northern temperate range.

Methods used to identify individual organisms consistently over time have been invaluable tools in ecological studies, enabling reliable assessments of time-dependent parameters such as growth and mortality, and an accurate determination of their variance. These methods have proved to be particularly amenable to gastropods owing to the presence of an external shell on which marks or tags can be applied with little or no adverse effects on the animal. Marking and tagging techniques have enabled the study of several ecological parameters in adult marine gastropods, including growth (Frank, 1965; Hughes, 1972; Palmer, 1983; Gosselin & Bourget, 1989), mortality (Frank, 1965; Hughes, 1972), movements (Frank, 1965; Chapman, 1986), and foraging behaviour (Menge, 1974; Hughes et al., 1992). Small organisms, however, can pose considerable problems for individual marking (Southwood, 1978). As a result, marking and tagging methods have seldom been applied to newly hatched or recently settled juvenile marine gastropods. Several methods have been developed for simultaneously labelling large numbers of invertebrate larvae (Levin, 1990), and some of these methods may be applicable to juvenile gastropods. The usefulness of these methods, however, is limited because all animals receive the same label and, consequently, individual animals cannot be recognized. To my knowledge, no method of individually marking very small juvenile marine gastropods has been documented. In fact, it is sometimes perceived that small juveniles cannot be individually marked due to their small size and sensitivity (Frank, 1965; Palmer, 1990). The object of this paper is to present a simple method of marking early juvenile gastropods, which consists of applying colour codes to the shells of individuals as small as 0·9 mm in length.

The mean annual towing speed of the Continuous Plankton Recorder (CPR) varied systematically between 1946 and 1991. By mounting a pressure transducer on the CPR to record towing depth, it was shown, however, that changes in towing speed did not cause a significant change in towing depth, although the mean towing depth (6–7 m, SD=l-7 m, N=77) was shallower than the previously assumed towing depth of 10 m. Thus the observed changes in towing speed are unlikely to have caused discontinuities in the CPR time-series by affecting sampling depth.

Long-term data sets play an important role in attempts to understand the causes of fluctua- tions in plankton abundance. The Continuous Plankton Recorder (CPR) survey provides multi- decadal information on plankton abundance in the North Sea and North Atlantic (McGowan, 1990), and is one of the longest standing marine plankton abundance time-series. However, while the CPR time-series has great potential, as with all other data sets spanning many years, questions may be asked regarding the consistency with which the data have been collected and hence the true continuity of the time-series.

Chromosomes of Haliplanella luciae (=H. lineata) (Verrill) were studied by a simple method that involved examination of Giemsa-stained preparations. The preparations were made from early embryos after fertilization in the laboratory. This is the first report of chromosome number for the acontiate sea anemones. A modal diploid number of 32 chromosomes was observed in metaphase plates. The method reported here is applicable to studies of chromosomes of other Actiniaria in which external fertilization occurs, with mature gametes being released from individuals of both sexes.

Living cells of the ciliate Mesodinium rubrum were observed and photographed during summer red-water events in the Southampton Water estuary, southern England. These blooms were characterized by increases in maximum cell diameter and range of cell size, a pronounced morphological variation of the ‘oral’ hemisphere, and the presence of free-swimming ‘fragments’ of larger cells.

Red-water occurrences caused by the planktonic, phototrophic ciliate Mesodinium rubrum (Lohmann) Hamburger & Buddenbrock, have been characterized by some of the highest recorded levels of chlorophyll and primary productivity for natural populations of marine phytoplankton (Lindholm, 1985; Taylor, 1982). However, as these events are rather unpredictable and all attempts to culture M. rubrum have failed, descriptions of the morphology of living cells have been rather limited. A study into the impact of red-tides caused by M. rubrum in the Southampton Water estuary presented a useful opportunity to observe morphological variation in living cells. Water samples were taken with a ‘Van-Dorn’ sampler, and transported in polyethylene bottles in a cool box. Living cells were observed and photographed at 400x magnification using the phase-contrast optics of an Olympus BH2 photomicroscope. Autofluorescence of living cells was examined using a Zeiss fluoresence microscope.

Statoliths of Loligo gahi were sampled in the fishery region 45–47°S on the Patagonian shelf during September 1989. Peculiarities of the growth zones in the ground statoliths of adults are described. Maximum age of large maturing and mature females (130–160 mm of mantle length, ML) was estimated to be 325–345 d, that of large mature males (250–290 mm ML) ranged from 360 to 396 d.

The squid Loligo gahi d'Orbigny, 1835, occurs in temperate shelf and upper slope waters of the Atlantic and Pacific coasts of South America and is caught commercially by the international fleet in the southern part of the Patagonian shelf within the Falkland Islands Interim Conservation Zone (FICZ) (Roper et al., 1984; Csirke, 1987). Occasionally, dense shoals of L. gahi appear in the fishery region 45–47°S off the Exclusive Economic Zone of Argentina (EEZA) and have been caught in significant numbers by trawlers at depths of 120–150 m in September-October (Chesheva, 1990). Loligo gahi is a medium sized loliginid; in Falkland waters males attain 350 mm ML, females 210 mm ML (Hatfield, 1991), while in the fishery region 45–47°S maximum size is 260 mm and 160 mm, respectively (Chesheva, 1990). Patterson (1988) revealed two Falkland spawning stocks of L. gahi of unclear status, spring-spawners and autumn-spawners (austral seasons) and pointed out that the life span of squid of each stock lasted ~1 y. Recently Hatfield (1991) used statoliths to elucidate Patterson's (1988) estimations of age and growth of Falkland stocks of L. gahi and confirmed the 1-y duration of L. gahi's life span.