Since November 1954, the natant epifauna in depths greater than 20 fm. off the Northumberland coast has been sampled at a number of stations with the object of obtaining information on its constitution and fluctuations. The survey has been limited to those species caught with a net of f in. mesh. Seasonal and yearly fluctuations in this fauna must have a considerable effect on the inshore fisheries, for these animals form an important part of the food of marketable fish, yet, this fauna has never beensubject to a detailed analysis over a number of years.

Samples have been taken as regularly as weather and other laboratory commitments have allowed. In practice this has been of the order of one sample each month, butat times sampling has been more frequent than this (Table 8). Although sampling is being continued, the material collected so far gives much information on the epifaunaas a whole and the biology of the constituent natant Crustacea and Mollusca.

Many workers have experienced difficulties in trying to identify species within the genus Enteromorpha. The difficulties arise from our lack of knowledge of the range of variation for the characters used to delimit the taxa and of the sources of the variation shown.

Enteromorpha intestinalis (L.) Link was originally described by Linnaeus (1753) under the name Ulva intestinalis as ‘Ulva tubulosa simplex’ and Enteromorpha compressa (L.) Grev., also by Linnaeus (1753) under the name Ulva compressa as ‘Ulva tubulosa ramosa compressa’. In their interpretations by later authors, the two species differ only in that the former is unbranched and the latter branched. In their cell size, in the unordered arrangement of the cells and in the single pyrenoid in the chloroplast, they seem to belong together. Whether or not a plant is branched would seem to be a straightforward character to use in practice, but for an alga of this kind this is not necessarily so. In its development the unbranched tube of the thallus begins life as a zoospore or zygote which at first divides transversely to form a short uniseriate filament and later by radial longitudinal divisions, the subsequent expansion of which leads to the formation of the hollow tube. In the formation of branches, individual cells, usually towards the base of the frond, divide by a single periclinal division. The outer cell of the pair thus formed then divides transversely forming a single-celled filament, later dividing by radial longitudinal divisions and repeating the structure of the main axis.

Uptake and incorporation of [3H]glycine from 1 μM solutions was observed in the tissues of larval oysters, Crassostrea gigas, Ostrea edulis, and mussels, Mytilus edulis. In all cases, radiolabel first appears in the larva's velum. Following increasing exposure time, label begins to appear in other organs. In newly settled larvae of the oyster, C. gigas, and the scallop, Pecten maximus, uptake occurs via the developing gill buds. All experiments provide evidence of direct epidermal uptake of soluble nutrients without any participation of the digestive tract. Scanning electron micrographs show that there is no bacterial population visible on the surface of the velum that might act as an intermediate step in nutrient transport. These studies on veligers, pediveligers and settled larvae link the phenomenon of larval uptake with the extensive literature on the direct uptake of soluble nutrients by adult bivalves.

Huvadhoo Atoll is a little-known and generally uncontaminated atoll of the southern Maldives, although the human pressure is increasing. This study represents the first attempt to characterize the meiofaunal and nematode assemblages of its lagoon both from a taxonomic and functional point of view. The nematode assemblage was made up of a total of 131 genera in 33 families. Desmodoridae, Chromadoridae and Xyalidae represented the richest and most abundant families, followed in terms of abundance by Selachinematidae and Comesomatidae. The nematode richness was overall higher than that reported in the previous studies carried out in the Central part of the archipelago. The diversity patterns revealed higher values than those reported for the back-reefs platforms, so confirming the positive influence of the water depth on the biodiversity of the nematode assemblage. The statistical analysis highlighted a significant taxonomic difference of the assemblages between the stations characterized by fine and medium-coarse sands, respectively, in line with the auto-ecological preferences of the taxa detected. The use of some nematode descriptors for assessing the ecological quality status (EQS) of the lagoon has revealed a slight disturbance in the station close to Viligili, one of the most urbanized islands. However, the summarization of all the descriptors used allows the highlighting of the good EQS of the Huvadhoo lagoon. Thus, the results of this study may be taken as the starting point for the future monitoring of the potential and real impact of the anthropogenic activity on the area over time.

Microhabitat use by nine species of caprellid amphipods in the genus Caprella inhabiting a Japanese Sargassum bed could be divided into three major categories. Differences in the patterns of use were closely related to the nature of the mother–young association and morphological characteristics of young. Pattern A was shown by three species Caprella danilevskii, C. okadai and C. subinermis that produced large first instar young (>1.6 mm in body length, BL) with no maternal care, and directly use Sargassum thalli as habitat substrata throughout their lives. Two different patterns of microhabitat use occur in the six other species, which produce small first instar young (<1.3 mm BL) and have trouble using Sargassum thalli as their primary habitat. Pattern B comprised of C. decipiens, C. monoceros and C. scaura in which females care for their young until they become large enough to disperse onto the seaweed thalli. The first instar young of these three maternal care species have specialized pereopods. In Caprella monoceros and C. scaura, which show a ‘cling-to-mother’ type of maternal care, each pereopod has a concaved margin on the propodus and a long dactylus, well adapted for clinging to the mother, and C. decipiens, which show a ‘stay-around-mother’ type of maternal care, have comparatively slender and longer pereopods to hold onto seaweed branches near their mother. Pattern C included C. arimotoi, C. glabra and C. penantis which showed no maternal care and use thin branches of epizoites such as epiphytic hydroids as their primary substrata. It is concluded that caprellids that live on seaweed with thick thalli and branches such as Sargassum patens have different solutions to the problem of where the small first instar young can live: species with larger young emerge directly onto seaweed thalli, but species with smaller young use an epiphytic secondary habitat or depend on maternal care.

This paper reports the results of a hydrographic survey and the successful deliberate deep droguing of a meddy (Pinball) and the seeding of its core with two ALACE floats. The drogued buoy results give important kinematic properties of the eddy core in real timesemicolon the ALACE have allowed the position of the meddy to be tracked for seven months. Pinball was found against the continental slope near Lisbon canyon. The maximum core salinity was 36·564 psu, at a depth of 1260 m, but the maximum rotation rate with period ~2·5 d was in the upper core near 700 m, where temperatures reached 13·2°C. The azimuthal transport to a radius of 50 km was ~13 Sv. Pinball moved from the continental slope near Lisbon to the central Tagus Abyssal Plain, returned towards the continental slope and then moved westwards crossing the central Tagus Abyssal Plain a second time. At times it had a marked remote sensing infra-red sea-surface signature. It moved ~550 km over 204 d and the near real-time data meant that, in principle, this eddy could have been re-surveyed, redrogued or reseeded with floats during this period.

During a study of the relation between temperature and cirral activity of barnacles, reported in Part I of this series (Southward, 1955), specimens for investigation were collected from those habitats and tide-levels where the particular species was most abundant. However, it is possible that some variation in behaviour may arise from local environmental factors such as tide-level and degree of exposure to wave action, and experiments were carried out to test this possibility.

An estimate is made of the mean value of residual flow through the Dover Strait for each month over the 24–year period from 1949 to 1972. The estimates are based on results from a modelling investigation by Prandle (1978) where it was shown that the residual flow consists of three components, (a) a tidal residual, (b), a wind-driven residual and (c) a flow due to a long-term gradient in mean sea level. The components (a) and (c) are assumed to be constant and the value of (b) is deduced using wind data recorded by Dutch Light Vessels located in the southern North Sea.

The mean flow over the whole period amounts to 155 × 103 m3 s–1 into the North Sea with a maximum value of 364 x 103 m3 s–1 and a minimum of – 15 × 103 m3 s–1 (out of the North Sea). One notable feature of the complete time series is the surprisingly small variation in the annual mean flows; perhaps this stability in the annual flow is of significance to the marine biology of the area.

The validity of the computed time series is established by reference to comparable data including a 9–year record, from cross-channel submarine cables, of the potential induced by the flow of water through the Earth's magnetic field. Additional comparisons are also made with the results of a previous study of daily-mean flows.

INTRODUCTION

Studies of established populations of Laminaria hyperborea (Gunn.) Fosl. have indicated that there is often less change of growth rate with depth than might be expected to result from the decrease in irradiance (Kain, 1967; Lüming, 1969; Jupp & Drew, 1974). This has been attributed to self-limitation by the canopy of Laminaria fronds (Lüning, 1969; Kain et al. 1976). The removal of this canopy can result in fast growth in shallow water (Kitching, 1941; Svendsen, 1972) and a marked differential in growth rate over a small depth range (Svendsen, personal communication). A series of rocky subtidal areas at two depths off the Isle of Man was cleared of vegetation at various times (Kain, 1975a). This provided an opportunity to make growth measurements on individuals of known age in the absence of a canopy formed by older plants.

The morphology and microanatomy of Platymonas impellucida sp.nov. have been investigated using light and electron microscopes and unusual stages of cell division studied. The anatomical features closely resemble those recently described for Platymonas convolutae (cf. Parke & Manton, 1967). As in that species the pyrenoid is penetrated from many directions by cytoplasmic canaliculi lined with the double plastid membrane but unlike that species a starch shell is not developed around the pyrenoid. In whole cells of P. impellucida therefore, it is extremely difficult, in most cases impossible, to detect the presence of the pyrenoid. This new information on the absence of a starch shell in a member of the Prasinophyceae is of importance since pyrenoid structure appears to be of major importance for taxonomic purposes. Apparent fusion stages have been shown to be a variation in vegetative division not previously encountered in the genus Platymonas.

Introduction

Recent studies on members of the Prasinophyceae have assisted greatly in characterizing this class of green-pigmented algae although the limits are not as yet entirely defined. Fine-structure investigations have, in addition, elucidated certain features of generic significance. The genus Platymonas is now well described and can be unequivocally distinguished from Prasinocladus, a closely related genus. Previously these two genera were separated on the presence or absence of non-motile dendroid colonies, but such colonies are now known in both genera (Parke & Manton, 1967).

The remaining significant diagnostic generic characteristic is the structure of the pyrenoid. In Platymonas the branched canaliculi invading the pyrenoid either from a direction facing the nucleus (Gibbs, 1962; Manton & Parke, 1965) or from many directions (Parke & Manton, 1967) contain cytoplasm rather than protrusions of the nucleus as in Prasinocladus (Parke & Manton, 1965).

During remotely operated vehicle operations on the UK continental shelf to the west of Shetland (60°6′N 4°4′W) at a depth of 400 m, Munida sarsi, a common benthic crustacean was observed actively preying on the northern krill Meganyctiphanes norvegica. Video footage shows the individual using its chelipeds to catch prey items as they swarm around its burrow. These initial observations indicate that predation forms a new feeding strategy for a species previously believed to be an active scavenger.

A population of Cucumaria elongata (Düb & Kor.), found in muddy sand off the Northumberland coast, has been sampled from 1961 to 1964. Densities of more than 20 per m were common.

Cucumaria is a suspension feeder, and uses its tentacles to trap suspended paniculate matter. In the absence of mucous glands or cilia on the tentacles, suspended matter is held fast in a covering of mucus which is produced by glands in the pharynx and oesophagus. Each time the tentacles are introduced into the pharangeal lumen in the course of feeding, they pick up a fresh complement of mucus.

The feeding behaviour is seasonal. During the early part of October the animals stop feeding, and remain dormant until late April/early May of the following year.

The results of monthly experiments to determine the oxygen consumption, percentage of total lipid and the volume/dry-weight ratio, have led to the conclusion that during the winter months Cucumaria hibernates.

The effect of temperature on the feeding behaviour is discussed.

Regular quantitative sampling has shown that Cucumaria is slow growing, and over the area surveyed, four different age-groups were found. These have been designated groups I, A, B and C. Group I was estimated to be 2 years old; group A, 6 six years; group B, 8 years; and group C, 10 years old.

Although active sperm and apparently mature eggs were found in specimens collected as far back as 1962, there is no evidence to suggest that any of the age-groups has reproduced.

Experiments have been carried out with 203Hg-labelled n-amylmercuric chloride (n-C5H11HgCl) and mercuric chloride (HgCl2) to study the modes of action of these compounds as poisons to some crustaceans.

Differences between the susceptibilities of Artemia salina and Elminius modestus to the poisons do not reflect differences between the quantities of these compounds which the animals can tolerate in their tissues, but are directly related to the rates at which the poisons are accumulated. Thus, experiments with either species have shown that Hg is taken up at approximately the same rate from equitoxic solutions of the two poisons; and the rates at which Hg is accumulated by the two species from equitoxic solutions of either poison are of the same order.

Experiments with reduced glutathione have given results consistent with the view that most of the Hg taken up by either species penetrates into the tissues of the test animals and does not act simply by becoming attached to their surfaces.

Direct evidence of the penetration of Hg compounds into a crustacean has been obtained from experiments with Leander serratus. Considerable amounts of Hg have been detected in the antennary glands.

As long ago as 1911, Henze first showed that the ascidian, Phallusia mammillata has the ability to accumulate vanadium from the surrounding sea water into its tissues. Since this report, many other workers have demonstrated vanadium as well as other metals such as iron (Koval'kii, Rezaeva & Kol'tsov, 1962; Milanesi & Burighel, 1978; Macara, McLeod & Kustin, 1979a), manganese (Noddack & Noddack, 1939) and niobium (Carlisle, 1958) in various tunicate species.

A checklist of the fishes of Ascension Island is presented. The species Rhincodon typus, Alopias superciliosus, Isurus oxyrinchus, Carcharhinus obscurus, Galeocerdo cuvier, Sphyrna lewini, Hexanchus griseus, Manta birostris, Gymnothorax vicinus, Hippocampus sp., Epinephelus itajara, Cookeolus japonicus, Apogon pseudomaculatus, Phaeoptyx pigmentaria, Remora albescens, Caranx bartholomaei, Carangoides ruber, Decapterus tabl, Seriola dumerili, Thalassoma sanctaehelenae, Cryptotomus sp., Ruvettus pretiosus, Acanthocybium solandri, Auxis rochei, Auxis thazard, Euthynnus alletteratus, Katsuwonus pelamis, Thunnus alalunga, Thunnus obesus, Xiphias gladius, Istiophorus platypterus, Kajikia albida, Makaira nigricans, Tetrapturus pfluegeri, Hyperoglyphe perciformis, Schedophilus sp., Cantherhines macrocerus, Sphoeroides pachygaster and Diodon eydouxii are recorded for the first time from Ascension Island. We have recognized two previous records as identification errors and indicate 11 other records as doubtful. Including the 40 new records, we now list 173 fish species from Ascension Island, of which 133 might be considered ‘coastal fish species’. Eleven of these (8.3%) appear to be endemic to the island and a further 16 species (12%) appear to be shared endemics with St Helena Island.

a shark tagging programme along the portuguese coast was initiated in 2001 in collaboration with the national marine fisheries service. from a total of 168 blue sharks (prionace glauca) tagged, 34 sharks were recaptured (20% return rate) providing important information on this species' movement patterns for the area. a total of 28 sharks travelled less than 1000 km while at liberty for time periods ranging from 22 to 1294 days. the remaining fish travelled long distances to north-west africa, central atlantic and the bay of biscay. only one shark made a transatlantic migration, being recaptured 3187 km from the tagging site. north–south movements seem to be related to seasonal sea-surface temperature variation in the north-east atlantic. seasonal segregation of different life stages also occurs.

The submerged coral reefs of Brunei, little-impacted by human activity and characterized by high live coral cover, have no recorded history in recent decades of the presence of the crown-of-thorns (COT), Acanthaster planci. This sea star, first recorded on Brunei reefs in 2008, attained outbreak densities in 2010. At Littledale Shoal its impact on corals at permanent transect sites has been quantified; mean live coral cover reduced by half from 2006 to 2010 due predominantly to predation. Line intersect transect data confirm a predisposition for tabular Acropora species, a prominent feature at this site, although other scleractinian taxa were also predated. Other regional outbreaks are reviewed, including episodes, and their timing, within the neighbouring Coral Triangle (CT). Mounting evidence implicates nutrient-enhanced increases in primary production as a primary cause of COT outbreaks. However, this stands in contrast with a report of global oceanic phytoplankton decline in the past century, and there is little evidence of such a link in the CT, even though this region is characterized by high precipitation, erosional plumes and seasonal upwelling-associated phytoplankton blooms. Furthermore, until survivorship and competency for a wider spectrum of mass-spawned invertebrate planktotrophs in relation to elevated phytoplankton densities is better understood, such evidence, suggesting release from food limitation as the principal cause of enhanced COT recruitment, should be interpreted with caution.

Beds of the seagrass Zostera capricorni are an integral part of the estuarine landscape along the east coast of Australia, forming an important habitat for juvenile fish. Seagrass beds can vary in their size, shape and patchiness of seagrass cover as well as their distance from the estuary mouth. We tested for a correlation between these features and small fish assemblages in seagrass. Fifteen beds were selected from three size-categories (small, 980 to 2300 m2; medium, 3375 to 4090 m2; and large, 5335 to 6630 m2). We found that the size of beds, the patchiness of seagrass cover and location within the estuary (distance from estuary mouth) were all related to differences in fish assemblages. There were greater densities of fish species in small (10.3 ±0.79 species .net-1) compared to medium (7.6 ±0.6) and large (8.2 ±0.5) beds. This occurred regardless of bed placement within the estuary, its patchiness or time of sampling (day and night). The fish assemblages within seagrass beds also changed as bed distance to estuary mouth increased. Six species had greater densities in beds closer to the estuary mouth, while only two species were in greater densities far from the mouth. Fish assemblages were different between beds with patchy and continuous cover, although total densities of all fish species combined were similar. There were greater densities of four species in continuous beds compared to two species that were greater in patchy beds. Overall, an important finding was that even small patchy seagrass beds contain greater densities of small fish species than larger beds with continuous seagrass cover.

A good deal is known about the growth in culture of Phaeodactylum tricornutum Bohlin (Nitzschia closterium W. Sm. forma minutissima Allen & Nelson) (see Spencer, 1954; Harvey, 1955; Provasoli, McLaughlin & Droop, 1957). This organism, however, is a somewhat aberrant member of the Chrysophyta, and other marine and brackish-water representatives of the group, e.g. Syracosphaera carterae Braarud & Fagerland (Braarud & Fagerland, 1946; Provasoli, McLaughlin & Pintner, 1954), Prymnesium parvum Carter (Reich & Kahn, 1954; Droop, 1954), and certain other species (Droop, 1954, 1955 a, b) have been studied much less intensively from this point of view. It has therefore seemed worth while making a general study, similar to that reported in the first paper of this series for the diatom Asterionella japonica Cleve & Müller ex Gran, of the growth requirements of a representative of the Chrysophyceae. Isochrysis galbana Parke, a flagellate of some importance as a food organism of the oyster, has been selected for this purpose. Johnston (1955) has used unialgal cultures of this species in studies of dissolved organic matter in sea water and, since the investigation being described was carried out, Droop (1957) has reported that it has a requirement for cobalamin.

The accumulation of 137Cs from sea water has been examined in relation to potassium metabolism in the lobster Homarus vulgaris and in the prawn Palaemon serratus. In unfed animals 137Cs is taken up and lost far more slowly than 42K. Although all the inactive K in the animals can be exchanged with 42K, higher whole-animal concentration factors are reached for 137Cs (about eight for lobsters and twenty-five for prawns). This is because both species have higher plasma/medium ratios for 137Cs than K at equilibrium despite the selective excretion of 137Cs. Also, except for the hepatopancreas in lobsters and fed prawns, all soft tissues can probably attain higher tissue/plasma ratios for 137Cs than inactive K.

Uptake of both isotopes has also been studied in the freshwater crayfish Austropotamobius pallipes pallipes. In crayfish in o-i % sea water 137Cs is not concentrated to the same extent as K by whole animals (50-200 for 137Cs against about 4500 for K). Although the situation between plasma and tissues resembles that in the marine animals, 137Cs cannot be accumulated in the plasma to the same degree as K. Crayfish selectively excrete 137Cs in the urine relative to K at a lower concentration than in the plasma.

In the accumulation of 137Cs by all species, muscle is the principal limiting factor in uptake and loss, but with 42K the body surface becomes more limiting.

Experiments on the absorption of 137Cs from food in prawns and freshwater crayfish have been carried out. In prawns in a constant environment, feeding is probably less important than uptake over the body surface while in crayfish feeding is probably much more important.