This study used analytical flow cytometry (AFC) to monitor the abundance of phytoplankton, coccoliths, bacteria and viruses in a transect that crossed a high reflectance area in the western English Channel. The high reflectance area, observed by satellite, was caused by the demise of an Emiliania huxleyi bloom. Water samples were collected from depth profiles at four stations, one station outside and three stations inside the high reflectance area. Plots of transect data revealed very obvious differences between Station 1, outside, and Stations 2–4, inside the high reflectance area. Inside, concentrations of viruses were higher; E. huxleyi cells were lower; coccoliths were higher; bacteria were higher and virus:bacteria ratio was lower than at Station 1, outside the high reflectance area. This data can simply be interpreted as virus-induced lysis of E. huxleyi cells in the bloom causing large concentrations of coccoliths to detach, resulting in the high reflectance observed by satellite imagery. This interpretation was supported by the isolation of two viruses, EhV84 and EhV86, from the high reflectance area that lysed cultures of E. huxleyi host strain CCMP1516. Basic characterization revealed that they were lytic viruses approximately 170 nm–190 nm in diameter with an icosahedral symmetry. Taken together, transect and isolation data suggest that viruses were the major contributor to the demise of the E. huxleyi population in the high reflectance area. Close coupling between microalgae, bacteria and viruses contributed to a large organic carbon input. Consequent cycling influenced the succession of an E. huxleyi-dominated population to a more characteristic mixed summer phytoplankton community.

A pure-cone retina has been reported in the larval stages of teleosts from three families, viz. the salmon Oncorhynchus spp. by Ali (1959), the herring Clupea harengus by Blaxter & Jones (1967) and plaice Pleuronectes platessa by Blaxter (1968 a). There is also an absence of any retinomotor responses (movement of retinal masking pigment and changes in the relative positions of the visual cells) until the rods develop, which is usually at metamorphosis where this is clear-cut. Most adult teleosts are known to have a duplex retina.

INTRODUCTION

One of the longstanding problems in marine biology has been to determine the quantitative importance of bacteria in the regeneration of the inorganic nutrients. There probably still is no entirely satisfactory way of studying this. It is currently believed that although a variety of marine organisms may utilize soluble organic compounds, bacteria dominate this activity. Thus, a measurement of the amount of soluble organic material oxidized will give a first approximation of bacterial activity. Such an estimate may have to be revised at a later date to allow for the activity of other micro-organisms.

INTRODUCTION

Marine bivalve molluscs have in recent years attracted considerable attention for a variety of reasons, not least of which is their importance as a source of food for man. Much of this research has concentrated on studies of reproduction; Mytilus viridis (India: Nagabhushanam & Mane, 1975), M. edulis aoteanus and Aulacomya maoriana (New Zealand: Kennedy, 1977);Choromytilus meridionalis and Aulacomya ater (South Africa: Berry, 1978); Mytilus (= Perna) perna (Brazil: Lunetta, 1969); M. edulis planulatus (Australia: Wilson & Hodgkin, 1967); Mytilus californianus and M. edulis (U.S.A.: Hines, 1979); Mytilus galloprovincialis (France: Lubet, 1959) and M. edulis (U.K.: Chipperfield, 1953; Seed, 1975; Bayne et al. 1978). A review of the literature revealed that in the majority of studies cytology was used as a descriptive tool for the ‘staging’ (Chipperfield, 1953; Lubet, 1957; Seed, 1975, 1976) of the developing gametes and certain anomalies were apparent with regard to the nomenclature of the connective tissue matrix of the mantle lobes.

The byssal apparatus appears during post-larval life when its secretion permits brief attachment during metamorphosis when the animal assumes the form which fits it for life in the adult habitat.

The byssus persists for continued temporary attachment in animals which may lose it in adult life, e.g. Mya arenaria, or in which it becomes an organ of permanent fixation, e.g. Mytilus edulis, Pododesmus macroschisma and Tridacna crocea

Marine organisms possess the capacity to produce a variety of unique and biologically potent natural products for treating human diseases, many of which are currently commercially available or are in advanced clinical trials. Here we provide a short review on progress in the field and discuss a case study of an EU-funded project, PharmaSea, which aims to discover novel products for the treatment of infections, inflammation and neurodegenerative diseases. Research in this sector is opening new doors for harnessing the potential of marine natural products with pharmaceutical properties.

Trophic positions (TP) were estimated for the blue shark (Prionace glauca), shortfin mako (Isurus oxyrinchus), thresher shark (Alopias vulpinus), and basking shark (Cetorhinus maximus) using stable isotope ratios of carbon (δ13C) and nitrogen (δ15N). The basking shark had the lowest TP (3·1) and δ15N value (10·4‰), whereas the thresher shark had the highest values (4·5, 15·2‰). Mako sharks showed considerable variation in TP and isotopic values, possibly due to foraging from both inshore and offshore waters. Thresher sharks were significantly more enriched in δ15N than blue sharks and mako sharks, suggesting a different prey base. The δ13C values of thresher sharks and mako sharks varied significantly, but neither was significantly different from that of blue sharks. No statistical differences were found between our TP estimations and those derived from published stomach contents analyses, indicating that stable isotope data may be used to estimate the trophic status of sharks.

Changes in O2 concentration were measured during in situ incubation of whole, young Laminaria hyperborea and used to evaluate primary production and respiration over a 3-y period (1995–1998). The exudation of dissolved organic carbon (DOC) during incubation was also measured. Total carbohydrates and polyphenols in the exudates and the regional seawater were determined and fractionated into low molecular weight (LMW) and high molecular weight (HMW) species.  Net production rates varied significantly, being highest during the growth phase (March), while respiration rates did not vary significantly. The exudation rates correlated with the plant strategy of growth and production in which high requirements for growth led to a lower proportion of fixed carbon being exuded. More fixed carbon was exuded during the non-growth phase. The annual exudation of DOC is estimated to be ∼26% of fixed carbon and amounts to ∼1·29 kgC m−2 y−1. The annual amount of carbon retained by the kelp (the difference between fixed and exuded carbon), assumed to contribute to growth, corresponds to a biomass increase of 3·0 kgC m−2 y−1, a value similar to those reported using direct measurements of biomass increase in the region.  Carbohydrate concentrations in the exudates were lower during March than in other months, in accordance with the plant growth strategy. Phenols, on the other hand, which are assumed to function as predator deterrent, showed no significant variations in the exudate. The fraction is dominated by carbohydrates while phenols occurred mainly in the LMW fractions.

1. Church Reef, in Wembury Bay, near Plymouth, was selected for a survey of common intertidal plants and animals.

2. Four traverses were accurately levelled relative to Ordnance Datum, and their floras and faunas examined.

3. The relation between predicted tide levels and probable actual levels is discussed, and the importance of the “splash zone” is stressed.

4. As an outcome of 2 and 3, it appears that on Church Reef the most critical levels on the shore, for the species examined, are: (a) between Mean and Extreme Low Water Springs; (b) between Mean Low Water Neaps and Springs; (c) at Extreme (Lowest) High Water Neaps. The least critical level is Mean Low Water Neaps.

5. Two special problems are presented by the upper limits of Littorina saxatilis and L. neritoides, and by the frontiers between Ascophyllum and Fucus spiralis and between F. spiralis and Pelvetia, where the algæ do not overlap.

6. The work of previous authors is discussed for comparison with the present paper.

7. An important difference is suggested between the nature of the zonation of sedentary animals and plants on the one hand, and that of animals capable of locomotion on the other hand.

The stomach contents of 16 bottlenose dolphins Tursiops truncatus (Cetacea: Odontoceti) stranded in the Spanish Mediterranean coast were examined. Remains and size of prey were analysed and correlated with the ecological characteristics and behavioural patterns of this dolphin. Fish and cephalopods represented the main diet components, and hake Merluccius merluccius was the most important prey. The food habits were considered as mainly demersal according to the characteristics of the prey. The study suggested ontogenic and sexual differences in feeding behaviour based on diet composition and hake size. The potential causative factors, particularly as they relate to dolphin social structure, are discussed.

In previous papers we have shown that high temperature and low food levels result in a decline in the body condition of mussels, Mytilus edulis, which have been kept in the laboratory (Bayne & Thompson, 1970; Gabbott & Bayne, 1973). In spite of the loss of body reserves, M. edulis is able to continue gonad development at an increased rate, when the temperature is above ambient (Gabbott & Bayne, 1973; Bayne, 1975). Although gametogenesis appears to be normal under these conditions, there is evidence that stress in the adult affects subsequent larval development in M. edulis (Bayne, 1972) and in the oyster, Ostrea edulis (Helm, Holland & Stephenson, 1973). In mussels, stress resulted in an increase in abnormal embryonic development during cleavage, gastrulation and development to the first shelled larval stage (Bayne, 1972). In oysters the viability of the larvae, assessed in terms of growth rate and percentage yield of spat, was less in larvae from adults kept at low ration than in larvae from adults kept at high ration. Irrespective of the feeding regime, the viability of the larvae fell as the length of the conditioning period increased, and this was related to a decline in the body condition of the adult oysters. The growth of the larvae in the 96 h period following liberation was significantly correlated with the lipid level in the newly released larvae (Helm, Holland & Stephenson, 1973).

It is well known that if a beaker of water, to which a little sand has been previously added, is stirred, then the sand moves along the bottom and accumulates in the centre. The result is the same whether the beaker is stirred clockwise or anticlockwise. It is perhaps less obvious, but equally true, that if the beaker is placed on a rotating table, then stirring clockwise and anticlockwise produces different effects. Any stirring rate in the sense of rotation may produce a concentration of sand towards the centre (better effects may be observed with less dense material – tea leaves for example). However, if the stirring is against the rate of rotation, then it is necessary to exceed the rotation rate before sand will accumulate in the centre of the beaker. In an analogous manner, ‘spinup’ of the table produces dispersion of bottom material, whereas spin-down results in a concentration of material towards the centre of the beaker.

A micro-analytical scheme for the determination of protein, total carbohydrate, freereducing substances, total lipid, phospholipid and RNA levels in marine invertebrate larvae is described and discussed. The scheme is designed for use with 1–2 mg dry weight of tissue. Values of 171·0, 15·03, 50·4 and 11·58 μg/mg dry weight of larvae (flesh + shell) are given for the levels of protein, total carbohydrate, total lipid and RNA respectively, in newly released larvae of Ostrea edulis L.

Adult European flat oysters, Ostrea edulis L., receiving a food supplement of the unicellular alga Tetraselmis suecica (Kylin) Butch, during laboratory conditioning for spawning produced more broods of larvae than oysters receiving only the natural phytoplankton in the seawater supply. Many of the broods from adults receiving this extra food were liberated sooner, and these larvae grew at an enhanced rate and provided greater spat yields than the broods from the control stock. The viability of larvae, which was significantly correlated with their lipid, and in particular neutral lipid, proportion at the time of liberation, declined as the length of the stock-conditioning period prior to female spawnings increased. This may be related to the decline in the dry meat weight and the condition factor of the adult oysters during the experiments irrespective of the feeding regime. The extra algal ration provided a check to the decline in dry meat weight of the food-supplemented adults.

The morphology and microanatomy of two species of Platymonas have been investigated and certain stages of cell division studied. The anatomical features closely resemble those recently described for the motile phase of Prasinocladus except for characteristic differences in pyrenoid structure (cf. Parke & Manton, 1965). The flagella ofPlatymonas are indistinguishable from those of Prasinocladus, being covered with two layers of scales beneath a layer of structureless mucus which obscures their presence except in sections. Caducous hairs resembling those ofPrasinocladus and related genera are also borne on the flagella.

In a recent study (Butler, Corner & Marshall, 1969) it was found that the excretion of nitrogen and phosphorus in soluble form by Calanus finmarchicus caught at Garroch Head in the Clyde sea-area was significantly higher in spring when plant food was plentiful, than in autumn when plant food was in relatively short supply. The present survey has extended this earlier study to include more detailed data at all times of the year, particular attention being paid to the spring diatom increase of 1969 when plant food in the sea near Garroch Head rose above the level which Beklemishev (1962) regards as inducing superfluous feeding, a wasteful process partially involving the inefficient assimilation of foodstuffs (see ‘Discussion’, p. 549).

Measurements were made on the intact retinae dissected from freshly caught deep-sea fish. The unbleached retinae of such fish are not rose-pink like the retinae of most coastal fish or purple like the retinae of most freshwater fish, but are golden in colour.

The golden colours are of photosensitive pigments which give retinal absorption curves similar in shape to frog's rhodopsin, but with maxima of absorption displaced on the average about 15 mμ. towards the blue end of the spectrum. The names ‘chrysopsins’ or visual golds are suggested for this group of pigments.

The density of such photosensitive pigments is often very high. Retinal density changes on bleaching of more than 1.0 has been found for several deepsea fish. These probably correspond to absolute retinal densities of pigment of about 1.3, i.e. the absorption of 95% of blue-green light striking the retina.

The conger and silver freshwater eels have retinae containing similar golden-coloured pigments. These eels begin their lives in the deep ocean and return there when mature to spawn.

The significance of this type of photosensitive pigment in the vision of deep-sea fish is discussed, and an estimate is made of the depths at which deepsea fish will see daylight.

The Plymouth Laboratory is well situated for the study of the herring, and its commercial fishery, and since the winter of 1924–25, advantage has been taken of the varied facilities for research thus afforded. From time to time reports have been published in the Journal of the Marine Biological Association as a series, entitled: “Herring Investigations at Plymouth” and these have dealt with many seemingly distinct subjects of study, including experiments with larvæ from laboratory-fertilised eggs; studies of growth, migration and structure of young and old fish; and accounts of the commercial operations during the winter drift-fishery at Plymouth. It has now been considered advisable to bring together the several results in one paper, in an endeavour to show their essential bearing upon the problems of the practical fishery.

Twenty-six species of marine planktonic algae, belonging to 8 taxonomic divisions, were tested tinder axenic-culture conditions for their capacity to grow, under cool-white light, on nitrate, nitrite, ammonium, urea, glycine, D-glucosamine or hypoxanthine as sole nitrogen source. The culture medium was composed of Mediterranean oligotrophic sea water enriched with phosphate, silicate, trace-metal ions and vitamins, and buffered at pH 7.5–80. Each nitrogen compound was tested at a fixed concentration of 500 μg-at. N per litre.

Our lack of knowledge of nanoplankton organisms is due largely, no doubt, to the necessity for examining them alive and the comparative difficulty of observing them, and also to their being, apparently, of no more than indirect importance in the ecology of fishes, except when their occasional presence in great abundance has been accompanied by unfavourable hydrographical changes. An adequate survey of life in the sea is bound to take them into account. Since they are frequently abundant, at least in inshore waters, and propagate rapidly, they probably form an important constituent of the food of adult filter-feeding invertebrates. They are likely to be of still greater importance as the essential food of many planktonic larvae, particularly in the early stages. Oyster larvae (Ostrea edulis L.) can ingest nothing larger than about 10 μ and appear to rely for food on minute flagellates (Cole, 1936,1939; Bruce, Knight & Parke, 1940). The food of other marine larvae has not been closely investigated.