A non-linear numerical model is used to derive both the maximum bottom stress and the mean stress on the shelf sea-bed around Britain, due to tidal streaming. It is shown that these two vector distributions will be important in sand transport studies. It is further expected that the results will be relevant to other benthic studies.

A comparison has been made between the concentrations of eleven trace metals in the tissues of two species of scallops, Pecten maximus (L.) and Chlamys opercularis (L.), collected from the same area of the English Channel. Although there was considerable variation between individual animals, the mean concentrations of Ag, Co, Cr, Cu, Mn, Ni, Pb and Zn were higher in the whole body of Chlamys than in Pecten but concentrations of Al, Cd and Fe were lower. In both species, seasonal changes in the concentrations of Co, Cu, Fe, Mn, Ni, Pb and Zn were observed and, in general, the highest values were found in the autumn and winter months. These changes may be related to food supply, since concentrations were generally highest when phytoplankton productivity was low and tended to fall in the spring as productivity increased rapidly to its annual peak. Despite problems arising from individual and seasonal variation, the kidneys and digestive gland of scallops appear to have potential as biological indicators of trace metals.

The results obtained for Pecten and Chlamys are compared with those in the literature for species from the family Pectinidae.

The lipids of four marine coccolithophorids (class Haptophyceae), Emiliania huxleyi, Hymenomonas carterae, Isochrysis galbana and Crystallolithus hyalinus, were examined by capillary gas chromatography-mass spectrometry. Fatty acids ranged from C14 to C22 and were predominantly of even chain length. The major acids were polyunsaturated C18 acids, 22:6 and either 14:0 or 16:0. C20 fatty acids were of low abundance. Significant amounts of octadecapentaenoic acid (18:5), previously thought to be unique to dinoflagellates, were identified in three of the algae. A small amount of a di-unsaturated C36 w-alkenoic acid was identified in E. huxleyi, which is the first report of such a long-chain fatty acid in any alga. Traces of wax esters, which are reportedly uncommon inalgae, were found in three of the species. The sterol distributions were very simple, with two or three compounds accounting for > 99% of the total sterols. In each case, the major component was 24-methylcholesta-5,22E-dien-3β-ol. H. carterae and C. hyalinus also contained 24-ethylcholesta-5,22E-dien-3β-ol and significant amounts of cholest-5-en-3β-ol were found in E. huxleyi and I. galbana. An unusual sterol, 23,24-dimethylcholesta-5,22E-dien-3β-ol, was identified in H. carterae. These sterols were mostly non-esterified although small amounts of sterol esters were identified in E. huxleyi. The lipid composition of E. huxleyi is distinctive in that it contains, in addition to the C36 fatty acid, novel C37–C39 unsaturated ketones and C31–C38 alkenes. Of the other coccolithophorids only I. galbana contained small quantities of one of the C3l alkenes.

The seasonal variations in the total ash, crude proteins, mannitol, laminarin and alginic acid contents are given for monthly samples of the Laminariaceae, L. cloustoni, L. digitata and L. saccharina from November 1946 to October 1948, samples of L. digitata and L. saccharina having been taken at different localities to determine the effect, if any, of the degree of exposure on the chemical composition.

The results agree favourably with those of the first 2 years examined and indicate that, with only a few exceptions, results might be reproducible in the corresponding season of any year, and it should be possible, therefore, to predict the approximate composition in subsequent years.

As before, the marked seasonal variations in chemical constitution occur in the fronds, where the bulk, if not all, of the photosynthesis occurs. The stipes undergo some variation parallel to that in the fronds, but within narrower limits, while laminarin is absent throughout the year.

An attempt is made to explain the great variations in gross shell morphology noted in field populations of Mytilus edulis.

In any one mussel population, variation in shell form can be attributed to differences in age, old mussels having proportionately heavier shells where width often exceeds shell height. This is invariably accompanied by down-turned, divergent umbones and varying degrees of incurvature of the ventral shell margin.

Variations in the age structure of mussel populations from different habitats can also account for local variability in shell morphology. Localities where the life expectancy of mussels is increased due to absence of predators (especially in the upper shore) reveal a high incidence of old ‘ungulate’ individuals, whereas populations in which the mussel turnover is more rapid show a preponderance of relatively young mussels.

Shell morphology is greatly influenced by growth rate and density. These probably exert their effect through physical compression which is maximum in localities of fast growth and high density and least in areas of slow growth and low density. High compression leads to an elongate form whereas low compression results in higher, more triangular shaped shells. Growth rates and densities, even within the same habitat, are, however, exceedingly variable.

Since all environmental conditions vary in both time and space, wide variation in shell morphology is to be expected, even in animals from the same locality.

Transplantation experiments indicate that variation in shell morphology is essentially phenotypic, older animals being more likely to exhibit a form which is characteristic of their particular habitat. Smaller mussels from widely different habitats show remarkable similarity in shell morphology.

Rates of occurrence and degrees of imposex, and tissue concentrations of organotin compounds (tributyltin, TBT; dibutyltin, DBT; butyltin, MBT; triphenyltin, TPT; diphenyltin, DPT; and phenyltin, MPT) in the rock shell, Thais clavigera and T. bronni (Mollusca: Gastropoda) were investigated at 32 sites in Japan from May 1990 to October 1992. The rate of occurrence of imposex was 100% in both species, at almost all sites surveyed. Degrees of imposex indicated by relative penis length (RPL) index reflected the pollution levels not only of TBT, but also TPT. In heavily polluted areas, many individuals were found with oviducts which were blocked by vas deferens development, and capsule glands which were filled with aborted egg masses. These organisms were thought to be sterile.

The filtering rate of four species of marine planktonic copepods was measured by estimating the rate at which they consumed cultures of Chlamydomonas.

The filtering rate was independent of the concentration of the food organism and it is concluded that the copepods were acting as filter feeders.

The filtering rates were much greater than those reported by Fuller & Clarke (1936) and Fuller (1937), but agreed with those reported by Harvey (1937).

Some evidence was obtained that grazing was restricted to some only of the 24 hr., most probably to the hours of darkness.

The filtering rates were approximately proportional to the square of the linear dimensions of the copepod.

The purely mechanical selection suggested by Fuller (1937) to account for differences in filtering rates obtained with different species of diatoms cannot account for all the differences which have been observed.

It is probable that the copepods could obtain sufficient particulate food in the sea by filtering a daily volume of water corresponding to the filtering rates found.

The superficial red muscle fibres of gnathostome fishes run more or less longitudinally, but the deeper muscle fibres are arranged in complex three-dimensional patterns in which some of them make angles of 30° or more with the long axis of the fish. There are two basic patterns, of which one is found in all the myomeres of selachians, primitive bony fishes, Anguilla and Salmo. In the other teleosts which were examined this pattern is restricted to the last few myomeres, and a quite different pattern is found more anteriorly.

In a fish with muscle fibres running longitudinally the lateral fibres would be able to contract far more than those near the vertebral column. However, from mathematical analyses included in this paper it appears that both the patterns which have been found should result in all the white fibres in a myomere contracting to a fairly similar extent when the fish bends. This seems likely to be advantageous because a muscle fibre of given intrinsic speed produces maximum power output at one particular rate of contraction.

A given rate of contraction of the muscle fibres results in faster bending if the fibres are arranged in the typical teleost pattern than if they are arranged in the selachian pattern.

The selachian pattern is probably retained in the caudal peduncles of teleosts because the faster bending is obtained only at the expense of weaker bending moments. The caudal peduncle is slender and would be less able to transmit large forces to the caudal fin if the teleost pattern of muscle fibres were continued to its posterior end.

The English Channel may conveniently be divided into a western basin and an eastern basin separated by a line drawn approximately between the Cherbourg peninsula and the Isle of Wight. In these basins, the environmental factors are very different. Thus the water of the western basin is on average warmer and slightly more saline than that of the eastern basin and its temperature variation is less extreme. The French side of the Channel is warmer than the English coast only in the western basin. The tidal oscillations in the two basins are out of phase with each other and the strongest tidal currents occur where the two basins join. The main residual flow is up-Channel with minor coastal eddies.

The shores at the western end of the Channel are generally rocky, they are close to deep water, and so are exposed to frequent heavy swells. The shores of the eastern basin are generally erodible, and accumulations of sand and shingle tend to reduce the force of the waves. The water of the eastern basin generally contains more suspended matter and the shores are usually scoured by sand and shingle.

The distribution of the following animals is given in some detail and compared with earlier records: Ammonia sulcata, Actinia equina, Chthamalus stellatus, Balanus balanoides, B. perforatus, B. crenatus, B. improvisus, Elminius modestus, Verruca stroemia, Hemioniscus balani, Patella vulgata, P. depressa, P. aspera, Monodonta lineata, Gibbula umbilicalis, G. pennanti, G. cineraria, Littorina saxatilis, L. littoralis, L. littorea, L. neritoides, Paracentrotus lividus. The distribution of certain other species is also discussed: Balanus balanus, Haliotis tuberculata, Gibbula magus and Calliostoma zizyphinum.

The swimbladder is recognized as responsible for a major part of the acoustic backscattering from fish. In most fishes it has the function of a buoyancy regulator but in others its main function is rather unclear. Based on methods for exact mapping of the swimbladder shape, observations of deviations from normal appearance and shape are discussed in relation to possible effects on target strength. Evidence for both periodic variations, as from uncompensated vertical migrations, and seasonal variations, caused by the fat cycle and gonad development, are presented.

The majority of studies of the physiological ecology of organisms have been concerned with changing a single environmental variable at a time, but more information on the relationships between biological responses and environmental factors would be provided by experimental techniques that emulate the multi-dimensional character of the natural environment.

Fauna associated with the common kelp along the Norwegian coast, Laminaria hyperborea, was sampled at four sites covering 1000 km of coastline. Exploitation of the kelp habitat by the fauna, and the ways in which habitat size and seasonal variations affect the kelp fauna community were analysed. The study focused on mobile macrofauna, of which 238 species were found on 56 kelps sampled, with an average density of almost 8000 individuals per kelp. Amphipods and gastropods were the most diverse and abundant fauna groups. The species composition was different on the lamina, stipe (with epiphytic algae) and holdfast. A similar pattern of epiphyte- and holdfast-fauna composition was found for all regions. Lowest diversity and abundance were found on the lamina, and highest diversity in the holdfast. Highest abundance was found on the stipe in summer, but there were large variations between sites and seasons, from a few individuals to more than 80 000 animals per stipe. Neither seasonal changes nor variation in habitat volume affected the number of species significantly, but abundance was significantly related to season and habitat volume. These variations were most pronounced for stipe fauna. Laminaria hyperborea offers a heterogeneous habitat exploited by a diverse and abundant invertebrate community, its abundance depending on local and regional variations in kelp size.

A certain variation in level of the fucoid zone with latitude is demonstrated. The belt of Fucus vesiculosus and F. serratus lies lower on the Devon coast than on either the Manx or the Argyll coast.

The conditions for the optimum germination of fertilized eggs are dissimilar to those for maximum rate of frond-extension.

Normal growth-rates have been established for both species for the first 3 years of life. In F. vesiculosus the average rate of elongation per week is 0·48 cm. on the Devon coast, 0·45 cm. on the Manx coast and 0·68 cm. on the Argyll coast. In F. serratus the average rate of elongation per week is 0·49 cm. on the Devon coast, 0·68 cm. on the Manx coast and 0·85 cm. on the Argyll coast. The rate of growth is shown to vary with the conditions of the environment. Shelter from rough water tends to enhance growth-rate, and there is an indication that greater stature is achieved by the plants from the Argyll station than from either of the other stations.

The use of diversity and evenness indices is well established in recent ecological literature. Many indices have been proposed, to such an extent that the choice of a suitable index became somewhat of a problem. Recently, however, Hill (1973) introduced a unifying notation where diversity numbers are denned in relation to Rényi's definition of a generalized entropy. Hill showed that his diversity numbers Na of the oth, 1st and 2nd order coincide with three important diversity measures which have been frequently used, No = S, N1 = eH and N2 = 1/SI, where S is the number of species, H is the shannon-Wiener information function –Σpi In pi and SI is Simpson's index . According to this notation, evenness should be calculated by dividing two of Hill's diversity numbers, e.g. N2/N1 = eH/S. This index was proposed by Sheldon (1969), but its use in ecological literature has been negligible. The most commonly used evenness index has been the one proposed by Pielou (1966), e = H/Hmax, with Hmax = lnS. Contrary to Hill's (1973) statement, it shares with Hill's continuum of evenness measures the property of remaining constant when the number of individuals of all species is multiplied with a constant factor. Intuitively, this seems to be a necessary property of an evenness index.

Sea water probably contains all the chemical elements, although a number of them have not yet been detected. Considerable information is available on the occurrence of various elements in marine plants and animals, but it is far from complete for any one biological group. Except for recent work by Spooner (1949), on the absorption of radioactive strontium and yttrium by marine algae, no detailed study of the trace elements in the brown algae, nor any attempt to correlate the trace elements in sea water with those in the algae, appears to have been carried out. The following is a brief résumé of the work that has been done in this field.

Deposit-feeding by Scrobicularia planaScrobiculariaplana (Da Costa) along the mud surface occurs throughout the period of low tide if the water table remains at the surface. The rate of deposit-feeding is unaffected by the time after emersion at low tide except where excessive drainage prevents feeding along the mud surface, in which case it is possible that animals feed from the sides of their burrows at or below the level of the water table.

The Celtic Sea extends from the south of Ireland and the St Georges Channel across the continental shelf, with the Bristol and English Channels as its eastern limits (Fig. 1) (Cooper, 1967). Although various investigations of the physical oceanography (Matthews, 1914; Cooper, 1967) and zooplankton (Russell, 1934, a, b, 1936; Corbin, 1947; and more recently Southward, 1962; Bary, 1963) of this area have been carried out, there is little or no information on seasonal changes in levels of chlorophyll ‘a’ and inorganic nutrients, and on the importance of tidal mixing in determining these distributions. Since the speeds of the tidal streams range from weak (∼ 0.5 knot) in the northern part of the Celtic Sea to strong (∼ 3 knots) around the Scilly Isles and Ushant (Fig. 2), the vertical stability of the water column as well as the duration of the seasonal thermocline (Pingree, 1975) are likely to be important factors in determining spatial and temporal variations of phytoplankton production. In this paper the influence of water-column stability on phytoplankton distributions (in spring, summer and autumn) in the Celtic Sea is described, using data for temperature, salinity, chlorophyll ‘a’ and inorganic nutrients obtained during seven cruises in 1975. An account of the red tide conditions that occurred in late July to the north-west of Ushant has already been published (Pingree, Pugh, HoUigan & Forster, 1975).

Three levels of oxygen consumption rate are identified, viz. standard, routine and active. Animals fed above the maintenance energy requirement adjust their oxygen consumption rate to a routine level. Animals fed below the maintenance requirement reduce their oxygen consumption rate to a standard level within 35–40 days. The routine rate is seasonally variable, with high values in the winter and low values in the summer. The standard rate also varies seasonally. The exponent that relates routine oxygen consumption to body size varies from a high value in the summer to a lower value in the winter.

It has been found that a reagent containing sulphuric acid, ammonium molybdate and ascorbic acid may be used as a single-solution reagent for the determination of phosphate in sea water. Development of the molybdenum-blue colour is complete in 24 h at room temperature and in 30 min at 60° C; the colour is stable for at least 3 days. Beer's law is obeyed closely up to at least 500 μg PO43−-P/1. The salt error is approximately 4% with sea water of chlorinity 19·3%. The interference due to either arsenate or silicate at their concentrations in sea water is negligible.