The combustion of fossil fuels and the resultant impacts on climate may now represent one of the largest environmental threats. In the Mediterranean Sea, changes in bio-chemical and physical seawater properties resulting from global warming are likely to alter marine biodiversity and productivity, trigger trophic web mismatches and encourage diseases, toxic algal bloom and propagation of thermophilic species. This review highlights the current and potential threats of climate change to the Mediterranean marine ecosystems, including cetaceans, and stresses the emergent necessity for more integrated regulations and policies for the protection of marine biodiversity. For instance, in the Mediterranean Sea, the distribution and abundance of the small euphausid species Meganyctiphanes norvegica is correlated with specific hydrobiological parameters including seawater temperature, salinity and current patterns. Situated at the northern limit of its ecological tolerance, this species, which constitutes the only known food supply of the fin whales (Balaenoptera physalus) in this region, might be affected by climate change-induced alteration of ocean circulation.

Considerable differences were found in the size compositions of populations of Asterias rubens off Plymouth. These differences were not correlated with age.

Laboratory observations on rate of growth showed that well fed starfishes grow fast during summer and autumn and somewhat slower in winter. Poorly fed starfishes did not increase in size, but were able to survive for long periods with a minimum of food.

Marine debris is a major challenge threatening ocean and coastal environment with no easy solution in coming years. The problem is totally manmade and extendeds to coastal areas around the world. The accumulation of marine debris is largely due to lack of awareness and environmental education among the public reinforced with mismanagement of municipal litter in coastal cities. Iran has about 2415 km of coastlines in the north and south of the country that suffer severely from a marine debris problem. Despite the great scale of the problem that leads to the shutdown of some beaches to beachgoers, there are no documented data on the abundance, composition and sources of marine debris dispersed on beaches. With the cooperation of marine biology student volunteers, we surveyed beaches at two scales, 100 m and 1 km searching for litter in varying ranges. The results revealed that the most common items are made of plastic/polystyrene. Tourism and recreational activities are responsible for more than 90% of litter production on the study beach. Fisheries and aquaculture are the second source of most abundant marine litter found on the beach with considerable distance from tourism activities. We conclude that lack of education about the consequences of marine litter is the main reason for marine debris at the study beach. Another reason is related to rapid construction of coastal areas and development of coastal cities with no proper infrastructure to manage municipal littering.

The inter-tidal habitats of the common limpet, Patella vulgata L,, have been investigated in relation to constant lunar tidal levels and tidal zones. The habitats of some common shore organisms which occur at approximately definite tidal levels or zones—and can therefore be used with discretion for zoning the habitats of Patella—are shown in a chart.

A study of the distribution of the common limpet on the shores of Devon and Cornwall has shown that limpets are absent or rare on those parts of the foreshore above high-water neaps which are subjected to prolonged periods of direct insolation. In the same locality limpets may be totally absent from the high-water region on cliff-faces or rocks facing southerly, but present on adjacent ones facing northerly or north-westerly. Strongly insolated habitats appear to be unviable as a result of the direct effect of the insolation on the animal, but the apparent deficiency of food in such habitats is probably also a limiting factor of importance.

The importance of the splash-line of any tidal level is emphasised. It is shown that in Devon and Cornwall the occurrence of low-water spring tides at about midday (and midnight) results in exposing to strong sunshine (and correlated factors) those regions of the shore above high-water neaps which face in a southerly direction. In other localities where high-water spring tides occur about midday, equivalent regions of the foreshore are not so strongly nor so persistently insolated as in the former.

Viable habitats may therefore occur in different regions on the shore in different localities or at different latitudes according to the local orientation of the substratum and local tidal phenomena.

Inspection videos of four offshore platforms in the central and northern North Sea were used to study the development of fouling communities on clamps and guides of oil export risers over an 11-y period (1989–2000). Results from multivariate analyses (multi-dimensional scaling and analysis of similarities) indicated that distinct assemblages developed in different geographical locations. These differences were mainly due to the protracted development of the Metridium senile (Cnidaria: Actinaria) zone on the northern sector platforms. The vertical zonation of fouling organisms was similar on all installations, although the water depth at platform locations varied from 80 to 169 m, indicating that fouling organisms display a wide bathymetric tolerance. This study has highlighted the value of long-term data present in operational inspection videos for the study of fouling communities.

Rotifers are microscopic aquatic animals that comprise more than 1800 species. Most rotifer species live in freshwater and limno-terrestrial habitats, while thalassic environments (brackish+seawater) are thought to host few species. No recent review of saline rotifers is available. Here we report the results of a review of the literature concerning rotifers from saline environments, distinguished into three categories: stenohaline, euryhaline, and haloxenous, and found both in truly marine habitats and/or in inland saline waters. A total of about 200 studies, mentioning fully identified rotifers from saline waters, allowed us to list as many as 443 rotifer taxa at either specific, subspecific and infrasubspecific rank, corresponding to 391 nominal species. Truly thalassic taxa, not found in inland saline waters only, accounted for 289, including the ‘stenohaline’ (143) and the euryhaline (146) ones. As for freshwaters, the majority of the thalassic rotifers inhabit the psammon, or display a benthic–periphytic way of life, while the plankton likewise is less species rich and less abundant. The geographical distribution of the brackish and marine rotifers largely reflects the distribution of rotifer investigators, therefore, no biogeographical analysis can be performed yet. In conclusion, the analysis of literature citing rotifers in salt waters, uncovers an unexpected rotifer fauna: the apparent richness of the group in thalassic environments is worthy of being addressed by further investigations, as many species have been reported only by their description, suggesting either considerable endemism or taxonomic errors.

The sub-structure of Atlantic cod (Gadus morhua) stocks in the North Sea has important consequences for fisheries management as the Common Fisheries Policy moves towards a more regional approach. We investigated the movements, distribution and behaviour of cod in the southern North Sea (ICES IVc) and English Channel (ICES VIId) by re-analysing historic data from conventional tagging experiments, and by conducting new experiments with electronic tags. Cod tagged and released in IVc showed a northwards shift in distribution during the feeding season consistent with a homing migration away from spawning grounds along the coasts of the UK and the Netherlands. In contrast, cod tagged and released in VIId did not exhibit a consistent pattern of seasonal movement. Many cod released in VIId were subsequently recaptured close to their release position, although some moved out of the Channel and into the southern North Sea. Overlap between the recapture areas of cod released in the different management areas was no more than 25% in either the spawning or feeding season. Behavioural data from electronic tags suggest that cod in IVc make use of tidal streams to migrate northwards and eastwards in spring, whereas selective tidal stream transport was rarely exhibited by cod tagged and released in VIId. Overall, the evidence suggests that there are behavioural differences between cod in IVc and VIId that limit the mixing of cod from these two areas during the feeding and spawning seasons.

The Periwinkle, Littorina littorea (L.), is one of the most abundant gastropods on the shore, and can live under widely varying conditions. It is found on clean, alga-covered rocks, among small stones, on gravel, on soft mud, and rarely even on sand. It ranges from about high water of neap tides to extreme low water of spring tides, and in some places even slightly below this, although in most localities it is restricted to a much smaller part of the tidal zone. It occurs also from shores with high wave-exposure to sheltered and even polluted estuaries, where it is tolerant of considerable lowering of the salinity. The material for the present study was collected at intervals throughout 1934—1936 from three localities near Plymouth, the details of which are as follows.

The chitin from pogonophore tubes is shown to be essentially the same as that from the pen of the squid Loligo and is classified as β-chitin (as are the known chitins in annelids). However, certain important differences in detail are seen when comparing X-ray diffraction photographs and infra-red absorption spectra of the chitin from the two sources. These matters are of interest in defining the systematic position of the Pogonophora as well as in reaching an understanding of the functions of the protective tube.

Six species of algae, Chlorella marina Butcher, Dunaliella tertiolecta Butcher, Isochrysis galbana Parke, Monochrysis lutheri Droop, Phaeodactylum tricornutum Bohlin and Hemiselmis virescens Droop were fed to oyster larvae in bacteria-free culture. In addition, cultures of Chlorella stigmatophora Butcher, Isochrysis galbana and Phaeodactylum tricornutum containing bacteria were also used. Cultures of galbana containing bacteria were used as controls in all series of experiments. In each series various densities of food, expressed both as cell numbers and as packed cell volume, were fed to the larvae of Ostrea edulis L. for 22–46 h and the change in the mean size of the larval population was used as the index of the value of the food.

The experiments with Chlorella confirmed previous work that organisms of this genus have little value as food for larvae. With Dunaliella and Phaeodactylum growth was better at low food densities with some (but not all) batches of larvae compared with Isochrysis. The comparison of cultures of Isochrysis and Phaeodactylum with and without bacteria showed no consistent improved growth with either food. Monochrysis had about the same food value as Isochrysis. With Hemiselmis some growth was obtained but not as much as with Isochrysis.

Photosynthesis in the open sea is due mainly to two groups of organisms, the diatoms and the dinoflagellates. In British seas the diatoms are so much more numerous that the chemical changes which are due to photosynthetic activity can be almost entirely ascribed to their influence. Recent work on these chemical changes has shown that they do not extend deeper than about 30 metres. Of the external limiting factors light is among the most important and the depth to which photosynthesis can go on must, of course, depend on the light intensity. In the study of the phytoplankton under natural conditions the results are complicated by the interaction of many other factors such as temperature, viscosity, or lack of food salts, so that it is difficult to come to definite conclusions on the effect of light alone.

The reproductive cycles of the two cockles Cerastoderma edule (L.) and C.glaucum (Poiret) (= Cardium lamarcki Reeve) from a mixed population in the Crouch estuary, Essex, have been investigated. Reproductive maturity was estimated by assessment of gonad condition. A difference in maturity related to shore level was noted. The reproductive cycles of the two cockles were found to be essentially similar. Rapid gametogenesis occurred in both cockles in spring, C. edule then spawned in May, whereas C. glaucum did not spawn until July. The difference in time of spawning appears to be responsible for the maintenance of the two genotypes in a sympatric association, as hybridization experiments showed an absence of isolation at the gamete level. The relationship between C. edule and C. glaucum is discussed.

This study was undertaken to increase our very incomplete knowledge of the annual cycle inascidians.

Berrill (1950) states that ‘the age of ascidians, with one exception, is practically impossible to estimate, unless a certain inhabited area is followed closely through seasons and years’. In the present work the method has been to follow certain aspects of the ascidian population of a chosen area for a period of nearly two years. The area was the Old Dock in Ardrossan Harbour, Ayrshire, and the ascidian population contained four species: Diplosoma listerianum (Milne Edwards), Ciona intestinalis (Linnacus), Ascidiella aspersa (Müller) and Botryllus schlosseri (Pallas). Diplosoma belongs to the order Enterogona, suborder Aplousobranchiata; Ciona and Ascidiella to the order Enterogona, suborder Phlebobranchiata; and Botryllus to the order Pleurogona, suborder Stolidobranchiata. Thus each of the three main suborders is represented, and the four ascidians studied are amongst the commonest British species.

Nutritionally, there are three basic types of Dinophyceae: (1) free-living photosynthetic autotrophs; (2) parasitic heterotrophs living on or in other organanisms and (3) free-living phagocytic or chemosynthetic heterotrophs. Representatives of the first type, the free-living photosynthetic autotrophic species, have been extensively investigated at the fine-structural level (for a review see Dodge, 1971). There are fewer species of the second type, the parasitic Dinophyceae, but many of these have been investigated in the electron microscope (Cachon & Cachon, 1966, 1970, 1971a, b; Cachon et al. 1968; Soyer, 1969 c; Manier, Fize & Grizel, 1971; Siebert & West, 1974). The third type, the free-living heterotrophic Dinophyceae, probably comprises the greatest number of species in the class; as Kofoid & Swezy (1921) state ‘One cannot work with the marine unarmored Dinoflagellata for even a short time without being struck by the fact that the majority of the individuals observed show evidence of holozoic nutrition and that the number actually containing chromatophores is relatively small throughout the entire Dinoflagella’. While the free-living heterotrophic Dinophyceae comprise the largest proportion of the class they have been, by far, the most poorly studied at the fine structural level. Investigations on these organisms have been limited to a comprehensive study of Oxyrrhis marina (Dodge & Crawford, 1971a, b, 1974) plus studies on specific parts of Cryptothecodinium cohnii (Kubai & Ris, 1969; Pokorny & Gold, 1973) and Noctiluca miliaris (Afzelius, 1963; Soyer, 1968, 1969a, b; Zingmark, 1970).

1. A method, due to Poole & Atkins, is described for computing the total available energy at any depth in the sea, in joules or g.-cal.

2. The oxygen production of pure cultures of the diatom Coscinodiscus excentricus Ehr. was measured by the Winkler method after exposure of the diatoms in bottles at known depths in the sea. 3. The results of simultaneous measurements of oxygen production and of energy are given for 6 days in July and August 1933 and 1934.

4. Factors, other than light, that might affect the rate of oxygen production in the experiments are discussed and shown to be negligible. It is assumed that diatoms can use energy for photosynthesis equally well in all parts of the visible spectrum.

5. When the energy flux during the exposures is less than 75 joules or i-8 g.-cal. per cm.2 per hr., the oxygen production is directly proportional to the energy. The utilization of the available energy then amounts to about 7%.

SOND Cruise 1965 aboard the R.R.S. ‘Discovery’ afforded the opportunity for short-term estimation of the penetration of daylight at midday into three regions of the eastern North Atlantic, evaluation of the fluctuations in the character of noonday light at depth in a restricted area over a 2-month period, and a determination of the penetration of moonlight in this area at the full of the moon.

A large number of nanoplankton species originally found in the sea around Britain have now been collected from other northern temperate waters (see Leadbeater, 1972 c; Manton & Leadbeater, 1974). It was, therefore, of considerable interest to collect nano-plankton from warmer waters such as those of the Adriatic and Mediterranean. The larger plankton of both the Adriatic and Mediterranean has been the subject of investigation by a succession of scientists from many countries (for references see Tregouboff, 1952). Whilst many workers acknowledged the importance of the smaller plankton from these areas (e.g. Bernard, 1958; Lalami-Taleb, 1971) only a few have attempted to study and identify species belonging to this group. In this respect the meticulous work of Lohmann (1902a, 1911) and Schiller (19136, 19256) requires special mention. Lohmann (1902a), working on the phytoplankton from the coast of Sicily, first used the technique of pumping sea water through filter paper and in this way he was able to collect and identify many minute species for which he later suggested the name ‘ Nannoplankton’ (Lohmann, 1911). On a later excursion to the Atlantic Ocean, Lohmann (1911) found the gentle centrifugation of sea-water samples was a more satisfactory and less destructive way of concentrating small cells. Schiller's most important contribution concerns a phytoplankton study carried out as part of an international hydrobiological survey of the Adriatic Sea during the years 1911–14. Schiller's findings confirmed many of Lohmann's previous observations and added a further range of new species including many green flagellates (Schiller, 1913 6, 1925b).

At least a quarter of the world's cetaceans were recently confirmed as endangered and the situation may be worse as the status of many others remains unclear. Climate change is affecting the oceans and a number of studies have recently highlighted its potential impact on cetacean species - for example, there are important linkages between sea ice and krill, the primary prey for baleen whales in Antarctica. This paper provides a synthesis of new information available on this theme and considers its implications for the future conservation and management of cetacean populations and species.

The more mobile (or otherwise adaptable) cetaceans may be able to respond to climate related changes, although the extent of this adaptability is largely unknown. However, there is broad agreement that certain species and populations are likely to be especially vulnerable to climate related changes, including those with a limited habitat range, or those for which sea ice provides an important habitat for the cetacean population and/or that of their prey. International conservation bodies, such as the Convention for Migratory Species and the International Whaling Commission, are striving to address these issues. The challenges presented by climate change require an innovative, large scale, long term and multinational response from scientists, conservation managers and decision makers. This response that should encompass a precautionary approach, including addressing the detrimental effects of other factors negatively impacting populations and species.

A micro-analytical scheme for the determination of protein, carbohydrate, lipid and RNA levels in marine invertebrate larvae has been described in a previous paper (Holland & Gabbott, 1971). This addendum describes minor modifications to the scheme so that the level of DNA may be determined and includes a different procedure for the determination of RNA by u.v. absorption. DNA and RNA levels were determined in a number of nauplii and veliger larvae.

Fourteen specimens of the hepatopancreas of the Pacific white shrimp, Penaeus vannamei, were prepared for examination with the transmission and scanning electron microscopes and with the light microscope. The histology and ultrastructure of this organ is similar to that seen in other Decapoda. At the ultrastructural level, it was observed that B-cells rupture at approximately the level of gap junctions located on the lateral plasma membranes of the cells, and discharge the contents of their large vacuoles into the intercellular space. This efflux of enzymatic material may be the mechanism by which cells are released from the wall of the tubule at the proximal end: the rupture and collapse of a B-cell may be analagous to the removal of the keystone which supports an arch. Deprived of support, and lacking structural adaptations for cohesion (there are no desmosomes or interdigitations in the epithelium) and with the intercellular material digested, the remaining intact cells collapse into the lumen of the tubule. The lysis of individual cells of all types - R-, F-, and B-cells - may contribute to the tubules’ total complement of digestive enzymes.