Fourteen species of benthic invertebrates, found to be indicators of hydrographic conditions by Blacker (1957), were recorded during research cruises between Finmark and north Spitsbergen during the summers of 1978, 1979, 1980 and 1981. The distributions were compared with those found during surveys carried out between 1949 and 1959.Both Atlantic and Arctic species were found to the north of Bear Island and along the west coast of Spitsbergen, and the temperature ranges at which they were found were greater than those found by Blacker (1957).

Introduction

During the past century the annual mean temperature of the Arctic regions has undergone a considerable change. The warming of the regions began about 1885 (Willett, 1950) and peaked around 1938, when the mean air temperature of Spitsbergen was nearly 6 °C warmer than at the turn of the century (Hoel, 1953). The warming of the seas in the region seems to have started later - Jensen (1939) suggests 1917 - and sea temperature changes were detected north of Spitsbergen in 1921 (Schokalsky, 1936). This warming resulted in the reappearance of cod in great quantities on the Bear Island Bank, after the absence of any sustained quantities for about 40 years (Blacker, 1957).

The marine benthos of Svalbardf was surveyed during the latter part of the last century and the first half of this century (1878–1914,1923–31) when the benthos was recorded during several cruises in the region (see Blacker (1957) for review). The benthos was again recorded between 1949 and 1955 (Blacker, 1957) and 1955 and 1959 (Blacker, 1965); see Fig. lA.

A karyometric analysis of the diploid complement of Procerodes dohrni (Turbellaria: Tricladida) was carried out on mitoses from regenerative blastema. P. dohrni has seven pairs of homologous chromosomes. Chromosome lengths decrease gradually and homologous pairs cannot be grouped. With reference to centromere position, chromosomes 1, 2, 3, 4 and 6 are metacentric, their centrometric indices vary from 46·74 to 39·82, while chromosomes 5 and 7 are submetacentric, their centromeric index being 34·63 and 29·86 respectively.

Cytokinesis is described for the first time in a pelliculate dinoflagellate that retains its thecal plates during cell division. In Heterocapsa niei cytokinesis proceeded in a manner that differed from that described for other dinoflagellates. The thecal plates separated along the fission line before the development of a cleavage furrow. A distinct cleavage furrow developed as cytokinesis progressed. The outer membrane and the outer plate membrane expanded during division to enclose the enlarging cell undergoing cytokinesis; however, as the cleavage furrow deepened, these membranes were not continuous with the cytoplasm. The pellicle was occasionally intermittent in the region of the cleavage furrow, possibly facilitating movement of material from the cytoplasm to the developing outer membranes. Thecal plate formation occurred within the thecal vesicle from unrecognizable precursors.

The herring is a physostome with no gas secretion mechanism in the swimbladder. The swimbladder volume was measured in fish from about 3–33 cm in length. It was rarely large enough to give the fish neutral buoyancy at the sea surface. Swimbladder volumes were also measured after periods of up to 1 week at pressures from 1·9 to 5·5 ATA (0·9–4·5atm above atmospheric pressure) in a laboratory pressure vessel and in a sub-surface cage in the sea. The swimbladder gas was lost within a few hours in the larval herring and in a few days in smaller juvenile fish; no change was found in older fish under experimental conditions. The findings were in accord with measurements of the guanine content of the swimbladder wall which was low in those fish which lost gas quickly. This supports the view that gas diffusion is limited by guanine crystals. While it seems likely that larger fish can exist for several weeks without the need to replenish the swimbladder gas some large spawning herring were caught at sea with empty swimbladders, suggesting a long stay near the sea bed. Analysis of swimbladder gas showed that oxygen tended to diffuse out more quickly than nitrogen. Behaviour experiments showed that fish with artificially emptied swimbladders could refill them by swallowing air at the surface, in some cases very quickly and efficiently. Fish with empty swimbladders and no access to the surface suffered a high mortality. The ecological implications of these results and their relevance to the interpretation of sonar ‘target strength’ measurements are discussed.

The maximum habitation depths of chambered cephalopods are dictated by the mechanical properties of the shell. All chambered cephalopods have a depth at which ambient pressure is sufficient to implode the gas-filled shell portions. Experiments on Sepia elegans D'Orbigny, S. officinalis Linne and S. orbignyana Férussac from the Mediterranean Sea show these three species to have differing depth limits and modes of shell implosion. Large S. officinalis implode between 150 and 200 m, whereas newly hatched and advanced embryonic specimens implode between 50 and 100 m. The larger S. officinalis are occasionally caught at depths greater than the implosion depth of the juvenile shell parts. They apparently avoid implosion of the early shell portions by refilling these first-formed chambers with cameral liquid later in life. Implosion in S. officinalis generally resulted in the crushing of all or most of the septa in a band extending from the embryonic region to the anterior part of the shell. Implosion was generally accompanied by fatal rupture of underlying tissue into the implosion zones. Implosion of S. orbignyana occurred between 550 and 600 m and was very different in form from that in S. officinalis, occurring mostly within the smooth zone of the last-formed several chambers, and rarely extending back into the siphuncular region (striae zone). Increasing depth caused episodic implosion of sequentially older chambers in the smooth zone. The shallower implosions were accompanied by little soft-tissue damage. Massive internal injury only occurred in the deepest implosions (700 m or greater). Implosion in S. elegans occurred betw en 400 and 600 m. Too few specimens were available to allow generalizations about morphology of implosion in this species.

It is conclusively shown that cyprids of the barnacle Balanus balanoides (L.) use a secretion released onto the antennulary discs for temporary attachment. This secretion does not stain with conventional histochemical techniques but was shown to be proteinaceous by staining blue in Bio-Rad protein-dye reagent normally used in protein assay. The discovery of this proteinaceous secretion adds further evidence to suggest that cyprids use a form of Stèfan adhesion for temporary attachment during exploration prior to settlement.

Introduction

Although recent advances have been made in the measurement of cyprid temporary adhesion (Yule & Crisp, 1983), the question of the precise mechanism has remained speculative. Earlier suggestions that the attachment organs of the antennules operated by suction (see Saroyan, Lindner & Dooley, 1969) were challenged on morphological grounds by Nott & Foster (1969) and finally disproved by the force measurements of Yule & Crisp (1983).

Nott (1969) and Nott & Foster (1969) were able to show numerous unicellular glands opening out, individually, onto the surface of the antennulary disc arranged in two concentric rings, one near the margin, and the other around the central sense organ. It was considered that these glands could produce a tacky secretion used for temporary adhesion. Yule & Nott (unpublished, reported in Yule & Crisp, 1983) failed to find any traces of such a tacky secretion on glass surfaces after cyprids had walked across them. To establish the presence or absence of a fluid secretion on the antennulary disc is fundamental to the further understanding of the type of temporary adhesion employed by cyprids.

The gonadial, pyloric caecal and somatic cycles over three consecutive years in a subtidal population of the starfish Marthasterias glacialis from Plymouth Sound are described. The study area lies towards the eastern limit of the up-Channel range of this species, and this is reflected in only partial reciprocity between gonadial and pyloric indices, and also by the apparent utilisation of somatic material during the build-up of gametes. The sequence of events at the cytological level during gonadial build-up is described.

Much evidence has suggested that calcification in Carcinus and certain other marine organisms may arise at least partly by the local formation of base. The extent of changes of pH needed to precipitate calcium carbonate from sea water or from the blood of the crab are not known with certainty. These have been investigated, using sea water and crabs from the coast of Maine.

Mean sea water pH, mostly as measured in aerated samples used for experiments in the laboratory, was 8·00, a little below the values commonly found close to the shore in summer. The corresponding mean blood pH was 7·12. Crushing calcified crab cuticle in sea-water raised the pH, showing the sea water to be below saturation with the salts concerned. The rise in pH was slightly greater in the more dilute suspensions, an effect attributed to the mixed composition of the calcifying salts. Thus in one group of experiments cuticle crushed in sea water in proportions 1:20 and 112·7 raised its pH by 0·66 and 0·62 units respectively, and extrapolation suggested that interstitial fluid of almost zero volume would equilibrate at 0·38 pH units above sea water. Crushing cuticle in crab blood in proportion 1:2·7 raised its pH by 1·03 units, showing the plasma also to be unsaturated with carbonate.

Carbonates were precipitated from sea water by rendering it alkaline with sodium hydroxide; in four experiments the first crystallites were found in samples in which in 3 days after addition of base pH had fallen to between 8·46 and 9·30. In a longer series of experiments with crab plasma, crystals were first seen in samples in which after three days the mean pH had fallen to 8–09. Crystallites at the surface formed mosaics of spherulites closely resembling those of normal crab cuticle.

Gonadial, pyloric caecal and somatic indices and oocyte size-frequencies are compared over a 3-year period for the starfish Asterias rubens from an intertidal nutritionally rich site and a subtidal impoverished site from the English Channel off south-west Britain. The intertidal population showed significantly higher values for all three indices over most of the study period compared with the subtidal population, and its spawning occurred later. The somatic index of the subtidal population showed a steeper rise than the intertidal population over that part of the cycle in which the gonads were undergoing enlargement, which gives further support to the suggestion that starfishes deprived of sufficient food may give priority to maintenance of the body-wall over enlargement of either the food-storage tissues of the pyloric caeca or the gonads.

Spatial pattern of settlement of cyprids of the barnacleBalanus balanoides (L.) was examined from photographs taken every low tide during the first 20 days of the settlement season. The locations of pits and cracks and the bases of detached adults were mapped in order to measure specificity of settlement in relation to surface contour and chemical cues associated with conspecifics. Cyprids were identified as to their date of settlement. Distances to nearest neighbours were computed for newly settling cyprids relative to each other, for newly settling cyprids relative to previously settled cyprids, and for newly settling cyprids relative to newly metamorphosed spat.

The mortalities and subsequent recolonization of a rocky shore in S.W. Ireland following a bloom of the toxic dinoflagellate, Gyrodinium aureolum in 1979 are described. Selective mortalities of key animal species notably grazing gastropods were followed by a marked increase in fucoid algae. Enteromorpha spp. blooms were a feature of vertical surfaces only. In general planktonic recruiting gastropods exhibited the most rapid recovery. Forty-two months after the red tide, fucoid algae still dominate both vertical and horizontal surfaces at the study area.

Introduction

Dinoflagellate blooms ('red-tides'), chiefly of Gyrodinium aureolum Hulburt have been recorded several times in Southern Ireland since 1976 (Ottway et al. 1979; Cross & Southgate, 1980; Jenkinson & Connors, 1980; Leahy, 1980; Roden, Ryan & Lennon, 1980; Wilson, 1982) and have resulted in mortalities of farmed rainbow trout in sea-cages in Dunmanus Bay (Parker, 1981). Other species of pelagic and demersal fish on the south coast were also affected by a toxic red-tide in 1976 (Ottway et al. 1979). Owing to the unpredictability of occurrence of dinoflagellate blooms, few studies on the effects of red tides on littoral fauna, and on the subsequent recolonization following the events have been carried out. Previous studies in Dunmanus Bay, Ireland (Leahy, 1980) suffered from a lack of the shores prior to the of information about the structure and dynamics occurrence of a red-tide.

Regular monitoring of the rocky shore biota at Dunmanus Bay (Myers, Southgate & Wilson, 1980) has been carried out since May 1978 and is continuing. The red tide of August 1979 caused dramatic mortalities of a wide range of taxa at Pointabulloge in Dunmanus Bay (Cross & Southgate, 1980).

The ultrastructural organization of various metal-containing cells of Littorina littorea is described. These cells occur in the connective tissue, digestive gland, kidney, stomachand ctenidia. Specimens were compared from animals collected from clean and metal-polluted sites and it was shown that the majority of the metals were bound to intracellular ligands. These are usually compartmentalized within membrane-delineated structures.

The basophil cells and connective tissue calcium cells appear to contain oxygen donor ligands which mainly bind class A metals (e.g. Ca, Mg, K, Mn). The pore cells and ctenidium contain sulphur donor ligands which mainly bind copper. Ligands of unknown composition occur in the nephrocytes and stomach epithelial cells. The ligands in the basophil cells and the nephrocytes appear to bind a wide range of metals and may therefore serve a detoxification function. Ligands in the connective tissue calcium cells and pore cells are very specific in their binding characteristics, and this presumably reflects some particular metabolic pathway within these cells. Ligands associated with the stomach and ctenidial epithelia appear to be responsible for preventing the penetration of metals through these layers.

The effects of ligand specificity, induction and turnover rates are discussed in relation to the use of L. littorea as a monitoring system for metal pollution.

Introduction

The use of biological organisms to monitor the levels of pollutant metals in the environment has attracted extensive interest in recent years (Phillips, 1980). In the most arbitrary use of this procedure, the animal is simply regarded as a biological sink' which traps and accumulates the pollutants which gain access across its epithelial layers. The net result of the retention or excretion of these captured metals is represented by the final body load that is then related to the environmental levels of the metal.

The development of a unispecies bloom of phytoplankton in the Rade de Villefranche (N.W. Mediterranean, near Nice) during June 1982 coincided with the disappearance of salps from the area. A phytoplankton haul was taken on 24 June and examined in detail. The sample consisted of virtually a unispecies diatom population; Rhizosolenium spp., together with a few small medusae and crustaceans. The diatom cells were unusual in that they appeared to be associated with large amounts of extracellular mucus.

The appearance of this virtually monospecies bloom provided a rare opportunity to examine in detail the biochemical composition of a natural field diatom species (see discussion in Ballantine, Lavis & Morris, 1979 and Morris, 1984). After removal of zooplankton the phytoplankton were collected on a 30 μm clear nylon filter. A detailed biochemical analysis was carried out as previously described (Morris, McCartney & Robinson, 1983; Morris, 1984).

The Rhizosolenium spp. sample was composed of almost equal amounts of lipid (23 mg), insoluble carbohydrate (19 mg) and protein (24 mg) with much smaller amounts of soluble carbohydrate (009 mg). The lipid was composed mainly of polar lipids (70% total lipids), neutral glycerides (20% total lipids) and sterols (8% total lipids). The detailed fatty acid and sterol composition of these major lipid fractions are shown in Tables 1 and 2.