Determinations of total phosphorus in water samples have shown areas in the western English Channel with water containing as little as 10 mg. P/m.3, and other areas with double, and more than double, this concentration.

The integral mean concentration of total P in the water column, 20 miles off-shore from Plymouth, has fluctuated between 10 and 16 mg. P/m.3 since June 1947.

The changes which have taken place in this integral mean concentration are attributed to different water masses, of different total phosphorus concentration, passing through the area, rather than to a seasonal change in the total phosphorus content of a water mass. No marked deposition of phosphorus-containing detritus could be found.

Changes in this integral mean were not coincident with changes in salinity. The geographical distribution of total phosphorus does not coincide with the geographical distribution of salinity.

Populations of three species of juvenile Sparidae (Diplodus puntazzo, Diplodus sargus and Diplodus vulgaris) were sampled at different spatial scales in the north-western Mediterranean Sea over two years to follow growth after settlement. Length–frequency distributions were collected each week for periods of six months following the arrival of off-shore larvae in inshore habitats. Data were collected by underwater visual census along permanent transects.

Growth rate measured as the slope of the linear relationship between mean size and time varied between species. Diplodus puntazzo (0.160 mm d−1) and D. vulgaris (0.202 mm d−1), which are settling in winter experienced slower growth than D. sargus (0.567 mm d−1) which settles in summer. It is concluded that the difference was in part due to water temperature. Analysis of growth rate within each species also revealed significant differences among sites probably related to the currents and the water mass temperatures.

The behaviour and physiological responses of Mytilus edulis L. to increased concentrations of copperare dependent on the absolute copper concentration present and not the rate of increase of concentration. The sequence of behavioural responses isolating the animal from heightened sea-water copper concentration is similar to that observed in response to lowered salinities. The effects of copper onthe oxygen consumption of intact and ‘propped open’ and animals whose posterior adductor muscles havebeen severed suggest that only measurements of animals in the latter state give a true reflexion of the effects of copper on the oxygen consumption of the tissues of Mytilus. The effects of increased sea-water copper concentrations on the filtration and ventilation activity of mussels are assessed, but consideration of the data in terms of Dejour's equation of gaseous exchangesuggest that indirect measurement of ventilation activity gives rise to differing results. The adaptive advantage of theresponse of Mytilus to heightened sea-water copper concentrations is considered.

Analyses of the jaws of Nereis virens have shown that various metals are present in detectable quantities; in order of decreasing concentration these are (with ranges (μg/g dry weight) in brackets) – zinc (10130–18360), sodium (1150–2690), magnesium (616–1080), calcium (531–1130), iron (444–1180), manganese (510–952), potassium (270–960) and copper (4–80), with also lead (8·7), cadmium (0·1) and silver (< 0·1). The most concentrated metal, zinc, is not uniformly distributed throughout the jaw, the highest level occurring in the distal tip (45740 μg/g), falling to a much lower level in the basal part (1790 μg/g). The contribution of some jaw metals to the total body burden varies according to body size: in small worms the jaw zinc accounts for over 40% of the total but in large worms it accounts for 30% or less; jaw manganese contributes over 50% of the total in small worms, dropping to about 20% with increasing size. For silver, cadmium, copper, iron and lead the jaws generally contribute less than 1% to the total body burden.

The haustoriid amphipods Bathyporeia pilosa and B. pelagica are common in intertidal sand deposits around the British Isles. Both species live in the surface sediments and B. pilosa is typically a high-shore species, while B. pelagica is restricted to beach levels below the high-water mark of neap tides. Gravid females are readily identified by the presence of blue-pigmented eggs held in the brood pouch where they undergo direct development. The extent of the breeding season varies with locality (Salvat, 1967; Fish & Preece, 1970) and on the west coast of Wales B. pilosa breeds throughout the year and B. pelagica from March to October (Fish & Preece, 1970). At this locality, however, the breeding cycles of the two species are similar in that they show reproductive peaks in spring and autumn and it has been suggested that the spring peak is caused by breeding of the overwintering generation, the progeny of which mature to reproduce in the autumn of the same year (Fish & Preece, 1970). In common with many amphipod species, brood size of Bathyporeia is related to body length. Salvat (1967) has shown that the brood size of B. pelagica on the west coast of France doubles from February to April, but apart from his study adequate data on brood size are lacking. This paper describes embryonic development, hatching and brood size of overwintering and summer generations of both species.

Some understanding of the mechanisms involved in the development and maintenance of forests of Laminaria hyperborea (Gunn.) Fosl. can be gained from the analysis of populations under different conditions. The main variable is depth and unfortunately the available depth range of suitable substrata in the Isle of Man is limited. For this reason two visits were made to western Scotland and the Outer Hebrides, in 1970 and 1976. This paper, which is intended as the last in this series, reports on results obtained rom there and from certain sites in the Isle of Man.

Natural populations of Aurelia aurita scyphopolyps, settled on a wreck in the northern Adriatic Sea, were monitored for 22 months in order to study their seasonal cycle. The trend of Aurelia polyps is strongly dependent on water temperature with a peak of abundance in summer and low densities in winter. The strobilation process occurs only once a year, during the cold season, and the estimated number of released ephyrae is 780,000–2,600,000/m2. The species has been recorded only on the iron wreck while it is completely lacking from the close rocky cliff of Conero Promontory, suggesting that the increase of underwater structures of anthropogenic origin could be related to the increases of jellyfish biomass.

Stomach content analyses were performed in 28 dolphins stranded between 1994 and 2007 on the beaches of Rio de Janeiro State (23°06′S 44°18′W/22°14′S 41°54′W), Brazil, comprising six delphinid species: Stenella frontalis (N = 10), Steno bredanensis (N = 7), Tursiops truncatus (N = 4), Delphinus delphis (N = 5), Lagenodelphis hosei (N = 1) and Stenella coeruleoalba (N = 1). Fish otoliths and cephalopod beaks were used to identify the prey species and to estimate the original length and weight. Seven different cephalopod species from six families and 15 fish species belonging to 10 families were identified. Although the fish contribution could be underestimated, cephalopods constituted the group of higher importance, revealing that these invertebrates may represent an important source of energy for delphinids in the region. In this context, the squid Loligo plei should be highlighted due to its important contribution. Most preys were coastal and demersal, and such consumption could indicate coastal foraging habits of the quoted dolphin species. Although dolphins consumed many species of prey in common, they fed on different size-classes of prey. The foraging area of the dolphins could be the same region used by fishing operations, which would represent a risk for incidental capture.

Immersed shannies (Blennius pholis) showed peak locomotory activity coincident with daylight high tides. Emersion caused cessation of breathing and bradycardia though Q02 was little affected. Q02 fell, however, when the abdomen was enclosed in an impermeable sheath to block cutaneous respiration. Gulping of air into the extensively vascular oesophagus probably also acts as a means of aerial respiration. Reimmersion of fish caused a transient bradycardia followed by a tachycardia and a fall in Q02 followed subsequently by a rise. The results are discussed in relation to the behavioural, circulatory, respiratory and morphological adaptations of the shanny to the intertidal habitat.

The harpacticoid copepod genus Tigriopus is characteristic of shallow upper shore rock pools in both hemispheres. Tigriopus are necessarily physiologically tolerant as the pools feature extreme physicochemical conditions; their lower limit on the shore is apparently set by competition/predation. There are several species, differentiated by relatively minor morphological distinctions; speciation appears to be favoured by restricted gene flow between populations, even over short distances. This paper briefly reviews the literature concerned with the taxonomy, physiology and ecology of the genus, and compares environmental conditions and salinity/thermal tolerance data for three species: T. brevicornis from Scotland, T. fulvus from Madeira, and a previously undescribed population of the Southern Ocean ‘T. angulatus’ group from subantarctic South Georgia. Particularly interesting was a low upper lethal temperature in ‘T. angulatus’ (21·9°C) that probably restricts the species to relatively large pools that buffer environmental thermal extremes. Unlike the other species, T. fulvus cannot withstand freezing conditions. Evidence is presented to show that the South Georgian Tigriopus differs slightly, but significantly, in its morphology from two sibling species that inhabit the subantarctic Kerguelen and Crozet Islands but which cannot interbreed. If the South Georgian copepods are indeed a separate species and do not occur elsewhere (e.g. the Falklands), this indicates rapid speciation within the genus; the coasts of South Georgia were covered by an icecap until 10,000–14,000 years ago and no rock pool habitats were then available. It is suggested that Tigriopus may have reached South Georgia by rafting within Enteromorpha tubes.

Global warming is facilitating the poleward range expansion of plant and animal species. In the Mediterranean Sea, the concurrent temperature increase and abundance of (sub)tropical non-indigenous species (NIS) is leading to the so-called ‘tropicalization’ of the Mediterranean Sea, which is dramatically evident in the south-eastern sectors of the basin. At the same time, the colder north-western sectors of the basin have been said to undergo a process of ‘meridionalization’, that is the establishment of warm-water native species (WWN) previously restricted to the southern sectors. The Gulf of Genoa (Ligurian Sea) is the north-western reach for southern species of whatever origin in the Mediterranean. Recent (up to 2015) observations of NIS and WWN by diving have been collated to update previous similar inventories. In addition, the relative occurrences of both groups of southern species have been monitored by snorkelling between 2009 and 2015 in shallow rocky reefs at Genoa, and compared with the trend in air and sea surface temperatures. A total of 20 southern species (11 NIS and 9 WWN) was found. Two WWN (the zebra seabream Diplodus cervinus and the parrotfish Sparisoma cretense) and three NIS (the SW Atlantic sponge Paraleucilla magna, the Red Sea polychaete Branchiomma luctuosum, and the amphi-American and amphi-Atlantic crab Percnon gibbesi) are new records for the Ligurian Sea, whereas juveniles of the Indo-Pacific bluespotted cornetfish Fistularia commersonii have been found for the first time. While temperature has kept on increasing for the whole period, with 2014 and 2015 being the warmest years since at least 1950, the number of WWN increased linearly, that of NIS increased exponentially, contradicting the idea of meridionalization and supporting that of tropicalization even in the northern sectors of the Mediterranean basin.

Data on habitat use by marine tucuxis (Sotalia guianensis) were collected in Guanabara Bay (GB), south-eastern Brazil, over a two-year period. Diurnal activities of marine tucuxis were dominated by behaviour related to feeding/foraging (58% of all recorded time). Dolphins spent more time in feeding/foraging activities in the morning with a secondary peak in late afternoon. Dolphins were seen in waters of 2 to 35 m (11.63±6.05; median=12.0). Depths used by S. guianensis groups significantly differed from depths available in GB (Kolmogorov–Smirnov test; Z=5.72; P<0.001). Most groups (69.8%) were sighted in depths between 5.1 and 15.0 m. Dolphins occupied an area of 136.9 km2, which represents about 42% of the entire water surface of GB. Individuals selected areas within GB and avoided the most degraded ones, which suggests that habitat degradation may affect S. guianensis distribution. Diurnal distances travelled by individuals ranged from 3.3 to 27.2 km in a same day. Dolphins found in main channel and adjacent waters moved along the north–south axis of GB throughout the day and covered distances three times greater than dolphins which concentrated their activities in north-eastern areas.

Ultrastructural, histological and histochemical studies were performed on the gonad of adult Pecten maximus at various intervals during the reproductive cycle in St Brieuc Bay, France, in order to understand better the sources and transfers of energy to developing gametes in scallops. In addition to the well-known pathways of energy acquisition through feeding and transfer of somatic reserves, a number of novel pathways were demonstrated. These were grouped into two categories: atretic recycling and intestinal loop transfer. Evidence is presented for the recovery of lytic material (resulting from gamete atresia) in the gonad acini, gonoducts, and integument; and the direct transfer of metabolites from the gonad intestinal loop to the developing gametes via vesicular cell-haemocyte couples, which appear to follow fibrous pathways within the loose connective tissue extending from the base of the intestinal epithelium to the acini. A schematic diagram summarizes the sources and transfer mechanisms of the energy exchanges involving the developing gametes in Pecten maximus.

Since the late 19th century, the accidentally introduced Gastropoda Crepidula fornicata has been invading sheltered coastal waters of western Europe. The consequences of this proliferation on macrozoobenthic communities were studied in the Bay of Marennes-Oléron, France. Crepidula fornicata was found in a wide range of sediment grain sizes and depths, with however, a predilection for shallow muddy areas where abundance and biomass reached 4770 ind m−2 and 354 g DW m−2, respectively. Soft-sediment macrofaunal assemblages were compared in similar habitats, in the presence and absence of C. fornicata. In muddy and medium sand areas, abundance, biomass and species richness of macrofauna were generally greater in presence of C. fornicata, with Annelida dominating, although the differences were significant (P<0.05) only in one location out of five. The species composition was moderately different in the presence of C. fornicata. In coarse sand, the abundance of C. fornicata was low and did not affect abundance, biomass and species richness of the macrofauna. However, species composition differed where C. fornicata was absent, with a higher proportion of mobile Crustaceana. The effect of C. fornicata on benthic communities differs in relation to the habitat they colonize: in muddy sediments, the presence of C. fornicata apparently stimulates zoobenthic community diversity and abundance (mostly deposit-feeders), whereas in coarser sediments, macrofauna community is different (more suspension-feeders) from the community associated with C. fornicata.

Maerl grounds are comparable to sea grass beds in terms of their high biodiversity, and are characterized by abundant juveniles of species such as the queen scallop, Aequipecten opercularis. Maerl grounds impacted by towed demersal fishing gears are structurally less heterogeneous than pristine, un-impacted maerl grounds, diminishing the biodiversity potential of these habitats.

During five annual ground fish surveys of the North Sea, all the benthic invertebrates trawled at 48 primary stations were recorded. The data were subjected to classification analysis, which showed a basic division between northern and southern North Sea benthos. The southern North Sea was further divided into three benthic regions, and the northern North Sea into four benthic regions (including one to the west of Shetland). The factors influencing the faunal assemblages in the various regions were discussed.

On 5 November 1958 our attention was drawn, by Mr A. K. Nagabhushanam, to the presence in Port Erin bay of large numbers of swimming gastropods. These gastropods proved on examination to be Pleurobranchus membranaceus (Montagu), a species generally believed to be exclusively benthic in habit. This paper is a report on this occurrence and on some aspects of the biology of P. membranaceus.

For 4 days these animals were abundant in the bay and hundreds could have been captured with a hand-net from the steps of the Raglan Pier. Only approximately forty specimens were taken, this number being ample for our purpose. Between 5 and 9 November, numbers were stranded on the beach by the receding tide. Although many local fishermen consented to look out for these easily recognizable animals, and the Port Erin research vessels were out each day, no record of their swimming outside the bay was obtained, although specimens were occasionally dredged. On 9 November they disappeared from the bay without trace, and otter trawl and D-net hauls in the bay yielded only two further specimens; none were found on frequent shore collecting expeditions. However, on 2 December five more specimens were captured swimming near the Raglan Pier and occasional individuals were seen in the same place on 9 December. During the periods of their abundance it was ascertained that they swam during the hours of darkness as well as in daytime.

A molecular assay was designed to distinguish the common sea louse Caligus elongatus from its sympatric relatives. The method identifies the parasites at all developmental stages. Fragments of the mitochondrial Cytochrome C Oxidase 1 (COI) gene from identified adult caligids were amplified by polymerase chain reaction (PCR) and sequenced. Analysis of sequence data from unknown samples permitted identification by clustering of the samples with their appropriate genetic relative. Nucleotide sequences obtained were used for preliminary investigations of the population genetic structure of Caliguselongatus. Aligned sequences from the COI gene from this speciesindicate that our C. elongatus material divides into two distinct clades, possibly revealing two closely related species. The two genotypes do not appear to be associated with sample site, parasite gender, sample time or host species. Parasites from both groups were found on Atlantic salmon (Salmosalar), sea trout (Salmotrutta), pollack (Pollachiuspollachius), saithe (Pollachiusvirens), and Atlantic herring (Clupeaharengus).

Mortality patterns of marine turtles entangled in fishing gear, found dead at sea or stranded dead on and around the coast of Britain in the period 1992–1996 are described. Of a total of 38 dead turtles identified, 35 were leatherback turtles (Dermochelys coriacea) and three were loggerhead turtles (Caretta caretta). All D. coriacea were considered adults or subadults nearing sexual maturity. Six individuals were assessed as females, ten were classified as males and 19 were not sexed. Dermochelys coriacea (N=20 measured) ranged from 120 to 210 cm in curved carapace length (mean, 152 cm). The three C. caretta were juveniles, and ranged from 15 to 30 cm curved carapace length. Possible origins, causes of mortality and interactions with fisheries are discussed. In addition, contaminant levels were determined in the tissues of three D. coriacea. Concentrations of organic contaminants determined were found to be low.

The experiments to be described below were proposed by the Ministry of Agriculture and Fisheries and were carried out under the auspices of the Marine Biological Association, being subject to the direction of Dr. E. J. Allen, F.R.S., and Dr. E. S. Russell. Mr. Harvey, hydrographer to the Association, directed the construction of the sea-water pond and the fish boxes during the early stages of the preliminary work and assisted in organising supplies whenever alterations were made to the apparatus.