The evolution of a Phaeocystis bloom off Plymouth in spring 1990 is described. Data were obtained (1) during weekly visits to station El to measure physical parameters, nutrient concentrations, primary production and grazing pressure and (2) by regular tows of an Undulating Oceanographic Recorder around a circuit of five stations including El to detect stratification, monitor the geographical distribution of chlorophyll and determine vertical profiles at each station.

The data show that the Phaeocystis bloom emanated from near-shore, its spread towards the south-east correlating with the wind direction prevailing at the time. Due to bad weather, seasonal stratification had not been established at the time of the bloom so that a major diatom outburst had not occurred and nutrients remained high as the Phaeocystis moved offshore.

Zooplankton populations at El, averaged over 50 m, decreased whilst Phaeocystis was present, resulting in very low grazing pressure. Termination of the bloom was not, therefore, due to consumption by herbivores. It was, instead, caused by Phaeocystis colonies becoming nutrient-depleted and releasing single cells which were transported downwards. As a result of this, chlorophyll concentrations near the bottom remained high for some time after the Phaeocystis had disappeared from the surface water.

A scenario is proposed to explain the observations in terms of our current understanding of the ecophysiology of Phaeocystis.

The scorpaenid Maxillicosta scabriceps (Teleostei) and the platycephalid Platycephalus longispinis (Teleostei) were trawled seasonally for a year from shallow (5–15 m) and deeper (20–35 m) waters in four distantly-located regions of the inner continental shelf of south-western Australia. The former species was more abundant in southern regions, which is consistent with its temperate distribution, while the latter species was more abundant in deep than shallow waters. Unlike M. scabriceps, P. longispinis with total lengths < 110 mm were rarely caught, indicating that this latter species only moves on to the sandy substrate of the inner shelf when it reaches a certain size. As M. scabriceps increased in size, the contributions of mysids, amphipods and oxyrhyncan crabs to the diet declined, while those of carid decapods and brachyrhyncan crabs increased. The invertebrate fauna ingested by the smallest length-class of P. longispinis, 110–139 mm, was similar to that of the same and largest length-class of M. scabriceps. However, unlike M. scabriceps, this length-class of P. longispinis consumed teleosts, despite having a relatively smaller mouth. The contribution of teleosts subsequently increased as P. longispinis increased in size, a feature reflected by the relatively low dietary breadth of large fish. The marked shift in the types of prey ingested by P. longispinis as it increased in size accounted for the fact that, in contrast to M. scabriceps, there was limited dietary overlap between the larger and smaller members of this platycephalid. The ability of P. longispinis to ingest other fish is presumably related to the fact that platycephalids lie just under the substrate surface and are thus concealed from their potential prey, and that they are able to emerge rapidly and pursue their prey.

The behaviour of two ectosymbiotic animals, Peregrinamor ohshimai (a bivalve attached to the ventral cephalothorax of the host), and Phyllodurus sp. (a bopyrid isopod attached to the second pleopod of the host), during ecdyses of the host thalassinidean Upogebia shrimps was studied by time-lapse video of infested shrimps. In the intermoult stages of the hosts, both ectosymbionts did not move. However they moved on to the newly emerged body of the host at the time when the host moulted. Peregrinamor ohshimai began to move just after the host started moulting, whereas Phyllodurus sp. moved prior to ecdysis of the host and waited near the fissure from which the newly moulted body emerges first. There are highly correlated morphological relationships between the symbionts and the hosts. It is suggested that both ectosymbionts grow with the same host individuals after infection, keeping morphological affinity with their hosts without being discarded during ecdyses of the hosts.

We report the first complete genome sequence of the marine diatom-infecting, positive-sense single-stranded RNA (ssRNA) virus, Rhizosolenia setigera RNA virus (RsRNAV). The genome is 8877 nucleotides (nt), polyadenylated, lacking a cap structure, and has two large open reading frames (ORFs): ORF-1 (4818 nt), a polyprotein gene coding for replicases, e.g. RNA helicase, RNA-dependent RNA polymerase (RdRp); and ORF-2 (2883 nt), a polyprotein gene coding for structural proteins. The ORFs are separated by a 323 nt intergenic region (IGR), flanked by a 624 nt 5′-untranslated region (UTR) and a 229 nt 3′-UTR. The deduced amino acid sequences for ORF-1 and ORF-2 respectively show considerable similarities to the non-structural and structural proteins of a marine raphidophyte-infecting virus HaRNAV (Heterosigma akashiwo RNA virus). Phylogenetic analyses of concatenated amino acid sequences of RNA helicase and RdRp domains supported the monophyly of RsRNAV, HaRNAV and a marine protist-infecting virus SssRNAV (Schizochytrium single-stranded RNA virus) with moderate bootstrap values of 79–83%, but not at the family level, whilst their monophyly was only weakly supported (50–55%) in the phylogenetic tree based on RdRp whole domain. As a result, comparison of the genome organization and sequence suggests RsRNAV is not a member of any currently defined virus family. In the RdRp tree, the positive-sense ssRNA viruses infecting Stramenopiles (RsRNAV, HaRNAV and SssRNAV) and Alveolata (HcRNAV (Heterocapsa circularisquama RNA virus)) were categorized into phylogenetically distant clades, which suggests a host/virus coevolution. Our study supports the hypothesis that a diverse array of ssRNA viruses exists in marine environments.

Arbacia dufresnii is a common and abundant sea urchin in Argentinean waters. The gonad index cycle was studied for this species in Golfo Nuevo, Patagonia, from May 2001 to March 2003. Comparative studies of gonad index and gonad histology were performed for the three years of 2001, 2002 and 2003. The gonad index reflects gonadal stages, and the results showed two spawning peaks for the studied period. The first spawning event occurred during spring and a second major spawning occurred in summer. Proliferation and differentiation of gametes, and the presence of mature gonads were synchronous among males and females. Male and female individuals spawned synchronically. Gonad resorption was observed for males and females. Histological examination data reflected gonad index analysis, providing together a good estimation of the reproductive cycle of A. dufresnii. Statistical analyses showed a positive correlation between gonad index and photoperiod. The mean fresh oocyte diameter observed was 87.1 µm (SD = 1.3 µm) with a jelly coat of 12.7 µm (SD = 0.9 µm), which corresponds to planktotrophic larval development.

Relatively little is known of the exact role of the thyroid gland in teleosts. Although the results of a few studies have suggested that the thyroid influences respiratory metabolism, as in the higher vertebrates, a greater number of experiments have failed to show that either treatment of fish with thyroid hormones or inactivation of the gland produces any significant effect upon the oxygen consumption of the fish. Thyroid activity has been linked with reproduction in some fish, although there is little evidence to show that the relation-ship is more than coincidental. The thyroid has also been connected with osmoregulation, but reviewing this work Pickford (1957) concludes that the relation with osmoregulation is only a secondary or collateral one. Recently Hoar (1953, 1955) has suggested that the thyroid may control the migratory response of fish. However, in the migratory species which have been studied in detail, the salmon, Salmo salar L. and Onchorhynchus spp. and the eel, Anguilla vulgaris, changes in the salinity of the environment during their migrations were complicating factors since salinity changes alone have been shown to stimulate thyroid activity in non-migratory fish (Olivereau, 1954).

This study investigated whether associated meiobenthic communities, especially harpacticoid copepods, differed amongst habitats. Five pre-defined habitats within and next to the Posidonia oceanica seagrass meadow were sampled: living seagrass canopy leaves (LL), small (SMF) and large (LMF) macrophytodetritus fragment accumulations and sand, bare (BS) and covered (CS). The highest meiofauna abundances were recorded in the BS for the core sampled habitats (BS, CS, SMF and LMF) and in the LMF for seagrass material habitats (SMF, LMF and LL). Harpacticoid copepods were the most abundant taxon in all habitats. The assemblage composition at copepod family level showed two distinct habitats clusters: a leaf (LMF and LL) and a sediment cluster (BS, CS and SMF). Subsequently, stable isotope analyses were conducted to analyse the relationship between copepods and their potential food sources in seagrass material habitats. Based on δ13C isotopic analyses and SIAR mixing model, harpacticoid copepods relied for 70% on epiphytes and for 30% on P. oceanica leaf material in the LMF and LL habitats.

1. The diameters of samples of Rhizosolenia stylijormis taken in the S. W. North Sea between 1932 and 1934 revealed the presence of large and small populations. The largest diatoms were found in 1933, in which year, or late in 1932, it was thought that auxospore formation might have taken place.

2. The large and small groups mentioned in (1) gave indications of a continuous diminution of size judging by an inspection of their modes. Notwithstanding this there appears to have been some selection of the larger cells, as the whole samples tended to increase in size with a rise of temperature.

3. The correlation coefficient between the temperature at 20m. and the mean diameters was 0-59. That for salinity in the same circumstances was 0-59. The inverse correlation with salinity is thought to be due to the topography of the area.

The Zeiss Pulfrich photometer, with its eight spectral niters covering narrow spectral bands within the visible spectrum, has been used to investigate the penetration of light into an estuary under winter and summer conditions.

Throughout the visible spectrum, extinction coefficients in Hamoaze are always higher, in winter often very much higher, than in the English Channel. In marked contrast to the open sea, red light penetrates as well or better than green, and blue is cut down most rapidly

1. The limitations of the Conical Dredge as used in obtaining a sample for quantitative estimation of the fauna of a ground are discussed, and are found to be related to

(a) The great distance over which the instrument must be hauled, with consequent inability to detect patchiness of fauna.

(b) The inability of the dredge to capture members of the epifauna.

2. The nature of the shell gravel, its position relative to the Eddystone reef, and the various factors conditioning the degree of coarseness of the deposit and the segregation of its elements are considered. The main points of note are,

(a) There are three well-defined areas, within which the gravels have their own particular characteristics.

(1) The Inner Shell Gravel area and the Middle Gravel area, composed of material of inorganic and organic origin, the former being gneissic in character, and the latter being formed of the remains of animals which normally live on this particular type of deposit.

(2) The Outer Shell Gravel area, a mixture of matter of local and of outside origin. The area is more extensive on the western than on the eastern side of the reef.

(b) Segregation of particles according to size occurs, and is illustrated by the movement of the valves of a number of species of molluscs. Wave action and the action of gravity are considered to be the chief factors in inducing movement of particles, which movement occurs in directions radiating from the reef outwards.

3. The epifauna of the rocky bottom is referred to briefly.

4. The infauna of the shell gravel has been examined quantitatively and qualitatively, and the range of the various species over the ground noted.

5. The nature of the shell-gravel community and its relation to some of the important environmental factors, are discussed.

6. Mortality among the lamellibranchs, and the depredations of the gastropod Natica alderi are considered; figures relating to the numbers of lamellibranchs killed by N. alderi are given.

The meiofauna of the St Lawrence estuary was investigated in the intertidal zone of the Parc du Bic (Quebec, Canada). Five nematode assemblages were distinguished by a cluster analysis: A1 and A2 (upper-tide level); A3 (mid-tide level); A4 and A5 (low-tide level). Discriminant function analysis showed that exposure time during low tide was the most important environmental factor in determining differences between assemblages. Chlorophyll-a, phaeopigments, sediment water content, and per cent of silt followed in the same order. Nematode densities (400–1500 ind 10 cm−2) were found to be lower than those generally reported for other estuarine intertidal zones of the eastern Atlantic coast. Mean nematode biomass in the five assemblages ranged between 96±14 and 248±86 μg Corg 10 cm−2. Deposit feeders were generally the dominant nematode feeding group in terms of abundance and biomass. Correlation of epigrowth-feeders with chlorophyll-a and phaeopigments, respectively, suggested that in the upper-tide level, old or partially degraded phytodetritus contribute more to the diet of this nematode feeding group; and in the low-tide level epigrowth-feeders may rely more on ‘fresher’ phytodetritus.

The lagoon of Boughrara is the largest lagoon in Tunisia. For several decades it has been subject to the impact of increasing anthropogenic activities, and also to environmental stressors due to climate change and the low renewal of its waters. The present work is a contribution to the study of the functional organization of the benthic macrofauna of the lagoon of Boughrara 3 years after the extension of the channel ‘El Kantra’ which connects this lagoon to the open sea. In total, 13 stations facing the main prospective sources of disturbance and in areas likely to be more polluted were seasonally sampled during 2009–2010. Seasonal monitoring of the abiotic parameters shows a spatial heterogeneity linked to environmental and anthropogenic factors, including hydrodynamics, sedimentary texture and anthropogenic activities. The community of benthic macrofauna is generally poorly diversified at lagoonal-marine stations undergoing influences of both the marine and lagoon environment. The extreme seasons in terms of temperature and salinity seem to have an important role in the reduction of biodiversity in the lagoon of Boughrara. The trophic structure of the macrobenthic community is generally dominated by selective deposit feeders, and seems to be linked more to the availability of trophic resources than to disturbance.

Ninety-six species (97, 677 individuals) were collected over the course of 6 h in five suprabenthic sledge hauls from a very dense Ampelisca fine sand community from the Bay of Morlaix (western English Channel). All the species migrated into the water column at night (98% of the specimens collected in the suprabenthos were found in the night hauls). The 23 most abundant species collected were classified into five groups based on their height within the water column, but two groups predominated: the upper suprabenthic species, abundant at 0–80–145 m above the sea-bed; and the lower suprabenthic species which were abundant only near the sea bottom (-0–1–0–75 m high). Three different patterns of nocturnal vertical migration were distinguished based on the timing of maximum swimming activity: at dusk; at the beginning of the night; or later in the night. Sexually dimorphic patterns of free-swimming behaviour was observed in Ampelisca and some other species of Amphipoda (Bathyporeia teniupes, Metaphoxusfultoni), and Cumacea (Bodotria pulchella, Pseudocuma longicornis), with many more males than females migrating into the water column at night. Finally, the density of suprabenthic crustaceans in nocturnal hauls was amongst the highest reported from infralittoral or circalittoral suprabenthic studies on other parts of the Atlantic Ocean sampled during spring.

Recent phylogenetic analyses of demosponges have suggested that the order Poecilosclerida is monophyletic and nested within the paraphyletic ‘order’ Hadromerida. Until now, this result has rested upon very limited taxon sampling of SSU sequences and partial LSU sequences. We collected and analysed additional full-length SSU and LSU sequences to test the validity and position of the poecilosclerid/hadromerid clade within demosponges, and we sampled a short segment of the LSU from diverse hadromerids to explore the internal relationships of Hadromerida. Our data strongly support the existence of a hadromerid/poecilosclerid clade that is sister to a poorly characterized group of halichondrid and agelasid species (‘Clade C’). We find support for the monophyly of the hadromerid families Polymastiidae, Placospongiidae and Timeidae, and conditional support for the family Suberitidae. Furthermore, both LSU and SSU data support a clade that includes a mixture of species assigned to the families Tethyidae and Hemiasterellidae (TETH/HEM) and a mixed clade including members of the families Clionaidae and Spirastrellidae (CLIO/SPIR). The family Placospongiidae is reconstructed as sister to the clade CLIO/SPIR and the family Timeidae is supported as sister to the clade TETH/HEM. The order Poecilosclerida is most closely allied with the Placospongiidae/CLIO/SPIR clade.

The endogenous rhythm of swimming activity shown by Corophium is reset by pulses of sub-zero temperature, the activity maxima being rephased to the time of rewarming at the end of the cold period. Chilling is not equally effective at all stages of the tide, pulses applied during the flood tide causing a phase delay, while those applied during the ebb advance the rhythm. Chilling at the time of low water induces arrhythmic swimming and it is suggested that the rhythm enters a state of equivocation at this time when an advance and a delay in phase are both equally probable. This results in the loss of synchronization between individuals and the disappearance of the overt rhythm from the sample population.

The first record of Musculista senhousia in the Taranto seas (eastern-central Mediterranean Sea) is reported. The species was mostly found on bottoms with pleustophytic algal felt where densities up to 3800 specimens per square metre were estimated. The sizes in the sampled population ranged from 5·16 to 30·59 mm. Two main modal components were detected around 11·67±0·67 mm and 18·00±2·38 mm.

An important aspect of marine biodiversity studies is identification of species and subspecies complexes. Here we present a number of examples from marine algae in which allozymes, DNA sequences and RAPDs are used to identify cryptic species and explore phylogenetic-population level relationships over several biogeographic spatial and temporal scales. In addition to evidence for recent dispersal over large distances, effects of present and past climates are reflected in the phylogenetic history of many biogeographic complexes. In some cases temperature adaptations can also be detected. Phylogeographic studies on coastal seaweeds and oceanic phytoplankton which utilize molecular genetic data contain a wealth of previously unrecognized information relevant to biodiversity.

acoustic surveys were carried out in three regions of the aegean sea where fish farming zones have been established in order to study the mesoscale effect of fish farms on the spatial structure of wild fish communities. in each area two sites were sampled during may and september. one site was close to the fish-farming zone while the other (reference site), was located in a place with similar topography at a mean distance of 20 nautical miles from the fish-farming zone. geostatistical techniques (omnidirectional and exhaustive variograms) were used to analyse and visualize the spatial structure of the wild fish assemblage in each site. the spatial structure of wild fish aggregations at all three fish farming zones showed consistently a pronounced directionality during both sampling periods, indicating that the wild fish patch was oriented towards a specific direction. this was not observed in the respective reference areas. the observed directionality suggested a response at a mesoscale level of the wild fish biota to the presence of the fish farms in the adjacent coastal area.

This study examined the role of predation in restricting early benthic phase (EBP) lobsters to shelter-providing substrata. In the field, the survival of animals provided with cover in the form of cobble and gravel substrata was significantly higher than unsheltered controls. Small benthic fish, particularly gobies Pomatoschistus minutus and rockling Ciliata mustela were the primary predators subtidally while crabs Carcinus maenus appeared to be the dominant intertidal predator. Predatory attack primarily occurred within minutes of the lobsters being deployed. The study reinforces the role played by predation in restricting EBP European lobsters to shelter-providing substrata.

Buoys differ from the intertidal area in that they are constantly immersed near the surface of the water and the slope and texture of their surface is constant. The horizontal and vertical distribution of the macrofauna and macroflora on a series of buoys stretching from the open sea up the Tamar estuary is given.

There are differences in estuarine penetration even among species belonging to the same genus. Distribution is likely to be affected by the time of laying the buoys and the period in the water. But the six buoys farthest from the sea were laid down and lifted at approximately the same time. For these, at least thirty species were available for colonization, but little more than half that number was found even on the most seaward; and the number decreased up-river.