The unicellular sporophyte phase of the filamentous green alga, Acrosiphonia (Codiolales), is endophytic in the bladed red alga, Mazzaella splendens in southern British Columbia, Canada. Since endophyte maturity coincides with decreased host abundance (winter storms dislodge Mazzaella blades), many endophytes lose their host before zoospore release has occurred. We investigated whether the endophytes can reach reproductive maturity within decaying host tissue (drift blades) or as free-living entities once their host has disappeared. We demonstrate that both occur. Suspension of M. splendens blades, colonized by the endophyte phase of Acrosiphonia, in seawater tanks in winter, resulted in the germination and growth of filamentous Acrosiphonia plants (gametophytes) in spring. Net primary productivity of 132·2 g dry wt/m2/mo was estimated by harvesting total Acrosiphonia biomass after a one-month growing season. An estimate of Acrosiphonia survivorship from zoospore to macroscopic adult gametophyte (0·01–0·89%), is in close approximation with kelp spore survivorship to microscopic gametophyte (0·005–0·1%), but is 102–105 times higher than kelp survivorship from spore to macroscopic adult sporophyte. Differential survivorship in the field and in experimental tanks and among different study sites can be explained by variable mortality factors for spores and germlings and Acrosiphonia's success in colonizing highly disturbed environments.

Surplus production models were used to assess the fishery condition of red seaweed Gelidium robustum off the west coast of the Baja California Peninsula from 1985 to 1997. The maximum sustainable yield and optimum effort estimated by the Schaefer model were 705 tn and 457 teams, while the Fox model estimated 670 tn and 510 teams. The determination coefficients were r2=0·62 for the Fox and r2=0·58 for the Schaefer model. These results suggest that the resource is not overexploited. Fitting the data to Hilborn & Walters' dynamic model was not satisfactory.

Much speculation and some evidence suggest that jellyfish and ctenophore populations have increased in recent decades. Unfortunately, few past records exist with which to compare current populations, and our knowledge of how environmental factors affect jellyfish population size is meagre. Human enterprise has wrought many changes in the ocean that are hypothesized to favour jellyfish, including eutrophication, reduction of fish stocks, and global warming. In addition to anthropogenic changes, natural climate cycles may affect jellyfish populations. Records of jellyfish and ctenophore abundance that appear to be related to indices of climate variations (temperature, salinity, North Atlantic Oscillation, North Pacific Decadal Oscillation, El Niño Southern Oscillation) are reviewed. In eleven species studied from subtropical, temperate and subarctic environments, warm temperatures were related to large population sizes; three scyphozoan species in the North Sea, and one mesopelagic hydromedusan were exceptions to that trend. One tropical scyphomedusan species was decimated by unusually warm, salty El Niño conditions in Palau. Because climate changes have complex ecosystem-level effects, the proximate causes of jellyfish increases are difficult to deduce. Therefore, the effects of temperature, salinity and prey on asexual production of new medusae from the benthic polyps of scyphomedusae and hydromedusae also are reviewed. Experiments on temperate species show greater and more rapid production of medusae at warmer temperatures. Salinity also had significant effects, and was especially important for estuarine species. Temperature and salinity affect asexual reproduction rates directly through metabolism, and indirectly through prey capture. Ocean warming may shift the distributions, expand the seasonal occurrence, and increase the abundances of temperate-boreal species. Populations living near their thermal maximum may suffer negative consequences of warming.

the uk government's strategy for reducing greenhouse gas emissions to meet carbon mitigation obligations and the wider aims on sustainable development has provided the impetus for a rapid growth in activity associated with offshore renewable energy, particularly offshore wind farms. recently, consents for offshore renewable energy development (ored) were approved in three strategic areas—the outer thames estuary, the greater wash and the eastern irish sea. the scale of the planned developments means that each will have a large environmental footprint and multiple ored will have a cumulative effect on the environment. here we discuss current understanding of ored construction, operation and decommissioning with regard to the potential interaction with elasmobranchs because of the worrying status of elasmobranch populations within the uk coastal zone. based on the likely interactions between elasmobranchs and ored a framework is proposed which aims to promote cooperative initiatives between elasmobranch conservation management and the offshore renewables industry.

The morphological characteristics of a new isolate of a dorso-ventrally flattened athecate dinoflagellate obtained from Hong Kong (HK) waters is described. Partial sequences of the large subunit ribosomal RNA gene were obtained and a high degree of similarity was observed with various species within the genus Karenia. Phylogenetic comparison suggested the Karenia sp. HK forms a clade with the newly described species K. papilionacea from New Zealand but not with authentic K. brevis from North America. Karenia sp. HK is the first K. brevis-like dinoflagellate characterized by molecular cladistics from the South China Sea and the results call for re-examination of the status of other K. brevis-like morphotypes described from the region.

This paper reports the first study of breeding in the boreo-arctic barnacle Semibalanus balanoides in which latitudinal variation in timing of egg mass hardening has been examined simultaneously over the geographical scale involved, thereby excluding temporal confounding of the data. The timing of autumn egg mass hardening on the middle shore was established in 2002 and 2003 at ten stations ranging latitudinally from Trondheim (63°24′N) to Plymouth (50°18′N). To assess variation at local scale (<10 km), breeding was studied on three shores at each of two Irish locations (Cork and Galway). At Oban (Scotland) and Cork, the effect of shore height on timing of breeding was investigated. A strong influence of latitude and day length on timing of breeding was found in both 2002 and 2003. In both years, barnacles bred much earlier (when day length was longer) at high rather than low latitudes. No significant effect of environmental temperature or insolation on timing of breeding was detected. Shores no more than 10 km apart showed minimal difference in middle shore breeding date (<4 days). However, upper shore barnacles bred significantly earlier (by 7–13 days) than middle shore animals. The data indicate that breeding is controlled by period of daily darkness, with high shore animals encountering longer effective ‘nights’ because of the opercular closure response to emersion (which will reduce light penetration to tissues). Predictions concerning the effects of global changes in climate and cloud cover on breeding and population distribution are made. It is suggested that increased cloud cover in the northern hemisphere is likely to induce earlier breeding, and possibly shift the present southern limit of Semibalanus southwards.

current concerns about the population levels of the basking shark (cetorhinus maximus) in the north-east atlantic have prompted a need to understand population distribution, habitat preference and centres of abundance. in this study, spatial distribution maps derived from satellite-tag geolocations, boat surveys and public sightings data were compared. the broad distribution patterns revealed by these different methods are similar, but there are considerable differences in density distributions. surface sightings data show high densities, or ‘hotspots’ in the hebridean sea, clyde sea, irish sea and close inshore around devon and cornwall. tag geolocations, in contrast, identified two areas where individuals spent considerable time outside the distributions indicated by surveys and public sightings: the celtic sea and western approaches of the english channel. the reason for this disparity and its implications for population estimates for the species are discussed.

Oikopleura dioica is the only recorded appendicularian in the Black Sea. During the last two decades major changes in the O. dioica population size as well as total zooplankton community structures were recorded when invasive ctenophore species appeared in the Black Sea ecosystem. The state of the O. dioica population, before the invasion of ctenophores Mnemiopsis leidyi and Beroe ovata, is reviewed. The effect of the invasion of these ctenophores on the total zooplankton and particularly on the O. dioica standing stock is summarized from our long-term data and published information. The abundance, biomass and species composition of zooplankton greatly decreased after the ctenophore Mnemiopsis leidyi invasion due to predation by M. leidyi. Specifically, the abundance of O. dioica declined at that period. But with increasing numbers of a new invader, the ctenophore Beroe ovata, a predator of M. leidyi, in 1999, the zooplankton community began to recover. The population density of Oikopleura dioica also gradually increased to a level that was within the range of its abundance before the M. leidyi outbreak and even higher due to increasing its prey bacteria, which was provoked by the mucus released by B. ovata.

A biometric analysis was performed on crabs (Paguristes eremita) collected in the soft bottom of the Sicilian Channel (southern Mediterranean Sea), on associated suberitid sponges (Suberites domuncula), and on shells inside sponges. Populations of crabs living in sponges overgrown on shells were compared with populations of crabs living in shells associated with the sea anemone Calliactis sp. Results from multivariate ordinations (principal component analysis, non-metric multidimensional scaling) and univariate linear regression analysis were discussed considering two possible models: (1) sponges are preferred to clean shell because they are a growing home; and (2) sponges are not preferred: they are used as an ‘emergency’ refuge by crabs searching for shells suitable for carrying sea anemones. Differences in shell assemblages and in biometric variables between populations living in sponges and populations living in shells associated with anemones, suggest that crabs, especially small ones, may live briefly in sponges and that sponges may be inhabited by a series of crabs over a long period.

The Purbeck Marine Wildlife Reserve lies within the boundary of the Dorset and East Devon World Heritage Site on the south coast. This study investigated the influence of visitors on intertidal biodiversity at Kimmeridge Bay, the only accessible part of the reserve. The assemblages present on two rock ledges were compared: Washing Ledge, which is regularly visited and utilized by people, and Yellow Ledge, which is more isolated and visited much less regularly. At each ledge, three habitat types were investigated: open rock, rockpools and the fucoid zone. Multivariate statistical analysis revealed significant differences in assemblages between ledges and among habitat types. The differences observed in the communities of the two ledges can be explained to some extent by natural ecological processes, but human impacts were also detected. The most obvious contrast associated with trampling was a reduction in the larger, branching species of algae and an increase in ephemeral and crustose species in the more heavily utilized areas.

amid concern about the status of skates and rays in welsh waters the present work set out to provide up-to-date information on the population biology of raja clavata in caernarfon bay. the von bertalanffy growth parameters were l∞=100.9 cm, k=0.18 y−1 and t0=−0.95 y for males; and l∞=117.6 cm, k=0.16 y−1 and t0=−0.7 y for females. male r. clavata reached 50% maturity at 58.8 cm and 3.9 y, which was smaller and younger than females (l50 and a50 were 70.5 cm and 5.3 y, respectively). although previously over-exploited, the present estimate of total mortality (z) was 0.48–0.49 y−1 which, in terms of replacement mortality (calculated as 0.7 y−1), suggests no immediate prospect of recruitment failure for r. clavata in caernarfon bay. the potential for the recovery of a depleted population is discussed in relation to the allee effect.

A large planktonic ciliate, Pseudotontonia cornuta, was observed during a cruise in the North Sea, Denmark, in summer 2001. Live cells as well as fixed and protargol-stained specimens were studied. The species possessed the characteristic tail of Tontoniidae, somatic ciliature classifying it as a Pseudotontonia, and cell proportions and oral ciliature corresponding to P. cornuta. Observation of live cells, however, revealed distinctive features as chloroplast-containing tentacles emerging just below the apical membranelles and an S-shaped proximal rim of the left margin of the oral cavity. These characters are eye-catching in live specimens, but have passed unnoticed till now because all previous studies on P. cornuta have been made on fixed samples.

A new species of the planktonic copepod Tortanus (Atortus) (Calanoida: Tortanidae), T. (A.) magnonyx is described from the Seychelles, Mauritius and Madagascar. This is the sixth species of the Indian Ocean recticauda species group, of the Indo-West Pacific recticauda species complex, that has been described from the western Indian Ocean. The inshore areas where these copepods are found have been poorly surveyed, so the number of species found implies a high diversity.

Several bacteria have been isolated from different tropical ecosystems (tropical rain forest, seawater, and marine sediments) from the island of Puerto Rico. These microorganisms were screened for carbohydrase activity using chromogenic substrates (amylose, pullulan, cellulose, dextran, arabinan, galactomannan, and xylan). The results indicate that 2–9% of cultured organisms show carbohydrase activity. Isolates were identified by partial sequence analysis of the polymerase chain reaction amplified small subunit rRNA gene. GenBank database comparison of the most versatile strains gave a match with Bacillus sp., Staphylococcus sp., Halomonas sp., and a gamma proteobacterium. Growth curves indicate that all strains assayed can grow as well in at least one complex carbohydrate as in glucose. A high β-xylosidase activity was detected in the Bacillus sp. strain crude enzyme preparation and this activity seems to be almost entirely cell associated. Our results show that tropical environments can be potentially good sources of bacteria with novel carbohydrases.

Twenty species of calycophoran siphonophores were identified from the central and south Adriatic Sea in spring 2002. Highest abundance and species diversity were noted at the deepest stations in the south Adriatic. Highest total abundance was found in the upper 100 m. The dominant species above 100 m were Lensia subtilis, Eudoxoides spiralis and Sphaeronectes gracilis, none of which showed diel migration. The first two species correlated significantly with the vertical abundance of microzooplankton, and the last with that of copepods. The most abundant species in the 100-400 m layer was Lensia meteori, whereas Lensia conoidea and Chlausophyes ovata were most abundant below 400 m.

A new species of Cladorhizidae, from the Aleutian Islands is described and compared with all known species of Cladorhiza worldwide. Cladorhiza corona sp. nov. has a unique growth form with two planes of differently shaped appendages. Appendages are inserted directly at the stalk; a spherical or conical body at the stalk is lacking. It is the only species reported where different spicule types occur in three morphologically different areas of the sponge. The spiculation of the basal plate is characterized by the occurrence of short, thick anisoxeas and the lack of anisochelae. Anisochelae are found in the stalk and the basal appendages only. Flattened sigmancistras and (sub-)tylostyles are restricted to the crown. The arrangement of spicules is different in the basal plate, the stalk with the basal appendages, and in the distal appendages. The dimensions and combination of spicule types separate C. corona sp. nov. from all known members of the genus.

although depleted throughout the european continental shelf, the relatively high density of thornback rays raja clavata, in the thames estuary (uk) makes it an important stock centre and potential focus for species management. to describe spatial and temporal distribution, 197 thornback rays were tagged with electronic data storage tags (dsts) and released in the thames estuary in october 1999 and 2000, and 100 rays tagged with conventional tags in 2000. fifty-one per cent of dsts and 48% of conventional tags were returned. fishery-independent estimates of position (‘geolocations’) between the time of release and recapture using the tidal location method were possible using 75 individual data records of between 31 and 423 days. ninety-six per cent of rays were recaptured within the thames estuary. the rays were located in water of 20–35 m depth during the autumn and winter, then migrated into shallower water (<20 m depth) during the spring. fishery-independent analysis of distribution demonstrated that the rays were more widely distributed in the southern north sea during the autumn and winter. the range contracted in spring, when the fish moved into the inner thames estuary. no gross behaviour differences were observed between males and females. displacement and dispersion coefficients calculated from geolocation data demonstrated clear annual cycles, indicative of migration. these movements were not apparent from the mark–recapture data, a fishery-related effect. the extent of migration as determined from experiments with dsts was approximately three times greater than that suggested by conventional tagging data alone.

The toxic dinoflagellate Alexandrium tamarense was studied along with surrounding oceanographic parameters from May 1998 to May 1999 in Scapa Flow, Orkney. Nutrient concentrations were higher in winter and showed a phase of depletion in late spring and summer. Dinoflagellates tended to be abundant in late spring and summer. Alexandrium tamarense was detected in the water column almost year round, with the exception of the winter months (September to December). The growth of the A. tamarense population in Scapa Flow was not reflected in a monospecific bloom but rather in moderate to small biomass levels and always in co-occurrence with other species of diatoms and dinoflagellates. The highest concentration recorded was 1600 cells l−1 but concentrations of 200–400 cells l−1 were more typical. The oceanographic parameters indicate that the occurrences of vegetative cells of A. tamarense seem to be explained in part by instability of the water column, low temperature and low nutrient concentrations.

Biodiversity of cnidarian and ctenophore forms in Toyama Bay, Japan Sea, was lower than that in Sagami Bay, north-western Pacific, according to all the indices investigated. Highest richness of forms occurred in the 400—600 m depth layer in Sagami Bay, while in Toyama Bay richness was low in most layers. New forms continued to occur with increasing depth in Sagami Bay but not in Toyama Bay and species composition differed remarkably between the two bays. Putative secondary deep-sea gelatinous forms were identified. Horizontal patchiness in normalized abundances was the rule rather than the exception and for accurate calculations of biodiversity indices incorporating evenness or equitability, the necessity for multiple submersible dives in a single area and survey period was noted. Vertical migration and predation were identified as possible factors contributing to the higher diversity in the 400—600 m depth layer in Sagami Bay.

The genus Desmoxya Hallmann, 1917, erected for south-east Australian Higginsia lunata Carter, 1885, was assigned to the synonymy of Higginsia Higgin, 1877 (Porifera: Halichondrida) by the latest revision of the taxonomy of the Porifera (Hooper & van Soest, 2002). The discovery of an undescribed species living in the bathyal reefs of the North Atlantic Rockall Bank with characters closely similar to H. lunata justifies the resurrection of Desmoxya. Accordingly the North Atlantic material is described as a new species in Desmoxya, viz. D. pelagiae sp. nov. The new species differs from its Australian congener in habit (smooth thin crusts vs massive with digitiform processes) and spicule sizes (smaller megascleres, twice-sized acanthoxeas and single vs two sizes of trichodragmas). A probable third member of this genus is Higginsia anfractuosa Hooper & Lévi, 1993, described from shallow-water reefs near New Caledonia. For reasons of priority the name of the family to which Higginsia and Desmoxya are assigned needs to be changed from Desmoxyidae Hallmann, 1917 to Heteroxyidae Dendy, 1905, as this senior synonym was overlooked when Heteroxya was assigned to the same family as Higginsia and Desmoxya in Hooper & van Soest, 2002.