Microzooplankton community composition, abundance, biomass and grazing impact were assessed, along with measurements of ciliate growth and mortality, during the onset of the spring bloom in the north-east Atlantic. The study was undertaken as part of the UK Biogeochemical Ocean Flux Study during 1 May to 15 June 1990. The microzooplankton community was composed of protozoans and metazoan developmental stages with respective mixed-layer depth integrated biomass values ranging from 127 to 638 and 74 to 394 mg C m−2. High numbers of aloricate ciliates (up to 35,000 cells l−1) dominated the microzooplankton community during early May prior to the onset of the spring bloom. Ciliate abundance then declined rapidly during mid-May with community growth rates ranging from −0·71 to 0·23 d−1. High abundances of metazoplankton (up to 400 l−1) were also recorded at this time and may have contributed to the decline in ciliate numbers. In late May and early June the protozoan community comprised a more even mix of dinoflagellates, tintinnids and aloricate ciliates. Phytoplankton mortality rates, measured using a dilution technique, ranged from 0·2 to 0·5 d−1. The microzooplankton consumed 8 to 44 μg C l−1 d−1, equivalent to between 16 and 40% of the chlorophyll biomass and 38 and 154% of primary production. These high rates of herbivory reflect the predominance of small (<5 μm in length) phytoplankton cells present throughout the first half of the study and support previous studies demonstrating the microzooplankton to be the main grazers of phytoplankton in the north-east Atlantic. However, there is also evidence that a disparity between predator and prey may have prevented a response by the microzooplankton to rapid increases in phytoplankton biomass and production during the spring bloom.

Zooplankton and hydrography of the upper 200 m was studied in coastal and pelagic waters off central Greece (eastern Mediterranean) during July 1998. The spatial distribution of the main environmental (temperature, salinity, fluorescence) and zooplankton (abundance, dry-weight, dominant groups) features of the area was delimited over an intense grid of 124 stations. The complex topography of the surveyed area comprised an interesting field for the study of pelagic–coastal interaction and its influence on the taxonomic composition of zooplankton.

A typical summer thermal stratification was observed over the entire study area. Marked differences were found in surface-salinity between the eastern (Aegean Sea) and the western (Ionian Sea) part of the study area, which was attributed to the presence of less saline waters originating from the Black Sea. A deep fluorescence maximum was present in both coastal and pelagic stations. Zooplankton abundance and biomass showed an inshore–offshore gradient with coastal areas being significantly richer than pelagic areas. The taxonomic composition of zooplankton varied greatly both along the inshore–offshore gradient and among the different semi-enclosed Gulfs. Copepods were the dominant group in the pelagic waters comprising 67–78% in terms of mean relative abundance. In coastal areas, copepods were less important with cladocerans (especially the species Penilia avirostris) being the dominant group (44–51%). Appendicularians and chaetognaths comprised an important component of the zooplankton community over the entire surveyed area with mean relative abundance ranging from 2·5 to 14% and 0·6 to 5·8%, respectively.

Mesozooplankton distribution was investigated over an intensive grid of 124 stations in coastal and pelagic waters of central Greece (eastern Mediterranean) during July 1998. The complex topography of the area consisted of various semi-enclosed gulfs as well as open-sea areas and provided excellent fieldwork for determining species assemblages, their relationships to environmental parameters and the distribution and abundance patterns of the copepod species.

Three coastal and one pelagic group of stations were revealed by cluster analysis. Inverse analysis of species affinities defined distinct ‘coastal’ and ‘pelagic’ species assemblages. All coastal areas were dominated by a small number of species (e.g. Penilia avirostris, Podon spp., Ctenocalanus vanus, Paracalanus parvus and Centropages typicus) all belonging to the ‘coastal’ assemblage. Differences among these coastal areas were mainly due to small changes in relative abundance of a common-species list. On the contrary, pelagic stations were characterized by higher species diversity, low dominance and the presence of characteristic epipelagic and mesopelagic species of the Mediterranean Sea (e.g. Calocalanus spp., Haloptilus longicornis, Lucicutia flavicornis, Mecynocera clausi, Farranula rostrata, Mesocalanus tenuicornis and Oncaea mediterranea).

The observed differences in taxonomic composition and abundance of zooplankton were related to the marked differences in salinity values observed between the eastern and western part of the surveyed area. Bathymetry, temperature and fluorescence were also related with the inshore–offshore gradient of the zooplankton community observed in the pelagic areas as well as with the discrimination of the zooplankton communities of the various semi-enclosed gulfs of the region.

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.

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.

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.

The morphology and infraciliature of two planktonic marine ciliates, Cyclotrichium cyclokaryon, type species of the genus and C. taniguchii sp. nov. were investigated on live and protargol-impregnated specimens collected from the Jiaozhou Bay at Qingdao, China. Based on the present as well as previous studies, an improved diagnosis for the poorly defined genus Cyclotrichium is suggested: Didiniidae with ovoid to barrel-shaped body; cell-surface densely ciliated except in the domed proboscis region; anterior ends of kineties with long cilia forming one circumoral wreath of pectinelles; one circumoral kinety composed of a zig-zag structure; dorsal brushes absent. Cyclotrichium taniguchii is distinguished from its congeners by the combination of the following features: ellipsoid body shape, marine habitat, details of ciliature, and lack of a posterior tuft. Based on the characters of the ciliary pattern, a new genus, Dicyclotrichium gen. nov., with the type species Dicyclotrichiumsphaericum comb. nov. is established. The new taxon differs from Cyclotrichium by having two wreaths of pectinelles. Two known morphotypes are suggested to be assigned into this genus: Dicyclotrichium faurei comb. nov. [basionym: Askenasia faurei] and D. humilis comb. nov. [basionym: Askenasia humilis].

Sphaerotylus antarcticus is a common Antarctic sponge characterized by a dense spicule fur that covers its surface. This sponge has been sampled at Terra Nova Bay from 22 November 2001 to 29 January 2002 at weekly intervals. On its spicules, a rich assemblage of benthic diatoms has been observed, mainly composed of Hyalodiscus sp., a centric sessile diatom, forming short colonies. The temporal trend of the abundances of these diatoms showed a maximum of 115×106 cells g−1 dry weight (dw) at the end of December. Almost all the diatom frustules observed in the sponge choanosome belonged to the planktonic species Fragilariopsis curta, which displayed a peak (50×106 cells g−1 dw) in the second half of January. Diatoms that were observed in the choanosome were of a size comparable to that of the inhalant pores, suggesting that sponges actively engulf diatoms, due to the pumping activity of their choanocyte chambers. Sponges, as active filter feeders, therefore represent one important vector in the transfer of energy from planktonic to benthic trophic chains in Antarctic habitats.

The genus Heterogorgia is reported for the first time from the shallow waters of the Galápagos Archipelago, and a new species found in the southern islands is described. The new species is distinguished from the other species of the genus described thus far by having thick branches with large, densely packed calyces, being mostly unbranched, and having larger sclerites. The occurrence of Heterogorgia verrucosa is also reported.

The edible cockle (Cerastoderma edule), a common marine bivalve in semi-sheltered sandflats, is a natural host for many parasite species of the genus Himasthla (Echinostomatidae: Trematoda). In a previous paper, Wegeberg et al. (1999) showed segregation of cockle infection by three Himasthla species (H. interrupta, H. continua, H. elongata) in relation to host tissue (foot, mantle, siphon) and host size (1·5 to 14 mm shell length). Following the same experimental procedure, a fourth species, H. quissetensis, an introduced dominant parasite of cockles in Arcachon Bay (south-west France) was investigated. The infection pattern was very similar to the patterns shown by H. elongata and H. continua. Cercariae (the free-living stage shed from prosobranch snails and encysting as metacercariae in bivalves) were most successful in the shell-length range of 6–14 mm, where 74% of the added cercariae were recovered as metacercariae. The comparison with the other Himasthla species supports the previous conclusion that the efficiency of cercariae to infect cockles depends on host size.

In the north-east Atlantic, the dominant reef-framework forming coral species, Lophelia pertusa and Madrepora oculata, form a symbiotic association with the polychaete worm Eunice norvegica. The polychaete–coral symbiosis was studied by visually observing and photographing live animals in aquaria over many months and using time-lapse video under infra-red lighting to record activity patterns. The polychaetes act as reef aggregating agents by joining coral colonies and enhancing the development of reef patches in deep water. The symbiosis was investigated using samples collected from a relatively shallow site in a Norwegian fjord and from a deeper open ocean site in the Porcupine Seabight. The potential functional roles of this symbiosis are considered. The reef aggregating behaviour of the polychaete symbiont allied with the ability of the coral host to anastomose its branches, the polychaete tubes and debris falling onto the reef structure will help to shift the balance between reef growth and (bio)erosion in favour of growth.

The present study reports the occurrence of two exotic species of polychaetes in Izmir Bay, the eastern Mediterranean: Streblospio gynobranchiata, newly reported for the Mediterranean, and Polydora cornuta. Their establishment in the area is most probably transport by ballast water since these two species greatly dominated polluted muddy bottoms near and in Alsancak Harbour. The maximum density and biomass of S. gynobranchiata in the area were 34,270 ind m−2 and 9·4 g wwt m−2, and those of P. cornuta were 3170 ind m−2 and 2·1 g wwt m−2, respectively. These two species accounted for more than 60% of total faunal populations in the majority of samples collected in winter. Both species are capable of reproducing in the area both in summer and winter. The morphological, ecological and distributional characteristics of these species as well as their impacts on the prevailing ecosystem are analysed and discussed.

Seven hundred and six specimens of Scolelepis cf. chilensis and 551 specimens of Scolelepis goodbodyi were analysed. Individuals of each species were classified according to sex (male, female, and immature individuals). Width (w) and height (h) of setigers 3 and 5, the position of the first and the last gametogenic setigers, the total number of setigers, and the total length of each worm were measured. The area and volume of the setigers were estimated. Discriminant analysis was used to determine whether there were sexually dimorphic features, apart from the presence of gametes. Linear regression analysis was used to evaluate the relationship between each parameter and the number of setigers. Scolelepis cf. chilensis was found to be significantly larger than S.goodbodyi (t=21·71 and t=36·44, P<0·05 for length and number of setigers, respectively). These species also differed in the position of the first gametogenic setiger, which averaged 27 (SD=3) in S. cf. chilensis and 22 (SD=1) in S.goodbodyi (t= 29·18, P<0·05). There were no sexually dimorphic features in either sex of S. cf. chilensis (Wilks' lambda=0·9675, P>0·05, eigenvalue=0·034) or S.goodbodyi (Wilks' lambda=0·8429, P>0·05, eigenvalue=0·186). The total length showed the strongest correlation with the number of setigers in both species (r2=0·887 and 0·850 for S. cf. chilensis and S.goodbodyi, respectively), followed by the width and the volume of setigers.

Ophelia bicornis sensu lato is a polychaete living in intertidal sandy habitats of Mediterranean and European Atlantic coasts, whose systematics have been strongly debated in the past few decades. In the present work the count of nephridiopores was coupled with genetic analysis carried out with DNA markers (inter simple sequence repeats) for a total of 30 individuals collected at six Italian beaches. Exact test, analysis of molecular variance, non-metric multidimensional scaling and assignment tests clearly separated individuals with five nephridiopore pairs from those with six pairs. This finding validated results of a recent allozyme study in which O. bicornis sensu lato was split into O. bicornis sensu stricto (six nephridiopore pairs) and O. barquii (five nephridiopore pairs). This paper represents a further contribution to the estimation of biodiversity within marine invertebrates.

During the 2002 Antarctic Deep-sea Biodiversity (ANDEEP) programme to the Drake Passage, Weddell Sea Basin and South Sandwich Slope and trench, a new deep-water species of orbiniid polychaete was collected: Orbiniella andeepia sp. nov. Orbiniella andeepia appears to be most closely related to O. marionensis but differs in capillary setal structure, the type and number of acicular spines found in each podial lobe. Orbiniella andeepia is only the third deep-water species of Orbiniella to be discovered. It exhibits both a wide depth- and geographic-range within the Antarctic slope and abyssal sediments.

Patterns in larval supply and recruitment of the invasive European green crab, Carcinus maenas, were examined at two sites in Nova Scotia, Canada: a typical Atlantic coastal site with high salinity (∼33) and strong tidal signal (Terence Bay); and a microtidal site in the Bras d'Or Lakes, where surface salinity fluctuated from 0 to 23 (Benacadie Pond). Abundance of all life history stages (zoeae, megalopae, juveniles and ovigerous females) was sampled approximately biweekly at each site from June 2001 to June 2002. The reproductive season, based on the presence of ovigerous females, is ∼5 months (June to October) at both sites. Zoeae-I were collected from June to July 2001 and in June 2002 at Terence Bay, and from June to August 2001 at Benacadie Pond. We did not collect later zoeal stages at either site. Megalopae were collected from September to October 2001 at Terence Bay, and from August to September 2001 at Benacadie Pond. Juveniles 1–6 mm carapace width (CW) were present throughout the summer at Terence Bay, and only in autumn at Benacadie. Juveniles 6–12 and 12–27 mm CW were present throughout the summer and autumn at both sites. At Terence Bay, densities of 1–6 and 12–27 mm CW juveniles did not vary among intertidal zones. In contrast, the 6–12 mm CW size-class appeared to move higher in the intertidal through the season, possibly due to effects of predation.

Libidoclaea granaria was collected as part of the by-catch of the Zygochlamys patagonica (Bivalvia: Pectinidae) fishery, between 36° and 39°40′S and at 80 to 128 m depth. Crab densities ranged from 0 to 150 individuals 100 m−2, with a mean of 9·8±20·4 individuals 100 m−2. Mature males and females ranged from 24 to 61 mm, and from 16 to 48 mm, carapace width (CW), respectively. The largest immature female measured 22·5 mm CW. The number of eggs carried by a female ranged from 1200 to 9300. Sponges were the most frequent epizoic organisms, followed by the lepadomorph cirriped Ornatoscalpellum gibberum, Serpulidae and Spirorbidae worms. Since all these organisms were reported on Z. patagonica beds, crabs are camouflaged to match their habitat. Small crabs usually had naked carapaces, indicating a high moult frequency. Larger crabs instead, had epibionts on their carapaces, suggesting a lesser moult frequency. The erosion of carapace spines and the heavy epibiosis of large specimens suggest the existence of a terminal anecdysis.

The pilumnid crab Pilumnus limosus is known from Gonzaga Bay, Baja California, Mexico, to Zorritos, Paita, Peru. Larvae from a female collected in the intertidal rocky shore in Mazatlán, south-eastern Gulf of California, Mexico, were reared in the laboratory from Zoea I to megalopa. A complete description and illustration of larval features is provided and a comparison with closely related species showing known larval development is presented. As in most species of this genus, P. limosus larval development consists of four zoeae. All features observed in P. limosus are similar to those of P. reticulatus and P. sayi. All those larvae have lateral processes on abdominal somites 2–5 (2 or 3 in other species); posteromarginal denticles on abdominal somites 2–6 (absent in other species of the genus).

Reproductive patterns such as gonad maturation, production and release of gametes, fecundity and moulting play a major role in the continuity of populations and their adaptations to the environment they inhabit. The present study assesses the breeding cycle, moult activity and egg production in the hairy crab Pilumnus vespertilio, a typical inhabitant of intertidal pebble and rocky substrates of East African coasts. A total of 930 crabs was collected between January and December 2002 at Inhaca Island, southern Mozambique. Both oogenesis and spermatogenesis exhibit a continuous and synchronized pattern. Maturation of the female and male gonads occurs from early winter to mid summer and spawning is in summer. Moulting females showed two major peaks (January–March and October–December) whereas a single peak was recorded in males (October–December). Pilumnus vespertilio breeds continuously with high incidence in March and December and a strong decrease from April to July. Results revealed that both temperature and rainfall were positively associated with the relative abundance of egg-bearing females. The number of eggs carried by ovigerous females increased with size, ranging from 300 to 8000. The high reproductive activity of P. vespertilio may enhance larval survival and development, which guarantees juvenile recruitment in the study area.

The population structure and fecundity of the hermit crab Dardanus deformis were studied. Monthly samples were obtained between January and December 2003 at Costa do Sol, Maputo Bay, southern Mozambique. A total of 604 individuals was analysed of which 273 were males, 164 non-ovigerous females and 167 ovigerous females. The overall size–frequency distributions were unimodal, with males reaching larger sizes than both ovigerous and non-ovigerous females. Females were slightly more abundant than males, but the overall sex ratio did not differ significantly from 1:1. Dardanus deformis showed continuous reproduction throughout the study period. A small number of juveniles was obtained, suggesting that recruitment may take place in a different habitat than that occupied by the adults. The egg number increased with female size, and the high incidence of ovigerous females, may suggest a higher reproductive activity probably as a result of the rapid embryonic development in the study area.