The spatial and temporal structure of the zoobenthos associated with the invasive red alga Womersleyella setacea was studied in the northern Aegean Sea, Greece. Five replicate quadrats (20×20 cm) were collected, seasonally from July 1997 to August 1998, by SCUBA diving at four sites and two depth levels (15 and 30 m) in the Chalkidiki peninsula. We collected 23,090 specimens representing 278 animal species. Multivariate analysis showed mainly spatial differences in community structure, while the temporal ones were minimal. The ordination of sites showed a clear zonation pattern according to the different algal forms that cover the rocky substrate, with inclination the only environmental factor involved. The epifauna associated with the invasive alga was differently structured compared with three native seaweeds, showing increased species richness and abundance. The filamentous alga W. setacea was dominant in all seasons and depth levels, creating a stable habitat that contributed to the loss of seasonality in zoobenthic community structure.

This special issue on marine mammals marks the 20th anniversary of the European Cetacean Society (ECS). The Society's 2006 conference was held in Gdynia, Poland in April, with the theme of ‘Marine mammals and man in coastal ecosystems: can they co-exist?’ Several of the papers contained in this volume describe work that was presented at this conference, and most relate to research carried out by ECS members.

Comparative studies were conducted on intertidal algal and faunal communities associated with Sargassum muticum and native algae on the Isle of Cumbrae, Scotland. Significant differences were detected in the structure and composition of the communities. The abundance of the dominant native algae Dictyota dichotoma was found to be reduced in areas dominated by S. muticum and displacement through competition for substrate or light is inferred. Elevated faunal abundances were associated with S. muticum and evidence indicates that increased detrital input may be a possible contributory factor. Differences in faunal community composition were most pronounced in the sessile epifauna below the S. muticum canopy. Faunal communities associated with S. muticum were less heterogeneous in composition than those associated with native algae at equivalent shore positions. Some of the compositional differences may be coincidental and attributable to factors favouring the establishment of S. muticum rather than to the direct influence of the S. muticum canopy.

In this study, we analyse spatial patterns of macrobenthic communities of the Río de la Plata system, and assess the species turnover or beta diversity and its relationship with environmental gradients. Macrobenthic samples and physico-chemical parameters were collected from 20 sampling sites along a transect of 560 km, including the freshwater (FW), estuarine (ES) and marine (MA) sectors. Three main assemblages corresponding to the above mentioned sectors were defined with multivariate analysis (cluster, MDS). In total 134 taxa were recorded, 81 in MA, 33 in FW and 38 in ES, represented mainly by polychaete, mollusc and crustacean species. Depth, salinity and %clay showed the strongest correlation with the observed faunal patterns (ρw=0.62; BIO-ENV analysis). Beta diversity varied between dominant taxonomic groups and was positively correlated with changes in salinity. The high variability in the composition of assemblages was reflected in beta diversity, reaching its highest values at the boundaries between the defined sectors. This study suggests that beta diversity represents a useful tool to define ecological boundaries for benthic communities in the Río de la Plata.

Sponges are an integral part of marine benthic communities with a high-impact role in benthic–pelagic coupling processes, as an important source of food for demersal grazers and predators, as hosts of a highly diverse microbial biomass, and as bio-eroders. Sponges provide age-old (hygienic) services to humans and continue to be of interest in modern times as sources of an unprecedented array of useful substances.

The reflected patterns and colours of terrestrial animals often show a sexual dimorphism associated with visual display, mate recognition and selection. In the sea the structures associated with bioluminescence may also show a marked sexual dimorphism. Some apparent bioluminescent dimorphisms (e.g. differences in photophore numbers) are probably secondary functions of sexual differences in size. A role in sexual communication is much more likely where specific photophores are developed or enlarged in mature specimens of one sex only but the presence of light organs in female anglerfishes (but not in males) is complicated by a significant size dimorphism. Dimorphisms in dragonfishes and lanternfishes primarily involve the relative enlargement of particular photophores in the males. A sexual role is assumed, but the morphological differences are often small. Most male ponyfishes have enlarged light organs; behavioural observations of free-swimming animals have clearly demonstrated that the males use them to generate bioluminescent sexual signals.

This paper presents the new concept of passive acoustic tomography which allows ocean data collection with a passive acoustic remote sensing process. The originality lies in using acoustic sources of opportunity such as surface noise, radiated ship noise and marine mammal calls. Such use of passive tomography is a promising way to reduce acoustic emissions in oceans. A review is first presented, including the description of new concepts of covert active, assisted passive and autonomous tomography, followed by applications on real world data. Under the assumptions of multipath propagation and measurements performed by a sparse network of hydrophones, a time–frequency processor is proposed to simultaneously estimate the source location and the impulse response of the propagation channel for marine mammal calls used as opportunistic sources (multipath structure, time delay and attenuation are estimated). Promising results are obtained on real data coming from the Laurentian channel where wideband beluga calls (1 to 3 kHz) are measured by a sparse network of 6 bottom hydrophones.

The distribution and abundance of intertidal organisms can be affected by short-term events, such as rain. We compared the effects of rain on intertidal mobile invertebrates in four common microhabitats with differing amounts of shelter (namely beds of oysters, coralline turf, bare patches and crevices) on sea walls in Sydney Harbour. There was an effect of rain on some, but not all taxa, although this was not consistent between locations or times. Effects of rain were observed for some species of gastropods and crustaceans, but not for polychaetes. Manipulative experiments using artificial rain indicated that rain, without the presence of run-off and independent of potential temporal confounding from differences in weather conditions, has a negative effect on abundances of amphipods in coralline turf. Pulse responses by mobile organisms to short-term rain events should be considered when designing experiments looking at temporal variability and processes responsible for observed patterns of distribution of marine organisms.

Ecological studies of diversity at different spatial scales are important for our understanding of community processes. Here the patterns in the invertebrate fauna associated with the turf-forming red alga, Corallina officinalis, with increasing tide pool depth and in pools of different surface area and at different tidal heights are presented for two similar shores in north Wales. Corallina turf supports a diverse assemblage of invertebrates achieving high densities of individuals which makes an important contribution to local biodiversity. Overall 123 different taxa were identified with the most dominant species being the polychaete Spirorbis corallinae and small individuals of the mussel Mytilus edulis. There are significant differences in the invertebrate assemblage at different depths in tide pools and higher diversity and richness at shallower depths nearer the edge of pools where the alga is shorter and more compact than at deeper depths. Pool size and tidal height were also clearly important in structuring the assemblage where there were significant differences in diversity, richness and assemblage pattern, although these differences were not consistent between shores. Some measures of habitat complexity, such as algal volume, correlate well with species richness, though occasionally diversity is negatively correlated with the number of holdfasts. Variations in physical conditions afforded by different depths and in tide pools of different size at different tidal heights at the scales measured clearly play an important role in structuring both the complexity of habitat and its associated assemblage

A new sponge species Coelocarteria agglomerans sp. nov. (Isodictyidae: Mycalina: Poecilosclerida) is described from the reef slopes of Bunaken National Marine Park, North Sulawesi, Indonesia. The new species can be separated from the other two congeneric species: C. singaporensis and C. spatulosa by several characters concerning sponge surface, fistule shape, form and size of the spicules and habitat. In detail it differs from C. singaporensis in the presence of strongyles instead of oxeas as main megascleres and of spines in the shaft of palmate isochelae. It differs from C. spatulosa in the absence of characteristic fistules with spatula shaped hoods and in spicule size, because both categories of strongyles and palmate isochelae are remarkably larger in the latter.

This study evaluates the role of protozoa in larval fish feeding by describing protozoa in larval fish diets and testing the hypothesis that, in the Irish Sea, larval fish feed on protozoan prey at rates that potentially sustain their food requirements. Gut contents of 11 taxonomic groups of larval fish were examined, and protist prey occurred in the diet of all of them. Protozoan prey were identified, which provided an insight into their trophic role. Most of the protozoan prey were autotrophic or mixotrophic. In general, larval fish diets were constant over the spring/summer period, regardless of prey availability in the field and the composition of larval fish assemblage (taxonomy and size). A laboratory experiment on ingestion rates of flounder larvae as a function of ciliates concentration was conducted. Combined laboratory and field data showed that, in the Irish Sea, it is unlikely that ciliates are often the primary food source of flounder larvae, and, by implication, other larval fish as well. However, ciliates and other protozoa could be a substantial component of the larval fish diet, and they may potentially prevent food limitation.

Pico-size cells with a red fluorescence signature similar to marine free-living prochlorophytes have been detected by flow cytometry throughout the fresh and brackish waters of the Changjiang Estuary in August 2005. These cells could be discriminated from Synechococcus by their lack of orange (phycoerythrin) fluorescence, from Prochlorococcus by their larger side light scatter, and from picoeukaryotes by their smaller side light scatter and much lower red (chlorophyll) fluorescence. The maximum abundances of these Prochlorococcus-like particles reached 3×104 cells ml-1 in the low salinity zone upriver and declined rapidly seaward. While Synechococcus was scarce and Prochlorococcus vanished in the brackish regions, the Prochlorococcus-like cells overnumbered the picoeukaryotes and became the predominant pico-size auto- fluorescing particles there, implying they might play an important role in this estuarine ecosystem and worthy of further investigation.

In the Mar Piccolo of Taranto (southern Italy, Mediterranean Sea), an enclosed basin with lagoonal features, Acanthophora nayadiformis is one of the major components of the free-living seaweed community to which the related attached population does not contribute consistently. Loose thalli of A. nayadiformis exhibit morphological features very different from those of the attached specimens and possess a peculiar vegetative cycle including an overwintering phase. Free-living morphs are characterized by monopodial stoloniferous growth; in contrast, both determinate and indeterminate branching as well as the typical ramisympodial growth pattern of the species are lacking. In autumn, free-living thalli fragment giving rise to stolon pieces which undergo deep structural changes in their sub-apical parts including both storage of floridean starch and extensive cortical thickening. Soon afterwards the uncorticated parts decay, whilst the modified fragments are able to overwinter and give rise to new fronds during next spring.

The competition for space among fluorescent and nonfluorescent Anemonia species was monitored in the Mediterranean Sea in order to see whether the fluorescent species A. sulcata var. smaragdina was a better competitor in shallow water habitats. Over a period of 11 years, A. sulcata var. smaragdina convincingly out competed the nonfluorescent A. rustica. We thereby found support for the notion that the GFP-like pigments may increase competitive ability in anthozoans.

The colonization of epilithic diatoms on artificial hard substrates (marble, quartzite and slate) was investigated on a seasonal basis in a subtidal site of the northern Adriatic Sea to determine if substrate-dependent differences in colonization occurs and to define the seasonal variations of microepilithic communities in terms of abundance, biomass and community structure. Artificial substrates (smoothed small discs mounted on a Plexiglas sheet) were placed at a depth of 8 m in April 2003, July 2003, January 2004 and February 2004. The discs were collected after 6–7 weeks for counting and taxonomic identification of the diatoms. The community structure of epilithic diatoms showed a dominance of motile species over the entire study period, followed by erect, adnate and tube-dwelling diatoms. Diatom density showed a marked seasonal variability, ranging from 365±407 (winter 2004) to 557156±82602 cells cm-2 (spring 2004). Biomass ranged from 0.02±0.01 to 17.53±3.20 μg C cm-2. Abundance and biomass values did not present any significant differences for the three substrates examined.

Three new species of the boring genus Aka, A. coralliirubri, A. microterebrans and A. ruetzleri are described respectively from the Mediterranean Sea, Celebes Sea and Caribbean Sea. The Indo-Pacific A. maldiviensis, known only for the structure of its epilithic fistules, is here described in more detail. The new species confirm that the sponges comprising the genus Aka are able to bore in biogenic substrata only, in particular coral rock, bivalve shells and the scleraxis of the precious coral Corallium. The study of the macroscopic excavation shows that three different patterns can be described: producing discrete boring chambers, large undivided cavities and interconnecting microtunnels giving rise to a spongious aspect of the substratum.

We investigated the feasibility of using a T-POD, a passive acoustic dolphin detector system, to monitor bottlenose dolphins in the Shannon Estuary, Ireland, from 27 June to 18 August 2005. A v.3 T-POD, logging alternate minutes, was moored in view of an observation site. Land-based theodolite tracking was used to record the position of the closest animal, school size and activity of the closest dolphin school to the T-POD. All cetacean detections on the T-POD synchronous with shore watches in sea states ≤2 were analysed. A total of 94 schools were observed at distances up to 8000 m from the observer. Acoustic detections corresponded well with visual detections, with 82% of the dolphin schools observed within 500 m of the T-POD detected acoustically. The furthest distance dolphins were observed from the T-POD during periods of acoustic detection was 1246 m. Twelve acoustic encounters were logged without corresponding visual detections, four of which may represent false positives. School size did not affect the acoustic detectability of the dolphins, as there was no difference in the size of schools observed with or without corresponding acoustic detections (Kruskal–Wallis, P=0.64). Similarly no relationship was found between acoustic detections and school sizes at different distances to the T-POD (linear regression P=0.5, r2=0.01). Acoustic encounters did not vary in relation to diel patterns (Mann–Whitney, P=0.13) but were related to tidal state (χ2=40.2, P=0.00, df=11) with more encounters logged in the 4 h after high water, probably reflecting prey-related changes in habitat use. T-POD detections correlated well with visual observations and although detection is likely to vary according to T-POD specification, sensitivity and the conditions at the deployment site, the T-POD is a useful tool that has been shown to offer the possibility of continuous monitoring, something that is difficult to achieve with visual methods alone.

Here we report the first direct underwater observations of extensive human-caused impacts on two remote seamounts in the Corner Rise complex (north-western Atlantic). This note documents evidence of anthropogenic damage on the summits of Kükenthal peak (on Corner Seamount) and Yakutat Seamount, likely resulting from a limited Russian fishery from the mid-1970s to the mid-1990s, highlighting how bottom trawling can have long-term detrimental effects on deep-water benthic fauna.

Marine invertebrate larvae represent a transitory, but nonetheless important component of planktonic communities. Assessing their contribution to plankton diversity has been hindered by numerous methodological difficulties, notably at the identification step. For many sessile invertebrates, planktonic larvae also play a crucial role, as they are their sole dispersal vectors. Understanding connectivity patterns among marine populations is fundamental for managing coastal ecosystems and their associated resources. Indirect approaches, relying on population genetics models, have widely contributed to elucidate population structure and gene flow patterns, but show, in some cases, conflicting results with larval dispersal potential. In an attempt to facilitate surveys of larval distributions and abundances, an in situ hybridization on whole larvae method was tested over a range of marine invertebrate larvae collected from environmental plankton samples. Ribosomal RNA-targeted oligonucleotide probes were used for hybridization, followed by a colorimetric reaction allowing signal detection at the light microscope. Promising results were obtained, showing an unambiguous positive hybridization signal with a eukaryotic (positive) probe, but no signal with a negative probe. Using species-specific probes, the method could be applied to resolve key current questions in marine ecology, addressing both wide and fine scales.

The vocal repertoire of many delphinid odontocetes includes narrowband tonal whistles used mainly for communication. The aim of this study was to describe the whistle repertoire of short-beaked common dolphins, Delphinus delphis, recorded in the Celtic Sea between May and August 2005. The 1835 whistles recorded were classified into six broad categories and 30 sub-types, of which simple upsweeps and downsweeps were the most common. Furthermore, the parameters duration, inflections, steps and various frequency variables were measured. The whistles covered a frequency span from 3.56 kHz to 23.51 kHz and had durations between 0.05 and 2.02 seconds. Whistle parameters varied with behavioural context, group size and between encounters. The whistle repertoire of Celtic Sea common dolphins was compared to that of D. delphis from the Western Approaches of the English Channel, recorded during a survey between January and March 2004. The relative abundances of the broad whistle types did not differ between the two locations, but most whistle parameters were significantly different: almost all frequency variables measured were significantly higher in English Channel whistles. This may indicate some degree of population structuring of short-beaked common dolphins around Britain. Alternatively, the common dolphins in the English Channel may have shifted the frequencies of their vocalizations up to avoid masking by low-frequency ambient noise produced by high levels of vessel traffic in this area.