Area-specific temporal changes of species composition and species-specific range shifts in rocky-shore mollusks associated with warming Kuroshio Current

Increases of low-latitude species in various sea areas and poleward shifts of ranges of many species have been reported and linked to warming environments. To examine the generality of these trends for mollusks, we conducted 7 quadrat surveys during 1978–2006 on Pacific rocky shores in Japan (26.6–45.0°N). Results showed that the dominance of southern species increased on 11 of the 15 shores in a southern, warming sea area but on only 1 of the 6 shores in a northern area with no warming trend. The latitudes of species ranges increased on average but showed large interspecific variations which showed a weak, positive correlation with interspecific taxonomic distance. The differences of these results from the previously reported trends are discussed in relation to the unique current patterns in our study area and the phylogenetic constraints of species-specific responses to a warming environment.     

Phylogeography and demographic history of <Emphasis Type="Italic">Atherina presbyter</Emphasis> (Pisces: Atherinidae) in the North-eastern Atlantic based on mitochondrial DNA

A fragment of the mitochondrial control region was used to assess phylogeographic patterns and historical demography of the sand-smelt Atherina presbyter in the North-eastern Atlantic, covering its geographical range. A striking result is the highly marked differentiation between the Canary Islands population and western European ones. A genetic structure among European populations of A. presbyter was revealed, with a pattern of isolation-by-distance or a gradient effect at a scale of hundreds kilometres, an uncommon pattern likely related to the biological and life-history traits of the sand-smelt. The northern European populations present a much lower genetic diversity when compared to southern populations, which is consistent with a recent colonization from southern populations. The results showed signs of Pleistocene signatures, with the population age estimates for the European populations being clearly older than the Last Glacial Maximum (18,000 years bp). Nevertheless, paleotemperature reconstructions show that the sand-smelt could not have inhabited the western European shores during the last glacial phase. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Lack of mtDNA and morphological differentiation between two acorn barnacles <Emphasis Type="Italic">Tetraclita japonica</Emphasis> and <Emphasis Type="Italic">T. formosana</Emphasis> differing in parietes colours and geographical distribution

Tetraclita japonica and T. formosana are common intertidal barnacles with similar morphology, which leads to uncertainty in their species status. In the present study, we try to elucidate the taxonomic status of the two taxa using morphology and mitochondrial control region and cytochrome c oxidase subunit I (COI) sequences of the barnacles in their distribution range. The two taxa were found to be morphologically similar; a diagnostic difference between them was only observed in the colour of the parietes and opercular plates. Little genetic differentiation was detected in the control region and COI (Φ_CT < 0.025 for both markers) between two taxa, but differentiation was found between the southern (Taiwan and Hong Kong) and northern (Japan) populations of T. japonica/T. formosana, which might be the result of isolation by distance and upwelling in summer. Our data suggest that the two presently recognized species probably represent two colour morphotypes of the same species exhibiting different geographical distribution. T. japonica is abundant in Japan and southeast coast of China, whereas T. formosana is only abundant in Taiwan. The heterogeneous environment might exert a divergent selection pressure leading to asymmetric distribution of the two colour morphotypes. The different colours might be a result of either phenotypic plasticity adaptive to environmental variables or genetic hitchhiking of local adaptive genotypes. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Genetic diversity of blackspot seabream (<Emphasis Type="Italic">Pagellus bogaraveo</Emphasis>) populations off Spanish Coasts: a preliminary study

Genetic diversity among four natural samples of Blackspot seabream (Pagellus bogaraveo, Brünnich, 1768) from different fishing grounds exploited by Spanish fisheries was analyzed through the use of 12 microsatellite markers. The samples were captured off the Spanish coasts from the Mediterranean Sea to the Cantabrian Sea within the same continental slope. High levels of genetic diversity were revealed for every population and every locus was polymorphic at the 0.95 level. The average number of alleles, average heterozygosity and PIC were found to be 15.75, 0.833 and 0.818, respectively. In general, population differentiation was not detected in these samples. Through AMOVA, a low level of variation between regions (Mediterranean vs. Atlantic samples) was observed, though this was not significant. A larger percentage of total variation was observed inside the ‘within populations’ class. Thus, AMOVA did not reveal any significant population substructure. Moreover, no correlation was found between geographical and F_ST estimates and the observed results did not allow the improvement of a model of isolation by distance. The high homogeneity revealed by means of these markers could indicate the absence of physical frontiers between the geographical areas analyzed in this survey, especially between Atlantic and Mediterranean areas.     

Role of peat organic matter on isotopic composition of most abundant benthic organisms in intertidal habitats of SW Iceland

The transfer of peat organic matter (OM) from tidal pools of upper littoral to downstream rocky shores and its potential incorporation into marine biota were investigated using the stable isotope approach. Samplings were carried out in September 2004 in two SW Icelandic sites (Osar and Hvassahraun), where we selected (1) areas with shores where grass gently declined towards rocks and, on reaching the sea line, formed small tidal peat pools and (2) areas where grass and rocky shores were not contiguous, rather the grass lower limits were several hundreds of meters back from the shore. In both grass and no grass areas, in the intertidal zone, all benthic organisms and all potential OM sources were sampled. Dominant macroalgae were Ascophyllum nodosum ([Linnaeus] Le Jolis) and Fucus vesiculosus Linnaeus. In grass sites, organisms partially reflected the isotopic composition of peat OM, while in no grass sites, peat represented only a negligible amount of available OM, or its signal was totally absent from the environment. Intertidal organisms could rely on peat both directly by suspension feeding, grazing or scavenging and indirectly by predation (crabs) on low level consumers (barnacles).     

Dispersal of phytoplanktotrophic shipworm larvae (Bivalvia: Teredinidae) over long distances by ocean currents

Shipworms or Teredinidae may be dispersed either as adults in floating wooden objects or as pelagic larvae drifting near the sea surface. Five shipworm species, i.e., half of those having an amphi-Atlantic geographical distribution, are known also to have pelagic phytoplanktotrophic larvae which can be carried by ocean currents. From a series of 742 plankton samples taken from throughout the temperate and tropical North Atlantic Ocean, it can be shown that shipworm larvae are not uncommon in the open sea. Teredinid veligers were found in 19% of all samples taken. One species of larvae, identical in all details to that described by Rancurel (1965), is particularly prevalent and is tentatively identified as Teredora malleolus (Turton). A definitive identification will be possible only after the pelagic larvae of the other Atlantic species are known. The larvae of Teredora malleolus are found throughout the North Atlantic Gyre and the adjacent temperate and tropical seas, and from scattered records in the South Equatorial Current. Larvae of other unidentified Teredinidae species were also found. The distance that larvae may be transported depends upon the length of pelagic larval development and the velocity of the currents. From the known current velocities it can be shown that, even in a few weeks, larvae may be dispersed many hundreds of kilometers. The geographical distribution of shipworm larvae suggests that they are carried along the coasts of continents and even across ocean basins, and that this dispersal must be an important factor in the geographical distribution of the adult forms and in the maintenance of genetic continuity between populations otherwise isolated from one another.Contribution No. 2555 from the Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA     

Distribution and ecology of leptocephali of the congrid eel, Ariosoma scheelei, around Sulawesi Island, Indonesia

A survey for leptocephali around Sulawesi Island in the central Indonesian Seas during May 2001 found that the leptocephali of the congrid eel, Ariosoma scheelei, were present in all seven areas that were sampled. A total of 551 leptocephali (22–166 mm TL) were collected, and A. scheelei was by far the most abundant species of leptocephali collected during the survey. The wide range of sizes in most areas indicated that spawning had occurred during a period of several months in many different areas, although the exact spawning locations were not determined. The larger size classes were more abundant in all areas except in Tomini Bay on the northeast side of Sulawesi Island. The highest catch rates were observed at the eastern edge of the Java Sea and to the north in the Celebes Sea near Makassar Strait. Premetamorphic leptocephali were also collected in surface samples at 11 stations (N=62), but metamorphosing leptocephali (N=86) were only caught in IKMT tows that fished from the surface to about 200 m. Metamorphosing leptocephali were collected primarily at two stations in the Java Sea and Makassar Strait where a surface layer of lower-salinity water was detected. Their total lengths (105.3–153.3 mm) and the largest premetamorphic individuals suggested that this species can reach maximum sizes of about 165 mm before beginning to metamorphose. It is hypothesized that this species may be abundant in the Indonesian Seas region and that it has ecological traits such as large size at recruitment and a small size at reproduction that have made it successful in many regions of the Indo-Pacific.     

The role of colonization in determining spatial patterns of Proscoloplos bondi sp. nov. (Orbiniidae: Annelida) in coralline algal turf

We describe Proscoloplos bondi sp. nov., a new species of orbinid polychaete found in coralline algal turf on rocky intertidal shores near Sydney, Australia. We used field sampling to describe P. bondi's patterns of spatial and temporal variation on a number of shores. P. bondi was significantly more abundant in low- than in mid-shore areas (ANOVA, P<0.05), but local populations were extremely variable in space and time. Despite extensive sampling, we did not find evidence of sexual reproduction in P. bondi, but commonly observed worms with regenerating heads and tails, which indicated the importance of asexual reproduction. We, therefore, tested the hypothesis that adult colonization contributes to its patterns of abundance. First, patches of artificial turf were placed near to and away from natural coralline turf and sampled after 2, 4 and 12 months. Generally, populations established themselves more quickly in patches of new habitat directly adjacent to coralline turf than in patches that were isolated. Second, patches of turf were deployed for 2-week periods in low- and mid-shore areas (repeated four times). Proscoloplos bondi were found significantly more often in patches in low-shore areas than in mid-shore areas and at some sites more than others (ANOVA, P<0.05), demonstrating the importance of adult colonization in determining patterns of abundance. Overall, the limited dispersal from spatially and temporally ephemeral populations of P. bondi combined with the patchiness of coralline turfs suggest that metapopulation dynamics may be important in the persistence of P. bondi on rocky shores.Communicated by G.F. Humphrey, Sydney     

Interlinked temporal changes in environmental conditions, chemical characteristics of sediments and macrofaunal assemblages in an estuarine intertidal sandflat (Seto Inland Sea, Japan)

Five field surveys were conducted in an estuarine intertidal sandflat of the Seto Inland Sea (Japan) between April 1994 and April 1995. Chlorophyll a, pheopigments, total organic carbon and acid-volatile sulphides (AVS) of surface and subsurface sediments, and macrofaunal assemblages were investigated in parallel at 15 stations. Monthly hydrological data of low-tide creek water adjacent to the flat were used as a complementary environmental characterisation of the study area. Strong temporal changes were found among sampling dates, most remarkably in autumn with a major increase of algal detritus and AVS, a sharp reduction in macrofaunal abundances and species richness, and a massive mortality of the clam Ruditapes philippinarum. This dystrophic event was preceded by a photoautotrophic and hypertrophic spring–summer characterized by abundant fresh (i.e., living) algal material, including microphytobenthos and macroalgae (Ulva sp.). In summer, abundant macrofaunal assemblages reached the highest biomass values (455 g wet weight m⁻² or 60.6 g ash free dry weight m⁻²), with a major contribution of filter-feeding bivalves Musculista senhousia and R. philippinarum. These are among the highest values reported in the literature for sedimentary shores. From autumn, there was a progressive recolonisation of macrofauna, initiated by few opportunistic polychaetes (e.g., Cirriformia tentaculata and Polydora sp.), apparently promoting a fast sediment recovery in winter, and followed by new bivalve recruits in the next spring. This study provides the first evidence of significant and interlinked within-year changes in chemical characteristics of sediments and macrofaunal assemblages in an estuarine intertidal flat at a small spatial scale (i.e., tens of meters). This demonstrates the high temporal variability of species–environment relations in these systems and a close relationship in seasonally driven trophodynamic processes among primary producers and benthic consumers. We conclude that a thorough parallel evaluation of the temporal changes in chemical characteristics of sediments should be taken into account in assessing the year-round distribution and changes of intertidal macrofauna, particularly in eutrophic, estuarine intertidal flats.An erratum to this article can be found at     

Genetic structure of a scleractinian coral, Mycedium elephantotus, in Taiwan

The genetic structure of Mycedium elephantotus (Pallas, 1766) populations from three regions around Taiwan was examined using allozyme electrophoresis. Eight loci were scored from seven enzyme systems. Seven loci were polymorphic under the 95% criterion. The high ratio of observed to expected genotypic diversities at the collection sites (G _O:G _E=0.8 to 1.0) indicate that M. elephantotus propagates predominantly by sexual reproduction. Allele frequencies of M. elephantotus differed significantly among regions (D=0.024 to 0.256, F _ST=0.032 to 0.218, p < 0.001), while populations among collection sites within each region were homogeneous (D=0.000 to 0.015, F _ST=0.010 to 0.022, p > 0.05). Genetic differentiation between populations from southern Taiwan and the Penghu Islands is greater than that between southern and northern Taiwan populations, although the former two regions are much closer geographically. The UPGMA dendrogram based on Nei's unbiased genetic distance showed a clear subdivision of populations into two groupings, northern Taiwan/Penghu Islands and southern Taiwan. A higher level of gene flow was found between M. elephantotus populations in northern Taiwan and the Penghu Islands (N _m=7.56) than that between populations in southern Taiwan and other regions (N _m=0.90 to 1.72). The pattern of genetic subdivision among regions is consistent with the pattern of ocean currents, indicating that genetic differentiation is likely driven by surface circulation vicariance. Received: 2 December 1997 / Accepted: 15 September 1998     

Blue mussels, Mytilus edulis, at the edge of the range: population structure, growth and biomass along a salinity gradient in the north-eastern Baltic Sea

The blue mussel, Mytilus edulis, is the most conspicuous animal species in the northern Baltic rocky sublittoral. In the studied area the species lives at the margin of its salinity tolerance. Although dwarfed by the low-salinity conditions, blue mussels in the northern Baltic are very abundant and have a decisive role in the benthic and pelagic ecosystems. We studied abundance, size distribution, biomass and growth rate of blue mussels along a 270 km salinity gradient in the northern Baltic Sea. Samples (n=317, 1998-1999) from moderately exposed and exposed rocky shores at seven study areas were collected in the southern Archipelago Sea in the west and into the central Gulf of Finland in the east, where the species is becoming increasingly rare. The results show a marked decline in mean mussel size and biomass from the saline west to the less saline east. The growth rate also decreased with lower ambient salinity. However, abundance of small mussels was considerably higher in the central and eastern parts of the study area. Vertically, the highest biomass was recorded at intermediate depths (5 and 8 m), being lower at both shallower (3 m) and deeper bottoms (12 m). It is concluded that salinity is the foremost factor determining size structure and growth rate among populations within the area. The results suggest that predation further influences the population structure of blue mussels living at the edge of their range in the central Gulf of Finland ultimately set by their salinity tolerance.     

Mesozooplankton communities in the Aegean and Black Seas: a comparative study

An attempt was made for a comparative study of the mesozooplankton communities between the Aegean and Black Seas. These areas are in connected through the Sea of Marmara, the Bosporus and the Dardanelles straits. The comparison was mainly based on data collected both in coastal and offshore waters, by the Hellenic Centre for Marine Research (Greece), the Shirshov Institute of Oceanology (Russia), the Institute of Biology of Southern Seas (Ukraine) and the Institute of Oceanology (Bulgaria). Our data revealed important differentiation in terms of species composition and interannual fluctuations of zooplankton quantity. Among the common copepod species, those presenting an eurytherm and/or euryhaline character (e.g. Acartia clausi, Paracalanus parvus, Penilia avirostris, Podon polyphemoides) were found dominant in the Black Sea and common in the Aegean Sea. Decreased dissimilarity of species composition seems to exist between the North Aegean Sea and the Black Sea, as well as between the coastal areas of the Black Sea and those affected by pollution in the Aegean Sea. A common feature of both seas is the existence of spatial differentiation in terms of the quantity of zooplankters due to anthropogenic and/or natural influences. The pattern of this differentiation seems to vary interannually in the Black Sea, depending either on the abundance of mesozooplankton predators (indigenous or invasive species) or on global climatic changes. Although the Black Sea is generally richer in zooplankton than the Aegean Sea, the significant decrease in the quantity of zooplankton from the early 1980s to the mid-1990s, due to the above factors, resulted in quasi-similar values in both areas. Black Sea mesozooplankton has revealed strong interannual variability both quantitatively and qualitatively, whereas no significant variability was detected in the Aegean Sea. This difference could be attributed both to variant anthropogenic forcing on these ecosystems and to the sensitive character of the semi-enclosed Black Sea.Communicated by M.E. Vinogradov, Moscow     

Seasonal changes in antibacterial activity of North Sea water

During 1969 and 1970, the antibacterial activity of North Sea water was investigated at Helgoland (southern North Sea). Tests were performed with resting cells of Escherichia coli, Staphylococous aureus and Serratia marinorubra, inoculated in freshly sampled sea water used raw or after filter sterilization. Simultaneously, growth of indigenous bacterial populations which occurred in the presence, as well as in the absence (only 1970), of test bacteria was controlled. Seasonal changes in inactivation of test cells and multiplication of marine bacteria were correlated with the life cycles of several diatom species. Breakdown of phytoplankton flowerings produced the most pronounced influence on antibacterial activity of sea water. Sometimes, enhancement of kill rate could be established during growth periods of various algal species, too. From the results obtained, it is concluded that the inactivation capacity of sea water depends, to a considerable degree, on the availability of nutritive organic matter, the concentration of which changes according to phytoplankton development. Strain-specific differences in resistance to inimical action of sea water are, in part, correlated with the ability of test cells to use, and to compete with, marine bacteria for nutrients from the sea. A somewhat modified interpretation of antibacterial activity of sea water is presented.     

Distribution of euphausiid assemblages in the Mediterranean Sea

Eleven species of euphausiids from 24 Isaac-Kidd Midwater Trawl (IKMT) night collections taken at stations throughout the Mediterranean Sea were counted. The frequency of occurrence and dominance of individual species and percent similarity faunal analysis of the euphausiid community were used to describe changes in faunal composition between geographical areas and differences in vertical distribution. Although most species were widespread, three distinct patterns of abundance were apparent: Euphausia krohnii, Nematoscelis megalops, Meganyctiphanes norvegica, and Stylocheiron abbreviatum predominated in western basin areas west of the Tyrrhenian Sea; Euphausia hemigibba, Thysanopoda aequalis, and Stylocheiron longicorne predominated in the Tyrrhenian Sea and eastern Mediterranean Sea; Euphausia brevis and Stylocheiron suhmii predominated in the eastern Mediterranean Sea. Percent similarity analysis of data from the IKMT samples and data from Ruud (1936) indicates the Tyrrhenian Sea fauna at the time of the collections was more similar to eastern Mediterranean areas than to most other areas in the western basin, although the degree of similarity was dependent, to some extent, on the depth at which the samples were collected. The composition of euphausiids living above 150 m at night in this area was more similar to eastern basin areas, while the composition of deeper living forms was more similar to those of the rest of the western basin. Comparison of euphausiids collected at three points over a 60 year time-span in the Balearic Sea shows the similarity in composition to be greater within the area over time than between adjacent areas in the western Mediterranean Sea.Contribution No. 2732 from the Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA. This research was supported by the Atomic Energy Commission Contract AT (30-1)-3862, ref. NYO-3862-49, National Science Foundation Grant GA 29303 and Office of Naval Research Contract N00014-71-C-0284.     

Killing of marine phytoplankton by a gliding bacterium Cytophaga sp., isolated from the coastal sea of Japan

A marine gliding bacterium Cytophaga sp. (strain J18/M01) was isolated from Harima-Nada, eastern Seto Inland Sea, Japan in 1990. This bacterium preys upon various species of marine phytoplankton. All of the five raphidophycean flagellates, all of the four diatoms, and one of the two dinoflagellates examined were killed within a few days when cultured with the bacterium. The bacterium presumably achieves this by direct attack, because the culture filtrate in which host organisms were totally destroyed had no significant effects on the growth of the same host organism (Chattonella antiqua). If one or a few bacterial cells were inoculated into C. antiqua culture, all of the host organisms were killed. The bacterium proliferated in filter-sterilized seawater, suggesting its ubiquitous existence in the coastal sea. The killing of phytoplankton by bacteria such as Cytophaga sp. J18/M01 may be a significant factor influencing the population dynamics of phytoplankton in nature and may contribute to the sudden disappearance of red tides in the coastal sea. Bacterial destruction of phytoplankton may also be a factor that regulates primary productivity in marine ecosystems.     

Seasonal fluctuations in the abundance of populations of marine cladocerans and their resting eggs in the Inland Sea of Japan

Seasonal fluctuations in the abundance of resting eggs of four species of marine cladocerans, Penilia avirostris Dana, Podon polyphemoides (Leuckart), Evadne tergestina Claus and Evadne nordmanni Lovén, were investigated in association with their planktonic populations in the central part of the Inland Sea of Japan for a period of over two years. Most numerous were the eggs of P. avirostris, followed by those of the species in the aforementioned order. There was a marked seasonal fluctuation in the number of eggs that was closely correlated with the occurrence of the planktonic population for each species. The egg-number was highest just before the planktonic population disappeared from the water column, and gradually decreased thereafter until a minimum value was reached shortly before the new planktonic population appeared in the next season. The pattern of fluctuation in number was found to be very similar among all four species, indicating strongly that the cladoceran populations in this warm temperate sea may persist either as plankton in warmer seasons or as benthic resting eggs in colder seasons. The possible causes of the decrease in egg density in bottom sediments are discussed.     

Hierarchical population genetic structure in the commercially exploited shrimp <Emphasis Type="Italic">Crangon crangon</Emphasis> identified by AFLP analysis

The coastal shrimp Crangon crangon is an ecologically and commercially important species but there is limited knowledge of its genetic population structure. We utilised amplified fragment length polymorphisms (AFLPs) to investigate population differentiation among eight sampling locations comprising paired sites from north- and south-western Britain, the eastern English Channel and the Baltic Sea. Initial AMOVA and cluster analysis suggested strong differentiation, but outlier analysis identified three loci that might be subject to selection, one of which showed significant latitudinal variation in allele frequencies. Following exclusion of these outlier loci, and also of a divergent, genetically-impoverished sample from the UK Bristol Channel, cluster analysis revealed three major groupings, corresponding to geographical regions: western Britain, the eastern English Channel and the Baltic Sea. AMOVA identified significant differentiation both within and among these regions, with similar variation explained by each hierarchical level. C. crangon shows greater genetic structuring than has been found in many decapod crustaceans studied to date, and our results are consistent with unstable population sizes and gene flow restricted by distance and probably also hydrographic features. Further investigation of temporal stability in population structure is required, but broad-scale homogeneity of fishery stocks should not be assumed.     

Sewage discharges in oceanic islands: effects and recovery of eulittoral macrofauna assemblages

Sewage discharges are among the most common anthropogenic stressors on rocky shores. However, studies on benthic invertebrates’ responses to sewage pollution on insular assemblages are rare. In order to fulfil this gap, (i) the effects of sewage pollution and (ii) the recovery capacity of eulittoral insular assemblages were examined. The study was conducted on Terceira Island (Azorean Archipelago, Portugal), in four distinct areas: one impacted area (outfall in operation), one post-impacted area (decommissioned outfall) and two undisturbed reference areas. Results showed that the abundance of the dominant species changed between reference and impacted areas. More specifically, the abundance of limpets Patella candei, and barnacles Chthamalus stellatus decreased, while the abundance of littorinids Tectarius striatus and Melarhaphe neritoides increased near the sewage discharges. Seventeen months after removal of the outfall, limpet and barnacle populations had partially recovered, but littorinid populations had still not fully recovered. This study confirms the negative effects of sewage discharges on eulittoral assemblages, and provides information on the resilience of benthic species following the cessation of sewage disposal.