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  • image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
    Authors: Felden, Janine; Wenzhöfer, Frank; Boetius, Antje;

    The Hakon Mosby Mud Volcano is a highly active methane seep hosting different chemosynthetic communities such as thiotrophic bacterial mats and siboglinid tubeworm assemblages. This study focuses on in situ measurements of methane fluxes to and from these different habitats, in comparison to benthic methane and oxygen consumption rates. By quantifying in situ oxygen, methane, and sulfide fluxes in different habitats, a spatial budget covering areas of 10-1000 -m diameter was established. The range of dissolved methane efflux (770-2 mmol m-2 d-1) from the center to the outer rim was associated with a decrease in temperature gradients from 46°C to < 1°C m-1, indicating that spatial variations in fluid flow control the distribution of benthic habitats and activities. Accordingly, total oxygen uptake (TOU) varied between the different habitats by one order of magnitude from 15 mmol m-2 d-1 to 161 mmol m-2 d-1. High fluid flow rates appeared to suppress benthic activities by limiting the availability of electron acceptors. Accordingly, the highest TOU was associated with the lowest fluid flow and methane efflux. This was most likely due to the aerobic oxidation of methane, which may be more relevant as a sink for methane as previously considered in submarine ecosystems.

    image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/ PANGAEA - Data Publi...arrow_drop_down
    image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
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      image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/ PANGAEA - Data Publi...arrow_drop_down
      image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
  • image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
    Authors: Ingels, Jeroen; Billett, David; Kiriakoulakis, Kostas; Wolff, George A; +1 Authors

    Samples collected at two different depths (ca. 3200 and ca. 4200 m) in the Setúbal and Cascais canyons off the Portuguese coast, during the HERMES RRS Charles Darwin cruise CD179, were analysed for (1) sediment biogeochemistry (TOC, TN) and (2) composition, and structural and trophic diversity of nematode communities. Multivariate PERMANOVA analysis on the nematode community data revealed differences between sediment layers that were greater than differences between canyons, water depths, and stations. This suggests that biogeochemical gradients along the vertical sediment profile are crucial in determining nematode community structure. The interaction between canyon conditions and the nematode community is illustrated by biogeochemical patterns in the sediment and the prevalence of nematode genera that are able to persist in disturbed sediments. Trophic analysis of the nematode community indicated that non-selective deposit feeders are dominant, presumably because of their non-selective feeding behaviour compared to other feeding types, which gives them a competitive advantage in exploiting lower-quality food resources. This study presents a preliminary conceptual scheme for interactions between canyon conditions and the resident fauna.

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    image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
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      image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
  • image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
    Authors: Morris, K. J.; Herrera, S.; Gubili, C.; Tyler, P. A.; +2 Authors

    Despite being an abundant group of significant ecological importance the phylogenetic relationships of the Octocorallia remain poorly understood and very much understudied. We used 1132 bp of two mitochondrial protein-coding genes, nad2 and mtMutS (previously referred to as msh1), to construct a phylogeny for 161 octocoral specimens from the Atlantic, including both Isididae and non-Isididae species. We found that four clades were supported using a concatenated alignment. Two of these (A and B) were in general agreement with the of Holaxonia–Alcyoniina and Anthomastus–Corallium clades identified by previous work. The third and fourth clades represent a split of the Calcaxonia–Pennatulacea clade resulting in a clade containing the Pennatulacea and a small number of Isididae specimens and a second clade containing the remaining Calcaxonia. When individual genes were considered nad2 largely agreed with previous work with MtMutS also producing a fourth clade corresponding to a split of Isididae species from the Calcaxonia–Pennatulacea clade. It is expected these difference are a consequence of the inclusion of Isisdae species that have undergone a gene inversion in the mtMutS gene causing their separation in the MtMutS only tree. The fourth clade in the concatenated tree is also suspected to be a result of this gene inversion, as there were very few Isidiae species included in previous work tree and thus this separation would not be clearly resolved. A~larger phylogeny including both Isididae and non Isididae species is required to further resolve these clades.

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  • image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
    Authors: Bienhold, Christina; Pop Ristova, Petra; Wenzhöfer, Frank; Dittmar, Thorsten; +1 Authors

    Large organic food falls to the deep sea - such as whale carcasses and wood logs - support the development of reduced, sulfidic niches in an otherwise oxygenated, oligotrophic deep-sea environment. These transient hot spot ecosystems may serve the dispersal of highly adapted chemosynthetic organisms such as thiotrophic bivalves and siboglinid worms. Here we investigated the biogeochemical and microbiological processes leading to the development of sulfidic niches. Wood colonization experiments were carried out for the duration of one year in the vicinity of a cold seep area in the Nile deep-sea fan (Eastern Mediterranean) at depths of 1690 m. Wood logs were deployed in 2006 during the BIONIL cruise (RV Meteor M70/2 with ROV Quest, Marum, Germany) and sampled in 2007 during the Medeco-2 cruise (RV Pourquoi Pas? with ROV Victor 6000, Ifremer, France). Wood-boring bivalves played a key role in the initial degradation of the wood, the dispersal of wood chips and fecal matter around the wood log, and the provision of colonization surfaces to other organisms. Total oxygen uptake measured with a ROV-operated benthic chamber module was higher at the wood (0.5 m away) in contrast to 10 m away at a reference site (25 mmol m-2 d-1 and 1 mmol m-2 d-1, respectively), indicating an increased activity of sedimentary communities around the wood falls. Bacterial cell numbers associated with wood increased substantially from freshly submerged wood to the wood chip/fecal matter layer next to the wood experiments, as determined with Acridine Orange Direct Counts (AODC) and DAPI-stained counts. Microsensor measurements of sulfide, oxygen and pH were conducted ex situ. Sulfide fluxes were higher at the wood experiments when compared to reference measurements (19 and 32 mmol m-2 d-1 vs. 0 and 16 mmol -2 d-1, respectively). Sulfate reduction (SR) rates at the wood experiments were determined in ex situ incubations (1.3 and 2.0 mmol m-2 d-1) and fell into the lower range of SR rates previously observed from other chemosynthetic habitats at cold seeps. There was no influence of wood deposition on phosphate, silicate and nitrate concentrations, but ammonium concentrations were elevated at the wood chip-sediment boundary layer. Concentrations of dissolved organic carbon were much higher at the wood experiments (wood chip-sediment boundary layer) in comparison to measurements at the reference sites, which may indicate that cellulose degradation was highest under anoxic conditions and hence enabled by anaerobic benthic bacteria, e.g. fermenters and sulfate reducers. Our observations demonstrate that, after one year, the presence of wood at the seafloor had led to the creation of sulfidic niches, comparable to what has been observed at whale falls, albeit at lower rates.

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      image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/ PANGAEA - Data Publi...arrow_drop_down
      image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
  • image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
    Authors: Duffy, G. A.; Horton, T.; Billett, D. S. M.;

    Submarine canyons have often been identified as hotspots of secondary production with the potential to house distinct faunal assemblages and idiosyncratic ecosystems. Within these deep-sea habitats, assemblages of scavenging fauna play a vital role in reintroducing organic matter from large food falls into the wider deep-sea food chain. Free-fall baited traps were set at different depths within three submarine canyons on the Iberian Margin. Amphipods from the traps were identified to species level and counted. Scavenging amphipod assemblages were compared at different depths within each canyon and between individual canyon systems. Using data from literature, abyssal plain assemblages were compared to submarine canyon assemblages. Samples from canyons were found to contain common abyssal plain species but in greater than expected abundances. It is proposed that this is a result of the high organic carbon input into canyon systems owing to their interception of sediment from the continental shelf and input from associated estuarine systems. Community composition differed significantly between the submarine canyons and abyssal plains. The cause of this difference cannot be attributed to one environmental variable due to the numerous inherent differences between canyons and abyssal plains.

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    Authors: Pop Ristova, Petra; Wenzhöfer, Frank; Ramette, Alban; Felden, Janine; +1 Authors

    Cold seep ecosystems are highly productive, fragmented ecosystems of the deep-sea floor. They form worldwide where methane reaches the surface seafloor, and are characterized by rich chemosynthetic communities fueled by the microbial utilization of hydrocarbons. Here we investigated with in situ (benthic chamber, microprofiler) and ex situ (pore water constituents, turnover rates of sulfate and methane, prokaryote abundance) techniques reduced sites from three different seep ecosystems in the Eastern Mediterranean deep-sea. At all three cold seep systems, the Amon Mud Volcano, Amsterdam Mud Volcano and the Nile Deep Sea Fan Pockmark area, we observed and sampled patches of highly reduced, methane-seeping sulfidic sediments which were separated by tens to hundreds of (kilo)meters with non-reduced oxygenated seafloor areas. All investigated seep sites were characterized by gassy, sulfidic sediments of blackish color, of which some were overgrown with thiotrophic bacterial mats. Fluxes of methane and oxygen, as well as sulfate reduction rates varied between the different sites.

    image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/ PANGAEA - Data Publi...arrow_drop_down
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    Authors: Feseker, Tomas; Boetius, Antje; Wenzhöfer, Frank; Blandin, Jérome; +5 Authors

    Submarine mud volcanoes are considered an important source of methane to the water column. However, the temporal variability of their fluid transport including mud and methane emissions is largely unknown. Assuming that this transport was continuous and at steady state, methane emissions were previously proposed to result from a dynamic equilibrium between upward migration and consumption at the seabed by methane-consuming microbes. Here we have investigated non-steady state situations of vigorous mud movements and their reflection in fluid flow, seabed temperature and bathymetry. Time series of pressure, temperature, pH and seafloor photography were collected by a benthic observatory (LOOME) for 431 days at the active Håkon Mosby mud volcano. These new data document eruptions, which were accompanied by pulses of hot subsurface fluids and triggered rapid sediment uplift and lateral movement, as well as emissions of free gas.

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    Authors: Ingels, Jeroen; Tchesunov, Alexei; Vanreusel, Ann;

    The Gollum Channels and Whittard Canyon (NE Atlantic) are two areas that receive high input of organic matter and phytodetritus from euphotic layers, but they are typified by different trophic and hydrodynamic conditions. Sediment biogeochemistry was analysed in conjunction with structure and diversity of the nematode community and differences were tested between study areas, water depths (700 m vs 1000 m), stations, and sediment layers. The Gollum Channels and Whittard Canyon harboured high meiofauna abundances (1054-1426 ind. 10 cm**-2) and high nematode diversity (total of 181 genera). Next to enhanced meiofauna abundance and nematode biomass, there were signs of high levels of organic matter deposition leading to reduced sedimentary conditions, which in turn structured the nematode community. Striking in this respect was the presence of large numbers of 'chemosynthetic' Astomonema nematodes (Astomonema southwardorum, Order Monhysterida, Family Siphonolaimidae). This genus lacks a mouth, buccal cavity and pharynx and possesses a rudimentary gut containing internal, symbiotic prokaryotes which have been recognised as sulphur-oxidising bacteria. Dominance of Astomonema may indicate the presence of reduced environments in the study areas, which is partially confirmed by the local biogeochemical environment. The nematode communities were mostly affected by sediment layer differences and concomitant trophic conditions rather than other spatial gradients related to study area, water depth or station differences, pointing to small-scale heterogeneity as the main source of variation in nematode structure and function. Furthermore, the positive relation between nematode standing stocks, and quantity and quality of the organic matter was stronger when hydrodynamic disturbance was greater. Analogically, this study also suggests that structural diversity can be positively correlated with trophic conditions and that this relation is tighter when hydrodynamic disturbance is greater.

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    Authors: Guerreiro, Catarina Alexandra Vicente, 1978-;

    A presente tese de doutoramento tem por objectivo contribuir para o conhecimento geral dos cocolitóforos na transição costeiro-neritico-oceânica, a sua distribuição ao largo de Portugal, e o seu potencial enquanto traçador (paleo)ecológico e (paleo)ceanográfico no contexto de canhões submarinos. Para compreender a relação entre os coccolitóforos e as condições ambientais, os resultados foram interpretados numa perspectiva multidisciplinar, integrados num conjunto significativo de dados relativos às características ecológicas e hidrológicas das massas de água superficiais da margem Portuguesa central (i.e. nutrientes, clorofila, temperatura, salinidade, turbidez, dados de vento e de satélite), e às caracteristicas sedimentológicas dos fundos marinhos (i.e. composição, textura e acumulação sedimentar). As variações ecológicas mais significativas observadas nas comunidades de cocólitoforos ao largo de Portugal ocorreram ao longo do gradiente costa-oceano. Dois grupos taxonómicos principais de comportamento ecológico oposto foram observados na zona fótica, marcando a transição de espécies adaptadas a regimes mais estáveis (K-selected) preferencialmente distribuídas no domínio oceânico, para espécies oportunistas (r-selected) mais frequentes nas regiões neritico-costeiras. Este gradiente também foi observado nas associações de cocólitos preservadas nos sedimentos superficiais do fundo marinho, tanto ao longo dos canhões submarinos como nas suas áreas adjacentes, embora várias diferenças tenham sido reconhecidas entre os dois tipos de ambientes. Na zona fótica, as espécies Emiliania huxleyi e Gephyrocapsa oceanica revelaram um comportamento claramente r-selected, tendo sido as principais responsáveis pelo bloom de cocolitóforos observado ao largo do Cabo Carvoeiro. Este bloom ocorreu em resposta à combinação favorável de descarga fluvial de final de inverno com ventos predominantes de norte sobre a plataforma, e condições de céu limpo. Em apenas alguns dias, as concentrações de cocolitóforos e biomassa de fitoplâncton (Chl-a) mais do que triplicaram, indicando claramente a capacidade destes organismos em tirar partido das condições favoráveis em luz e nutrientes providenciadas pela pluma fluvial superficial. As duas espécies desenvolveram-se em conjunto com outros fitoplânctónicos oportunistas (Chaetoceros s.l., Thalassiosira s.l, Skeletonema s.l.), confirmando o seu papel enquanto espécies r-selected de primeiro estádio da sucessão fitoplanctónica, caracterizadas por terem um potencial de desenvolvimento rápido em ambientes ricos em nutrientes. Coronosphaera mediterranea e Syracolithus dalmaticus também responderam positivamente às condições favoráveis no decorrer do cruzeiro, embora menos notavelmente do que as espécies anteriores. Pelo contrário, os grupos Syracosphaera spp. e Ophiaster spp. revelaram características típicas de espécies K-selected, consistentemente mais abundantes em águas mais oceânicas e menos eutróficas, afastadas da influência da pluma fluvial, ou distribuídas em níveis abaixo da pluma nas regiões mais neritico-costeiras. Gephyrocapsa ericsonii e Gephyrocapsa muellerae dominaram a comunidade de cocolitóforos sob condições de baixa produtividade na plataforma, mas não quando as águas de regiões nerítico-costeiras se tornaram favoráveis ao bloom de espécies oportunistas. No sedimento superficial de fundo, enquanto as espécies C. mediterranea, Helicosphaera carteri e a G. oceanica (e, em menor grau, Coccolithus pelagicus) registaram uma distribuição marcadamente costeira, os cocólitos produzidos pelas espécies Calcidiscus leptoporus, Umbilicosphaera sibogae, Umbellosphaera irregularis e Rhabdosphaera spp. foram observados preferencialmente distribuidos para offshore e para sul, possivelmente indicadoras de uma maior influência da ENACWst na zona mais meridional da area de estudo (i.e. a sul do Esporão da Estremadura). G. muellerae revelou ser, de longe, a espécie mais abundante e amplamente distribuída, embora geralmente mais oceânica, particularmente nas regiões adjacentes aos canhões submarinos. Enquanto certas especies mais robustas (i.e. C. leptoporus, C. pelagicus, H. carteri) tiveram um registo mais relevante no sedimento em comparação com a coluna de água, géneros de morfologia mais frágil e de menores dimensões (i.e. Syracosphaera spp., Ophiaster spp., S. dalmaticus) não foram observadas no sedimento, provavelmente traduzindo os efeitos da dissolução e fragmentação selectiva. No entanto, quando considerando percentagens de espécies de cocólitos de dimensão semelhante (≥3 μm), não foi observada qualquer evidência mais consistente de que tenha havido transporte ou preservação preferencial de especies individuais, confirmando que o signal preservado no sedimento apresenta uma forte componente (paleo)ecológica, e não meramente tafonómica. Em termos de dinâmica de canhão submarino, o Canhão da Nazaré foi observado a ter o efeito de conduta preferencial de águas oceânicas para regiões bastante proximais da plataforma continental Portuguesa, as quais se encontravam empobrecidas em nutrientes em comparação com as massas de água neríticas e costeiras durante o período de final de inverno monitorizado durante o cruzeiro. A ocorrência singular de Discosphaera tubifera e Palusphaera vandelii na cabeceira do canhão, juntamente com C. leptoporus é interpretada enquanto traçadora do deslocamento preferencial de ENACWst intensificado ao longo do troço superior do canhão, durante o inverno. Um “hotspot” de diversidade de cocolitóforos foi observado na coluna de água desta área, incluindo tanto espécies oceânicas-oligotróficas como espécies costeiras oportunistas, tendo sido interpretado enquanto reflexo da capacidade do canhão em promover trocas de massas de água entre regiões neritico-costeiras e regiões mais oceânicas, particularmente durante o inverno. Adicionalmente, a persistente ocorrência de elevadas concentrações de Chl-a à superfície obtidas por imagens de satélite, particularmente entre Março e Outubro (2006-2011), sugerem a cabeceira do Canhão da Nazaré como sendo o sector mais persistentemente produtivo do troço superior-médio do canhão. Percentagens mais elevadas de cocólitos de espécies costeiro-neriticas em sedimentos da parte superior do Canhão da Nazaré corroboram esta hipótese, possivelmente traduzindo a forte proximidade da sua cabeceira à linha de costa, resultando numa maior influência da dinâmica costeira e na sua intensificação na cabeceira e área adjacente (i.e. upwelling, ondas internas), e em condições mais dinâmicas e ricas em nutrientes para as quais as espécies r-selected estão melhor adaptadas. Pelo contrário, percentagens mais elevadas de cocólitos de espécies oceânicas no Canhão de Lisboa-Setúbal parecem traduzir um ambiente em geral mais oceânico-pelágico neste No sedimento superficial de fundo, enquanto as espécies C. mediterranea, Helicosphaera carteri e a G. oceanica (e, em menor grau, Coccolithus pelagicus) registaram uma distribuição marcadamente costeira, os cocólitos produzidos pelas espécies Calcidiscus leptoporus, Umbilicosphaera sibogae, Umbellosphaera irregularis e Rhabdosphaera spp. foram observados preferencialmente distribuidos para offshore e para sul, possivelmente indicadoras de uma maior influência da ENACWst na zona mais meridional da area de estudo (i.e. a sul do Esporão da Estremadura). G. muellerae revelou ser, de longe, a espécie mais abundante e amplamente distribuída, embora geralmente mais oceânica, particularmente nas regiões adjacentes aos canhões submarinos. Enquanto certas especies mais robustas (i.e. C. leptoporus, C. pelagicus, H. carteri) tiveram um registo mais relevante no sedimento em comparação com a coluna de água, géneros de morfologia mais frágil e de menores dimensões (i.e. Syracosphaera spp., Ophiaster spp., S. dalmaticus) não foram observadas no sedimento, provavelmente traduzindo os efeitos da dissolução e fragmentação selectiva. No entanto, quando considerando percentagens de espécies de cocólitos de dimensão semelhante (≥3 μm), não foi observada qualquer evidência mais consistente de que tenha havido transporte ou preservação preferencial de especies individuais, confirmando que o signal preservado no sedimento apresenta uma forte componente (paleo)ecológica, e não meramente tafonómica. Em termos de dinâmica de canhão submarino, o Canhão da Nazaré foi observado a ter o efeito de conduta preferencial de águas oceânicas para regiões bastante proximais da plataforma continental Portuguesa, as quais se encontravam empobrecidas em nutrientes em comparação com as massas de água neríticas e costeiras durante o período de final de inverno monitorizado durante o cruzeiro. A ocorrência singular de Discosphaera tubifera e Palusphaera vandelii na cabeceira do canhão, juntamente com C. leptoporus é interpretada enquanto traçadora do deslocamento preferencial de ENACWst intensificado ao longo do troço superior do canhão, durante o inverno. Um “hotspot” de diversidade de cocolitóforos foi observado na coluna de água desta área, incluindo tanto espécies oceânicas-oligotróficas como espécies costeiras oportunistas, tendo sido interpretado enquanto reflexo da capacidade do canhão em promover trocas de massas de água entre regiões neritico-costeiras e regiões mais oceânicas, particularmente durante o inverno. Adicionalmente, a persistente ocorrência de elevadas concentrações de Chl-a à superfície obtidas por imagens de satélite, particularmente entre Março e Outubro (2006-2011), sugerem a cabeceira do Canhão da Nazaré como sendo o sector mais persistentemente produtivo do troço superior-médio do canhão. Percentagens mais elevadas de cocólitos de espécies costeiro-neriticas em sedimentos da parte superior do Canhão da Nazaré corroboram esta hipótese, possivelmente traduzindo a forte proximidade da sua cabeceira à linha de costa, resultando numa maior influência da dinâmica costeira e na sua intensificação na cabeceira e área adjacente (i.e. upwelling, ondas internas), e em condições mais dinâmicas e ricas em nutrientes para as quais as espécies r-selected estão melhor adaptadas. Pelo contrário, percentagens mais elevadas de cocólitos de espécies oceânicas no Canhão de Lisboa-Setúbal parecem traduzir um ambiente em geral mais oceânico-pelágico neste canhão, resultante da sua maior distância aos efeitos da dinâmica costeira e ausência de transporte sedimentar significativo ao longo do seu talvegue, na actualidade. Uma mistura mais acentuada de cocólitos produzidos pelas duas associações (paleo)ecológicas, i.e. a costeiro-neritica e a oceânica, foi observada nos sedimentos dos canhões, em comparação com as regiões da plataforma e vertente regiões adjacentes aos canhões onde o gradiente (paleo)ecológico costa-oceano é mais distintivo. Esta assinatura nos canhões confirma a capacidade destas estrutura em promover trocas de massas de água costeiras e oceânicas (sinal ecológico), embora o importante papel das ondas internas e dos ocasionais fluxos gravíticos de sedimentos em perturbar e homogeneizar o registo sedimentar (sinal tafonómico) nos canhões deva ser sempre considerado. Ao evitar os problemas estatísticos tipicamente associados às determinações percentuais, a Análise de Dados Composicionais (i.e. a abordagem isometric log-ratio) permitiu validar e confirmar o gradiente ecológico costa-oceano observado nas associações de cocólitos no sedimento. A boa concordância entre os dois métodos sugere que o sinal (paleo)ecológico preservado na cobertura sedimentar da margem Portuguesa central é robusto, mesmo junto à costa e no contexto das condições dinâmicas vigentes nos canhões submarinos. Pelo contrário, tanto as concentrações de cocólitos (nanno/g) como os fluxos (nanno/cm2/yr) revelaram padrões de distribuição espacial onde as relações ecológicas interespécies parecem estar “mascaradas” por factores sedimentares/tafonómicos, particularmente nas zonas costeiras e nos canhões. O aumento de cocólitos para offshore reflecte não só a natureza primordialmente oceânica dos cocolitóforos, mas também a ocorrência de selecção textural, resultando na acumulação preferencial de cocólitos em regiões menos energéticas da vertente continental média e inferior, e em certas zonas dos canhões as quais funcionam como armadilhas morfológicas temporárias de sedimentos. Fluxos mais elevados nos troços superiores dos canhões reflectem o seu papel enquanto depocentros preferenciais de sedimentos finos na plataforma continental, tanto de origem litogénica como biogénica, incluindo cocólitos provenientes de fluxos verticais (produtividade – sinal ecológico) e laterais (resuspensão e advecção – sinal tafonómico). Este estudo ilustra cabalmente a rapidez de resposta dos cocolitóforos a variações meteorológicas e hidrográficas de curto-prazo e ao surgimento de condições ambientais favoráveis na costa Portuguesa, contrariando a noção amplamente aceite de que estes organismos representam um grupo fitoplanctónico calcário uniforme típico de ambientes de baixa turbulência, baixo conteúdo nutritivo e intensa luminosidade. Embora haja ainda muito trabalho a fazer no que respeita ao impacto dos canhões submarinos sobre a dinâmica oceanográfica e fitoplanctónica ao largo de Portugal, as associações de cocólitos preservados no sedimento revelaram-se úteis enquanto traçadores de gradientes (paleo)ecológicos e (paleo)oceanográficos vigentes na margem Portuguesa central. Os resultados confirmam estudos anteriores focados na complexa dinâmica hidro-sedimentar vigente nos canhões submarinos da Nazaré e de Lisboa-Setúbal. This thesis aims to contribute to the knowledge of coccolithophores from coastal-neriticoceanic transitional settings, their distribution offshore central Portugal, and their potential as (paleo)ecological and (paleo)ceanographic proxy in the context of submarine canyons. In order to achieve a good understanding of the relationship of coccolithophores with the environmental setting, results were interpreted on a multidisciplinary basis, integrating a significant data set concerning the hydrological characteristics of surface waters of the central Portuguese margin (i.e. nutrients, chlorophyll, temperature, salinity, turbidity, wind data) and seabed sedimentological characteristics (i.e. sediment bulk composition, particle size and sediment accumulation). The most striking variations in phytoplankton communities off central Portugal occurred along the coastal-oceanic lateral gradient. Two principal groups of taxa of opposite ecological behaviour were observed in the photic layer, with K-selected taxa preferentially distributed in the open ocean, and r-selected taxa preferentially occurring in more coastal-neritic regions. Such gradient was also reflected in coccolith assemblages preserved in surface sediments on the seabed, both along the submarine canyons and on the adjacent shelf and slope areas, although several differences were noticed between the two environments. In the photic layer, Emiliania huxleyi and Gephyrocapsa oceanica exhibited the typical behaviour of r-selected species, being the main responsible for a coccolithophore bloom occurring in the Nazaré Canyon region (off Cape Carvoeiro). This bloom occurred in response to late winter continental runoff combined with northerly winds prevailing over the shelf, under clear sky conditions. Within a few days, coccolithophore cell densities and associated phytoplankton biomass (Chl-a) more than tripled, indicating that phytoplankton was taking profit from favourable nutrient and light conditions provided by the superficial buoyant plume. The two species were developing together with other opportunistic phytoplankton genera (Chaetoceros s.l., Thalassiosira s.l, Skeletonema s.l.), confirming their role as early succession r-selected taxa, capable of rapid growth within nutrient-rich environments. Coronosphaera mediterranea and Syracolithus dalmaticus also responded to the favourable conditions, but less so than E. huxleyi and G. oceanica. On the contrary, Syracosphaera spp. and Ophiaster spp. revealed typical characteristics of K-selected species, being consistently more abundant in more oceanic and less eutrophic waters, away from the influence of river runoff, and extending well below the nutrient-rich surface layer in the more coastal-neritic regions. Gephyrocapsa ericsonii and Gephyrocapsa muellerae dominated the coccolithophore community under steady-state low-productive conditions over the shelf, until shelf and coastal waters became favourable for rselected species to bloom. In the seafloor sediment, coccoliths from C. mediterranea, Helicosphaera carteri and G. oceanica (and to a lesser extent, Coccolithus pelagicus) exhibited a markedly coastal distribution, whereas coccoliths from Calcidiscus leptoporus, Umbilicosphaera sibogae, Umbellosphaera irregularis and Rhabdosphaera spp. were preferentially distributed further offshore and southwards, possibly tracing the preferential onflow of ENACWst into the southern part of the central Portuguese shelf (i.e. south of Estremadura spur). G. muellerae was by far the most abundant and broadly distributed species in the sediment, with highest abundances in the more oceanic areas, particularly outside the canyons. Whereas larger and more robust coccolith species (i.e. C. leptoporus, C. pelagicus, H. carteri) were better represented in the sediment in comparison to the overlying water column, smaller and more delicate species from the genera Syracosphaera spp., Ophiaster spp. and S. dalmaticus were not found in the sediments, most likely due to selective dissolution and breaking. Yet, considering the coccolith species assemblage preserved in the sediment, no consistent evidence for selective transport or preservation of individual taxa in relation to coccolith size was found, strongly suggesting the signal within the sediment is mostly (paleo)ecological rather than merely taphonomical. In terms of canyon dynamics, the Nazaré Canyon was observed to act as a preferential conduit for oceanic waters into very proximal regions of the Portuguese shelf, which were nutrient-depleted in comparison to neritic and coastal water masses during the monitored late winter period. The single occurrence of Discosphaera tubifera and Palusphaera vandelii in this proximal area, together with C. leptoporus, is interpreted as tracing the onflow of ENACWst intensified along the upper canyon during winter. A coccolithophore diversity “hotspot” was noticed in the canyon head, including both oligotrophic-oceanic and opportunistic-coastal taxa, interpreted as reflecting the canyon’s capacity to promote exchange of water masses between neritic-coastal and oceanic regions during winter. In addition, Chl-a time series obtained from satellite data (2006-2011) revealed that the canyon head is often the stage of high productivity between March and October, which makes this region the most persistently productive part of the upper-middle canyon and nearby shelf. Highest percentages of coastal-neritic coccoliths in sediments from the upper Nazaré Canyon support this hypothesis, possibly reflecting the greater proximity of the head of this canyon to the coastline. The stronger influence of coastal dynamics and their intensification in this area (i.e. upwelling, internal waves), gives rise to more dynamic and nutrient-rich conditions to which r-selected coccolithophore species are better adapted. On the contrary, higher percentages of coccoliths from oceanic taxa in the Lisbon-Setúbal Canyon suggest that a generally more oceanic-pelagic environment prevails in this canyon, explained by its greater distance from coastal dynamics and present-day lack of down-canyon sediment transport. Enhanced percentages of G. muellerae in the upper Lisbon-Setúbal Canyon may be indicating preferential onflow of oceanic water masses through the canyon and/or upcanyon transport of resuspended coccoliths in the bottom boundary layer. More pronounced mixing of coccoliths from both coastal-neritic and oceanic coccolith assemblages was observed in sediments from the canyons, in comparison to the canyons adjacent shelf-slope regions where the coast-ocean (paleo)ecological gradient is more distinctive, confirming the capacity of these structures in promoting the exchange between coastal and oceanic water masses (ecological signal). Nevertheless, the role of internal tides and occasional sediment gravity flows in disturbing and homogenizing the sedimentary record within canyons (taphonomical signal) should also be considered. While avoiding the major statistical problems potentially associated with percentages, Compositional Data Analysis involving the use of isometric log-ratios allowed validation of coast-to-ocean ecological trends determined from sediment coccolith percentages. The good agreement between the two methods suggests that the coccolith (paleo)ecological signal preserved in sediments of the central Portuguese margin is robust, even near the coast and in the context of the highly dynamic submarine canyons. On the contrary, both coccolith concentrations (nanno/g) and fluxes (nanno/cm2/yr) showed spatial trends in which ecological inter-relationships appear to be masked by sedimentary/taphonomical factors, especially towards the coast and in the submarine canyons. The general increase of coccoliths further offshore reflects the oceanic nature of coccolithophores, but also physical sorting, resulting in preferential accumulation of coccoliths within finer-grained hemipelagic sediments that accumulate in more calm environments of the middle and lower slope and in certain parts of the canyons acting as temporary sediment morphological traps. Highest coccolith fluxes in the upper canyons reflect their role as preferential depocenters of fine-grained particles both lithogenic and biogenic. Biogenic fine particles include coccoliths from vertical (productivity - ecological signal) and lateral fluxes (resuspension and advection – taphonomical signal). This study strikingly illustrates the rapid response of coccolithophores to short-term meteorological and hydrographic variability creating favourable conditions for growth off central Portugal. These results contradict the accepted notion of coccolithophores being a uniform functional group of calcifying phytoplankton thriving in low-turbulence, low-nutrients and high-light environments. Whereas much work still needs to be done concerning the impact of the canyons on both oceanography and phytoplankton dynamics off central Portugal, coccoliths preserved in the seabed sediment appeared to be useful tracers of the prevailing (paleo)ecological and (paleo)oceanographic trends. The results support previous studies focused on the complex hydro-sedimentary dynamics prevailing in the Nazaré and Lisbon-Setúbal canyons. Fundação para a Ciência e a Tecnologia (FCT, SFRH/BD/41330/2007, projeto Cd Tox-CoN PTDC/MAR/102800/2008); projetos, EUROSTRATAFORM, HERMES (GOCE-CT-2005-511234),“Lead in Canyons” e “Pacemaker” Tese de doutoramento, Geologia (Paleontologia e Estatigrafia), Universidade de Lisboa, Faculdade de Ciências, 2013

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    Authors: Hunter, William Ross; Jamieson, Alan J; Huvenne, Veerle A I; Witte, Ursula;

    The Whittard canyon is a branching submarine canyon on the Celtic continental margin, which may act as a conduit for sediment and organic matter (OM) transport from the European continental slope to the abyssal sea floor. In situ stable-isotope labelling experiments (JC36-042-Spre01; JC36-100-Spre01) were conducted in the eastern and western branches of the Whittard canyon testing short term (3 - 7 day) responses of sediment communities to deposition of nitrogen-rich marine and nitrogen-poor terrigenous phytodetritus. Isotopic labels were traced into faunal biomass and bulk sediments, and the bacterial polar lipid fatty acids (PLFAs). These data files provide the data on macrofaunal and bacterial uptake of the isotopically-labelled organic carbon and nitrogen, and macrofaunal community composition at the two stations within the Whittard canyon

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    Authors: Felden, Janine; Wenzhöfer, Frank; Boetius, Antje;

    The Hakon Mosby Mud Volcano is a highly active methane seep hosting different chemosynthetic communities such as thiotrophic bacterial mats and siboglinid tubeworm assemblages. This study focuses on in situ measurements of methane fluxes to and from these different habitats, in comparison to benthic methane and oxygen consumption rates. By quantifying in situ oxygen, methane, and sulfide fluxes in different habitats, a spatial budget covering areas of 10-1000 -m diameter was established. The range of dissolved methane efflux (770-2 mmol m-2 d-1) from the center to the outer rim was associated with a decrease in temperature gradients from 46°C to < 1°C m-1, indicating that spatial variations in fluid flow control the distribution of benthic habitats and activities. Accordingly, total oxygen uptake (TOU) varied between the different habitats by one order of magnitude from 15 mmol m-2 d-1 to 161 mmol m-2 d-1. High fluid flow rates appeared to suppress benthic activities by limiting the availability of electron acceptors. Accordingly, the highest TOU was associated with the lowest fluid flow and methane efflux. This was most likely due to the aerobic oxidation of methane, which may be more relevant as a sink for methane as previously considered in submarine ecosystems.

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    Authors: Ingels, Jeroen; Billett, David; Kiriakoulakis, Kostas; Wolff, George A; +1 Authors

    Samples collected at two different depths (ca. 3200 and ca. 4200 m) in the Setúbal and Cascais canyons off the Portuguese coast, during the HERMES RRS Charles Darwin cruise CD179, were analysed for (1) sediment biogeochemistry (TOC, TN) and (2) composition, and structural and trophic diversity of nematode communities. Multivariate PERMANOVA analysis on the nematode community data revealed differences between sediment layers that were greater than differences between canyons, water depths, and stations. This suggests that biogeochemical gradients along the vertical sediment profile are crucial in determining nematode community structure. The interaction between canyon conditions and the nematode community is illustrated by biogeochemical patterns in the sediment and the prevalence of nematode genera that are able to persist in disturbed sediments. Trophic analysis of the nematode community indicated that non-selective deposit feeders are dominant, presumably because of their non-selective feeding behaviour compared to other feeding types, which gives them a competitive advantage in exploiting lower-quality food resources. This study presents a preliminary conceptual scheme for interactions between canyon conditions and the resident fauna.

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  • image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
    Authors: Morris, K. J.; Herrera, S.; Gubili, C.; Tyler, P. A.; +2 Authors

    Despite being an abundant group of significant ecological importance the phylogenetic relationships of the Octocorallia remain poorly understood and very much understudied. We used 1132 bp of two mitochondrial protein-coding genes, nad2 and mtMutS (previously referred to as msh1), to construct a phylogeny for 161 octocoral specimens from the Atlantic, including both Isididae and non-Isididae species. We found that four clades were supported using a concatenated alignment. Two of these (A and B) were in general agreement with the of Holaxonia–Alcyoniina and Anthomastus–Corallium clades identified by previous work. The third and fourth clades represent a split of the Calcaxonia–Pennatulacea clade resulting in a clade containing the Pennatulacea and a small number of Isididae specimens and a second clade containing the remaining Calcaxonia. When individual genes were considered nad2 largely agreed with previous work with MtMutS also producing a fourth clade corresponding to a split of Isididae species from the Calcaxonia–Pennatulacea clade. It is expected these difference are a consequence of the inclusion of Isisdae species that have undergone a gene inversion in the mtMutS gene causing their separation in the MtMutS only tree. The fourth clade in the concatenated tree is also suspected to be a result of this gene inversion, as there were very few Isidiae species included in previous work tree and thus this separation would not be clearly resolved. A~larger phylogeny including both Isididae and non Isididae species is required to further resolve these clades.

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    Authors: Bienhold, Christina; Pop Ristova, Petra; Wenzhöfer, Frank; Dittmar, Thorsten; +1 Authors

    Large organic food falls to the deep sea - such as whale carcasses and wood logs - support the development of reduced, sulfidic niches in an otherwise oxygenated, oligotrophic deep-sea environment. These transient hot spot ecosystems may serve the dispersal of highly adapted chemosynthetic organisms such as thiotrophic bivalves and siboglinid worms. Here we investigated the biogeochemical and microbiological processes leading to the development of sulfidic niches. Wood colonization experiments were carried out for the duration of one year in the vicinity of a cold seep area in the Nile deep-sea fan (Eastern Mediterranean) at depths of 1690 m. Wood logs were deployed in 2006 during the BIONIL cruise (RV Meteor M70/2 with ROV Quest, Marum, Germany) and sampled in 2007 during the Medeco-2 cruise (RV Pourquoi Pas? with ROV Victor 6000, Ifremer, France). Wood-boring bivalves played a key role in the initial degradation of the wood, the dispersal of wood chips and fecal matter around the wood log, and the provision of colonization surfaces to other organisms. Total oxygen uptake measured with a ROV-operated benthic chamber module was higher at the wood (0.5 m away) in contrast to 10 m away at a reference site (25 mmol m-2 d-1 and 1 mmol m-2 d-1, respectively), indicating an increased activity of sedimentary communities around the wood falls. Bacterial cell numbers associated with wood increased substantially from freshly submerged wood to the wood chip/fecal matter layer next to the wood experiments, as determined with Acridine Orange Direct Counts (AODC) and DAPI-stained counts. Microsensor measurements of sulfide, oxygen and pH were conducted ex situ. Sulfide fluxes were higher at the wood experiments when compared to reference measurements (19 and 32 mmol m-2 d-1 vs. 0 and 16 mmol -2 d-1, respectively). Sulfate reduction (SR) rates at the wood experiments were determined in ex situ incubations (1.3 and 2.0 mmol m-2 d-1) and fell into the lower range of SR rates previously observed from other chemosynthetic habitats at cold seeps. There was no influence of wood deposition on phosphate, silicate and nitrate concentrations, but ammonium concentrations were elevated at the wood chip-sediment boundary layer. Concentrations of dissolved organic carbon were much higher at the wood experiments (wood chip-sediment boundary layer) in comparison to measurements at the reference sites, which may indicate that cellulose degradation was highest under anoxic conditions and hence enabled by anaerobic benthic bacteria, e.g. fermenters and sulfate reducers. Our observations demonstrate that, after one year, the presence of wood at the seafloor had led to the creation of sulfidic niches, comparable to what has been observed at whale falls, albeit at lower rates.

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    Authors: Duffy, G. A.; Horton, T.; Billett, D. S. M.;

    Submarine canyons have often been identified as hotspots of secondary production with the potential to house distinct faunal assemblages and idiosyncratic ecosystems. Within these deep-sea habitats, assemblages of scavenging fauna play a vital role in reintroducing organic matter from large food falls into the wider deep-sea food chain. Free-fall baited traps were set at different depths within three submarine canyons on the Iberian Margin. Amphipods from the traps were identified to species level and counted. Scavenging amphipod assemblages were compared at different depths within each canyon and between individual canyon systems. Using data from literature, abyssal plain assemblages were compared to submarine canyon assemblages. Samples from canyons were found to contain common abyssal plain species but in greater than expected abundances. It is proposed that this is a result of the high organic carbon input into canyon systems owing to their interception of sediment from the continental shelf and input from associated estuarine systems. Community composition differed significantly between the submarine canyons and abyssal plains. The cause of this difference cannot be attributed to one environmental variable due to the numerous inherent differences between canyons and abyssal plains.

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    Authors: Pop Ristova, Petra; Wenzhöfer, Frank; Ramette, Alban; Felden, Janine; +1 Authors

    Cold seep ecosystems are highly productive, fragmented ecosystems of the deep-sea floor. They form worldwide where methane reaches the surface seafloor, and are characterized by rich chemosynthetic communities fueled by the microbial utilization of hydrocarbons. Here we investigated with in situ (benthic chamber, microprofiler) and ex situ (pore water constituents, turnover rates of sulfate and methane, prokaryote abundance) techniques reduced sites from three different seep ecosystems in the Eastern Mediterranean deep-sea. At all three cold seep systems, the Amon Mud Volcano, Amsterdam Mud Volcano and the Nile Deep Sea Fan Pockmark area, we observed and sampled patches of highly reduced, methane-seeping sulfidic sediments which were separated by tens to hundreds of (kilo)meters with non-reduced oxygenated seafloor areas. All investigated seep sites were characterized by gassy, sulfidic sediments of blackish color, of which some were overgrown with thiotrophic bacterial mats. Fluxes of methane and oxygen, as well as sulfate reduction rates varied between the different sites.

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    Authors: Feseker, Tomas; Boetius, Antje; Wenzhöfer, Frank; Blandin, Jérome; +5 Authors

    Submarine mud volcanoes are considered an important source of methane to the water column. However, the temporal variability of their fluid transport including mud and methane emissions is largely unknown. Assuming that this transport was continuous and at steady state, methane emissions were previously proposed to result from a dynamic equilibrium between upward migration and consumption at the seabed by methane-consuming microbes. Here we have investigated non-steady state situations of vigorous mud movements and their reflection in fluid flow, seabed temperature and bathymetry. Time series of pressure, temperature, pH and seafloor photography were collected by a benthic observatory (LOOME) for 431 days at the active Håkon Mosby mud volcano. These new data document eruptions, which were accompanied by pulses of hot subsurface fluids and triggered rapid sediment uplift and lateral movement, as well as emissions of free gas.

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    Authors: Ingels, Jeroen; Tchesunov, Alexei; Vanreusel, Ann;

    The Gollum Channels and Whittard Canyon (NE Atlantic) are two areas that receive high input of organic matter and phytodetritus from euphotic layers, but they are typified by different trophic and hydrodynamic conditions. Sediment biogeochemistry was analysed in conjunction with structure and diversity of the nematode community and differences were tested between study areas, water depths (700 m vs 1000 m), stations, and sediment layers. The Gollum Channels and Whittard Canyon harboured high meiofauna abundances (1054-1426 ind. 10 cm**-2) and high nematode diversity (total of 181 genera). Next to enhanced meiofauna abundance and nematode biomass, there were signs of high levels of organic matter deposition leading to reduced sedimentary conditions, which in turn structured the nematode community. Striking in this respect was the presence of large numbers of 'chemosynthetic' Astomonema nematodes (Astomonema southwardorum, Order Monhysterida, Family Siphonolaimidae). This genus lacks a mouth, buccal cavity and pharynx and possesses a rudimentary gut containing internal, symbiotic prokaryotes which have been recognised as sulphur-oxidising bacteria. Dominance of Astomonema may indicate the presence of reduced environments in the study areas, which is partially confirmed by the local biogeochemical environment. The nematode communities were mostly affected by sediment layer differences and concomitant trophic conditions rather than other spatial gradients related to study area, water depth or station differences, pointing to small-scale heterogeneity as the main source of variation in nematode structure and function. Furthermore, the positive relation between nematode standing stocks, and quantity and quality of the organic matter was stronger when hydrodynamic disturbance was greater. Analogically, this study also suggests that structural diversity can be positively correlated with trophic conditions and that this relation is tighter when hydrodynamic disturbance is greater.

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    Authors: Guerreiro, Catarina Alexandra Vicente, 1978-;

    A presente tese de doutoramento tem por objectivo contribuir para o conhecimento geral dos cocolitóforos na transição costeiro-neritico-oceânica, a sua distribuição ao largo de Portugal, e o seu potencial enquanto traçador (paleo)ecológico e (paleo)ceanográfico no contexto de canhões submarinos. Para compreender a relação entre os coccolitóforos e as condições ambientais, os resultados foram interpretados numa perspectiva multidisciplinar, integrados num conjunto significativo de dados relativos às características ecológicas e hidrológicas das massas de água superficiais da margem Portuguesa central (i.e. nutrientes, clorofila, temperatura, salinidade, turbidez, dados de vento e de satélite), e às caracteristicas sedimentológicas dos fundos marinhos (i.e. composição, textura e acumulação sedimentar). As variações ecológicas mais significativas observadas nas comunidades de cocólitoforos ao largo de Portugal ocorreram ao longo do gradiente costa-oceano. Dois grupos taxonómicos principais de comportamento ecológico oposto foram observados na zona fótica, marcando a transição de espécies adaptadas a regimes mais estáveis (K-selected) preferencialmente distribuídas no domínio oceânico, para espécies oportunistas (r-selected) mais frequentes nas regiões neritico-costeiras. Este gradiente também foi observado nas associações de cocólitos preservadas nos sedimentos superficiais do fundo marinho, tanto ao longo dos canhões submarinos como nas suas áreas adjacentes, embora várias diferenças tenham sido reconhecidas entre os dois tipos de ambientes. Na zona fótica, as espécies Emiliania huxleyi e Gephyrocapsa oceanica revelaram um comportamento claramente r-selected, tendo sido as principais responsáveis pelo bloom de cocolitóforos observado ao largo do Cabo Carvoeiro. Este bloom ocorreu em resposta à combinação favorável de descarga fluvial de final de inverno com ventos predominantes de norte sobre a plataforma, e condições de céu limpo. Em apenas alguns dias, as concentrações de cocolitóforos e biomassa de fitoplâncton (Chl-a) mais do que triplicaram, indicando claramente a capacidade destes organismos em tirar partido das condições favoráveis em luz e nutrientes providenciadas pela pluma fluvial superficial. As duas espécies desenvolveram-se em conjunto com outros fitoplânctónicos oportunistas (Chaetoceros s.l., Thalassiosira s.l, Skeletonema s.l.), confirmando o seu papel enquanto espécies r-selected de primeiro estádio da sucessão fitoplanctónica, caracterizadas por terem um potencial de desenvolvimento rápido em ambientes ricos em nutrientes. Coronosphaera mediterranea e Syracolithus dalmaticus também responderam positivamente às condições favoráveis no decorrer do cruzeiro, embora menos notavelmente do que as espécies anteriores. Pelo contrário, os grupos Syracosphaera spp. e Ophiaster spp. revelaram características típicas de espécies K-selected, consistentemente mais abundantes em águas mais oceânicas e menos eutróficas, afastadas da influência da pluma fluvial, ou distribuídas em níveis abaixo da pluma nas regiões mais neritico-costeiras. Gephyrocapsa ericsonii e Gephyrocapsa muellerae dominaram a comunidade de cocolitóforos sob condições de baixa produtividade na plataforma, mas não quando as águas de regiões nerítico-costeiras se tornaram favoráveis ao bloom de espécies oportunistas. No sedimento superficial de fundo, enquanto as espécies C. mediterranea, Helicosphaera carteri e a G. oceanica (e, em menor grau, Coccolithus pelagicus) registaram uma distribuição marcadamente costeira, os cocólitos produzidos pelas espécies Calcidiscus leptoporus, Umbilicosphaera sibogae, Umbellosphaera irregularis e Rhabdosphaera spp. foram observados preferencialmente distribuidos para offshore e para sul, possivelmente indicadoras de uma maior influência da ENACWst na zona mais meridional da area de estudo (i.e. a sul do Esporão da Estremadura). G. muellerae revelou ser, de longe, a espécie mais abundante e amplamente distribuída, embora geralmente mais oceânica, particularmente nas regiões adjacentes aos canhões submarinos. Enquanto certas especies mais robustas (i.e. C. leptoporus, C. pelagicus, H. carteri) tiveram um registo mais relevante no sedimento em comparação com a coluna de água, géneros de morfologia mais frágil e de menores dimensões (i.e. Syracosphaera spp., Ophiaster spp., S. dalmaticus) não foram observadas no sedimento, provavelmente traduzindo os efeitos da dissolução e fragmentação selectiva. No entanto, quando considerando percentagens de espécies de cocólitos de dimensão semelhante (≥3 μm), não foi observada qualquer evidência mais consistente de que tenha havido transporte ou preservação preferencial de especies individuais, confirmando que o signal preservado no sedimento apresenta uma forte componente (paleo)ecológica, e não meramente tafonómica. Em termos de dinâmica de canhão submarino, o Canhão da Nazaré foi observado a ter o efeito de conduta preferencial de águas oceânicas para regiões bastante proximais da plataforma continental Portuguesa, as quais se encontravam empobrecidas em nutrientes em comparação com as massas de água neríticas e costeiras durante o período de final de inverno monitorizado durante o cruzeiro. A ocorrência singular de Discosphaera tubifera e Palusphaera vandelii na cabeceira do canhão, juntamente com C. leptoporus é interpretada enquanto traçadora do deslocamento preferencial de ENACWst intensificado ao longo do troço superior do canhão, durante o inverno. Um “hotspot” de diversidade de cocolitóforos foi observado na coluna de água desta área, incluindo tanto espécies oceânicas-oligotróficas como espécies costeiras oportunistas, tendo sido interpretado enquanto reflexo da capacidade do canhão em promover trocas de massas de água entre regiões neritico-costeiras e regiões mais oceânicas, particularmente durante o inverno. Adicionalmente, a persistente ocorrência de elevadas concentrações de Chl-a à superfície obtidas por imagens de satélite, particularmente entre Março e Outubro (2006-2011), sugerem a cabeceira do Canhão da Nazaré como sendo o sector mais persistentemente produtivo do troço superior-médio do canhão. Percentagens mais elevadas de cocólitos de espécies costeiro-neriticas em sedimentos da parte superior do Canhão da Nazaré corroboram esta hipótese, possivelmente traduzindo a forte proximidade da sua cabeceira à linha de costa, resultando numa maior influência da dinâmica costeira e na sua intensificação na cabeceira e área adjacente (i.e. upwelling, ondas internas), e em condições mais dinâmicas e ricas em nutrientes para as quais as espécies r-selected estão melhor adaptadas. Pelo contrário, percentagens mais elevadas de cocólitos de espécies oceânicas no Canhão de Lisboa-Setúbal parecem traduzir um ambiente em geral mais oceânico-pelágico neste No sedimento superficial de fundo, enquanto as espécies C. mediterranea, Helicosphaera carteri e a G. oceanica (e, em menor grau, Coccolithus pelagicus) registaram uma distribuição marcadamente costeira, os cocólitos produzidos pelas espécies Calcidiscus leptoporus, Umbilicosphaera sibogae, Umbellosphaera irregularis e Rhabdosphaera spp. foram observados preferencialmente distribuidos para offshore e para sul, possivelmente indicadoras de uma maior influência da ENACWst na zona mais meridional da area de estudo (i.e. a sul do Esporão da Estremadura). G. muellerae revelou ser, de longe, a espécie mais abundante e amplamente distribuída, embora geralmente mais oceânica, particularmente nas regiões adjacentes aos canhões submarinos. Enquanto certas especies mais robustas (i.e. C. leptoporus, C. pelagicus, H. carteri) tiveram um registo mais relevante no sedimento em comparação com a coluna de água, géneros de morfologia mais frágil e de menores dimensões (i.e. Syracosphaera spp., Ophiaster spp., S. dalmaticus) não foram observadas no sedimento, provavelmente traduzindo os efeitos da dissolução e fragmentação selectiva. No entanto, quando considerando percentagens de espécies de cocólitos de dimensão semelhante (≥3 μm), não foi observada qualquer evidência mais consistente de que tenha havido transporte ou preservação preferencial de especies individuais, confirmando que o signal preservado no sedimento apresenta uma forte componente (paleo)ecológica, e não meramente tafonómica. Em termos de dinâmica de canhão submarino, o Canhão da Nazaré foi observado a ter o efeito de conduta preferencial de águas oceânicas para regiões bastante proximais da plataforma continental Portuguesa, as quais se encontravam empobrecidas em nutrientes em comparação com as massas de água neríticas e costeiras durante o período de final de inverno monitorizado durante o cruzeiro. A ocorrência singular de Discosphaera tubifera e Palusphaera vandelii na cabeceira do canhão, juntamente com C. leptoporus é interpretada enquanto traçadora do deslocamento preferencial de ENACWst intensificado ao longo do troço superior do canhão, durante o inverno. Um “hotspot” de diversidade de cocolitóforos foi observado na coluna de água desta área, incluindo tanto espécies oceânicas-oligotróficas como espécies costeiras oportunistas, tendo sido interpretado enquanto reflexo da capacidade do canhão em promover trocas de massas de água entre regiões neritico-costeiras e regiões mais oceânicas, particularmente durante o inverno. Adicionalmente, a persistente ocorrência de elevadas concentrações de Chl-a à superfície obtidas por imagens de satélite, particularmente entre Março e Outubro (2006-2011), sugerem a cabeceira do Canhão da Nazaré como sendo o sector mais persistentemente produtivo do troço superior-médio do canhão. Percentagens mais elevadas de cocólitos de espécies costeiro-neriticas em sedimentos da parte superior do Canhão da Nazaré corroboram esta hipótese, possivelmente traduzindo a forte proximidade da sua cabeceira à linha de costa, resultando numa maior influência da dinâmica costeira e na sua intensificação na cabeceira e área adjacente (i.e. upwelling, ondas internas), e em condições mais dinâmicas e ricas em nutrientes para as quais as espécies r-selected estão melhor adaptadas. Pelo contrário, percentagens mais elevadas de cocólitos de espécies oceânicas no Canhão de Lisboa-Setúbal parecem traduzir um ambiente em geral mais oceânico-pelágico neste canhão, resultante da sua maior distância aos efeitos da dinâmica costeira e ausência de transporte sedimentar significativo ao longo do seu talvegue, na actualidade. Uma mistura mais acentuada de cocólitos produzidos pelas duas associações (paleo)ecológicas, i.e. a costeiro-neritica e a oceânica, foi observada nos sedimentos dos canhões, em comparação com as regiões da plataforma e vertente regiões adjacentes aos canhões onde o gradiente (paleo)ecológico costa-oceano é mais distintivo. Esta assinatura nos canhões confirma a capacidade destas estrutura em promover trocas de massas de água costeiras e oceânicas (sinal ecológico), embora o importante papel das ondas internas e dos ocasionais fluxos gravíticos de sedimentos em perturbar e homogeneizar o registo sedimentar (sinal tafonómico) nos canhões deva ser sempre considerado. Ao evitar os problemas estatísticos tipicamente associados às determinações percentuais, a Análise de Dados Composicionais (i.e. a abordagem isometric log-ratio) permitiu validar e confirmar o gradiente ecológico costa-oceano observado nas associações de cocólitos no sedimento. A boa concordância entre os dois métodos sugere que o sinal (paleo)ecológico preservado na cobertura sedimentar da margem Portuguesa central é robusto, mesmo junto à costa e no contexto das condições dinâmicas vigentes nos canhões submarinos. Pelo contrário, tanto as concentrações de cocólitos (nanno/g) como os fluxos (nanno/cm2/yr) revelaram padrões de distribuição espacial onde as relações ecológicas interespécies parecem estar “mascaradas” por factores sedimentares/tafonómicos, particularmente nas zonas costeiras e nos canhões. O aumento de cocólitos para offshore reflecte não só a natureza primordialmente oceânica dos cocolitóforos, mas também a ocorrência de selecção textural, resultando na acumulação preferencial de cocólitos em regiões menos energéticas da vertente continental média e inferior, e em certas zonas dos canhões as quais funcionam como armadilhas morfológicas temporárias de sedimentos. Fluxos mais elevados nos troços superiores dos canhões reflectem o seu papel enquanto depocentros preferenciais de sedimentos finos na plataforma continental, tanto de origem litogénica como biogénica, incluindo cocólitos provenientes de fluxos verticais (produtividade – sinal ecológico) e laterais (resuspensão e advecção – sinal tafonómico). Este estudo ilustra cabalmente a rapidez de resposta dos cocolitóforos a variações meteorológicas e hidrográficas de curto-prazo e ao surgimento de condições ambientais favoráveis na costa Portuguesa, contrariando a noção amplamente aceite de que estes organismos representam um grupo fitoplanctónico calcário uniforme típico de ambientes de baixa turbulência, baixo conteúdo nutritivo e intensa luminosidade. Embora haja ainda muito trabalho a fazer no que respeita ao impacto dos canhões submarinos sobre a dinâmica oceanográfica e fitoplanctónica ao largo de Portugal, as associações de cocólitos preservados no sedimento revelaram-se úteis enquanto traçadores de gradientes (paleo)ecológicos e (paleo)oceanográficos vigentes na margem Portuguesa central. Os resultados confirmam estudos anteriores focados na complexa dinâmica hidro-sedimentar vigente nos canhões submarinos da Nazaré e de Lisboa-Setúbal. This thesis aims to contribute to the knowledge of coccolithophores from coastal-neriticoceanic transitional settings, their distribution offshore central Portugal, and their potential as (paleo)ecological and (paleo)ceanographic proxy in the context of submarine canyons. In order to achieve a good understanding of the relationship of coccolithophores with the environmental setting, results were interpreted on a multidisciplinary basis, integrating a significant data set concerning the hydrological characteristics of surface waters of the central Portuguese margin (i.e. nutrients, chlorophy