133 research outputs found
Deep-sea habitat characterization using acoustic data and underwater imagery in Gazul mud volcano (Gulf of Cádiz, NE Atlantic)
Gazul is the shallowest mud volcano (MV) within the Shallow Field of Fluid Expulsion (SFFE) of the northeastern Gulf of Cádiz (NE Atlantic; 300–1200 m depth). The SFFE represents an important geo- and biodiversity area that was designated as a Site of Community Importance under the European Habitats Directive in 2014. In this study, geological features, habitats and associated biodiversity, as well as anthropogenic impacts, were characterized at Gazul MV from underwater imagery and multibeam bathymetry. Multivariate methods using the Bray-Curtis similarity index identified six main habitats, each of which harbored a characteristic faunal assemblage that included: (1) sandy ripple bottoms typified by the actiniarian Actinauge richardi; (2) sandy, muddy, coarse sand and bioclastic bottoms dominated by the solitary coral Flabellum chunii; (3) coarse sand and bioclastic bottoms, together with soft sediments covered by scattered methane-derived authigenic carbonates (MDACs) (mixed bottoms), characterized by the echinoid Cidaris cidaris; (4) hard bottoms comprising MDACs dominated by a wide variety of sponges and gorgonians; (5) coral-rubble bottoms typified by the presence of colonial scleractinian communities dominated by Madrepora oculata; and (6) mixed bottoms characterized by the presence of a styelid ascidian. Slope and water depth were the main factors explaining assemblages’ distribution, which was also supported by the presence of MDACs such as slabs, crusts and chimneys on the seafloor, as well as by the geomorphologic diversity of Gazul MV. The results highlight Gazul MV as an eco-biologically important area harboring different vulnerable marine ecosystem (VME) elements with indicator taxa such as scleractinians, sponges, gorgonians and black corals. ROV images revealed abandoned or lost fishing gears and marine debris on the seafloor, indicating anthropogenic impacts in Gazul MV and adjacent areas. Indeed trawling fisheries activities have also been detected in Vessel Monitoring System datasets. A fishery restricted area is recommended in Gazul MV due to the occurrence of diverse VMEs and species included in different conservation directives and conventions.Postprin
Spatial assessment of trawling activity in a shallow mud volcano field of the Gulf of Cádiz
The Gulf of Cadiz display a wide continental shelf at its northwestern part with a complex
oceanographic circulation, large extensions with soft bottoms, diapiric ridges, mud volcanoes,
channels, that promote geological and biological heterogeneity and also a wide variety of
commercial resources that are exploited by an important fishing sector. Fisheries activity in this area
has been studied using VMS and logbooks data during 2011. Fishing effort and captures maps for
some important species (Nephrops norvegicus and Parapenaeus longirostris) have been developed
for different areas which may be able to improve the spatial and quantitative information on
fisheries, and implement measures to improve ecosystem management and conservation of the
different vulnerable habitats of the Gulf of CadizVersión del edito
Optical guided dispersions and subwavelength transmissions in dispersive plasmonic circular holes
The light transmission through a dispersive plasmonic circular hole is
numerically investigated with an emphasis on its subwavelength guidance. For a
better understanding of the effect of the hole diameter on the guided
dispersion characteristics, the guided modes, including both the surface
plasmon polariton mode and the circular waveguide mode, are studied for several
hole diameters, especially when the metal cladding has a plasmonic frequency
dependency. A brief comparison is also made with the guided dispersion
characteristics of a dispersive plasmonic gap [K. Y. Kim, et al., Opt. Express
14, 320-330 (2006)], which is a planar version of the present structure, and a
circular waveguide with perfect electric conductor cladding. Finally, the modal
behavior of the first three TM-like principal modes with varied hole diameters
is examined for the same operating mode.Comment: 20 pages, 5 figures, 1 tabl
Identification and in vitro production of Lactobacillus antagonists from women with or without bacterial vaginosis
Vulnerable marine ecosystems and biological features of Gazul mud volcano (Gulf of Cádiz): A contribution towards a potential "Gulf of Cádiz" EBSA
The Gulf of Cádiz (GoC) represents an area of socioeconomic and scientific importance for oceanographic, geological and biological processes. An interesting feature of the GoC is the presence of a large amount of mud volcanoes (MVs) and diapirs that display different seepage, seabed types, oceanographic settings and biological communities. Detailed exploration of some MVs is still needed for detecting Vulnerable Marine ecosystems (VMEs) that seem to be rare in other areas of the GoC, improving the current knowledge on its biodiversity and ecological attributes. During different expeditions (MEDWAVES-ATLAS, INDEMARES-CHICA 0610 & 0412 and ISUNEPCA 0616) carried out in different years, biological samples and videos were obtained in Gazul MV (Spanish Margin of the GoC). The study of those samples and videos has revealed the presence of several ecologically important VMEs (e.g. 3 species of reef framework-forming corals, coral gardens including solitary scleractinians, gorgonians and antipatharians, as well as deep-sea sponge aggregations and chemosynthesis-related structures) and a large number of species occurring in this MV, including new records for the European margin, threatened species and non-previously described species. The combination of different environmental and anthropogenic factors allowed the present-day persistence of these VMEs in the GoC. Some of Gazul MV biological and ecological attributes fit several criteria of the Convention on Biological Diversity for EBSA description (e.g. 1,3,4,6) that, together with those of other areas of the GoC, may contribute to the future potential nomination of an EBSA in this area of the NE Atlantic
Effect of fluid emissions in the acoustic response on the seabed of the Gulf of Cádiz
Advances in remotely-sensed techniques have revolutionized mapping methods and our
understanding of the seabed environment. In particular, multibeam backscatter data nowadays
allows developing quantitative studies on the composition of the seafloor, which represents an
important baseline for habitat mapping. Usually, the acoustic response is considered as a direct
proxy of sediment texture, but seepage could affect significantly this relationship. A multibeam data
set from the Gulf of Cádiz, was grouped using an ISO-cluster analysis and results were compared
with 80 ground-truthing stations taken inside and outside cold seepage areas. Results show
significant differences between the acoustic response of sediments with the same texture depending
on the presence/absence of fluid emissions. Understanding this relationship is necessary to make
image-based backscatter classification that allows the production of sediment and habitat maps in
areas with extensive fluid emissions such as the Gulf of Cádiz.Versión del edito
Asociaciones de crustáceos decápodos de volcanes de fango y fondos adyacentes en aguas españolas del Golfo de Cádiz
Publicado
Environmental, fishing and benthic linkage in the mud volcano field of the Spanish margin of the Gulf of Cádiz
The Gulf of Cadiz is located in the boundary of two lithospheric plates, this tectonic activity
promote fluid rich hydrocarbon emissions from subsurface reservoirs and the formation of several
mud volcanoes. The seabed and sedimentological heterogeneity, the complex oceanographic
circulation, and the low fishing activity in certain areas may promote high biodiversity and complex
habitats (habitat 1170 and 1180, Natura 2000). Environmental variables (fishing activity, substrate
types, near bottom currents) and fauna collected with beam-trawl have been compared for several
mud volcanoes and adjacent bottoms in order to understand the spatial distribution of both habitats
and environmental/anthropogenic variables. The faunistic samples yielded high abundances,
biomass and species richness in Gazul, Pipoca and Chica but low ones in Anastasya. In relation to
environmental variables and fisheries activity, there is a strong correlation with the substrate type,
depth, salinity and near-bottom current as primary variables influencing the distribution of habitats
of different mud volcanoes. In this context, high species richness, abundance and biomass was found
in areas with authigenic carbonates, coarse sediments, high near-bottom current speed, low
salinities and low fishing activity.Versión del edito
Efeito da somatotrofina bovina (bST-r), do implante de progestágeno e do desmame por 72 horas na indução do estro e na taxa de prenhez em vacas
Modificações causadas pelo uso e a formação de camadas compactadas e, ou, adensadas em um latossolo vermelho-escuro textura média, na região do cerrado
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