Comunidades de coralígeno ligadas a procesos diapíricos de la plataforma española del golfo de Cádiz

The Gulf of Cádiz (GoC) represents an important area of seepage activity and of biological diversity due to the tectonic activity and subsoil fluid mobility, as well as the confluence of Atlantic and Mediterranean water masses and organisms from both basins. Some circalittoral and bathyal areas of the GoC remain still unexplored and they could harbour interesting communities and species that may deserve protection. In summer 2013, a geological expedition carried out between San Fernando and Conil de la Frontera, at water depths between 40 and 55 m and 10 M from Cádiz detected complex coralligenous communities that may be linked to diapiric processes. These communities represent a well preserved 1170 habitat type (Reefs) of the Habitat Directive and also contain ca. 20 spp. of invertebrates that are included in European, National and Local (Andalusian) threatened species lists. The area should be included in the Natura 2000 network as it represents one of the few circalittoral coralligenous communities from Spanish waters of the GoC.Versión del edito

Seabed morphology and bottom water masses related to benthic habitats at the Cristóbal Colón diapir (NW of the Guadalquivir ridge, Gulf of Cádiz)

The seabed morphology and the sub-superficial characteristics of the Cristóbal Colón diapir located on the continental slope of the Gulf of Cadiz have been analysed from data obtained in the framework of the LIFE+INDEMARES/CHICA project. The aim of this study is to recognize the morphological features and the geological processes generated by the bottom water masses and their influence on the habitats and associated benthic communities. The NACW affects the generation of morphological features on the summit, revealing that different oceanographic conditions favoured the carbonate mound growth in the past. The interface between the NACW and the MOW sweeps the bottom from the SE to the NW and the presence of benthic communities dominated by filter feeders on the contouritic drift indicates that this current is strong enough to favour the availability of nutrients and organic particles and to develop both the contouritic deposits on the SE flank and the moats on the N and W flanks.Versión del edito

Multidisciplinary study of mud volcanoes and diapirs and their relationship to seepages and bottom currents in the Gulf of Cádiz continental slope (northeastern sector)

The seabed morphology, type of sediments, and dominant benthic species on eleven mud volcanoes and diapirs located on the northern sector of the Gulf of Cádiz continental slope have been studied. The morphological characteristics were grouped as: (i) fluid-escape-related features, (ii) bottom current features, (iii) mass movement features, (iv) tectonic features and (v) biogenic-related features. The dominant benthic species associated with fluid escape, hard substrates or soft bottoms, have also been mapped. A bottom current velocity analysis allowed, the morphological features to be correlated with the benthic habitats and the different sedimentary and oceanographic characteristics. The major factors controlling these features and the benthic habitats are mud flows and fluid-escape-related processes, as well as the interaction of deep water masses with the seafloor topography. Mud volcano eruptions give rise to mud flows and/or aqueous fluid seepage. These processes sustain chemosynthesis-based communities, closely associated with fluid seepage. Large depressions in the nearby area are influenced by collapse-related phenomena, where active fluid escape and the erosive effect of bottom currents have been identified. When the extrusion activity of the mud volcano is low and the seepage is diffuse, authigenic carbonates form within the edifice sediments. The bottom current sweeps the seafloor from the SE to the NW. When the velocity is moderate, sedimentary contourite processes take place on both sides of the edifices. At high velocities, the authigenic carbonates may be exhumed and colonised by species associated with hard substrates. Small carbonate mounds are found at the summits of some volcanoes and diapirs. Living corals have been found on the tops of the shallowest mud volcanoes, revealing different oceanographic conditions and strong bottom currents that favour the availability of nutrients and organic particles. The edifices affected by very high current velocities are located in the channels where erosive processes dominate.Postprint2,517

The Interactive Role of Hydrocarbon Seeps, Hydrothermal Vents and Intermediate Antarctic/Mediterranean Water Masses on the Distribution of Some Vulnerable Deep-Sea Habitats in Mid Latitude NE Atlantic Ocean

In this work, we integrate five case studies harboring vulnerable deep-sea benthic habitats in different geological settings from mid latitude NE Atlantic Ocean (24–42° N). Data and images of specific deep-sea habitats were acquired with Remoted Operated Vehicle (ROV) sensors (temperature, salinity, potential density, O2, CO2, and CH4). Besides documenting some key vulnerable deep-sea habitats, this study shows that the distribution of some deep-sea coral aggregations (including scleractinians, gorgonians, and antipatharians), deep-sea sponge aggregations and other deep-sea habitats are influenced by water masses’ properties. Our data support that the distribution of scleractinian reefs and aggregations of other deep-sea corals, from subtropical to north Atlantic could be dependent of the latitudinal extents of the Antarctic Intermediate Waters (AAIW) and the Mediterranean Outflow Waters (MOW). Otherwise, the distribution of some vulnerable deep-sea habitats is influenced, at the local scale, by active hydrocarbon seeps (Gulf of Cádiz) and hydrothermal vents (El Hierro, Canary Island). The co-occurrence of deep-sea corals and chemosynthesis-based communities has been identified in methane seeps of the Gulf of Cádiz. Extensive beds of living deep-sea mussels (Bathymodiolus mauritanicus) and other chemosymbiotic bivalves occur closely to deep-sea coral aggregations (e.g., gorgonians, black corals) that colonize methane-derived authigenic carbonates.Versión del edito

Informe de Campaña INDEMARES-CHICA 0211

Informe de la campaña oceanográfica INDEMARES CHICA 0211, realizada a bordo del Cornide de Saavedra entre febrero y marzo de 2011. En esta campaña hemos centrado nuestra actividad en la zona del Caladero de pesca del Laberinto, al norte, frente a Cádiz, y en la zona de los Volcanes de Fango del campo Hespérides, al sur, frente al Estrecho de Gibraltar.Las zonas de trabajo se sitúan en el talud continental del margen del Golfo de Cádiz, frente a las localidades de Chipiona y Cádiz, para el Caladero de pesca del Laberinto, y frente a Barbate y Tarifa para la zona de Volcanes de Fango del campo Hespérides

A relict oasis of living deep-sea mussels Bathymodiolus and microbial-mediated seep carbonates at newly-discovered active cold seeps in the Gulf of Cádiz, NE Atlantic Ocean

Extensive beds of the deep-sea mussel Bathymodiolus mauritanicus (currently also known as Gigantidas mauritanicus) linked to active cold seeps related to fissure-like activity on Al Gacel mud volcano, Gulf of Cádiz, were filmed and sampled for the first time during the oceanographic expedition SUBVENT-2 aboard R/V Sarmiento de Gamboa. Al Gacel mud volcano is one of up to 80 fluid venting submarine structures (mud volcanoes and mud volcano/diapir complexes) identified in the Gulf of Cádiz as result of explosive venting of hydrocarbon-enriched fluids sourced from deep seated reservoirs. This mud volcano is a cone-shaped edifice, 107 m high, 944 m in diameter constituted by mud breccias and, partially covered by pavements of seep carbonates. Extensive beds of this deep-sea mussel were detected at the northern flank at 810–815 m water depth associated with bacterial mats around intermittent buoyant vertical bubble methane plumes. High methane concentrations were measured in the water column above living mussel beds. Other chemosymbiotic species (Siboglinum sp., Solemya elarraichensis, Isorropodon sp., Thyasira vulcolutre and Lucinoma asapheus) were also found in different parts of Al Gacel mud volcano. Al Gacel mud volcano may currently represent one of the most active mud volcanoes in the Gulf of Cádiz, delivering significant amounts of thermogenic hydrocarbon fluids which contribute to foster the extensive chemosynthesis-based communities detected. This finding is of paramount importance for linking extremophile bivalve populations along the North Atlantic, including cold seeps of the Gulf of México, hydrothermal vents of the Mid-Atlantic Ridge and now, detailed documented at the Gulf of Cádiz.Versión del edito

Micro-morphologies, habitats and associated biodiversity in a fluid venting submarine structure using ROV underwater images: Mercator mud volcano (Gulf of Cádiz)

Mercator mud volcano has been explored by direct visual observations using a ROV at 350 to 370 m depth. Underwater images, taken mainly at the summit, have allowed characterizing the fluid venting environment, where different microforms, habitats and associated biota, with typical seepage components have been identified. Chemosynthetic bacterial communities were detected and sampled at the northeastern side of the summit at 350 m, next to pockmark-like depressions with diameters ranging 1 to 3 m, bioturbation marks, sediment mounds and authigenic carbonates of different sizes (0.1-5m length). Chemosynthesis-based communities were mainly composed by bacterial mats (patch diameter 10-30 cm), however some remains of cold seep chemosymbiotic bivalves (Lucinoma asapheus) were also found on the sediment. Habitat types at Mercator MV are influenced by oceanographic and sedimentation processes deposition and favouring fauna colonizing diverse substrate types, such as large sponges on slabs and sea-pens and annelids on soft bottoms

Discards and impact associated with wedge clam fisheries in the Alboran Sea: composition, structure and spatio-temporal variability

The present study describes the composition, structure and damage caused by mechanized dredges on discarded species from the wedge clam (Donax trunculus Linnaeus 1758) fisheries in the Alboran Sea. Discard samples were collected on board artisanal fishing vessels in 95 commercial hauls performed in Fuengirola and Caleta de Vélez between March 2013 and March 2014. The collected fauna was characterized according to their abundance and biomass, and considering their damage type by using a three-level scale (no damage, intermediate damage and severe damage) defined for the different faunal groups identified. Data was analysed for contrasting variations in the different areas and seasons. A total of 87 species were identified, including Paguridae and Annelida. Molluscs were the best represented faunal group, followed by decapod crustaceans and echinoderms. Other groups did not usually exceed 1% of the total abundance and biomass such as fishes or sipunculids. Most discarded individuals displayed no damage after their capture, promoting therefore a high survival rate. Among the dominant taxa, echinoderms and crustaceans displayed the highest proportion of damaged individuals due to their fragile exoesqueletons, which make them to be highly vulnerable to the physical impact caused by mechanized dredges and the further processing on board.Versión del edito

Analysis of discards and benthic impact of mechanized dredges fishery of the stripped venus clam in the Alboran Sea

This study describes the composition and structure of discards of the stripped venus clam (Chamelea gallina) fishery, and the damage caused by mechanized dredges on discarded species in the Alboran Sea. A total of 106 commercial fishing hauls have been analyzed between March 2013 and March 2014. Samples were collected on board artisanal fishing vessels based in Fuengirola and Caleta de Vélez harbours (Málaga). The collected fauna was characterized considering the damage presented by using a three level scale: no damage, intermediate damage and severe damage. Quantitative and qualitative data were analyzed with multivariate methods for contrasting seasonal variability. A total of 98 species were identified, with molluscs being the best-represented taxa (e.g. Acanthocardia tuberculata, Mactra stultorum), followed by decapod crustaceans (e.g. Portumnus latipes, Liocarcinus vernalis) and echinoderms (e.g. Echinocardium cf. mediterraneum, Ophiura ophiura). Most individuals displayed no damage after their capture. Echinoderms displayed the highest proportion of damaged individuals, followed by mollucs and decapod crustaceans. The discard structure and damage on non-target species displayed significant seasonal differences, with the higher proportions of damaged individuals in winter.Versión del edito

First record of the starfish Luidia atlantidea Madsen, 1950 in the Mediterranean Sea, with evidence of persistent populations

The starfish Luidia atlantidea, an echinoderm known hitherto from infralittoral and circalittoral bottoms of the northwestern African coasts, is reported for the first time in the European margin and in the Mediterranean Sea. A total of 31 specimens of different sizes (disc diameters from 0.8 to 2.9 cm) were collected from the mechanized dredges fleet targeting four commercial bivalves (Acanthocardia tuberculata, Callista chione, Chamelea gallina, Donax trunculus) between February and July 2013 in the northern Alboran Sea (southern Spain). Most individuals had broken arms due to the collecting gear. The specimens were generally collected in low numbers, at shallower depths (1-11 m) than the bathymetric range reported for this species along the northwestern African coasts (10-80 m). The data provided here, and supported by old specimens collected between 1980-1990, suggests that local populations of L. atlantidea occur in shallow infralittoral soft bottoms of the northern Alboran Sea. This constitutes a new extended northeastern limit for the distribution of L. atlantidea and increases the known number of Luidia species in the Mediterranean Sea.Postprint0,708