Los campos de pockmarks en el sistema de cañones submarinos de Capbreton

En el marco del proyecto LIFE-IP-INTEMARES, se está realizando la caracterización de un sector del sistema de cañones submarinos de Capbreton, localizado en la región oriental del mar Cantábrico (golfo de Vizcaya), con el fin de mejorar el conocimiento para la declaración de nuevos espacios marinos protegidos de la Red Natura 2000 por su importancia para los diversos hábitats que los forman. Durante los años 2019 y 2020se llevaron a cabo dos campañas de investigación oceanográfica, en las cuales se prospectó una zona de interés de 3850 km2,(concretamente, un sector del curso meandriforme del cañón principal de Capbreton). Se han obtenido datos batimétricos, de reflectividad acústica del fondo marino y perfiles sísmicos de alta resolución del sub-suelo marino, así como muestras de roca y sedimentos, además de transectos de vídeo. Así, se han podido observar los cañones tributarios que atraviesan el talud continental, con orientación perpendicular a la línea de costa, y las plataformas intertributarias que presentan destacables campos de pockmarks(depresiones circulares o elípticas asociadas a escapes de fluidos).La batimetría de alta resolución obtenida para la zona ha permitido que, mediante técnicas manuales y semi-automáticas, se cartografíen más de 3000 pockmarks en un rango profundidades comprendido entre 400 y 1200 m. Se han estudiado las características principales de estos pockmarks (morfometría, localización, densidad, etc.) con el objetivo de conocer mejor su génesis y su relación con la evolución geológica de la zona. Estas morfologías, de dimensiones variables entre 20 y 550 m de diámetro y con depresiones que alcanzan los 80m,quese presentan de forma aislada, agrupada, múltiple (conteniendo unas a otras) o alineadas según orientaciones preferentes, sugieren un posible control tectónico. En ocasiones, aparecen conectados o asociados a zonas con pendientes inestables(en determinados sectores) donde se ha observado una gradación de tamaño. En los perfiles sísmicos de alta resolución adquiridos, se han podido localizar pockmarks tanto en la superficie del fondo marino, como sepultados dentro de los estratos sedimentarios, donde han quedado reflejados como paleo-pockmarks, actualmente cubiertos de sedimento

Ampliación del estudio geomorfológico del LIC Sistema de Cañones Submarinos de Avilés. Proyecto LIFE IP INTEMARES

Dentro de los objetivos del proyecto LIFE IP INTEMARES “Gestión integrada, innovadora y participativa de la Red Natura 2000 en el medio marino español”, cofinanciado por la UE, se pretende completar los trabajos y avances llevados a cabo en el marco del proyecto LIFE+ INDEMARES (2009- 2014) en algunas de las zonas que fueron declaradas como Lugar de Importancia Comunitaria (LIC), así como ampliar el conocimiento de estas zonas a partir del reprocesado con nuevas técnicas de los datos que fueron adquiridos, y que permitirán avanzar en el estudio de los hábitats de estas áreas gracias a datos más detallados y de mayor resolución. En el presente trabajo se muestran las mejoras realizadas en el procesado y análisis de los datos geofísicos adquiridos durante el proyecto INDEMARES, en el Sistema de Cañones Submarinos de Avilés, localizado en el margen Cantábrico al norte de la Península Ibérica, frente a la costa asturiana. Los últimos avances incorporados a la nueva versión del software de procesado utilizado han permitido mejorar la resolución de la batimetría (5 m) y obtener nuevos mosaicos de reflectividad y mapas de variables derivadas. Los trabajos se han centrado en la zona de la plataforma continental comprendida entre los 40 m y los 200 m de profundidad, donde las características del fondo marino formado por sustrato duro podrían ser óptimas para el desarrollo del hábitat “Arrecifes” 1170. La plataforma en esta zona es estrecha e irregular, con pendientes entre 0º y 4º, llegando a profundidades máximas de 600 m, donde se produce la ruptura de pendiente para dar paso al talud continental (Gómez-Ballesteros et al., 2014). La información utilizada para generar una nueva cartografía geomorfológica ha sido completada con perfiles sísmicos de alta resolución TOPAS y muestreos directos de sustrato previamente existentes

Morphosedimentary characterization of the Capbreton submarine canyon system, Bay of Biscay (Cantabrian Sea)

Various studies have been carried out to the declaration of new marine protected areas for their importance for habitats, according to the Natura 2000 Network. One of these sites is a sector of the Capbreton Submarine Canyon System, located in front of the Basque Country coast, in the Bay of Biscay (North Atlantic). During the Intemares_CapBreton 0619 and 0620 surveys; bathymetric, backscatter, high-resolution parametric data and samples of sediments, rocks and benthic communities from the seabed were acquired. The study was completed by recording video transects with the underwater vehicle ROTV Politolana from the IEO. The processing and analysis of the geophysical information has allowed obtaining a detailed bathymetry grid of 10 × 10 m, from which the first morphosedimentary characterization of the system of tributary canyons to the E-W trending main canyon and its interfluves has been made. One of the main features of this canyon system is the presence of a large pockmark field on adjacent platforms between canyons, located between 500 and 1000 m water depth. Within this field, pockmarks are shown as circular to elliptical depressions, most likely related to gas rich-fluid emissions to the subsurface.Versión del edito

MAPPING COMMUNITY INTEREST HABITATS IN THE COLUMBRETES ARCHIPELAGO, AN EXTRAORDINARY HOT SPOT OF BIODIVERSITY

The Columbretes Archipelago and their submerged surroundings are part of an unusual, Pleistocene volcanic field located in the Western Mediterranean designated as a Site of Community Importance (SCI) of the Natura 2000 Network. In the present study, 4 benthic habitats of community interest (1110, 1170, 1180 and 8330) have been identified by analyzing several sources of information. Generalized additive models (GAMs) have been used to model the potential distribution of reefs (1170) and maërl beds (1110). Our results highlight the diversity and extent of these habitats and allow comparisons to other marine SCIs of Spain. This can be attributed to the variability of the environment of this site. The Columbretes Islands combine a relatively shallow environment with volcanic structures, hydrothermalism with active degassing, current-driven sedimentary lobes and the influence of inland flows. Understanding high biodiversity spots is crucial as they offer natural laboratories to describe how ecosystems respond to the effects of global change. The knowledge obtained will be of paramount importance for the conservation of species and habitats. Furthermore, it will establish a baseline for future monitoring and assist in the development of effective management plans

Morphological characterization of pockmarks in the surrounding areas of Capbreton canyon

Capbreton canyon runs in an east-west direction parallel to the northern Spanish coast, in the Bay of Biscay, for more than 300 km reaching depths of more than 3,000 m. Within the framework of the European LIFE IP INTEMARES project, some marine areas are being studied and could be protected due to their importance for habitats, according to the Natura 2000 Network. One of these areas is a sector of the Capbreton submarine canyon system, off the coast of the Basque Country. During two oceanographic surveys carried out in the framework of this project, bathymetric, backscatter and high-resolution parametric data were acquired, as well as direct samples and video transects of the seabed. A geomorphological characterization of this sector is being carried out. The area includes a section of the main canyon with meandering morphology, where numerous terraces and erosive escarpments are observed. On its southern slope, there are tributary channels perpendicular to the Spanish coast, which intersect the slope and define intertributary platforms with extensive fields of pockmarks. These morphologies are circular or elliptical depressions related to submarine fluid leaks inside the sedimentary deposits under overpressure. Around 3000 pockmarks have been mapped in the area with automatic and manual techniques. They are located between 400 and 1000 m deep and have diameters from 30 to 900 m with depths ranging from a few meters to 80 m. Pockmarks can be single or have multiple sinks. In certain sectors, there are preferential alignments, which could respond to a tectonic control and a gradation in depth according to areas of fracturing. Connections between these morphologies are also frequent, giving rise to linear incisions or small detachments, suggesting a relationship between pockmarks and areas with unstable slopes. The origin of the pockmarks could be after the formation of these linear incisions, caused by fluid leakage in sediment-filled canyons. In the seismic profiles acquired, the characteristic reflectors of this type of fluid escape morphologies are observed, as well as paleo-pockmarks or pockmarks inside the sedimentary deposits that have not emerged

New records of birds in stomach contents of marine apex predators from the North Atlantic Ocean and Mediterranean Sea

Predation on seabirds by sharks or other large predators is a poorly documented issue. The blue shark is a known generalist predator that feeds on seabirds, among other prey. Bluefin tuna is a well-studied species, but to date no species of seabird has been cited as being the prey of any species of Scombridae. The present study reports the first record of Atlantic bluefin tuna (Thunnus thynnus) predation on a seabird (Cory’s shearwater Calonectris borealis). We also provide three new records of blue sharks (Prionace glauca) feeding on terrestrial and seabirds in the Northeast Atlantic Ocean and in the Mediterranean Sea. Seabirds can associate with other large marine predators, especially large tunas and marine mammals, in any oceanic region for the purpose of feeding. It is known that small pelagic fish try to flee from predators by approaching the surface of the sea, which is when seabirds take advantage of this situation by attacking them from the air to feed on them. Therefore, during the fishing frenzy, an individual bluefin tuna could have fed on the shearwater. This hypothesis is consistent with our observations. However, the case of seabirds found in the stomachs of blue sharks could imply the intentional and opportunistic predation by blue sharks on seabirds floating on the surface of the sea. On the other hand, exhausted migrating terrestrial birds (non-marine birds) could fall into the sea and thus become prey