Taxonomy, distribution and community composition of megabenthic non-crustacean invertebrates in the deep Catalan margin = Taxonomía, distribución y composición de la comunidad de invertebrados no crustáceos del megabentos del Mar Catalán profundo

Abstract

The study of the non-crustacean invertebrates dwelling on the deep Mediterranean Sea is of interest for different marine science disciplines, being the diversity of species and their distributions largely unexplored. In fact, the present Thesis conducted an effort in order to increase valid scientific information not only at taxonomical level, but also at the level of community composition and distribution. Detailed data on the reproductive biology and ethology was required for some group of ecological relevance in order to solve some relevant gaps of information. Ten multidisciplinary oceanographic cruises were conducted between October 2008 and April 2013 to sample the deep seafloor of the western Mediterranean Sea. The sampling areas included the Blanes Canyon and its adjacent open slope, the Palamós (also named La Fonera) and Cap de Creus Canyons, sea hills in the Gulf of Valencia and Eivissa Channel, and landslides on the Eivissa Channel. A total of 223 benthic trawls were completed resulting in a total swept area of 10.3 km². Samples were also observed by means of two ROV’s. Resulting from these ten cruises, this work evidenced and updated species bathymetrical and geographical distributions ranges of non-crustacean invertebrate species by different methodologies (i.e. traditional and technologically advanced sampling). As a result of that effort, new faunistic reports were described: two first records (i.e. Gracilechinus elegans (Düben & Koren, 1844) Dicopia antirrhinum C. Monniot, 1972), three rare species (i.e. Hedingia mediterranea (Bartolini Baldelli, 1914), Penilpidia ludwigi (von Marenzeller, 1893) and Phascolosoma (Phascolosoma) turnerae (Rice, 1985), and eleven extensions of maximum depth range of distribution. This new record for Dicopia antirrhinum increased the lower depth limit of this genus in the Mediterranean Sea from 500 to 1100m depth. This finding contributes to the knowledge of the poorly investigated Mediterranean deep ascidian fauna, in sharp contrast with the relatively well-known shallow-water Mediterranean ascidians. We also observed that densities and biomass of non-crustacean invertebrates were pointed to be significantly higher in submarine canyons than in surrounding open slopes. These findings suggest submarine canyon habitats of the north-western Mediterranean Sea as hotspots of benthic megafauna communities. The most abundant group in terms of density was the Phylum Echinodermata. A Phylum largely undescribed in deep Mediterranean waters, when compared with the faunistic data already available for the Atlantic. All specimen sampled of this Phylum were classified, described and their bathymetrical ranges re-defined. These results were compared and extended with the previous published literature, checking, validating (or discarding) all available information. The reproductive pattern of the most abundant species of Asteroidea in the present study, Ceramaster grenadensis was studied. The size pattern distribution of show a depth related trend showing smaller sizes at greater depths (dwarfism), as observed in other species of Atlantic Ocean. Additionally, juveniles were sampled at the deepest range of distribution of the species (i.e. 2250 m). Histological analysis of C. grenadensis gonads, revealed a semicontinous reproductive patterns, with a maximum of reproductive activity in autumn (maximum values of Gonadal Index). This finding coincides with some already published study for other deep-sea Mediterranean Echinoderm species such as B. lyrifera. The in situ faunal sampling with video technologies (i.e. Remotely Operated Vehicles; ROVs) showed the occurrence of different species assemblage compositions in different geomorphological habitats such as, submarine canyons, sea hills and landslides. Benthic cnidarian communities were observed in seamount rocky areas while submarine landslides fauna were mainly composed by vagil fauna as fishes and crustaceans. The description of characteristics seascape units might help to estimate taxonomical group in other similar but presently unexplored deep-sea areas. Finally, this study suggests that an increasing effort combining traditional and technologically-new sampling methods is advisable in order to obtain a more complete overview of species inhabiting the different deep-sea continental margins.

En el estudio de la presente tesis se pretende realizar una exhaustiva clasificación taxonómica de las especies de invertebrados no-crustáceos muestreados en el margen catalán profundo, así como determinar sus patrones de distribución y su composición faunística. El material utilizado fue recopilado a lo largo de 10 campañas oceanográficas realizadas entre octubre 2008 y abril 2013 en el Mediterráneo occidental en el marco de los Proyecto Nacionales y Europeos PROMETEO, DOSMARES, BIOFUN, PROMARES y EUROLEON. Las áreas de muestreo incluyeron el Cañón de Blanes y su talud adyacente, los cañones de la Fonera y Cap de Creus, dos montañas submarinas ubicadas en el Golfo de Valencia y el Canal de Ibiza, y dos deslizamientos submarinos del Canal de Ibiza. Adicionalmente se realizó una campaña transmediterránea en la cual se muestrearon tres áreas del Mediterráneo, oeste, central y este. Se utilizaron para la recolección de muestras tanto métodos de muestreos tradicionales (artes de arrastre) como nuevas tecnologías de muestreo visual (ROV). Las profundidades muestreadas mediante ROV fueron de entre los 60 m y los 1100 m de profundidad; y entre los 850 m y los 2850 m mediante muestreos tradicionales. Se obtuvieron 5877 individuos distribuidos en 8 Filos, 18 Clases y 69 especies. En la presente Tesis se describe por primera vez en el Mediterráneo la presencia de dos especies: el equinoideo regular Gracilechinus elegans (Düben & Koren, 1844) y la ascidia carnívora Dicopia antirrhinum C. Monniot, 1972. Igualmente se describió la presencia de tres especies consideradas ‘raras’: las holoturias endémicas Hedingia mediterranea (Bartolini Baldelli, 1914) y Penilpidia ludwigi (von Marenzeller, 1893) así como el sipúnculido Phascolosoma (Phascolosoma) turnerae Rice, 1985. Asimismo se amplió el rango de distribución batimétrica de 11 especies. Los datos se analizaron además de a nivel puramente taxonómico, a nivel poblacional, revelando mayores densidades (individuos • km -2) y biomasas (kg • km -2) en zonas de cañones submarinos. También se observó que a nivel faunístico el grupo más abundante fueron los equinodermos, representando el 57% del total de especímenes recolectados. Si pasamos a considerar los datos obtenido mediante imágenes de ROV, se recopilaron un total de 4520 observaciones faunísticas de los tres hábitats geomorfológicos descritos (un cañón, dos montes y dos deslizamientos submarinos) y entre los cuales se describieron similitudes en cuanto a comunidades faunísticas en función de parámetros tales como la profundidad, geomorfología y tipo de substrato.