Miguel Ángel Nombela

The mussel Xenostrobus securis: a well-established alien invader in the Ria de Vigo (Spain, NE Atlantic)

Biological and habitat characterization of the non-indigenous invasive species Xenostrobus securis was undertaken in the Ria de Vigo. This study included genetic identification of mussel samples collected from introduced and endemic areas, and the assessment of mussel size, population abundance, geographic distribution, pathological condition, and sediment composition of substrata type. The mussel had a marked patchy distribution, being more abundant in brackish sites with fine sediments and high organic matter content. Pathological analysis revealed that X. securis does not play any role as vector for introducing allochthonous pathogens in the Ria de Vigo. Nevertheless, depending on its invasiveness potential, the mussel could be a key host favouring spreading and epizootic outbreaks of marteliosis which is known to be harmful for local bivalve populations. Phylogenetic analyses of the COI gene placed all the resulting sequences in a clade within the genus Xenostrobus and its phylogeny congruent with an Australian/Pacific origin. The COI tree suggests two historical introductions in European waters. One of these invasions seems to have started in Galicia, moving from there towards Italy and France, while the geographical spread of the second invasion cannot be deciphered, although the Australian/Pacific origin of this invasion seems very possible. The 18S network is congruent with one invasion starting in Galicia or in Italy, as the Australian haplotype is closely related to the haplotype found in these areas. Several hypotheses accounting for the colonization history of this species in Galician waters are discussed.

The Corrubedo beach-lagoon complex, Galicia, Spain: Dynamics, sediments and recent evolution of a mesotidal coastal embayment

Abstract The Corrubedo beach-lagoon complex is situated in an embayment on the northwestern coast of Spain. The 4.1 m tidal range and southwesterly winds are the main agents of sediment transportation. The sediments are hybrid arenites (siliciclastic + bioclastic), with carbonate percentages ranging from 27.36 to 54.10%; silt, clay and organic matter occur in minor amounts. Repeated mapping and sampling of the beach, tidal channels, salt marshes and active and vegetated dunes recorded the vertical facies associations and their temporal evolution. Two peat layers at 0.6 and 1.7 m below the present-day marsh have yielded ages of 2280 ± 60 yrs B.P. and 1045 ± 125 yrs B.P. respectively. The possible causes of the relative sea-level rise are discussed.

El efecto de exposición en el patrón sedimen- tario del sector submareal de tres playas en la Ría de Muros y Noia (NO de España)

En este trabajo se presenta la comparacion de los sedimentos superficiales de la plataforma proximal de tres complejos playeros situados en las inmediaciones de la embocadura de la Ria de Muros y Noia. En cada uno de ellos, se han identificado las distintas poblaciones sedimentarias en funcion de los analisis granulometricos realizados. La aplicacion de un analisis estadistico de componentes principales a las fracciones granulometricas, contenido en carbonatos y materia organica, ha permitido diferenciar poblaciones de muestras y la interpretacion sedimentaria de las mismas. Las diferencias observadas en la distribucion de las poblaciones sedimentarias de los tres complejos estudiados son una consecuencia del grado de exposicion de cada complejo al oleaje dominante y de la presencia de afloramientos rocosos sumergidos que ejercen un efecto barrera.

Textural Characteristics might Influence Donax trunculus Shellfishing Banks Exploitability

In this study we combine textural and compositional information to characterize the intertidal sediments from three relevant shellfishing banks located in the Rías Altas (Vilarrube, Lombo das Navallas) and Rías Baixas (Playa America) of Galicia (NW Spain). The purpose of this study is to explore the relevance of the sediment characteristics as a key parameter in the decline of commercially exploitable populations of the bivalve Donax trunculus in two of the banks (Lombo das Navallas and Playa América) but not in the other (Vilarrube). The sediments of the three areas show their own distinctive sedimentary characteristics that became defined by their grain size parameters, mineralogical and elemental composition. This is the result of regional land supplies from the erosion of drainage areas and sea cliffs together with the contribution of modern carbonate bioclasts. Notably, the sediments of Vilarrube are characterized by moderately sorted to well sorted fine sand showing little spatial variability. According to our results, sediment texture seems to be a relevant parameter for the settlement and growth of commercial populations of Donax trunculus.