Asociaciones de crustáceos decápodos ligadas a fondos de algas fotófilas dominadas por Stypocaulom scoparium (Linnaeus) Kützig en el Mar de Alborán

Publicado

Asociaciones de crustáceos decápodos de volcanes de fango y fondos adyacentes en aguas españolas del Golfo de Cádiz

Publicado

Conectividad entre comunidades de decápodos asociadas a fondos infralitorales de algas y fanerógamas marinas. "Cuando pequeños fragmentos hacen un todo"

La diversidad de especies es, de forma general, mayor en fondos con cobertura vegetal (p.e. fanerógamas marinas, algas fotófilas) que en fondos blandos sin vegetación, por lo que una pérdida parcial de pradera debería traer consigo una pérdida de diversidad. Sin embargo, el efecto de la fragmentación del hábitat dependerá de varios factores, incluyendo el número y tamaño de los parches, la distancia entre ellos y los tipos de hábitats próximos. En este trabajo se ha analizado este último aspecto y para ello se escogieron dos zonas, situadas dentro del Lugar de Interés Comunitario Calahonda (ES6170030), localizado en el litoral de la provincia de Málaga (mar de Alborán). Estas zonas se caracterizan por presentar un mosaico de hábitats (desde ahora "biotopos") formado por praderas fragmentadas de Posidonia oceánica (Linnaeus) Delile, 1813 y Cymodocea nodosa (Ucria) Ascherson, 1870, así como fondos de rocas infralitorales cubiertos de algas fotófilas (Stypocaulon scoparium (Linnaeus) Kützing, 1843 principalmente) y fondos de arenas finas y medias. Él muestreo se realizó de manera estacional (5 réplicas por hábitat y estación del año), mediante buceo con escafandra autónoma y con el uso de una aspiradora submarina. Se ha analizado (1) la composición y estructura de las poblaciones de decápodos a partir de una serie de índices ecológicos (p.e. diversidad de Shannon-Wiener, equirrepartición, beta diversidad-β de Whittaker, índice de Jacarkd); (2) la preferencia e importancia que cada biotopo tienen para las especies más características, analizando la evolución estacional de las abundancias y de las tallas (se distinguieron dos grupos: juveniles-pequeñas tallas y adultos-tallas grandes), y (3) si la fragmentación tiene un efecto negativo sobre la biodiversidad. La hipótesis de partida es que se conservaría la estructura de las poblaciones de decápodos de los fondos con cobertura vegetal estudiados, como consecuencia de la conexión entre los diferentes biotopos. De hecho para la mayoría de las especies de decápodos, su hábitat (general) no es más que la suma de diferentes biotopos. En total se han capturado 4769 individuos pertenecientes a 48 especies y 21 familias. Las especies dominantes fueron, Pilumnus hirtellus (Linnaeus, 1761), Hippolyte leptocerus (Heller, 1863), Athanas nitescens (Leach, 1813 [in Leach, 1813-1814]), Pisidia longimana (Risso, 1816) y Sirpus zariquieyi Gordon, 1953, representando más del 50% del total de individuos capturados en el conjunto de biotopos. Se ha comprobado que ciertas especies tienen preferencia por determinados biotopos. Por ejemplo S. zariquieyi y Achaeus gracilis (Costa, 1839) están asociadas principalmente a algas; H. leptocerus a C. nodosa y P. longimana a P. oceanica. Los altos valores de equirrepartición y la similitud de los valores de βw entre biotopos muestran una elevada conexión entre ellos. De hecho el 50% de las especies están presentes en más de dos biotopos. Por otro lado algunas especies utilizan con mayor o menor intensidad (reflejado en los valores de abundancias) uno u otro según la estación del año, utilizándolos como “nursery”, refugio, lugar de puesta y/o alimentación. Los biotopos que mostraron las mayores abundancias de individuos y especies fueron P. oceanica y el sedimento presente bajo las algas, especialmente durante los meses de otoño e invierno. Las comunidades de algas fotófilas presentes en estos fondos actúan como conectores entre los diferentes rodales, compensando la falta de conexión debida a la fragmentación, proporcionando refugio y alimento a especies comunes.Versión del edito

A new species of pea crab from south-western Europe (Crustacea, Decapoda, Brachyura): species description, geographic distribution and population structure with an identification key to European Pinnotheridae

After the recent detection, by both morphology and DNA barcodes, of the larval stages of an unknown species of pea crab (Pinnotheres sp.) in European waters, adults of this crab are herein reported and described as a new species. The current known geographic distribution of the species comprises the Gulf of Cádiz in the eastern Atlantic and the adjacent Mediterranean waters of the south of the Iberian Peninsula (Alboran Sea), where this crab is well-established inside the anomiid bivalve Anomia ephippium. In the Gulf of Cádiz, the species displayed a relatively high prevalence: on average, 55.6–77.7%, in A. ephippium samples. The dominant demographic categories of the new species were soft females (61.8–77.0%) with fewer males (17.7–21.10%). Most of the host bivalves carried only one crab; in bivalves harbouring two crabs, heterosexual pairs were collected more frequently than expected by chance, which suggests that they could be mated pairs. A strong correlation between host size and soft female size was found (r = 0.73, P < 0.01) indicating that space availability within hosts seems to be relevant in determining the size of the sedentary phase of the new crab species

Bottom trawling activity, main fishery resources and associated benthic and demersal fauna in a mud volcano field of the Gulf of Cádiz (southwestern Iberian Peninsula)

Bottom trawling activity, commercial species and benthic and demersal assemblages were studied integrating Vessel Monitoring System data (VMS), fishing logbook data and otter trawl samples in a mud volcano (MV) field of the Spanish margin of the Gulf of Cádiz (GoC) in 2011. High trawling activity was detected around Anastasya MV and between the Cádiz and Guadalquivir diapiric ridges, and low trawling activity around Gazul MV and in the deepest areas (Huelva Channel and southwards). A total of 11 938 individuals from 126 benthic and demersal species were collected in the samples. Multivariate analyses mainly grouped samples according to depth and sediment type and 3 different assemblages were detected. The Stratum 1 assemblage (Gazul MV, 441–470 m depth, muddy sand, low trawling activity and high near-bottom current speed) was dominated by Parapenaeus longirostris, Leptometra phalangium and Plesionika antigai, among others, and displayed high species richness and abundance. The Stratum 2 assemblage (Anastasya and Tarsis MVs, Triangle, and the External zone, 528–622 m, mud/sandy mud, medium to high trawling activity and low near-bottom current speed) was dominated by P. longirostris, Plesionika martia, Nezumia aequalis and small chondrichthyans (mainly sharks), among others, and displayed low species richness, abundance and biomass. The Stratum 3 assemblage (Huelva Channel > 700 m, sand, low trawling activity and high near-bottom current speed) was dominated by similar species to Stratum 2, but also included large demersal sharks (Centrophorus granulosus, Galeorhinus galeus, Dalatias licha) that resulted in a high biomass. Depth and near-bottom current speed showed strong relationships with the benthic and demersal assemblages in Principal Component Analyses. The occurrence of medium to intense trawling activity in and around some MVs (Habitat 1180, Council Directive 92/43/ECC-Habitats Directive) should imply an effective regulation that allows a balance between sustainable fisheries and habitat conservation

Biodiversity and spatio-temporal changes of benthic and demersal assemblages of circalittoral soft bottoms of the bay of Málaga (northern Alboran Sea)

The Bay of Málaga is located in a high biodiversity and productivity area that harbours a wide variety of commercial species exploited by different fishing fleets. Benthic and demersal fauna from circalittoral soft bottoms have been studied using a benthic dredge (BD) (8 sampling stations) and an otter trawl (OT) (8 sampling stations on a seasonal basis). Some sediment and water column variables, as well as the trawling activity, have also been studied and used for analysing their linkage with the fauna. A total of 287 species have been found in these bottoms and fish, molluscs and crustaceans represented the most diverse and abundant faunistic groups. A new record of the decapod Hippolyte leptometrae for Spanish waters is also included in this study. Some multivariate analyses using BD samples indicated the presence of three assemblages, but these seem to represent different facies of a single benthic community due to the absence of acute sediment changes and significant differences in the fauna. OT samples only displayed differences related to seasons but not to sediment types or depth. These seasonal differences seem to be linked to biological and ecological features of both dominant and/or commercial species. Mud and organic matter contents (%OM) in sediment, as well as the temperature, were the main variables linked to the spatial distribution of the benthic community identified with BD, whereas medium and coarse sand as well as gravel contents were the main variables linked to the changes of the epibenthic and demersal assemblage resulting from OT samples. The information of this study is of importance for improving the knowledge on the biodiversity of circalittoral soft bottoms of the Mediterranean and Alboran Sea as well as for the potential creation of a Marine Fisheries Reserve in the Bay of Málaga

Composition, structure and distribution of epibenthic communities within a mud volcano field of the northern Gulf of Cádiz in relation to environmental variables and trawling activity

The Gulf of Cádiz represents an area of extensive seepage of the south-western Iberian Peninsula that is located between two continents and basins, where a high geomorphologic, sedimentary and environmental complexity occurs. In the present study, epibenthic communities were investigated in a mud volcano field containing four mud volcanoes (Gazul, Anastasya, Pipoca and Tarsis), one diapir/mud volcano complex (Chica) and several diapirs that are all located in the upper and middle slope of the Spanish margin of the Gulf of Cádiz (300–700 m depth). Faunistic samples were collected in 2010 and 2011 using a beam-trawl in different sectors of the mud volcano field, including fluid venting submarine structures and their adjacent seabeds. Environmental variables from the sediment and water column as well as the commercial bottom trawling activity were also measured in the same sampled areas for studying relationships with the fauna. A total of 325 taxa were found in the samples, including sponges, molluscs, cnidarians and decapods the most diverse groups. The epibenthic communities displayed differences between sectors that were related to depth, sediment features, characteristics of the water masses and the trawling activity. Six different assemblages were found including deep-sea sponge aggregations and cold-water coral banks in Gazul, echinoid and solitary coral aggregations in Gazul, sea-pen communities that were sometimes intermixed with sponge and gorgonian aggregations in Tarsis, Chica and Pipoca, and low density sea-pen communities with components of chemosynthesis-based communities in Anastasya. Species richness was higher in Gazul, Pipoca and Chica due to the presence of complex habitats (e.g. cold-water coral banks, sponge aggregations) and low in Anastasya due to the scarce epifauna, high trawling activity and low near-bottom current speed. Typical cold seep chemosymbiotic bivalves of the Gulf of Cádiz were not detected in beam-trawl samples due to their infaunal habit. The studied mud volcano field was declared a Site of Community Importance due to the presence of habitats and species with a conservation status, but several commercial species are exploited by bottom trawling. Therefore, a sustainable management of this mud volcano field is still needed according to current EU directives for combining fisheries and habitat conservation (Habitats Directive of the European Union, Council Directive - 1992/43/EEC; Marine Strategy Framework, Council Directive - 2008/56/EC)