Trawling disturbs benthic communities, eliminating the most vulnerable organisms and modifying habitat structure. While the cumulative effects of disturbance resulting from commercial trawling activities are poorly understood, several studies suggest that chronically disturbed communities are dominated by opportunistic organisms. This study focuses on changes in functional components of the benthic community occurring in muddy sediments in a NW Mediterranean trawling ground, including an area that has not been fished for 20 yr. In both disturbed and undisturbed areas, the overall benthic community from the fishing ground was dominated by burrowing epifaunal deposit feeders and predators, and deep burrowing infaunal deposit feeders. The fished area had a higher abundance of burrowing epifaunal scavengers and motile burrowing infauna, while the undisturbed area was characterised by higher abundance of surface infauna, epifaunal suspension feeders and predatory fish. This study clearly demonstrates that changes in the functional components of a benthic community can result from fishing in areas dominated by organisms not considered especially vulnerable to trawling activities. Thus, fisheries managers aiming to reduce ecosystem disturbance must consider the implications of trawling on the structure and functioning of all types of benthic communities.

Coastal ecosystems are often stressed by non-point source and cumulative effects that can lead to local-scale community homogenisation and a concomitant loss of large-scale ecological connectivity. Here we investigate the use of β-diversity as a measure of both community heterogeneity and ecological connectivity. To understand the consequences of different environmental scenarios on heterogeneity and connectivity, it is necessary to understand the scale at which different environmental factors affect β-diversity. We sampled macrofauna from intertidal sites in nine estuaries from New Zealand’s North Island that represented different degrees of stress derived from land-use. We used multiple regression models to identify relationships between β-diversity and local sediment variables, factors related to the estuarine and catchment hydrodynamics and morphology and land-based stressors. At local scales, we found higher β-diversity at sites with a relatively high total richness. At larger scales, β-diversity was positively related to γ-diversity, suggesting that a large regional species pool was linked with large-scale heterogeneity in these systems. Local environmental heterogeneity influenced β-diversity at both local and regional scales, although variables at the estuarine and catchment scales were both needed to explain large scale connectivity. The estuaries expected a priori to be the most stressed exhibited higher variance in community dissimilarity between sites and connectivity to the estuary species pool. This suggests that connectivity and heterogeneity metrics could be used to generate early warning signals of cumulative stress.

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SUMMARY: The present study aims to analyse the local and regional variability in the density and typology of marine debris on fishing grounds on the northern Mediterranean continental shelf, and to test relationships between marine litter and trawl fishing activity. Moreover, the colonization of plastics was examined in order to study the importance of plastics as a source of impact on marine communities and their further environmental implications. This study surveyed 11 sites, associated with trawling grounds and subjected to different levels of fishing intensity, located in four areas of the Mediterranean: one in Italy, the Central Tyrrhenian coast, one in Greece, the eastern Ionian coast, and two in Spain, the Murcian and Catalan coasts. Samples were collected during an oceanographic cruise undertaken from the 21 May to the 24 June 2009. Results showed geographical variation in the density of marine debris which ranged from 0 to 405 pieces per hectare in the surveyed areas, plastics being the dominant components. Variability within sites was higher than between areas, indicating small-scale patchiness in the distribution of the debris over the seafloor. Though the study areas were within trawling grounds, the density of debris was not significantly correlated with fishing effort. More than 30% of plastics were between 10 and 20 cm width/ length, and more than 40% of the plastics were colonized by a biofilm of microorganisms, suggesting indirect effects on benthic communities.Keywords: marine debris, seabed plastic accumulation, colonized benthic plastics, northern Mediterranean Sea. RESUMEN: Estudio dE rEfErEncia sobrE la distribución dE basura marina En fondos blandos asociados a caladEros dE pEsca dE arrastrE En El mEditErránEo nortE. -Este estudio tiene como objetivo analizar la variabilidad local y regional de la basura marina en caladeros de pescas de la plataforma continental mediterránea septentrional y estudiar la relación entre ésta y la actividad pesquera. En este estudio se examinaron once estaciones de muestreo asociadas a caladeros de pesca, sujetas a distintos niveles de esfuerzo y situadas en 4 áreas en el Mediterráneo: una en Italia, en la costa central del Tirreno (TC), otra en Grecia, en la costa jónica occidental (IC) y otras dos en España, en las costas murciana y catalana (MC y CC). Las muestras se obtuvieron durante una campaña oceanográfica llevada a cabo entre el 21 de mayo y el 24 de junio de 2009. Los resultados mostraron una variación geográfica en la densidad de basura marina comprendida entre 0 y 405 piezas por hectárea en las áreas muestreadas, siendo los plásticos el componente principal. La variabilidad entre estaciones resultó más alta que la variabilidad entre áreas, lo que indica una heterogeneidad a pequeña escala en la distribución de la basura sobre el fondo. Aunque las áreas de estudio estaban situadas en caladeros pesqueros, la densidad de basura no mostró una correlación significativa con el esfuerzo de pesca. Más del 40% de los plásticos se encontraron colonizados po...

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SUMMARY: This study focuses on 4 sites in the northwestern Mediterranean to investigate the response of benthic fauna across a gradient of trawling impact. One site was located in a heavily exploited fishing ground. The second site was enclosed in the fishing ground but had not been trawled in twenty years. The third site was located adjacent to a marine protected area and was subjected to occasional trawling. The fourth site was located inside the marine protected area, where trawling was banned thirty years ago. Side-scan sonar records of trawl marks on the seabed confirmed the gradient of trawling intensity. We investigated the response of benthic fauna to trawling disturbance at the mesoscale of a fishing ground. We compared the observed patterns of abundance, biomass, diversity and community structure for epifauna and infauna with responses predicted from previous studies. Results showed that those communities less impacted by trawling sustained more biogenically habitat-structured communities (e.g. more abundance of sessile suspension feeders at the less disturbed sites against higher dominance of small invertebrates at the disturbed site). Moreover, these results confirm the benefits of restricting trawling activities for benthic communities, with marine reserves as the paradigm for the conservation of Mediterranean fishing grounds.Keywords: benthos, community composition, ecosystem management, fishing, marine reserves, Mediterranean Sea. RESUMEN: Análisis del grado de perturbación ocasionado por la pesca de arrastre considerando comunidades bentónicas de caladeros fuertemente explotados en áreas protegidas. -El presente estudio se centra en 4 áreas del noroeste mediterráneo para investigar la respuesta de la fauna bentónica considerando un gradiente de niveles de impacto provocado por la pesca de arrastre. Un área se sitúa en un caladero fuertemente explotado. La segunda se halla en el interior del caladero pero no ha sido explotada en 20 años. La tercera está situada en una zona adyacente a un área marina protegida sujeta ocasionalmente a la pesca de arrastre. Finalmente, la cuarta se sitúa en el interior del área marina protegida donde la pesca de arrastre está prohibida hace treinta años. Mediante las marcas de arrastre del fondo obtenidas con el sónar de barrido lateral se pueden confirmar los gradientes de intensidad de pesca de arrastre. Se analiza la respuesta observada de la fauna bentónica a la pesca de arrastre a mesoescala de un calador de pesca, comparando los patrones de abundancia, biomasa, diversidad y estructura de la comunidad de la epifauna y la infauna, comparándola con respuestas ya predichas en previos estudios. En general, los resultados mostraron que las comunidades menos impactadas por el arrastre están constituidas por comunidades más estructuradas (por ejemplo, más abundancia de filtradores suspensívoros sésiles en las zonas menos perturbadas frente una mayor dominancia de pequeños invertebrados en las zonas perturbadas). Al mismo tiempo, estos resultados confirman los beneficio...