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Anthropogenic plastic pollution is a global problem. In the marine environment, one of its less studied effects is the transport of attached biota, which might lead to introductions of non-native species in new areas or aid in habitat expansions of invasive species. The goal of the present work was to assess if the material composition of beached anthropogenic litter is indicative of the rafting fauna in a coastal area and could thus be used as a simple and cost-efficient tool for risk assessment in the future. Beached anthropogenic litter and attached biota along the 200 km coastline of Asturias, central Bay of Biscay, Spain, were analysed. The macrobiotic community attached to fouled litter items was identified using genetic barcoding combined with visual taxonomic analysis, and compared between hard plastics, foams, other plastics and non-plastic items. On the other hand, the material composition of beached litter was analysed in a standardized area on each beach. From these two datasets, the expected frequency of several rafting taxa was calculated for the coastal area and compared to the actually observed frequencies. The results showed that plastics were the most abundant type of beached litter. Litter accumulation was likely driven by coastal sources (industry, ports) and river/sewage inputs and transported by near-shore currents. Rafting vectors were almost exclusively made up of plastics and could mainly be attributed to fishing activity and leisure/ household. We identified a variety of rafting biota, including species of goose barnacles, acorn barnacles, bivalves, gastropods, polychaetes and bryozoan, and hydrozoan colonies attached to stranded litter. Several of these species were non-native and invasive, such as the giant Pacific oyster (Crassostrea gigas) and the Australian barnacle (Austrominius modestus). The composition of attached fauna varied strongly between litter items of different materials. Plastics, except for foam, had a much more diverse attached community than non-plastic materials. The predicted frequency of several taxa attached to beached litter significantly correlated with the actually observed frequencies. Therefore we suggest that the composition of stranded litter on a beach or an area could allow for predictions about the corresponding attached biotic community, including invasive species.

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BackgroundThe introduction of exotic species can have serious consequences for marine ecosystems. On the shores of the Cantabrian Sea (North of Spain) there are no routine examinations of seaweeds that combine molecular and morphological methods for early detection of exotic species making it difficult to assess in the early stages their establishment and expansion processes as a result of anthropogenic activities (e.g., shipping and/or aquaculture).MethodsIn this work we used both morphological identification and molecular barcoding (COI-5P and rbcL genes) of red algae collected in Asturias, Bay of Biscay (Gijón and Candás harbours) and from the University of Oviedo’s herbarium samples.ResultsThe results confirmed the presence of exotic Asian seaweeds Pachymeniopsis gargiuli and Grateloupia turuturu Yamada on Cantabrian Sea shores. Several individuals of these species were fertile and developing cystocarps when collected, underlining the risk of possible expansion or continued establishment. This study constitutes the first report of the Asian P. gargiuli in this area of the Bay of Biscay.ConclusionsHere the presence of the exotic species of the Halymeniales P. gargiuli is confirmed. We hypothesize that this species may have been established some time ago as a cryptic introduction with G. turuturu in Galician shores. The detection of these species on the shores of the Cantabrian Sea is relevant since introductions of Pachymeniopsis species could have been overlooked on other European coasts, probably mixed with G. turuturu and P. lanceolata. Our results confirm one new alien seaweed species that has been detected using molecular methods (COI-5P region and rbcL genes barcoding) on North Atlantic shores: the Asian native P. gargiuli. This demonstrates that routine screening for early detection of exotic algae in the Cantabrian Sea can be used for risk assessment. Genetic barcoding should be done using both rbcL gene and COI-5P regions since, although COI-databases are still poorer in sequences and this inhibits successful outcomes in Grateloupia-related species identifications, it is nonetheless a useful marker for species-level identifications in seaweeds.

Paracentrotus lividus is a sea urchin with an important ecological role in the Cantabrian Sea ecosystem, where its populations are in severe decline and the regional government has implemented a population restoration strategy with the aim of preserving this valuable marine resource. In this study, genetic monitoring was conducted for the first time in the central area of the southern Bay of Biscay to describe the genetic diversity patterns of P. lividus and to assess the potential impacts of conservation and mitigation actions on the wild gene pool. Genetic analyses were performed using the mitochondrial cytochrome b gene and microsatellite loci. Asturian localities showed significant genetic heterogeneity, possibly due to genetic drift, and seemed to constitute a differentiated management unit with regard to other areas of the species’ distribution. The genetic diversity analyses comparing wild samples with those subjected to restoration experiments did not show significant negative effects on restored localities. Sea urchins from hatcheries represented 3.5% of the total recaptured individuals (95% accuracy). Even when low hatchery contributions were detected in this work, the results pointed to the necessity of improving the initial autochthonous breeder genetic pool and the aquaculture strategies applied when restoring wild populations to avoid future unwanted negative effects on wild gene pools.