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Abstract Shipping is understood to be a major vector for the introduction and spread of marine non-indigenous species (NIS). However, recreational boating is still unregulated and its influence as vector has not yet been assessed for the Mediterranean Sea, which is the second most popular recreational boating destination worldwide. This is the first large-scale study to examine this by a combined biological (analyzing hull and marina fouling) and social approach (boaters surveys on maintenance habits, travel patterns and awareness), focused on peracarid crustaceans. A surprisingly high number of NIS were found on vessels cruising Mediterranean waters, and species compositions suggest an exchange between marina and vessel assemblages. This means recreational boating presents a risk for NIS spread which should warrant regulation. Results also implied that regionally coordinated management should be supported by effective local-scale-based management in the Mediterranean, which could improve upon with targeted environmental education to solve lack of awareness. Highlights • This study examines boating as a vector of non-indigenous species (NIS) introductions. • Specifically, peracarid crustaceans are studied in marinas and boats in the Mediterranean. • Results show numerous NIS in marinas and vessels and suggest exchanges between them. • Vessel maintenance and travel patterns influence the likelihood of NIS occurrence. • There is a general lack of awareness of marine bioinvasions among recreational boaters. [ABSTRACT FROM AUTHOR]

The study aims to monitor the post-establishment success of the invasive skeleton shrimp Caprella scaura in the Atlantic-Mediterranean transition zone and understand its connectivity with other world areas, providing new information on the status of the introduced population and its global distribution. By using mitochondrial markers (16S and COI) we examined the temporal variation of populations in Cadiz Bay, Spain (hotspot for introductions in Europe) in between 2010 and 2017; as well as their linkage with foreign populations in its native and introduced distribution ranges. Cadiz Bay populations exhibited a connection with several European introduced populations (Iberian Peninsula, Canary Islands, Mediterranean Sea and The Netherlands), eastern USA, Sea of Japan and Australia. We found no evidence to support a Brazilian origin (one potential native area) of the Iberian Peninsula populations. We identified a progressive decrease in haplotype diversity and a low connectivity at the end of the monitoring period in one of the stations. Human-mediated changes in propagule pressure, and unfavorable environmental fluctuations are probably responsible for this. Meanwhile, populations in Cadiz Bay count on numerous foreign donors that could easily refuel the propagule input by exchanging gene flow. This implies that a vector regulation strategy has the potential of compromising the success of established non-native populations, which usually undergo vulnerability periods due to the challenging conditions of marinas. The use of molecular tools in a time series approach is then useful to identify the ideal time window to put in action management measures so that they are cost-effective., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

There is an increasing concern about the ecosystem consequences of altering macroalgal assemblages. Many macrophytes are foundation species in coastal habitats, supporting much of the biodiversity of these ecosystems by providing essential resources such as food and habitat. The addition of invasive species strongly contributes to habitat modification, but the bottom-up impacts of non-native macroalgae on higher trophic levels remains difficult to predict. The main aim of this study was to evaluate the effects of the invasive macroalga Asparagopsis taxiformis on biodiversity by comparing the mobile macrofauna inhabiting this species to the dominant native species Halopteris scoparia. This is the first comprehensive study of the possible effects of this widespread invasive species on higher trophic levels. A hierarchical sampling design with two different spatial scales was conducted to explore the consistency of the patterns observed. Fifty-nine species belonging to superorder Peracarida were found, accounting 90% of all organisms. A. taxiformis hosted an impoverished epifaunal assemblage in comparison to that associated with the native seaweed, showing significantly lower values of diversity, abundance and number of epifaunal species across study locations. The structure of the associated macrofauna (both in terms of species composition, variability among samples and relative abundance of the species) was also different. Our results highlighted the strong influence of A. taxiformis in the resident community, with differences among the two macroalgae in all the parameters considered. Finally, our results also reflect a biotic homogenization of the epifaunal assemblages associated to A. taxiformis, a scarcely explored consequence of invasive processes in marine environments. Future studies exploring the cascading effects of the observed changes in the epifaunal assemblages would be necessary in order to estimate system responses to macroalgal invasions., (Copyright © 2018 Elsevier Ltd. All rights reserved.)