First evaluation of neustonic microplastics in the Macaronesian region, NE Atlantic.

Marine microplastic pollution is an issue of great concern nowadays since high concentrations have been detected in the ocean, mainly in the subtropical gyres that accumulate this type of debris. The long-term effects of this pollution on ecosystems and marine biota are still unknown. The aim of this study is to quantify and characterise microplastics and neustonic zooplankton in sub-surface waters of the Macaronesian region, an area that has been little studied to date. Our results show a great variability in the concentration of microplastics with values between 15,283 items/km2 in Los Gigantes (Tenerife, Canary Islands) and 1,007,872 items/km2 in Las Canteras (Gran Canaria, Canary Islands). The main types of debris found were plastic fragments and fibres. The abundances of neustonic zooplankton were also very variable between the different sampling areas, being the main components copepods and eggs. Regarding the microplastics-zooplankton ratio, values were obtained between 0.002 and 0.22. In Las Canteras, the highest accumulation zone, was found twice as much microplastics as zooplankton for the 1-5 mm fraction in dry weight. These values highlight the potential hazard of microplastics - and its associated chemical contaminants - for marine biota, especially for large filter feeders.

Marine protected communities against biological invasions: A case study from an offshore island.

Biological invasions are a major threat to the world's biota and are considered a major cause of biodiversity loss. Therefore, world marine policy has recognized the need for more marine protected areas (MPAs) as a major tool for biodiversity conservation. The present work experimentally evaluated how protected communities from an offshore island can face the settlement and/or expansion of nonindigenous species (NIS). First, NIS colonization success in marine protected and marina communities was compared by deploying PVC settling plates at the Garajau MPA and Funchal marina (SW Madeira Island). Then, the settling plates from the MPA were transferred to Funchal marina to test their resistance to NIS invasion under high levels of NIS pressure. Results indicated that the structure and composition of fouling communities from the MPA differed from those collected in the marina. Interestingly, communities from the protected area showed lower NIS colonization success, suggesting some degree of biotic resistance against NIS invasion.

Invasion of Sargassum muticum in intertidal rockpools: patterns along the Atlantic Iberian Peninsula.

Spatial patterns of non-indigenous species show scale-dependent properties. Sargassum muticum is an invasive macroalga widely distributed along the Atlantic Iberian Peninsula. Despite being quite abundant from Norway to South Portugal, there is little information about its patterns of distribution, particularly at a large spatial scale (i.e. thousands of kilometres). Here, we examined the spatial variation in the invasion success of S. muticum from rockpools at multiple spatial scales using a hierarchical design. In addition, we analysed how the richness of native assemblages was related to its invasion success and how this relationship changed over different scales. Most of the variation in the invasion success was found at the smallest scales of pool and plot. Furthermore, the invasibility of native macroalgal assemblages was related to the native species richness, but causes that determined invasion success could not be separated from the effects provoked by the invader. Results suggest that small-scale (centimetres to metres) processes contribute considerably to the heterogeneity of S. muticum invasion success.