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Tiago Marques and Carolina Marques thank partial support by CEAUL (funded by FCT through the project UIDB/00006/2020). Aims The present study is the first attempt to grasp the scale and richness of marine biological invasions in Macaronesia. We pioneered a comprehensive non-native species (NNS), inventory in the region to determine their diversity patterns and native distribution origins. NNS were defined here as the result of both introductions and range expansions. We also used statistical modelling to examine relationships among NNS richness, anthropogenic activities, demographic and geographical variables across Macaronesia. Location Macaronesia. Methods A comprehensive literature search was conducted for marine NNS records in Macaronesia, registering the first record's location and year from 1884 to 2020. We used univariate and multivariate analyses to evaluate differences and similarities in community composition. By applying a Generalized Linear Model (GLM), we tested hypotheses regarding NNS richness as a function of anthropogenic activities, demographic and geographical variables. Results A total of 144 marine non-native species (NNS) were recorded for the whole of Macaronesia. The highest NNS richness was registered in the Canary Islands (76 NNS), followed by the Azores (66 NNS), Madeira (59 NNS) and finally Cabo Verde (18 NNS). Some differences amongst archipelagos were observed, such as the high number of non-native macroalgae in the Azores, fishes in the Canary Islands and tunicates in Cabo Verde. Overall, macroalgae, tunicates and bryozoans were the predominant taxonomic groups in the Macaronesian archipelagos. Madeira and Canary Islands were the archipelagos with more similarity in marine NNS, and Cabo Verde the most divergent. Finally, GLM suggested that non-native richness patterns across Macaronesia were dependent on the considered archipelago and strongly affected by (1) minimum distance to the mainland, (2) the total number of ports and marinas and (3) total marinas area (km2). Conclusions The model results and NNS listing in the present study will likely raise the awareness and response regarding marine NNS in the whole Macaronesia region, serving as a baseline for future research as well as implementing and enforcing regulations related to the introduction of marine NNS in oceanic islands. Publisher PDF

Global warming is increasing the frequency, duration and intensity of extreme events such as marine heat waves (MHWs). The effects of MHWs include a variety of negative environmental impacts. Extreme weather events can interact with other environmental stressors such as invasion by marine non-indigenous species (NIS). The aim of this study was to (1) compare the responses of fouling assemblages recruited within a harbour (highly invaded) with the responses of those recruited in natural habitats (not invaded) to simulated MHWs of different temperatures and durations, and (2) evaluate the legacy effects of those MHWs on the invasibility of both types of assemblage by deploying them in a marina environment (high NIS propagule pressure). Experimental assemblages were sampled after 5 or 10 d of exposure to 1 of 3 different temperature conditions to examine the effects of varying MHW conditions. Later those assemblages were deployed inside a marina facility to test the invasibility of heat-stressed assemblages. The results revealed that higher temperatures and longer MHWs had an overall negative impact on both native and non-indigenous assemblages. Shorter MHWs had greater effects on assemblages dominated by NIS, while longer MHWs affected native species more. Increasing MHW duration promoted increased variability in the resulting invasive assemblages. Winner and loser species and homogenisation could potentially alter the legacy effects of MHWs on the pattern of NIS recruitment. This study highlights the importance of interactions between environmental stressors to the conservation of coastal communities, crucial ecosystems on oceanic islands.

Anthropogenic pressures such as the introduction of non-indigenous species (NIS) have impacted global biodiversity and ecosystems. Most marine species spreading outside their natural biogeographical limits are promoted and facilitated by maritime traffic through ballast water and hull biofouling. Propagule pressure plays a primary role in invasion success mixed with environmental conditions of the arrival port. Moreover, with the current ocean sprawl, new substrates are offered for potential NIS recruits. Here, differences in the fouling assemblages thriving inside three different ports/marinas facilities in Madeira Island were assessed for comparison. The locations showed significant differences concerning assemblage structure. Most NIS were detected in plastic floating pontoons. Funchal harbour receives most of the marine traffic in Madeira, acting as the main hub for primary NIS introductions, being recreational boating involved in NIS secondary transfers. Our results highlight the need for future management actions in island ecosystems, particularly monitoring and sampling of recreational boating.

Globally, there is growing concern regarding the effects of the increasing anthropogenic pressures in marine communities. Artificial structures such as marinas and aquaculture facilities serve as invasion hotspots; hence, monitoring fouling communities on these structures can be valuable for detecting new invasions. In the current study, 24 settlement PVC plates were deployed for three months to compare the recruitment ability of these two artificial environments along the south coast of the offshore island of Madeira (NE Atlantic). The results showed higher variations in the species richness between regions (SW vs. SE) than between artificial habitats (sea-cages vs. marinas), although the community composition differed. Cnidaria and Bryozoa were the most representative groups in the aquaculture systems, while Bryozoa and Chordata were in the marinas. A sum of 18 NIS was recorded for the study, accounting for between 21.88% and 54.84% of the total number of species in the aquaculture facilities and marinas, respectively. The higher NIS percentage from the marinas was even more explicit in the SE coast, where Cradoscrupocellaria bertholletii, Parasmittina alba, and Botrylloides niger distinctly dominated fouling populations. The results suggest that at least some particular NIS previously reported in the studied marinas successfully colonized sea-cages. Future assessments need to address the potential role of aquaculture facilities as drivers for the secondary spread of NIS. Additionally, two new records are considered for Madeira: Eudendrium capillare and Ericthonius punctatus., SI

Highlights: • Sea urchin food consumption and gonad index followed thermal performance curves. • Body size and sex interacted with temperature and influenced food consumption rates. • Only body size, not sex, in addition to temperature influenced gonad indices. • Larger sea urchins were impacted to a greater extent by warmer temperatures. Rising sea surface temperatures affect the feeding behaviour and reproductive success of many coastal benthic invertebrates. This experimental study investigated the effects of ocean warming on macroalgal food consumption rates in the sea urchins Arbacia lixula and Paracentrotus lividus from Madeira Island to assess how the feeding pressure they exert may change under warmer ocean conditions. Additionally, in A. lixula, the relationship between temperature and the gonad index was examined to estimate potential future reproductive output. Over the course of 25 days, 180 individuals of each species were exposed to temperatures between 22 degrees C and 31 degrees C. After 20 days, consumption rates were assessed in 48-h feeding trials. Gonad indices of A. lixula were determined on the last day of the experiment. In the thermal range investigated, both traits were found to be unimodal functions of temperature. In addition to temperature, consumption rates in both species and the gonad indices in A. lixula were influenced by body size, while feeding in A. lixula also varied between sexes. Maximum food consumption rates (A. lixula and P. lividus) as well as maximum gonad indices (only A. lixula) were observed between 25 degrees C and 26 degrees C. These values are at the upper end of the temperature range that currently prevails around Madeira, and may become average summer temperatures by the year 2100. Consequently, both sea urchin species may thrive during future warm summers and may enhance their top-down control on local macroalgal populations.

Rocky intertidal communities have proved to be tractable systems for experimental ecology, contributing much to our general understanding of population and community ecology. Physical environmental factors are usually considered strong structuring elements for these assemblages. In this study, we adopted a mixed model sampling design to study the effects of substratum type and shore orientation (i.e. different wave exposure) on intertidal assemblages of Madeira Island (NE Atlantic) across time. We included both macrofauna and macroalgae and compare their abundance and distribution in boulders and rocky platforms on north and south coasts of the island. Generally, assemblages moderately differed between boulders and rocky platforms whereas orientation had little influence on the distribution of most taxa. A high variability was observed across a range of spatial and temporal scales, suggesting that interactions of both physical variables and biological parameters may be influencing distribution of intertidal organisms. The results obtained provide pioneer quantitative data on intertidal assemblages of Madeira.

Microbial biofilms can be key mediators for settlement of macrofoulers. The present study examines the coupled effects of microbial biofilms and local environmental conditions on the composition, structure and functioning of macrofouling assemblages. Settlement of invertebrates over a gradient of human-impacted sites was investigated on local biofilms and on biofilms developed in marine protected areas (MPAs). Special attention was given to the presence of non-indigenous species (NIS), a global problem that can cause important impacts on local assemblages. In general, the formation of macrofouling assemblages was influenced by the identity of the biofilm. However, these relationships varied across levels of anthropogenic pressure, possibly influenced by environmental conditions and the propagule pressure locally available. While the NIS Watersipora subatra seemed to be inhibited by the biofilm developed in the MPA, Diplosoma cf. listerianum seemed to be attracted by biofilm developed in the MPA only under mid anthropogenic pressure. The obtained information is critical for marine environmental management, urgently needed for the establishment of prevention and control mechanisms to minimize the settlement of NIS and mitigate their threats. Xunta de Galicia | Ref. I2C-B Xunta de Galicia | Ref. FEDER ED431D 2017/20 Xunta de Galicia | Ref. ED431C 2017/46 Agência Regional para o Desenvolvimento da Investigação Tecnologia e Inovação (ARDITI) | Ref. M1420-09-5369-FSE-000001 European Regional Development Fund | Ref. M1420-01-0145-FEDER-000001 Fundação para a Ciência e Tecnologia | Ref. UIDB/04292/2020 Fundação para a Ciência e a Tecnologia | Ref. CEECINST/00098/2018

While exploring the presence of non-indigenous fouling species colonizing settlement plates deployed in local marinas in Madeira Island (north-eastern Atlantic Ocean), two non-indigenous species (NIS) of free-swimming crustaceans, Paracerceis sculpta (Holmes, 1904) and Sphaeroma walkeri Stebbing, 1905 (Isopoda: Sphaeromatidae), were detected. Paracerceis sculpta is native to the Pacific Coast of North and Central America and has been introduced into many other regions worldwide. Sphaeroma walkeri is native to the northern Indian Ocean and nowadays is considered one of the most widely ship-transported species globally. Both species were collected in the marina of Funchal, Madeira Island, Portugal, during monitoring surveys in 2015. Moreover, several specimens of S. walkeri were also found in a foreign recreational yacht hull, during a dry dock inspection. These findings suggest that hull fouling is a significant vector for the introductions of marine invertebrates into the Madeira island system.

Plastic debris is one of the most extensive pollution problems our planet is facing today and a particular concern for marine environment conservation. The dimension of the problem is so large that it is possible our current era will generate an anthropogenic marker horizon of plastic in earth's sedimentary record. Here we present a new type of plastic pollution, the ‘plasticrusts’, plastic debris encrusting the rocky surface, recently discovered in the intertidal rocky shores of a volcanic Atlantic island. The potential impact that these new ‘plasticrusts’ may have needs to be further explored, as e.g. potential ingestion by intertidal organisms could suppose a new pathway for entrance of plastics into marine food webs. Consequently, its inclusion as a potential new marine debris category in management and monitoring actions should be pondered.

Hull fouling has been a driving force behind the development of most modern marine antifouling coatings that mainly contain copper based biocides to inhibit growth of fouling organisms. Despite these efforts, several non-indigenous species continue to be transferred via hull-fouling worldwide. In this study we designed a disturbance gradient with three commercial antifouling paints applied to PVC settling plates with different concentrations of copper oxide and allowed colonization of fouling communities in four marinas located at the Madeira Archipelago (NE Atlantic). Overall, the antifouling treatments were effective in decreasing the diversity of fouling communities and spatial variability across marinas was observed. Increasing exposure to metal pollutants decreases both species cover and total diversity, independently of their native or NIS condition. However, evidences found suggest that long-term effects of copper based antifouling coatings can be modulated by metal-resistant species allowing a secondary substrate for the epibiosis of other species to establish.

Ascidians are recognized as major invaders on a global scale, found from the poles to the tropics and from shallow to deep sea waters with approximately 3000 known described species worldwide. However, to date only a few opportunistic studies focusing on the ascidian diversity colonizing natural and artificial substrates have been conducted in the Madeira Archipelago (NE Atlantic). Furthermore, little is known about the community composition and distribution of native and non-indigenous ascidians in the islands of the archipelago. In this context, we conducted a 3-phase study that allowed us to report an updated list of ascidian records found on artificial substrates in the Madeira Archipelago. First, to assess ascidian biodiversity colonizing artificial substrates present in the Madeira Archipelago, we conducted standardized monitoring campaigns in four marinas and hull vessel surveys during dry dock inspections. Second, we complemented this inventory with a comprehensive literature search and Museum collection focused on ascidians colonizing both artificial and natural substrates. Third, we investigated the temporal and spatial variability on the recruitment and succession of young vs mature ascidian assemblages. We found 24 ascidian species in all four marinas, from which 13 are NIS and 11 are new records for Madeira Archipelago. In addition, a literature survey found a total of 27 ascidians occurring on both artificial and natural substrates. This study now reveals a total of 39 ascidian species colonizing both artificial and natural substrates and comprises the most up-to-date list for all shallow-water ascidians in the Madeira Archipelago. A total of 15 NIS are now currently known, 9 exclusively from Madeira Island, 1 exclusively from Porto Santo Island and 5 on the two main islands of the archipelago. This study also shows that the spatial and temporal variability of fouling ascidian assemblages are driven by recruitment and succession of NIS rather than by presence of native species. Finally, total ascidian richness and cover was significantly higher in 4-month-old communities than in 8 to 16-month-old communities across all marinas, suggesting that “bare” artificial substrates are the main drivers of NIS success in the region.

Seagrass meadows are globally recognized as important coastal habitats due to the various ecological functions and ecosystem services they provide. Substantial global decline of seagrass habitats has been recorded over the last decades, underlining the need for extensive studies, including monitoring and mapping these habitats across their distributional range. Cymodocea nodosa (Ucria) Ascherson is the only seagrass species reported in the archipelago of Madeira (NE Atlantic) and systematic or reliable information of its occurrence is very scarce and mostly anecdotal. This study reports the discovery of a yearly-persistent patch of C. nodosa in the southeast coast of Madeira and provides insights into key ecological and biological aspects (e.g. density, leaf length, associated fauna and flora). Seasonal monitoring surveys over a 3-year period, indicate that (1) the patch has increased in size and shoot density over the study period, and (2) leaf lengths follow a typical seasonal pattern over the year. Accounts of past destruction of seagrass meadows in the island, underline the importance of continuous monitoring of the patch and adjacent areas to reveal how the current seagrass patch develops (i.e. patch continuity and/or disappearance), if it integrates a larger meadow and whether anthropogenic pressures as coastal development and/or associated terrigenous sediment runoff events will affect its resilience.

The detection of marine non-indigenous species (NIS) continues to increase worldwide, and this is also the case in the Portuguese islands of the Azores and Madeira. Considering that the major vector of NIS introductions in these archipelagos is marine traffic and given the absence of legislation on hull biofouling management, the number of NIS introduced in the marinas of these archipelagos is also expected to grow. Moreover, tourism intensification has brought more attention on seascapes, resulting in an increased number of recreational divers in these islands. The potential impact of recreational boating as a vector of NIS secondary spread has been already addressed, but no studies have been conducted yet on the role of diving-boats in transport and local dispersion of NIS, e.g. from marinas to diving sites. In this context, we developed a fuzzy inference system to assess the risk of a diving site to receive NIS transported by diving boats. Furthermore, we have validated the model with observational data. In particular, our “free-ride” model is composed by three levels: Level 1 evaluates the risk of each marina to act as NIS source. Level 2 assesses the risk of a diving boat to transport NIS to a diving site. Finally, Level 3 calculates the risk of a diving site to receive NIS. Input variables were collected from questionnaire surveys and from environmental monitoring data. A strong positive relationship was found between the predicted risk value and the actual number of NIS identified in the diving site suggesting the efficiency of the “free-ride” model. Results have revealed that diving sites inside marine protected areas (MPAs) displayed a higher risk to receive NIS than those located outside MPAs highlighting the need to undertake management action to mitigate the transport of NIS by fouling. The “free-ride” model represents a valuable method to identify: “high-risk” marinas, diving-boats and diving sites. Our model enables to prioritize actions for diving centres to control local spreading of NIS and promote conservation of marine habitats.

In recent decades, maritime traffic has been increasing globally. Introduction vectors involving ships, hull fouling and ballast water are often cited as having high risk for introducing marine non-indigenous species (NIS) worldwide. Due to its geographical location, Madeira Island (Portugal) had a significant role in past maritime connections, with the ability to serve as a “port of call” facility. However, little is known about past temporal maritime traffic patterns in Madeira, and particularly its relationship with NIS introductions. In this context, the present study was designed to create a first and comprehensive baseline for historical maritime traffic data for Funchal port, Madeira’s main port, between 1936 and 2004. Official marine traffic data with stops in Funchal were documented, including information concerning last port, ship type, ship size, and residence time in port. In addition, a comprehensive literature search of NIS detected in Madeira Island until 2004 was conducted. Based on the frequency of ship arrivals from different origins five statistically different periods of maritime traffic were determined. The most common maritime traffic origin arriving at Funchal was from Portugal (mainland), Great-Britain, Canary Islands and Spain mainland (Mediterranean). The most relevant IUCN bioregions of Madeira’s maritime traffic origins were in accordance with the frequency of the native distribution of the island’s marine NIS inventories until 2004. The present study reports for the first time a significant and positive relationship with native regions of NIS present in Madeira until 2004 with the most relevant maritime traffic routes, confirming maritime traffic as one of the main vectors for the introduction of these species in Madeira Island. Finally, a continuous monitoring, update, and analysis of maritime traffic, identifying invading corridors, needs to be maintained as a fundamental tool for management NIS introductions in Madeira Island.

The introduction of non-indigenous species (NIS) in new environments represents a major threat for coastal ecosystems. A good understanding of the mechanisms and magnitude of the impact of NIS colonisation on native ecosystems is becoming increasingly crucial to develop mitigation measures and prevent new invasions. In this present study, we asked if distinct coastal benthic communities from an oceanic island can have different vulnerability to NIS colonisation process. First, PVC settlement plates were deployed for 1 year on the rocky shore of two different locations of Madeira Island (North versus South coast). Then, we implemented a mesocosm experiment where recruited plate communities were maintained under different levels of NIS propagule pressure in order to assess their vulnerability to NIS colonisation process. Results showed that NIS colonisation success was not influenced by the level of propagule pressure, but however, final colonisation patterns varied depending on the origin of the communities. This variability can be attributed to major structural differences between the preponderant species of each community and therefore to the biotic substrate they offer to colonisers. This study highlights how biotic features can alter the NIS colonisation process and importantly, shows that in an urbanisation context, the nature of the resident communities facing invasions risks needs to be closely assessed.

A survey to monitor for marine non-indigenous species in two marinas of the Archipelago of Madeira (Portugal) has detected the invasive caprellid Caprella scaura Templeton, 1836 in Madeira Island. This species was first described from Mauritius in the western Indian Ocean. During the 20 th century, Caprella scaura has been detected in numerous locations worldwide (Australia, California, Mediterranean) and most recently reported in southern Europe and northern Africa. Hull fouling was the most likely vector for the introduction of C. scaura to Madeira Island.

During a field survey to monitor marine non-indigenous species in several marinas of the Archipelago of Madeira (Portugal), the invasive sabellid polychaete Branchiomma bairdi McIntosh, 1885 was detected for the first time on Madeira Island, reaching densities of 238–516 ind.m -2 . B. bairdi was originally described from the western Atlantic (from Bermuda to Caribbean Sea) but the origin of this species is still unknown. This species has been recorded as an invasive species for the Pacific coast of Panama, Gulf of California, Mediterranean Sea, Canary Islands, and Australia. Hull fouling is the most likely vector for the introduction of the species.

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.

During a study investigating the identity and abundance of fouling non-indigenous species in marinas from the Madeira Archipelago, three species of bryozoans were detected on experimental settlement plates. These three species are described and figured. Celleporaria inaudita was previously only known from Vanuatu (South Pacific Ocean) and Safaga Bay (Red Sea). Parasmittina alba was previously only known from the Brazilian coast. The origin of Parasmitina multiaviculata sp. nov. is unknown. Secondary introduction by anthropogenic vectors (via hull fouling of recreational vessels) seems the most plausible explanation for the presence of these species in the Madeira Islands The work of J.S. was supported by the Austrian Science Fund (FWF, Lise Meitner Program M1444-B25 and Project Number AP28954-B29). P. Ramalhosa holds a research fellowship in the Project M1420-01-0145-FEDER-000001 — project Observatório Oceânico da Madeira (OOM). J. Canning-Clode was supported by a starting grant in the framework of the 2014 FCT Investigator Programme (IF/01606/2014/CP1230/CT0001) SI