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Species of Ulva Linnaeus are nearly impossible to identify using morpho-anatomy due to their simple thallus structure and phenotypic plasticity. The current solution to this problem is to sequence ...

Current usage of the name Ulva lactuca, the generitype of Ulva, remains uncertain. Genetic analyses were performed on the U. lactuca Linnaean holotype, the U. fasciata epitype, the U. fenestrata holotype, the U. lobata lectotype, and the U. stipitata lectotype. The U. lactuca holotype is nearly identical in rbcL sequence to the U. fasciata epitype, a warm temperate to tropical species, rather than the cold temperate species to which the name U. lactuca has generally been applied. We hypothesize that the holotype specimen of U. lactuca came from the Indo-Pacific rather than northern Europe. Our analyses indicate that U. fasciata and U. lobata are heterotypic synonyms of U. lactuca. Ulva fenestrata is the earliest name for northern hemisphere, cold temperate Atlantic and Pacific species, with U. stipitata a junior synonym. DNA sequences from type specimens provide an unequivocal method for applying names to Ulva species. This article is protected by copyright. All rights reserved.

Aquaculture and maritime traffic have been identified as the main vectors for introductions of alien marine species. Except for one notorious case of Caulerpa taxifolia, the role of aquarium trade towards the introduction of alien seaweeds has been largely unassessed. Here, we address the risk of accidental release of seaweed species from the aquarium trade market in European waters. We assessed the importance and diversity of seaweed species in the European online aquarium retail circuit. Our web survey revealed more than 30 genera available for online sale into Europe, including known introduced and invasive species. A second aspect of the study consisted in sampling algal diversity found in aquaria. While allowing direct and accurate identification of the specimens, this approach was targeting not only ornamental species, but also seaweeds that may be accidentally present in the aquarium circuit. By DNA-barcoding we identified no less than 134 taxa, 7 of which are flagged as introduced in Europe and 5 reported as invasive. Climate envelope models show that at least 23 aquarium species have the potential to thrive in European waters. As expected by the tropical conditions in most aquaria, southern Atlantic regions of Europe and the Mediterranean are the most vulnerable towards new introductions. Further predictions show that this risk will increase and shift northwards as global warming proceeds. Overall our data indicate that aquarium trade poses a potential risk of new seaweed introductions, and calls for a cautious approach.

The genus Ulva (Chlorophyta) is ubiquitous along Israeli Mediterranean shores where it has been studied extensively due to its important ecological role and potential value in biotechnology and aquaculture. Previous identifications of Ulva in Israel were based only on morphology. Here, we compare species found in 2002 and in 2014-2016. Analyses of ribulose-1,5-bisphosphate carboxylase/oxygenase ( rbc L) and elongation factor 1-alpha ( tuf A) plastid genes (2014-2016 samples only), combined with morphological data, identified six Ulva species, three of which are new records for Israel and probably originate from the Indo-Pacific. Ulva compressa , rarely found in 2002, is now the most abundant species and exhibits two fairly distinct morphologies correlated with different haplotypes for both genes. Ulva fasciata was found more commonly in 2002 than in 2014-16, whereas the morphologically similar, and closely related, invasive species U. ohnoi seemed more frequent in recent samples. The finely branched tubular Ulva tepida was found in 2002 and 2015/16, and U. chaugulii and U. mediterranea were discovered for the first time in 2015/16. The changing Ulva flora of the Israeli Mediterranean may be correlated with major environmental changes including 3°C increase in sea surface temperatures over the last two decades, as well as a generally increasing prevalence of non-native species. The local Ulva species now found in Israel could be of value for various industrial uses.

In a recent paper in Current Biology, Fennessy and colleagues [1] conclude that there are four species of giraffe and that their numbers are declining in Africa. Giraffes (Giraffa camelopardalis) are presently classified as one species, with nine subspecies, which are considered ‘Vulnerable’ on the IUCN Red List [2]. The present consensus of one species divided into nine subspecies has previously been questioned (Supplemental information), and Fennessy and colleagues [1] provide another viewpoint on giraffe taxonomy. The fundamental reason for different taxonomic interpretations is that they are based upon different datasets that adopt different statistical techniques and follow different criteria for nomenclature.

Mortality episodes have regularly been affecting the shellfish industry throughout its history. Some of these mortalities, especially in the oyster industry, have been attributed to herpesviruses. Purification of viral particles and molecular characterization have led to the development of routine monitoring, as well as improved taxonomic classification. Ostreid herpesviruses (Malacoherpesviridae), mostly affecting Pacific oysters Crassostrea gigas, have been sporadically recorded in the French oyster industry since the early 1990s (OsHV-1 ‘reference’). From 2008, a new variant of ostreid herpesvirus (OsHV-1 μVar) has emerged and seriously impacted oyster production in France and other European countries. Consequently, the presence of ostreid herpesviruses has been monitored in different oyster producing areas around the world. The present study compiles molecular data that are available from survey efforts and takes a biogeographical approach, in order to infer an origin for ostreid herpesviruses. The highest genotype diversity was found in East Asia, despite a lower survey effort in that area than in Europe. Genotype network analyses show that both populations of ostreid herpesviruses present in Europe (OsHV-1 ‘reference’ and OsHV-1 μVar) are closely related to genotypes recorded in Asia. Moreover, ostreid herpesviruses have been detected in wild and symptom-free populations of various Asian native Crassostrea species. In the rest of the world, ostreid herpesvirus genotypes were recorded from cultivated C. gigas, and mostly associated with mortality episodes. Results of this study are therefore highly suggestive of an Asian origin for these viruses, which can be pathogenic under farming conditions. It also highlights the risks of European stock improvements, by means of overseas shellfish imports.

With globalization, agriculture and aquaculture activities are increasingly affected by diseases that are spread through movement of crops and stock. Such movements are also associated with the introduction of non-native species via hitchhiking individual organisms. The oyster industry, one of the most important forms of marine aquaculture, embodies these issues. In Europe disease outbreaks affecting cultivated populations of the naturalized oyster Crassostrea gigas caused a major disruption of production in the late 1960s and early 1970s. Mitigation procedures involved massive imports of stock from the species' native range in the northwestern Pacific from 1971 to 1977. We assessed the role stock imports played in the introduction of non-native marine species (including pathogens) from the northwestern Pacific to Europe through a methodological and critical appraisal of record data. The discovery rate of non-native species (a proxy for the introduction rate) from 1966 to 2012 suggests a continuous vector activity over the entire period. Disease outbreaks that have been affecting oyster production since 2008 may be a result of imports from the northwestern Pacific, and such imports are again being considered as an answer to the crisis. Although successful as a remedy in the short and medium terms, such translocations may bring new diseases that may trigger yet more imports (self-reinforcing or positive feedback loop) and lead to the introduction of more hitchhikers. Although there is a legal framework to prevent or reduce these introductions, existing procedures should be improved.

A species previously confused with Ahnfeltiopsis devoniensis in Ireland and with Gymnogongrus crenulatus in eastern Canada and north-eastern USA has remained undescribed because of its cryptogenic origin. Our published research suggested a trans-Atlantic introduction, possibly with ship ballast rock, but the relationship with A. leptophylla from California required further investigation and a North Pacific origin was possible. Here, we report that 34 samples of this species from Northern Ireland (UK), New Hampshire (USA) and New Brunswick (Canada) were genetically identical at the cox2–3 spacer locus, consistent with a recent introduction. By contrast, in A. leptophylla, four haplotypes were found in 9 samples from three sites in California. This species (as G. crenulatus) was recently discovered in the North Pacific for the first time, during surveys in British Columbia for the Canadian Barcode of Life Project. Phylogenetic analysis of plastid-encoded rbcL and mitochondrial cox1 gene sequences s...

25 páginas, 9 figuras, 3 tablas., Zenetos, A. et al., More than 60 marine non-indigenous species (NIS) have been removed from previous lists and 84 species have been added, bringing the total to 986 alien species in the Mediterranean [775 in the eastern Mediterranean (EMED), 249 in the central Mediterranean (CMED), 190 in the Adriatic Sea (ADRIA) and 308 in the western Mediterranean (WMED)]. There were 48 new entries since 2011 which can be interpreted as approximately one new entry every two weeks. The number of alien species continues to increase, by 2-3 species per year for macrophytes, molluscs and polychaetes, 3-4 species per year for crustaceans, and 6 species per year for fish. The dominant group among alien species is molluscs (with 215 species), followed by crustaceans (159) and polychaetes (132). Macrophytes are the leading group of NIS in the ADRIA and the WMED, reaching 26-30% of all aliens, whereas in the EMED they barely constitute 10% of the introductions. In the EMED, molluscs are the most species-rich group, followed by crustaceans, fish and polychaetes. More than half (54%) of the marine alien species in the Mediterranean were probably introduced by corridors (mainly Suez). Shipping is blamed directly for the introduction of only 12 species, whereas it is assumed to be the most likely pathway of introduction (via ballasts or fouling) of another 300 species. For approximately 100 species shipping is a probable pathway along with the Suez Canal and/or aquaculture. Approximately 20 species have been introduced with certainty via aquaculture, while >50 species (mostly macroalgae), occurring in the vicinity of oyster farms, are assumed to be introduced accidentally as contaminants of imported species. A total of 18 species are assumed to have been introduced by the aquarium trade. Lessepsian species decline westwards, while the reverse pattern is evident for ship-mediated species and for those introduced with aquaculture. There is an increasing trend in new introductions via the Suez Canal and via shipping., The research leading to these results was partly supported by funding from the European Community’s Seventh Framework Programme ([FP7/2007-2013]) under grant agreement n° 287600 - PERSEUS project (Policy-oriented marine Environmental Research for the Southern European Seas). MAMIAS has been developed for the Regional Activity Centre for Specially Protected Areas of the UNEP/ Mediterranean Action Plan under contracts No 67, 68, 69, 70 and 71 /2011/RAC/RPA.

Synopsis Red algae (Rhodophyta) are an ancient group with unusual morphological, biochemical, and life-history features including a complete absence of flagella. Although the red algae present many opportunities for studying speciation, this has rarely been explicitly addressed. Here, we examine an aspect of paternal gene flow by determining fertilization success of female Neosiphonia harveyi (Ceramiales), which retains a morphological record of all successful and unsuccessful female gametes. High fertilization rates were observed except when there were no males at all within the tidepool, or in a submerged marina environment. Small numbers of reproductive males were able to saturate fertilization rates, suggesting that limited availability of sperm may be less significant in red algae than previously thought. In another member of the Ceramiales, Antithamnion, relatively large chromosomes permit karyological identification of polyploids. The Western Pacific species Antithamnion sparsum is closely related to the diploid species Antithamnion defectum, known only from the Eastern Pacific, and appears to have evolved from it. Molecular evidence suggests that A. sparsum is an autopolyploid, and that the European species known as Antithamnion densum is divergent from the A. sparsum/defectum complex.

The macroalga Ulva limnetica K. Ichihara et S. Shimada is the only known Ulva species to be distributed exclusively in freshwater and is restricted to freshwater bodies in the Ryuku archipelago. Molecular phylogenetic analysis suggests that U. limnetica originally evolved from marine forms of Ulva. The mechanisms of adaptation to freshwater in Ulva spp. are poorly understood. In this study, we isolated genes potentially involved in adaptation or tolerance to freshwater conditions in U. limnetica, using suppression subtractive hybridization between mRNAs of samples cultured in freshwater and seawater conditions. A total of 219 genes, up-regulated by the exposure of the macroalga to freshwater, were isolated. Reverse transcription–PCR (RT–PCR) revealed 39 clones, including malate dehydrogenase, soluble starch synthase, triosephosphate isomerase, plastid ribosomal protein, DnaJ-like protein, and chloroplast ascorbate peroxidase (APX), which were specifically or preferentially expressed in freshwater conditions. These 39 clones were also analyzed for their temporal transcriptional response to freshwater conditions. A large majority of these up-regulated genes showed a transient peak of expression after 1–4 h, followed in the next 24 h by a decrease to a stable level (over the 7 d of the experiment). After the initial response peak, the level of expression either remained higher than in the control (long-term response) or returned to a level similar to pretreatment level. A few genes showed a more delayed response (i.e., after several days) to freshwater exposure. Finally, we discussed the possible contributions of the freshwater-induced genes in the acquisition of freshwater adaptation or tolerance of U. limnetica.

Aim The oceans harbour a great diversity of organisms whose distribution and ecological preferences are often poorly understood. Species distribution modelling (SDM) could improve our knowledge and inform marine ecosystem management and conservation. Although marine environmental data are available from various sources, there are currently no user-friendly, high-resolution global datasets designed for SDM applications. This study aims to fill this gap by assembling a comprehensive,uniform,high-resolutionandreadilyusablepackageof globalenvironmental rasters. Location Global, marine. Methods We compiled global coverage data, e.g. satellite-based and in situ measured data, representing various aspects of the marine environment relevant for species distributions.Rasters were assembled at a resolution of 5 arcmin (c.9.2 km) and a uniform landmask was applied. The utility of the dataset was evaluated by maximum entropy SDM of the invasive seaweed Codium fragile ssp. fragile. Results We present Bio-ORACLE (ocean rasters for analysis of climate and environment), a global dataset consisting of 23 geophysical, biotic and climate rasters. This user-friendly data package for marine species distribution modelling is available for download at http://www.bio-oracle.ugent.be. The high predictive power of the distribution model of C. fragile ssp. fragile clearly illustrates the potential of the data package for SDM of shallow-water marine organisms. Main conclusions The availability of this global environmental data package has the potential to stimulate marine SDM.The high predictive success of the presenceonly model of a notorious invasive seaweed shows that the information contained in Bio-ORACLE can be informative about marine distributions and permits building highly accurate species distribution models.

Not all introduced (invasive) species in a region will spread from a single point of introduction. Long-distance dispersal or further introductions can obscure the pattern of spread, but the regional importance of such processes is difficult to gauge. These difficulties are further compounded when information on the multiple scale process of invasive species range expansion is reduced to one-dimensional estimates of spread (e.g. km yr −1 ). We therefore compared the results of two different metrics of range expansion: maximum linear rate of spread and accumulation of occupied grid squares (50 × 50 km) over time. An analysis of records for 54 species of introduced marine macrophytes in the Mediterranean and northeast Atlantic revealed cases where the invasion process was probably missed (e.g. Atlantic Bonnemaisonia hamifera ) and suggested cases of secondary introductions or erratic jump dispersal ( Dasysiphonia sp. and Womersleyella setacea ). A majority of species analysed showed evidence for an accumulation of invaded sites without a clear invasion front. Estimates of spread rate are increasing for more recent introductions. The increase is greater than can be accounted for by temporally varying search effort and implies a historical increase in vector efficiency and/or a decreased resistance of native communities to invasion.

In early July 2008, news agencies worldwide reported on a vast algal bloom that was threatening the upcoming Olympic sailing events in Qingdao, China. The identity of the culpable alga, however, remained undiscussed. We have identified the alga that caused the bloom by means of morphological and molecular data, including sequence data of the plastid encoded large subunit ribulose 1,5-bisphosphate carboxylase gene (rbcL) and the nuclear encoded rDNA internal transcribed spacer (ITS) region. The bloom-forming alga falls within the morphological limits of the green seaweed Ulva prolifera O.F. Muller ('Enteromorpha prolifera (O.F. Muller) J. Agardh') but our phylogenetic analyses show that it forms a clade with representatives of the Ulva linza-procera-prolifera (LPP) complex. The Chinese rbcL sequences are identical to those of specimens collected from Japan, New Zealand, Finland and Portugal, suggesting that the taxon is widely distributed. rDNA ITS sequences showed a close affinity with Japanese isolates of the species complex. The Qingdao bloom is a typical illustration of a green tide, which occurs increasingly along several coasts worldwide. © 2009 Japanese Society of Phycology.

Macroalgal blooms are a growing environmental problem in eutrophicated coastal ecosystems. Members of the green algal genus Ulva are significant contributors to blooms, which are typically dominated by only one of several co-occurring opportunistic species. Our understanding of bloom dynamics, such as the importance of clonality, is limited because previously used genetic markers such as internal transcribed spacer sequences have shown very little resolution. Microsatellites are the marker of choice for such studies, but to date, only five primer pairs have been developed for a single member of this genus, Ulva intestinalis. We have now developed four new microsatellite markers for U. intestinalis using genome screening and restriction–ligation and tested them on individuals from six populations in the Gulf of Finland, Finland. All new markers exhibited polymorphism in U. intestinalis, with the numbers of alleles ranging from 6 to 10. On the basis of assignment tests, FST estimates and analysis o...

It has traditionally been considered that areas with high natural species richness are likely to be more resistant to non-indigenous species than those with lower numbers of species. However, this theory has been the subject of a debate over the last decade, since some studies have shown the opposite trend. In the present study, a macroalgal survey was carried out at 24 localities in Northern Ireland and southern England, using a quadrat approach in the lower littoral. The two opposing hypotheses were tested (negative versus positive relationship between native and non-indigenous species richness) in this marine environment. The effect of the presence of ‘impacts’, potential sources of disturbance and species introduction (e.g. marina, harbour or aquaculture), was also tested. A positive relationship was found between the number of non-indigenous species and the native species richness at the three different scales tested (quadrats, sites and localities). At no scale did a richer native assemblage appear to restrict the establishment of introduced species. The analyses revealed greater species richness and different community composition, as well as more non-indigenous species, in southern England relative to Northern Ireland. The presence of the considered impacts had an effect on the community composition and species richness in southern England but not in Northern Ireland. Such impacts had no effect on the non-indigenous species richness in either area.

International audience; Seaweed assemblages represent the dominant autotrophic biomass in many coastal environments, playing a central structural and functional role in several ecosystems. In Europe, seaweed assemblages are highly diverse systems. The combined seaweed flora of different European regions hold around 1550 species (belonging to nearly 500 genera), with new species continuously uncovered, thanks to the emergence of molecular tools. In this manuscript we review the effects of global and local stressors on European seaweeds, their communities, and ecosystem functioning. Following a brief review on the present knowledge on European seaweed diversity and distribution, and the role of seaweed communities in biodiversity and ecosystem functioning, we discuss the effects of biotic homogenization (invasive species) and global climate change (shifts in bioclimatic zones and ocean acidification) on the distribution of individual species and their effect on the structure and functioning of seaweed communities. The arrival of new introduced species (that already account for 5-10% of the European seaweeds) and the regional extirpation of native species resulting from oceans' climate change are creating new diversity scenarios with undetermined functional consequences. Anthropogenic local stressors create additional disruption often altering dramatically assemblage's structure. Hence, we discuss ecosystem level effects of such stressors like harvesting, trampling, habitat modification, overgrazing and eutrophication that impact coastal communities at local scales. Last, we conclude by highlighting significant knowledge gaps that need to be addressed to anticipate the combined effects of global and local stressors on seaweed communities. With physical and biological changes occurring at unexpected pace, marine phycologists should now integrate and join their research efforts to be able to contribute efficiently for the conservation and management of coastal systems.

Hull fouling is thought to have been the vector of introduction for many algal species. We studied ships arriving at a Mediterranean harbour to clarify the present role of commercial cargo shipping in algal introductions. A total of 31 macroalgal taxa were identified from 22 sampled hulls. The majority of records (58%) were of species with a known cosmopolitan geographical distribution. Due to a prevalence of cosmopolitan species and a high turnover of fouling communities, species composition of assemblages did not appear to be influenced by the area of origin, length of ship or age of coating. In the light of the present results, hull fouling on standard trading commercial vessels does not seem to pose a significant risk for new macroalgal species introductions. However, a high proportion of non-cosmopolitan species found on a ship with non-toxic coating may modify this assessment, especially in the light of the increasing use of such coatings and the potential future changes in shipping routes.

Understanding how invasive species spread is of particular concern in the current era of globalisation and rapid environmental change. The occurrence of super-diffusive movements within the context of Levy flights has been discussed with respect to particle physics, human movements, microzooplankton, disease spread in global epidemiology and animal foraging behaviour. Super-diffusive movements provide a theoretical explanation for the rapid spread of organisms and disease, but their applicability to empirical data on the historic spread of organisms has rarely been tested. This study focuses on the role of long-distance dispersal in the invasion dynamics of aquatic invasive species across three contrasting areas and spatial scales: open ocean (north-east Atlantic), enclosed sea (Mediterranean) and an island environment (Ireland). Study species included five freshwater plant species, Azolla filiculoides, Elodea canadensis, Lagarosiphon major, Elodea nuttallii and Lemna minuta; and ten species of marine algae, Asparagopsis armata, Antithamnionella elegans, Antithamnionella ternifolia, Codium fragile, Colpomenia peregrina, Caulerpa taxifolia, Dasysiphonia sp., Sargassum muticum, Undaria pinnatifida and Womersleyella setacea. A simulation model is constructed to show the validity of using historical data to reconstruct dispersal kernels. Levy movement patterns similar to those previously observed in humans and wild animals are evident in the re-constructed dispersal pattern of invasive aquatic species. Such patterns may be widespread among invasive species and could be exacerbated by further development of trade networks, human travel and environmental change. These findings have implications for our ability to predict and manage future invasions, and improve our understanding of the potential for spread of organisms including infectious diseases, plant pests and genetically modified organisms.

The utility of species distribution models for applications in invasion and global change biology is critically dependent on their transferability between regions or points in time, respectively. We introduce two methods that aim to improve the transferability of presence-only models: density-based occurrence thinning and performance-based predictor selection. We evaluate the effect of these methods along with the impact of the choice of model complexity and geographic background on the transferability of a species distribution model between geographic regions. Our multifactorial experiment focuses on the notorious invasive seaweed Caulerpa cylindracea (previously Caulerpa racemosa var. cylindracea) and uses Maxent, a commonly used presence-only modeling technique. We show that model transferability is markedly improved by appropriate predictor selection, with occurrence thinning, model complexity and background choice having relatively minor effects. The data shows that, if available, occurrence records from the native and invaded regions should be combined as this leads to models with high predictive power while reducing the sensitivity to choices made in the modeling process. The inferred distribution model of Caulerpa cylindracea shows the potential for this species to further spread along the coasts of Western Europe, western Africa and the south coast of Australia.

We report the occurrence of four red macroalgae new to Europe. Two species were unambiguously determined to the species level with a DNA barcoding approach, while the remaining two species could only be assigned to a genus. Gelidium vagum was found in the Oosterschelde estuary (the Netherlands). Gracilariopsis chorda, Chondracanthus sp. and Solieria sp. were found in the Gulf of Morbihan in Brittany (France); Solieria sp. was also subsequently observed in the Thau Lagoon (France). Gelidium vagum and Gracilariopsis chorda are species originating from the north-western Pacific, around the Japanese archipelago. Phylogenetic analyses also show a likely Pacific origin for Chondracanthus sp. and Solieria sp. Three of these species are likely to have been introduced after 2008, indicating some active transport pathways between the Pacific and the north-eastern Atlantic. These findings also underline the importance of consistent and continuous local expertise (versus rapid assessment) in early warning systems.

Marine aliens are non-native species that have been transported across major geographical barriers by human activities, involving vectors that move propagules along pathways. Species may also be newly observed in a geographical area due to range shifts, generally in association with climate change. Artificial structures are considered to be either man-made materials or natural materials shaped or displaced to serve a specific function for human activities. All types of artificial structures are currently increasing dramatically in coastal zones due to increasing human populations on coastlines. Most of the significant marine vectors and pathways involve mobile artificial structures and are reviewed here. These include shipping (ballast water and hull fouling) and aquaculture, including stock transfer and unintentional introductions, all of which can move species into new biogeographical provinces. Some types of structures frequently move long distances but have low fouling loads (e.g., commercial shipping), whereas others (e.g., barges and pontoons) can be hyperfouled due to long stationary periods such that when moved they transport mature fouling communities. We also examine the presence of alien marine species on static (immobile) artificial structures, which support different communities from those on natural hard substrata. We consider the role of these structures, such as coastal defences, artificial reefs, and offshore platforms, in the dispersal and abundance of alien species. Marinas include both mobile and immobile structures and are apparently particularly favourable habitats for many aliens. For example, in coastal North America approximately 90% of the alien species inhabiting hard substrata have been reported from docks and marinas. Detailed case studies of alien marine species (two seaweeds and four invertebrates) are provided, with an analysis of their origin, vectors of transport, habitat in the introduced range, and potential impact. Although there are exceptions, a large majority of marine alien species seem to be associated, at least for some of the time, with artificial structures. It is clear that artificial structures can pave the way and act as stepping stones or even corridors for some marine aliens, as do urban areas, roads and riparian environments in terrestrial ecosystems. The observed acceleration of spread rates for marine invasions over the course of the last two centuries may partly be a result of the increase of artificial structures in coastal environments coupled with greater activity of vectors.

ARTICLE INFOArticle history:Received 12 October 2006Received in revised form25 January 2007Accepted 7 February 2007Available online 28 March 2007Keywords:Biological invasionsCrassostrea gigasShellsThau LagoonMarine macrophytesTransportElimination treatmentsABSTRACTIntroduction of non-indigenous species can alter marine communities and ecosystems. Inshellfish farming, transfer of livestock, especially oysters, is a common practice and poten-tially constitutes a pathway for non-indigenous introductions. Many species of seaweedsare believed to have been accidentally introduced in association with these transfers, butthere is little direct evidence.We experimentally simulated the transfer of oysters from the Thau Lagoon (France).These transfers involved increasing periods of aerial emersion and additional brine andhot water treatments. The brine and hot water treatments were evaluated as a means ofreducing the probability of algal introductions with oyster transfers. Shells were culturedfor 40 days in experimental tanks to identify the macroalgae likely to be introduced withany oyster transfer.A total of 57 macroalgal taxa, including 16 taxa not indigenous to the Thau Lagoon, wererecorded across all treatments and experiments. The abundance of some species increasedin several cases following aerial emersion. Elimination treatments (immersion in brine orhot water) significantly reduced algal diversity, with hot water treatments resulting in nospecies or only tubular Ulva spp. present.The results support the hypothesis that oyster transfers are effective as primary andsecondary vectors of macroalgal introductions. Relatively simple changes to the transferpractice (particularly hot water treatments) are suggested as a means of reducing the riskof non-indigenous algal introductions. 2007 Elsevier Ltd. All rights reserved.