Aim The introduction of aquatic non‐indigenous species (ANS) has become a major driver for global changes in species biogeography. We examined spatial patterns and temporal trends of ANS detections since 1965 to inform conservation policy and management. Location Global. Methods We assembled an extensive dataset of first records of detection of ANS (1965–2015) across 49 aquatic ecosystems, including the (a) year of first collection, (b) population status and (c) potential pathway(s) of introduction. Data were analysed at global and regional levels to assess patterns of detection rate, richness and transport pathways. Results An annual mean of 43 (±16 SD) primary detections of ANS occurred—one new detection every 8.4 days for 50 years. The global rate of detections was relatively stable during 1965–1995, but increased rapidly after this time, peaking at roughly 66 primary detections per year during 2005–2010 and then declining marginally. Detection rates were variable within and across regions through time. Arthropods, molluscs and fishes were the most frequently reported ANS. Most ANS were likely introduced as stowaways in ships’ ballast water or biofouling, although direct evidence is typically absent. Main conclusions This synthesis highlights the magnitude of recent ANS detections, yet almost certainly represents an underestimate as many ANS go unreported due to limited search effort and diminishing taxonomic expertise. Temporal rates of detection are also confounded by reporting lags, likely contributing to the lower detection rate observed in recent years. There is a critical need to implement standardized, repeated methods across regions and taxa to improve the quality of global‐scale comparisons and sustain core measures over longer time‐scales. It will be fundamental to fill in knowledge gaps given that invasion data representing broad regions of the world's oceans are not yet readily available and to maintain knowledge pipelines for adaptive management.

In recent decades, the world has witnessed an array of harmful invasions by exotic marine organisms. To provide the public and policymakers with better information on the status of exotic species in southern California waters, and to assess differences between port and non-port areas, a Rapid Assessment Survey of selected habitat types in sheltered waters between San Diego and Oxnard was conducted in the summer of 2000. The objectives included comparing the prevalence of exotic species among habitats and regions and between recent and past surveys; obtaining reference data for future assessments of changes in invasion status and the effectiveness of prevention or control efforts; detecting new invasions; and documenting significant range extensions. Twenty-two sites were sampled to include the three major commercial port areas in southern California, non-port-area marinas and lagoon sites. Sampling included dock fouling and adjacent soft-bottom benthos, nearby intertidal sites, and selected subtidal lagoon habitats. Samples were collected by a variety of manual techniques. Sixty-nine of the species collected are exotic, including representatives from two algal divisions and six invertebrate phyla. Ascidians are especially well-represented (14 exotic species) and widely occurring, and some bivalves and bryozoans also occur very widely. The numbers and proportions of exotic taxa were not significantly greater in port areas than in non-port areas.

No abstract

No abstract

Although plant-plant facilitations have been shown to be important structuring forces in salt marshes, less attention has been given to the potential role played by plant-animal facilitations in structuring these communities. We used a combination of sampling and field experiments to evaluate the effect of microenvironmental changes produced by plant cover on the distribution of the burrowing crab Chasmagnathus granulata, a dominant macroinvertebrate of high marshes of the southwestern Atlantic coast. Four questions were explored. Is there a relationship between the spatial distribution of C. granulata and the spatial distribution of rooted macrophytes or distance from the marsh edge? How important is plant cover for the establishment and survival of crabs in the high marsh? Does plant cover affect critical physical variables for crab establishment? How important are environmental conditions for the survival of crabs in the high marsh?Surveys of the marsh surface showed that: (1) there was a strong relationship between the presence of plant cover and the spatial distribution of Chasmagnathus granulata in the high marsh, and (2) both mean crab size and burrow density decreased from the marsh edge to high-marsh levels. By shading the substrate, live plants and experimental plant mimics were found to be equally efficient at buffering high temperature, dehydration, and soil hardness in the high marsh. Experimental amelioration of these harsh physical conditions led to higher crab densities. Crab burrows also buffered harsh environmental conditions, diminishing surface air temperature from ϳ46ЊC to 23ЊC. Finally, tethering experiments showed that stressful heating in the high marsh is lethal for crabs, and that plant cover is crucial for the establishment and long-term success of crabs in the high marsh.No predation was observed in tethering experiments.Our results suggest that plant cover is largely responsible for determining the spatial distribution of this dominant crab in the high marsh through facilitation. Thus, our work shows that plant-animal facilitations as well as plant-plant facilitations are important structuring forces in salt marsh communities.

Ports are a key factor in the understanding and solving of most problems associated with marine invasive species across regional and global scales. Yet many regions with active ports remain understudied. The aim of this work was to (a) identify and quantify the marine fouling organisms in all Patagonian ports of Argentina classifying them as native, exotic or cryptogenic species through a rapid assessment survey and experimental studies, (b) survey the environmental and anthropogenic variables of these ports and (c) analyze and discuss these results in the light of the South America context for the study of marine invasive species, legislation and commerce. We found 247 fouling species, including 17 introduced, one of which is a new record for the region, and other 15 species currently considered cryptogenic species that will need further attention to clarify their status. The analysis of mobile and sessile taxa, together with the environmental variables measured in this study and the port movement, allow us to discuss individual ports' vulnerability to future introductions. This is the first large scale study performed for this region on this topic, and it will help in developing monitoring programs and early detection plans to minimize new species introductions along the marine coastline of southern South America.

Several species of ecosystem engineers inhabiting coastal environments have been reported structuring different kinds of communities. The magnitude of this influence often depends on the habitat complexity introduced by the engineers. It is commonly accepted that an increase in habitat complexity will result in an increase in diversity and/or abundance in the associated fauna. The rocky salt marshes along the coast of Patagonia are dominated by cordgrasses, mussels, and barnacles forming a mosaic of engineered habitats with different complexity. This system allows us to address the following questions: how different is a macroinvertebrate assemblage when dominated by different ecosystem engineers? And, is there a positive relationship between increasing habitat complexity and the species richness, diversity and total density of the assemblages? To address these questions, we compared the three ecological scenarios with decreasing habitat complexity: cordgrass-mussel, mussel, and barnacle-engineered habitats. We found a total of 22 taxa mostly crustaceans and polychaetes common to all scenarios. The three engineered habitats showed different macroinvertebrate assemblages, mainly due to differences in individual abundances of some taxa. The cryptogenic amphipod Orchestia gammarella was found strictly associated with the cordgrass-mussel habitat. Species richness and diversity were positively related with habitat complexity while total density showed the opposite trend. Our study suggests that species vary their relative distribution and abundances in response to different habitat complexity. Nevertheless, the direction (i.e., neutral, positive or negative) and intensity of the community's response seem to depend on the physiological requirements of the different species and their efficiency to readjust their local spatial distribution in the short term.

Patterns of spatial variation of molluscan communities associated with coralline algal turfs were evaluated over 1,000 km of the coast of Argentinean Patagonia. A hierarchically-nested experimental design was used to determine the relative importance of molluscan assemblage variation at three different spatial scales (shores, sites and cores). Hypotheses were also tested about the potential role of habitat variables (frond density, frond length, sediment and epiphytes) for determining molluscan community structure. In total, 38 molluscan species were found comprising 16, 18 and 4 species of bivalves, gastropods and polyplacophorans, respectively. Densities of molluscs in coralline turfs reached ca 77,000 individuals per m 2 and were dominated by mussels, especially Perumytilus purpuratus. Multivariate and univariate analyses of assemblage structure consistently showed that variation at scales of metres and hundreds of kilometres dominated, with sites 20-50 m apart always contributing less than 24% of the total. Significant associations between molluscan community structure and both frond density and frond length demonstrated the potential importance of habitat structure in determining community structure at local scales. Variation in molluscan assemblages at the scale of shores, however, did not appear to correlate with latitudinal, temperature or wave exposure gradients, indicating that other processes must be operating. The compositions of molluscan assemblages in coralline turfs on the coast of Argentina were similar to those reported for central Chile. Comparisons of the richness of these South American assemblages to other parts of the world revealed some striking biogeographical patterns that warrant further investigation. Overall, this work highlights the general importance of small-scale variation in molluscan assemblages on rocky shores and the consistent influence of habitat complexity in determining the structure of diverse molluscan communities associated with mat-like habitats.