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Aim: Retrospective (pre‐ vs. post‐invasion) and cross‐sectional comparisons of ecosystems exposed to high and low bioinvasion pressure, provide an alternative approach to evaluate shifts in biological communities associated with non‐indigenous species (NIS) introductions. In this study, we aimed to examine general patterns of change in community composition, structure and function in six well‐studied and globally distributed marine ecosystems that had documented histories of biological invasions. Location: Global. Methods: By considering a range of regional datasets and different sampling approaches, we evaluated trends within and among ecosystems by comparing paired measures of community and functional structure in either space or time. Results: Our analyses revealed different patterns of structural and functional change at ecosystem scales, but direct comparisons across regions were hindered by confounding effects of study designs and other drivers of change. The most prominent shifts in community composition were observed in the retrospective studies, characterised by the greatest relative contribution of NIS. No uniform pattern of change in functional metrics was observed across study regions. However, functional evenness and dispersion showed a tendency to increase in systems under higher invasion pressure, refuting the hypothesis of selective accumulation of specific traits and functional homogenisation within ecosystems exposed to high invasion pressure. Main Conclusions: Accumulation of NIS within broader communities can be a subtle process, with inherent spatial and temporal variability. Nonetheless, not only do species' proportional contributions to communities change over time in areas subjected to high bioinvasion pressure, but trait profiles can incrementally shift, which alters the original ecology of an area. Planned, long‐term studies that incorporate a range of measures of environmental drivers and ecosystem response are crucial for better understanding of cumulative, community‐level and ecosystem‐scale change associated with biological invasions. [ABSTRACT FROM AUTHOR]

Susan Lynn Williams (1951–2018) was an exceptional marine ecologist whose research focused broadly on the ecology of benthic nearshore environments dominated by seagrasses, seaweeds, and coral reefs. She took an empirical approach founded in techniques of physiological ecology. Susan was committed to applying her research results to ocean management through outreach to decision-makers and resource managers. Susan's career included research throughout the USA in tropical, temperate, and polar regions, but she specialized in tropical marine ecology. Susan's scholarship, leadership, and friendship touched many people, leading to this multi-authored paper. Susan's scholarship was multi-faceted, and she excelled in scientific discovery, integration of scientific results, application of science for conservation, and teaching, especially as a mentor to undergraduate and graduate students and postdoctoral scholars. Susan served in a variety of leadership positions throughout her career. She embodied all facets of leadership; leading by example, listening to others, committing to the "long haul," maintaining trust, and creating a platform for all to shine. Susan was an important role model for women in science. Susan was also a loyal friend, maintaining friendships for many decades. Susan loved cooking and entertaining with friends. This paper provides an overview of the accomplishments of Susan in the broad categories of scholarship, leadership, and friendship. [ABSTRACT FROM AUTHOR]

The human-mediated introduction of marine non-indigenous species is a centuries- if not millennia-old phenomenon, but was only recently acknowledged as a potent driver of change in the sea. We provide a synopsis of key historical milestones for marine bioinvasions, including timelines of (a) discovery and understanding of the invasion process, focusing on transfer mechanisms and outcomes, (b) methodologies used for detection and monitoring, (c) approaches to ecological impacts research, and (d) management and policy responses. Early (until the mid-1900s) marine bioinvasions were given little attention, and in a number of cases actively and routinely facilitated. Beginning in the second half of the 20th century, several conspicuous non-indigenous species outbreaks with strong environmental, economic, and public health impacts raised widespread concerns and initiated shifts in public and scientific perceptions. These high-profile invasions led to policy documents and strategies to reduce the introduction and spread of non-indigenous species, although with significant time lags and limited success and focused on only a subset of transfer mechanisms. Integrated, multi-vector management within an ecosystem-based marine management context is urgently needed to address the complex interactions of natural and human pressures that drive invasions in marine ecosystems. [ABSTRACT FROM AUTHOR]

Aim For over 80 years, the Maine baitworm trade has shipped live polychaete worms and packing algae 'wormweed' to distributors world-wide, while also consistently transferring a wide diversity and abundance of hitchhiking organisms of all life stages to numerous recipient communities. Here, we investigate this potent, yet underestimated, invasion vector using an important recipient region (the Mid-Atlantic) to examine the stepwise species transfer and survival along four stages of the vector. Location Maine and Mid-Atlantic region (New Jersey, Delaware, Maryland, Virginia and North Carolina), USA. Methods We quantified taxonomic identities and abundances of organisms associated with packing algae at four stages along the vector pathway during summer 2011: (1) Maine source habitats; (2) bait boxes from Maine distributors; (3) bait boxes from distributors in five Mid-Atlantic States; and (4) bait bags from retailers in five Mid-Atlantic States. We also examined functional diversity based on significant physical and life history characteristics and assessed genetic diversity for two common hitchhiking snail species. Results We identified 17,798 live macro-organisms across 58 taxa, including marine macro-invertebrates, macroalgae, vascular plants and semi-terrestrial or aquatic invertebrates, present in bait boxes and bags. In all measures of diversity and abundance, we observed decreases of live marine macro-invertebrates across sequential stages of the vector from source to recipient regions. Significant differences in community composition were also observed between stages and were driven by isopods (taxonomic diversity) and isopods, amphipods and some gastropods (functional diversity). Main conclusions The lack of management in the face of the sheer magnitude and diversity of organisms that are transported via the live marine bait trade underscores how this is an underappreciated vector that could be a considerable source of successful invasions globally. [ABSTRACT FROM AUTHOR]

The known extent of biological invasions exhibits strong variation with respect to space, time, taxonomic group, and vector. Using a synthesis of nonindigenous species (NIS) occurrences in North America, we characterized the invasion history for coastal marine ecosystems by invertebrates and algae through 2010, to evaluate variation and existing patterns at a continental scale. This study updates a previous analysis of invasions for the same taxonomic groups in North America, providing a first assessment of changes in the last 11 year period (2000–2010). Overall, we documented 450 marine and estuarine NIS that are considered to have established populations in tidal waters of North America, representing a 51% increase in NIS richness compared to the earlier analysis. Of the 152 species added, 71 species (47%) have first documented records since the year 1999, and 81 species (53%) were additions attributed to earlier time periods due to recent reports and further analysis. Across all time periods, taxonomic groups with the largest contribution were Crustaceans (112 species) and Molluscs (80 species), together providing 43% of the total species richness for North America. Species richness was unevenly distributed among coasts, with most documented on the Pacific Coast (310 species) and fewer on the Atlantic Coast (189 species) and Gulf Coast (88 species). Commercial ships have contributed between (a) 44–78% of the initial (primary) invasions of all nonindigenous species to North America and (b) 52–82% of NIS in the last 30-year time interval, being driven by transfers associated with ballast water and hull biofouling. Importantly, invasion dynamics are a shifting landscape, where the past may not predict the future, especially with emerging trade patterns and global to local environmental changes. Thus, effective management to reduce future invasions requires a dynamic and multi-vector approach, instead of single vector strategies based on past history alone. [ABSTRACT FROM PUBLISHER]

Aim We examine fish invasions in the south-eastern Mediterranean as a model system for the invasibility of open coasts and provide perspectives through a review of global marine fish invasions. Location South-eastern Mediterranean ( Levant Sea). Methods We compare historical (1990-1994) and modern (2008-2011) trawl surveys from the Mediterranean continental shelf and upper slope of Israel to evaluate the relative abundance and biomass of Indo- Pacific fishes and their impact on diversity and trophic level ( Tr L). We examine resultant changes in community composition by both univariate and multivariate analyses, and compliment this study with a critical global review of open coast marine fish invasions. Results A staggering 55 Indo- Pacific fish species have established permanent populations in the Mediterranean in the last 142 years, more than any other marine ecosystem. This process is accelerating with 13 of 27 new arrivals having established in the 21st century alone. Invasive fish biomass and abundance proportions in the shallow open coast have doubled in just two decades and today the Levantine ecosystem is dominated by non-native species. This proliferation has resulted in significant declines of some indigenous species, some to near extirpation levels. Main conclusions Here, we show that non-estuarine ecosystems are much more susceptible to large-scale invasion pressures than previously thought. Our results place invasion in the same category with overexploitation, habitat destruction and pollution, processes normally considered as much more critical perturbations to coastal fish communities. We propose that despite these irreversible alterations, invasions have masked overall Tr L changes and diversity declines by replacing native fish with invasives of similar ecological position. As species extirpations increase, we anticipate further declines in indigenous biomass, abundance and diversity in the Mediterranean Sea. [ABSTRACT FROM AUTHOR]

Increases in temperature associated with global climate change are predicted to elicit drastic changes, especially to marine and freshwater ecosystems. Even small changes in water temperature (1–2°C) may alter rates of biological activity, with concomitant effects to communities and ecosystems. The biological erosion of marine habitats and structures is a rarely considered yet important activity that is likely to be influenced by changing ocean temperatures. We conducted an experiment to test how seawater temperature affects erosion by a non-native crustacean (Sphaeroma quoianum). Aquaria were maintained at one of thirteen temperatures (7.5°C–25.2°C). In each aquarium, twenty isopods were encaged with an expanded polystyrene foam block (800ml) and left to burrow. Polystyrene floats under docks are often damaged by isopods in the field. After two months, isopods created the longest burrows in the moderate seawater temperatures (13.8°C–18.3°C); these temperatures were 1.1–5.6°C higher than the mean ambient temperatures whence they came. Shorter burrows were observed for the coldest (7.5°C) and warmest seawater treatments (25.2°C). These results indicate that increasing seawater temperatures can exacerbate the bioerosive effects of non-native S. quoianum until a threshold, after which the impacts diminish. Because ocean temperatures are predicted to increase 1.5–2.6°C in the next 90years, our data suggest erosion by this non-native crustacean will increase 14.7–37.6% in Coos Bay/South Slough, Oregon (where isopods were collected). However, other invaded bays on the Pacific coast of North America may also experience mean increases of biological erosion of 6.6–29.8%. Since biological activity is tightly coupled with temperature in many species, we hypothesize that the biological erosion rates of other erosive species will also increase with rising water temperatures affecting marine habitats, communities, and structures. [ABSTRACT FROM AUTHOR]