Ballast water has been widely used by commercial vessels to control trim, draft and stability since the late 1870s. While the global transport of ballast water (and associated sediments) was first ...recognized as a potential dispersal mechanism for plankton in the late 1890s, quantitative research on the issue does not appear in the primary scientific literature until the mid-1980s. Following James T. Carlton's comprehensive review of the biology of ballast water in 1985, there was an explosion in research effort, with nearly 400 papers published in the last thirty years. This article provides a brief overview of the role that ballast water has played as a global vector for aquatic invasive species, summarizing the current state of ballast water research and emerging topics for future study, based on a review of articles in the primary scientific literature. Initially, the main research focus was to document the community composition of ballast water in ships arriving to ports around the world. In the late 1990s, risk ssessments examining shipping traffic patterns and environmental tolerances of species likely transported in ballast water dominated. By 2000, ballast water studies examining efficacy of various treatment strategies dominated, and papers exploring new tools and methods for more accurate/representative sampling and analysis of ballast water emerged as an important research topic. There is currently insufficient data to confidently quantify the probability of invasion associated with any particular inoculum density (or discharge standard), as a result, laboratory, field and modeling studies examining the relationship between invasion risk and the size of the initially released population (the ‘risk-release relationship’) are an emerging, high priority field of study.
Illumina sequencing allows rapid, cheap and accurate whole genome bacterial analyses, but short reads (<300 bp) do not usually enable complete genome assembly. Long-read sequencing greatly assists ...with resolving complex bacterial genomes, particularly when combined with short-read Illumina data (hybrid assembly). However, it is not clear how different long-read sequencing methods affect hybrid assembly accuracy. Relative automation of the assembly process is also crucial to facilitating high-throughput complete bacterial genome reconstruction, avoiding multiple bespoke filtering and data manipulation steps. In this study, we compared hybrid assemblies for 20 bacterial isolates, including two reference strains, using Illumina sequencing and long reads from either Oxford Nanopore Technologies (ONT) or SMRT Pacific Biosciences (PacBio) sequencing platforms. We chose isolates from the family
, as these frequently have highly plastic, repetitive genetic structures, and complete genome reconstruction for these species is relevant for a precise understanding of the epidemiology of antimicrobial resistance. We
assembled genomes using the hybrid assembler Unicycler and compared different read processing strategies, as well as comparing to long-read-only assembly with Flye followed by short-read polishing with Pilon. Hybrid assembly with either PacBio or ONT reads facilitated high-quality genome reconstruction, and was superior to the long-read assembly and polishing approach evaluated with respect to accuracy and completeness. Combining ONT and Illumina reads fully resolved most genomes without additional manual steps, and at a lower consumables cost per isolate in our setting. Automated hybrid assembly is a powerful tool for complete and accurate bacterial genome assembly.
Ballast water is recognized as a leading pathway for the introduction of aquatic non‐indigenous species which have caused substantial ecological damage globally.
Following international regulations, ...most international ships will install a ballast water management system (BWMS) by 2024 to limit the concentration of aquatic organisms in ballast water discharges; however, these new technologies may not operate as expected at global ports having variable water quality or may periodically malfunction.
Using simulations informed by empirical data, we investigated the risk of non‐indigenous species establishment associated with BWMS inoperability and evaluated potential mitigation strategies. Scenarios considered included bypassed or inoperable BWMS achieving no reduction in organisms, and partially functioning BWMS with discharged organism concentrations exceeding permissible limits. These scenarios were contrasted to outcomes with fully functioning BWMS and to voyages where ballast water exchange (BWE) was used to mitigate risk.
Partially functioning BWMSs were nonetheless beneficial, reducing organism concentrations in ballast and thus establishment risk. When a BWMS is bypassed or partially functioning, BWE is a useful emergency mitigation measure, reducing establishment risks more than partial BMWS. However, the greatest risk reduction was achieved when partial BWMS and BWE were combined.
Voyage‐specific characteristics such as concentration of organisms at uptake and destination port salinity can affect the optimal management strategy for voyages when the BWMS does not achieve compliant discharges.
Synthesis and applications. The risk of aquatic invasions and their associated ecological damages can be substantially reduced by using a ballast water management system (BWMS) and/or ballast water exchange (BWE). When a BWMS is inoperable, appropriate mitigation measures should be decided on a trip‐by‐trip basis considering voyage route and reason for BWMS inoperability (when known). BWE is a useful strategy for reducing invasion risk, except when uptake concentrations are very low. Combining BWE and partial BWMS always reduced risk compared with BWE alone, but did not greatly reduce risk when uptake concentrations were high.
The risk of aquatic invasions and their associated ecological damages can be substantially reduced by using a ballast water management system (BWMS) and/or ballast water exchange (BWE). When a BWMS is inoperable, appropriate mitigation measures should be decided on a trip‐by‐trip basis considering voyage route and reason for BWMS inoperability (when known). BWE is a useful strategy for reducing invasion risk, except when uptake concentrations are very low. Combining BWE and partial BWMS always reduced risk compared with BWE alone, but did not greatly reduce risk when uptake concentrations were high.
Social movements must mobilize participation from bystanders to survive, yet there is little research on how bystanders’ evaluations of social movements predict their likelihood to join. Charles ...Tilly offered a four-part theoretical “scorecard” by which people evaluate movements: worthiness, unity, numbers, and commitment. The authors created a novel and psychometrically valid measure (WUNC-12) and then used three online experiments to test its predictive validity for participatory action. They found broad support for WUNC as a mediating mechanism and show that WUNC perceptions are correlated with impressions of the legitimacy and efficacy of a movement. Finally, they found that movements that simultaneously signal a single-issue focus and the presence of a demographically heterogeneous set of members elicit greater WUNC perceptions and higher intentions to mobilize. With these results taken together, the authors demonstrate how social movement signaling translates into WUNC perceptions, which in turn mediate how signaling leads to social movement support and mobilization.
A recent model demonstrated that the adenosine triphosphate (ATP) content of spherical aquatic organisms with a 10 to 50 μm diameter is between 0.16 and 19.9 pg cell−1. Here, the model is validated ...by comparing microscopy-based counts with ATP concentrations from a commercial ATP kit.
The measured ATP content of both freshwater and marine organisms 10 to 50 μm size range falls in the 0.16 to 19.9 pg cell−1 model range. On average, freshwater organisms contain 0.33 pg ATP cell−1, have a spherical equivalent diameter (SED) of 13 μm, while marine organisms have 0.89 pg ATP cell−1 and a SED of 18 μm. In addition, their 13 to 18 μm size is within the 10 to 50 μm ballast water size range and in agreement with the 15 μm mean SED of a coastal plankton size-distribution model.
This study concludes that the ATP-model is reliable, emphasizing the need for caution when converting three-dimensional biomass proxies into linear cell concentrations.
•A recent model demonstrated that the ATP content of spherical aquatic organisms with a 10 to 50 μm diameter is between 0.16 to 19.9 pg cell-1. The model was validated by comparing microscopy-based counts with ATP concentrations from a commercial ATP kit.•On average, freshwater organisms contain 0.33 pg ATP cell-1, have a spherical equivalent diameter (SED) of 13 μm, while marine organisms have 0.89 pg ATP cell-1 and a sed of 18 μm.•The ATP content of both marine and freshwater organisms falls in the 0.16 to 19.9 pg cell-1 model range. Their 13 to 18 μm SED is within the 10 to 50 μm ballast water size range and in agreement with the average of 15 μm SED of a coastal plankton size-distribution model.•This study concludes that the ATP-model is reliable, emphasizing the need for caution when converting three-dimensional biomass proxies into linear cell concentrations.
Climate change and increased anthropogenic activities are expected to elevate the potential of introducing nonindigenous species (NIS) into the Arctic. Yet, the knowledge base needed to identify gaps ...and priorities for NIS research and management is limited. Here, we reviewed primary introduction events to each ecoregion of the marine Arctic realm to identify temporal and spatial patterns, likely source regions of NIS, and the putative introduction pathways. We included 54 introduction events representing 34 unique NIS. The rate of NIS discovery ranged from zero to four species per year between 1960 and 2015. The Iceland Shelf had the greatest number of introduction events (n = 14), followed by the Barents Sea (n = 11), and the Norwegian Sea (n = 11). Sixteen of the 54 introduction records had no known origins. The majority of those with known source regions were attributed to the Northeast Atlantic and the Northwest Pacific, 19 and 14 records, respectively. Some introduction events were attributed to multiple possible pathways. For these introductions, vessels transferred the greatest number of aquatic NIS (39%) to the Arctic, followed by natural spread (30%) and aquaculture activities (25%). Similar trends were found for introductions attributed to a single pathway. The phyla Arthropoda and Ochrophyta had the highest number of recorded introduction events, with 19 and 12 records, respectively. Recommendations including vector management, horizon scanning, early detection, rapid response, and a pan‐Arctic biodiversity inventory are considered in this paper. Our study provides a comprehensive record of primary introductions of NIS for marine environments in the circumpolar Arctic and identifies knowledge gaps and opportunities for NIS research and management. Ecosystems worldwide will face dramatic changes in the coming decades due to global change. Our findings contribute to the knowledge base needed to address two aspects of global change—invasive species and climate change.
This paper examines the current status and future risks of biological invasions in the marine environments of the Arctic, within the context of climate change, natural resource development, and expanded Arctic shipping. The number of nonindigenous species introductions varied across the region with the greatest number of introductions recorded in the Iceland Shelf, followed by the Barents Sea and the Norwegian Sea. Most introductions were attributed to vessels, natural spread, and aquaculture activities. Vector management, horizon scanning, early detection, rapid response, and a pan‐Arctic biodiversity inventory are recommended to address future invasion risks.
Despite the availability of research which has direct applications to environmental management, there is often a disconnect between scientific research and applied management that presents challenges ...for using academic knowledge in day‐to‐day operations by non‐scientists.
A science‐based decision support tool was developed in partnership with Canada's marine authority, Transport Canada, for use by ballast water inspectors in their daily operations to inform prioritization of ships for regulatory compliance inspections.
This science‐based tool combines information on the two primary pathway‐level predictors of species establishment success: environmental matching between source and recipient locations and propagule pressure (introduction effort), to generate risk estimates and relative rankings using data taken directly from ballast water reporting forms submitted by arriving ships.
This tool thus packages the best available scientific knowledge in such a way as to be readily accessible for day‐to‐day decision‐making. While this tool was developed for Canada, it could be applied in any country with very little, if any, modification. This tool can also be updated in the future to incorporate advances in scientific understanding of ballast‐mediated introductions of non‐indigenous species.
Synthesis and applications. Partnerships between scientists and managers are essential for ensuring that best‐available science translates into effective adaptive management. Recognizing a need to inform ballast water management compliance inspections, a tool was created that automatically estimates relative risk of establishment of non‐indigenous species for arriving ships. This information can be used by ballast water inspectors developing priorities for resource‐limited regulatory compliance inspections.
Résumé
Malgré la recherche disponible et ses applications directes sur la gestion de l’environnement, il y a souvent un décalage entre la recherche scientifique et la gestion appliquée. Le défi étant de permettre au personnel non‐scientifique l’utilisation des connaissances issues de la recherche dans ses opérations quotidiennes.
Un outil de support pour prendre de décisions basées sur la science a été développé en partenariat avec l’autorité maritime canadienne, Transport Canada. Cet outil sera utilisé par les inspecteurs des eaux de ballast lors de ses opérations quotidiennes afin de prioriser les navires qui devront passer les inspections de conformité réglementaire.
Cet outil scientifique combine l’information des deux principaux facteurs de prédiction au niveau des voies d’introduction dans le succès de l’établissement des espèces: un couplage environnemental entre les ports d’origine et de destination, ainsi que la pression de propagule (l’effort d’introduction). Ceci afin de générer des estimations des risques et des classements relatifs à l’aide de données tirées directement des formulaires sur l’eau de ballast soumis par les navires à l’arrivée.
Ainsi cet outil regroupe les meilleures connaissances scientifiques disponibles, de manière à être facilement accessible pour la prise de décision au quotidien. Bien que cet outil a été développé par le Canada, il pourrait être utilisé par d’autres pays avec très peu de modifications, voir aucune. Cet outil pourrait être mis à jour à l’avenir afin d’intégrer de nouveaux progrès scientifiques sur l’introduction d’espèces non‐indigènes via les eaux de ballast.
Synthèse et applications. le partenariat entre les scientifiques et les gestionnaires est essentiel pour garantir que les meilleures connaissances scientifiques soient disponibles pour une gestion adaptative efficace. En reconnaissant la nécessité d'éclairer les inspections de conformité sur la gestion des eaux de ballast, un outil a été créé pour estimer automatiquement le risque relatif d'établissement d'espèces non‐indigènes présentes à l'arrivée des navires. Ces informations peuvent être utilisées par les inspecteurs des eaux de ballast qui élaborent les priorités pour les inspections de conformité réglementaire avec des ressources limitées.
Partnerships between scientists and managers are essential for ensuring that best‐available science translates into effective adaptive management. Recognizing a need to inform ballast water management compliance inspections, a tool was created that automatically estimates relative risk of establishment of non‐indigenous species for arriving ships. This information can be used by ballast water inspectors developing priorities for resource‐limited regulatory compliance inspections.
Metabarcode surveys of DNA extracted from environmental samples are increasingly popular for biodiversity assessment in natural communities. Such surveys rely heavily on robust genetic markers. ...Therefore, analysis of PCR efficiency and subsequent biodiversity estimation for different types of genetic markers and their corresponding primers is important. Here, we test the PCR efficiency and biodiversity recovery potential of three commonly used genetic markers – nuclear small subunit ribosomal DNA (18S), mitochondrial cytochrome c oxidase subunit I (COI) and 16S ribosomal RNA (mt16S) – using 454 pyrosequencing of a zooplankton community collected from Hamilton Harbour, Ontario. We found that biodiversity detection power and PCR efficiency varied widely among these markers. All tested primers for COI failed to provide high‐quality PCR products for pyrosequencing, but newly designed primers for 18S and 16S passed all tests. Furthermore, multiple analyses based on large‐scale pyrosequencing (i.e. 1/2 PicoTiter plate for each marker) showed that primers for 18S recover more (38 orders) groups than 16S (10 orders) across all taxa, and four vs. two orders and nine vs. six families for Crustacea. Our results showed that 18S, using newly designed primers, is an efficient and powerful tool for profiling biodiversity in largely unexplored communities, especially when amplification difficulties exist for mitochondrial markers such as COI. Universal primers for higher resolution markers such as COI are still needed to address the possible low resolution of 18S for species‐level identification.
The environmental similarity scores between source and recipient locations are essential in ballast water risk assessment (BWRA) models used to estimate the potential for non-indigenous species (NIS) ...introduction, survival, and establishment, and to guide management strategies aiming to minimize biodiversity loss and economic impacts. Previous BWRA models incorporate annual-scale environmental data, which may overlook seasonal variability. In this study, temporal variation in sea surface temperature and salinity data were examined at global ports, and the influence of this variation on environmental distance calculations (and corresponding risk of NIS) was examined for ballast water discharges in Canada by comparing outputs from monthly and annual scale assessments in a BWRA model. Except for some outliers in the Pacific region, the environmental distances based on monthly scale data generally become smaller in all regions, demonstrating that the model using annual decadal average environmental data to inform environmental matching can underestimate risk of NIS survival and establishment in comparison to monthly data. The results of this study suggest future evaluations incorporating the date of ballast water uptake and discharge can provide a more sensitive assessment of risk reflecting seasonal variability compared to an annual average risk model.
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