Global hot spots of biological invasions: evaluating options for ballast-water management

Assessing and managing the risk of Aedes mosquito introductions via the global maritime trade network

The global shipping network (GSN) has been suggested as a pathway for the establishment and reintroduction of Aedes aegypti and Aedes albopictus primarily via the tire trade. We used historical maritime movement data in combination with an agent-based model to understand invasion risk in the United States Gulf Coast and how the risk of these invasions could be reduced. We found a strong correlation between the total number of cargo ship arrivals at each port and likelihood of arrival by both Ae. aegypti and Ae. albopictus. Additionally, in 2012, 99.2% of the arrivals into target ports had most recently visited ports likely occupied by both Ae. aegypti and Ae. albopictus, increasing risk of Aedes invasion. Our model results indicated that detection and removal of mosquitoes from containers when they are unloaded effectively reduced the probability of mosquito populations establishment even when the connectivity of ports increased. To reduce the risk of invasion and reintroduction of Ae. aegypti and Ae. albopictus, surveillance and control efforts should be employed when containers leave high risk locations and when they arrive in ports at high risk of establishment.

What Is the Impact of Accidentally Transporting Terrestrial Alien Species? A New Life Cycle Impact Assessment Model

Alien species form one of the main threats to global biodiversity. Although Life Cycle Assessment attempts to holistically assess environmental impacts of products and services across value chains, ecological impacts of the introduction of alien species are so far not assessed in Life Cycle Impact Assessment. Here, we developed country-to-country-specific characterization factors, expressed as the time-integrated potentially disappeared fraction (PDF; regional and global) of native terrestrial species due to alien species introductions per unit of goods transported [kg] between two countries. The characterization factors were generated by analyzing global data on first records of alien species, native species distributions, and their threat status, as well as bilateral trade partnerships from 1870-2019. The resulting characterization factors vary over several orders of magnitude, indicating that impact greatly varies per transportation route and trading partner. We showcase the applicability and relevance of the characterization factors for transporting 1 metric ton of freight to France from China, South Africa, and Madagascar. The results suggest that the introduction of alien species can be more damaging for terrestrial biodiversity as climate change impacts during the international transport of commodities.

A simulation study evaluating how population survival and genetic diversity in a newly established population can be affected by propagule size, extinction rates, and initial heterozygosity

The introduction and establishment of invasive species in regions outside their native range, is one of the major threats for the conservation of ecosystems, affecting native organisms and the habitat where they live in, causing substantial biological and monetary losses worldwide. Due to the impact of invasive species, it is important to understand what makes some species more invasive than others. Here, by simulating populations using a forward-in-time approach combining ecological and single polymorphic nucleotides (SNPs) we evaluated the relation between propagule size (number of individuals = 2, 10, 100, and 1,000), extinction rate (with values 2%, 5%, 10%, and 20%), and initial heterozygosity (0.1, 0.3, and 0.5) on the population survival and maintenance of the heterozygosity of a simulated invasive crab species over 30 generations assuming a single introduction. Our results revealed that simulated invasive populations with initial propagule sizes of 2-1,000 individuals experiencing a high extinction rate (10-20% per generation) were able to maintain over 50% of their initial heterozygosity during the first generations and that under scenarios with lower extinction rates invasive populations with initial propagule sizes of 10-1,000 individuals can survive up to 30 generations and maintain 60-100% of their initial heterozygosity. Our results can help other researchers better understand, how species with small propagule sizes and low heterozygosities can become successful invaders.

Population structure, dispersion patterns and genetic diversity of two major invasive and commensal zoonotic disease hosts (Rattus norvegicus and Rattus tanezumi) from the southeastern coast of China

Background: The invasive brownrat (Rattus norvegicus) and the Oriental rats (Rattus tanezumi) are common commensal murid that are important hosts for rodent-borne diseases in southeast Asia. Understanding their population structure and genetic diversity is essential to uncover their invasion biology and distribution dynamics that are essential for controlling rodent-borne diseases. Methods: TA total of 103 R. norvegicus and 85 R. tanezumi were collected from 13 to 9 coastal areas of six provincial monitoring sentinel sites, respectivelyto assess patterns in their microsatellite loci and their mitochondrial coxl gene region. Results: Eleven sampled populations of R. norvegicus were divided into two major clusters by region. The observed heterozygosity values of all regional populations were smaller than expected genetic diversity heterozygosity values and deviated from Hardy-Weinberg equilibrium Nine sample populations of R. tanezumi were divided into three clusters; two that included sample from Hainan and Fujian provinces, and one that included samples from the other provinces and cities. The genetic diversity of R. tanezumi was highest in samples from Jiangsu and Guangdong provinces. Conclusion: The data in this paper confirm the two invasive rodent species from the southeastern coastal region of China may have relied on maritime transport to spread from the southern region of China to the Yangtze River basin. R. tanezumi may then hanve migrated unidirectionally, along the southeastern provinces of China towards the north, while R. norvegicus spread in a complex and multidirectional manner in Hainan, Fujian, Zhejiang and Jiangsu Provinces of the country.

Facilitation of macrofaunal assemblages in marinas by the habitat-forming invader Amathia verticillata (Bryozoa: Gymnolaemata) across a spatiotemporal scale

Widespread habitat-forming invaders inhabiting marinas, such as the spaghetti bryozoan Amathia verticillata, allow exploring facilitation processes across spatiotemporal contexts. Here we investigate the role of this bryozoan as habitat for native and exotic macrofaunal assemblages across different ecoregions of Western Mediterranean and East Atlantic coasts, and a monthly variation over a year. While only 7 (all peracarid crustaceans) of the 54 associated species were NIS, they dominated macrofaunal assemblages in terms of abundance, raising the potential for invasional meltdown. NIS richness and community structure differed among marinas but not among ecoregions, highlighting the importance of marina singularities in modulating facilitation at spatial scale. Despite facilitation did not depend on bryozoan abundance fluctuations, it was affected by its deciduous pattern, peaking in summer and disappearing in late winter. Monitoring A. verticillata in marinas, especially in summer periods, may improve the detection and management of multiple associated NIS.

Estimation of the introduction risk of non-indigenous species through ship ballast water in the Port of Douala (Cameroon)

The transport of non-indigenous species in ship's ballast water represents a threat to marine biodiversity. This study is the first on marine bioinvasion in Sub-Saharan Africa. The Port of Douala (PoD), located in the Gulf of Guinea, is experiencing increasing maritime traffic, hence the importance of preventing biological invasions. PoD received ballast water from 41 ports and 20 ecoregions during the study period (2018-2021). We used a biological invasion model and showed that ships from the ports of Antwerp, Durban, Dar es Salaam, Pointe-Noire (Southern Gulf of Guinea) and Dakar (Sahelian Upwelling), with their associated ecoregions present a major invasion risk. Treating ballast water from these ships to IMO D-2 standards could reduce their probability of biological invasion by 97.18, 98.43, 98.80, 98.77 and 98.84 %, respectively. Climate change may also mitigate the risk of biological invasion, particularly for ships in the North Sea ecoregion from the port of Antwerp.

Environment and shipping drive environmental DNA beta-diversity among commercial ports

The spread of nonindigenous species by shipping is a large and growing global problem that harms coastal ecosystems and economies and may blur coastal biogeographical patterns. This study coupled eukaryotic environmental DNA (eDNA) metabarcoding with dissimilarity regression to test the hypothesis that ship-borne species spread homogenizes port communities. We first collected and metabarcoded water samples from ports in Europe, Asia, Australia and the Americas. We then calculated community dissimilarities between port pairs and tested for effects of environmental dissimilarity, biogeographical region and four alternative measures of ship-borne species transport risk. We predicted that higher shipping between ports would decrease community dissimilarity, that the effect of shipping would be small compared to that of environment dissimilarity and shared biogeography, and that more complex shipping risk metrics (which account for ballast water and stepping-stone spread) would perform better. Consistent with our hypotheses, community dissimilarities increased significantly with environmental dissimilarity and, to a lesser extent, decreased with ship-borne species transport risks, particularly if the ports had similar environments and stepping-stone risks were considered. Unexpectedly, we found no clear effect of shared biogeography, and that risk metrics incorporating estimates of ballast discharge did not offer more explanatory power than simpler traffic-based risks. Overall, we found that shipping homogenizes eukaryotic communities between ports in predictable ways, which could inform improvements in invasive species policy and management. We demonstrated the usefulness of eDNA metabarcoding and dissimilarity regression for disentangling the drivers of large-scale biodiversity patterns. We conclude by outlining logistical considerations and recommendations for future studies using this approach.

Identification of potential invasive alien species in Spain through horizon scanning

Invasive alien species have widespread impacts on native biodiversity and ecosystem services. Since the number of introductions worldwide is continuously rising, it is essential to prevent the entry, establishment and spread of new alien species through a systematic examination of future potential threats. Applying a three-step horizon scanning consensus method, we evaluated non-established alien species that could potentially arrive, establish and cause major ecological impact in Spain within the next 10 years. Overall, we identified 47 species with a very high risk (e.g. Oreochromis niloticus, Popillia japonica, Hemidactylus frenatus, Crassula helmsii or Halophila stipulacea), 61 with high risk, 93 with moderate risk, and 732 species with low risk. Many of the species categorized as very high or high risk to Spanish biodiversity are either already present in Europe and neighbouring countries or have a long invasive history elsewhere. This study provides an updated list of potential invasive alien species useful for prioritizing efforts and resources against their introduction. Compared to previous horizon scanning exercises in Spain, the current study screens potential invaders from a wider range of terrestrial, freshwater, and marine organisms, and can serve as a basis for more comprehensive risk analyses to improve management and increase the efficiency of the early warning and rapid response framework for invasive alien species. We also stress the usefulness of measuring agreement and consistency as two different properties of the reliability of expert scores, in order to more easily elaborate consensus ranked lists of potential invasive alien species.

Modelled dispersal pathways of non-indigenous species in the Danish Wadden Sea

The introduction-rate of non-indigenous species (NIS) to coastal water bodies has accelerated over the last century. We present a model study assessing the fate of NIS released in likely point sources of the Danish Wadden Sea. We show that NIS-particles released in the deep North Sea are generally transported away from the Wadden Sea, while those released in the coastal North Sea and the Wadden Sea show large variability in track pattern and settlement location. Consequently, the introduction of NIS from ships entering the port of Esbjerg pose a threat to the Wadden Sea through primary and secondary spreading, while transport of species from sources in the south likely causes a slow and steady settling of NIS in the Wadden Sea and coastal North Sea. The study points to the importance of enforcing an efficient monitoring system to ensure early detection of changes to the species composition of the Wadden Sea.

Assessing the effectiveness of filtration + UV-C radiation for the treatment of simulated ballast water at various holding times

In recent years, the issue of invasive alien species brought on by ballast water has drawn increasing attention, and advances in ballast water treatment technologies have been made. One of the most popular combined ballast water treatment technologies utilized in ballast water management systems (BWMSs) globally is filtration + UV-C radiation. During the actual voyage of the ship, ballast water is treated by the BWMS and then enters the dark ballast tanks until the ballast water is discharged. Marine organisms are able to complete DNA damage caused by UV radiation in dark ballast tanks. Therefore, the length of holding time affects the effectiveness of the BWMS in treating ballast water. The objective of this study was to examine the efficacy of filtration + UV-C irradiation treatment at different holding times for the removal or inactivation of phytoplankton and zooplankton populations during simulated ballast water treatment. Results indicate that the holding time after the filtration + UV-C radiation treatment increased the inactivating efficacy, especially for zooplankton in natural seawater. For phytoplanktons in ballast water, the strongest impact on the treatment efficacy was reached with a holding time of 24 h.

Half-century trends in alpha and beta diversity of phytoplankton summer communities in the Helsinki Archipelago, the Baltic Sea

We analyzed phytoplankton biodiversity trends in a 52 year (1967-2018) monitoring time-series from the archipelago of Helsinki, Gulf of Finland, the Baltic Sea. The community ordination revealed strong ordering of samples along the time axis (generalized additive model-gam fit: R ² = 0.9). Species richness increased in time and was the most influential alpha diversity descriptor related to the community structure (gam fit: R ² = 0.56-0.70). Changes in species richness accounted for 35-36% of the mean between-sample beta diversity. The remaining 64-65% was due to species turnover-the dominant component of the biodiversity trend. The temporal beta diversity trend reflected the eutrophication history of the geographically confined region, with a turning point in mid-1990s demarking the adaptation and recovery phases of the phytoplankton community. Trends in spatial beta diversity revealed homogenization of the communities in the outer archipelago zone, but not in the inner bays. The temporal decay of community similarity revealed high turnover rate, with 23.6 years halving time in the outer archipelago and 11.3 years in the inner bays, revealing the differences in eutrophication strength. The observed phytoplankton trends manifest the regional eutrophication history, and dispersal of new species to the unsaturated brackish species pool.

Using Import Data to Predict the Potential of Introduction of Alert Alien Species to South Korea

As globalization progresses, human activities, such as travel and trade, are rapidly increasing beyond national boundaries. It is increasingly recognized that places, such as ports and airports, where trade occurs play a major role as an introduction pathway for alien species. In this study, we focused on evaluating the possibility of introduction of Alert Alien Species (AAS) through trade data among countries. The natural and distribution range of AAS were analyzed along with import data by country. There were large differences between the number of AAS distributed in a country and the import weight of items related to the import of AAS from the country. Fish, which account for 76% of the import weight of AAS, 43 and 40 species of the 84 species of AAS were distributed in US and Russia, respectively. However, the import weight of items related to the import of fish designated as AAS from these countries were extremely low. This finding suggests that trade, which is the main introduction pathway, is not taken into account in the designation of AAS. For future management plans for non-introduced alien species, species with a high possibility of introduction into South Korea through trade should be prioritized using import data.

Modelling the likelihood of entry of marine non-indigenous species from internationally arriving vessels to maritime ports: a case study using New Zealand data

The establishment of marine non-indigenous species (NIS) in new locations can degrade environmental, socio-cultural, and economic values. Vessels arriving from international waters are the main pathway for the entry of marine NIS, via exposure due to ballast water discharge (hereafter, ballast discharge) and biofouling. We developed a systematic statistical likelihood-based methodology to investigate port-level marine NIS propagule pressure from ballast discharge and biofouling exposure using a combination of techniques, namely k-Nearest-Neighbour and random forest algorithms. Vessel characteristics and travel patterns were assessed as candidate predictors. For the ballast discharge analysis, the predictors used for model building were vessel type, dead weight tonnage, and the port of first arrival; the predictors used for the biofouling analysis were days since last antifouling paint, mean vessel speed, dead weight tonnage, and hull niche area. Propagule pressure for both pathways was calculated at a voyage, port and annual level, which were used to establish the relative entry score for each port. The model was applied to a case study for New Zealand. Biosecurity New Zealand has commissioned targeted marine surveillance at selected ports since 2002 to enable early detection of newly arrived marine NIS (Marine High-Risk Site Surveillance, MHRSS). The reported methodology was used to compare contemporary entry likelihoods between New Zealand ports. The results suggested that Tauranga now receives the highest volume of discharged ballast water and has the second most biofouling exposure compared to all other New Zealand ports. Auckland was predicted to receive the highest biofouling mass and was ranked tenth for ballast discharge exposure. Lyttelton, Napier, and New Plymouth also had a high relative ranking for these two pathways. The outputs from this study will inform the refinement of the MHRSS programme, facilitating continued early detection and cost-effective management to support New Zealand’s wider marine biosecurity system. More generally, this paper develops an approach for using statistical models to estimate relative likelihoods of entry of marine NIS.

Ballast water-mediated species spread risk dynamics and policy implications to reduce the invasion risk to the Mediterranean Sea

This study helps understand the ballast water-mediated species spread risk dynamics in the Mediterranean and examine potential policy options for ballast water management to further reduce species spread risk in the region. Results show that Gibraltar, Suez, and Istanbul remained high-risk ports from 2012 to 2018, and they are hub ports connecting several clusters. We reveal ballast water management implications for both the Mediterranean region and individual hub ports respectively. To further reduce the risks of individual Mediterranean hub ports beyond the IMO standards, the most effective (cost-effective) regulatory method is to set more stringent regulation towards such hub ports besides the IMO regulation. To further reduce the risks of the Mediterranean as a whole, the most effective (cost-effective) regulatory scenario is to set more stringent regulation towards all Mediterranean ports besides the IMO regulation. The barge-based method is the most cost-effective technology to achieve stricter regulations.

Economic and environmental impacts of ballast water management on Small Island Developing States and Least Developed Countries

The Ballast Water Management Convention can decrease the introduction risk of harmful aquatic organisms and pathogens, yet the Convention increases shipping costs and causes subsequent economic impacts. This paper examines whether the Convention generates disproportionate invasion risk reduction results and economic impacts on Small Island Developing States (SIDS) and Least Developed Countries (LDCs). Risk reduction is estimated with an invasion risk assessment model based on a higher-order network, and the effects of the regulation on national economies and trade are estimated with an integrated shipping cost and computable general equilibrium modeling framework. Then we use the Lorenz curve to examine if the regulation generates risk or economic inequality among regions. Risk reduction ratios of all regions (except Singapore) are above 99%, which proves the effectiveness of the Convention. The Gini coefficient of 0.66 shows the inequality in risk changes relative to income levels among regions, but risk reductions across all nations vary without particularly high risks for SIDS and LDCs than for large economies. Similarly, we reveal inequality in economic impacts relative to income levels (the Gini coefficient is 0.58), but there is no evidence that SIDS and LDCs are disproportionately impacted compared to more developed regions. Most changes in GDP, real exports, and real imports of studied regions are minor (smaller than 0.1%). However, there are more noteworthy changes for select sectors and trade partners including Togo, Bangladesh, and Dominican Republic, whose exports may decrease for textiles and metal and chemicals. We conclude the Convention decreases biological invasion risk and does not generate disproportionate negative impacts on SIDS and LDCs.

Assessment of dispersal and population structure of Norway rats (Rattus norvegicus) in a seaport setting

Seaports are introduction hotspots for invasive alien species (IAS). This is especially true for rodents, which have accompanied humans around the globe since the earliest days of ocean-going voyages. The rapid spread of IAS soon after arrival in a new environment is facilitated by further human-mediated transport or landscape features, like roads. By measuring genetic diversity and structure to investigate dispersal pathways, we gained insight into the transport, spread and establishment stages of a biological invasion, leveraging the most common rodent species (R. norvegicus) in this setting. We characterized the genetic structure of three Norway rat populations along a busy industrial road used by trucks to access the Port area in Paranaguá city (Brazil). A total of 71 rats were genotyped using 11 microsatellite markers. The results revealed a pattern of gene flow contrary to the expected stepping-stone model along the linear transect, with the two furthest apart populations being clustered together. We hypothesize that the observed outcome is explained by natural dispersal along the corridor being lower than human-mediated transport. The sampled area furthest from the port is a gas station frequented by trucks which are considered the most likely mode of transportation. In terms of management strategies, we suggest more emphasis should be put on cargo surveillance to lower the risk of Norway rat dispersal, not only for biosecurity, but also for sanitary reasons, as this port is a major grain trading point.

Integrated Biological Risk and Cost Model Analysis Supports a Geopolitical Shift in Ballast Water Management

This work evaluates efficacies of plausible ballast water management strategies and standards by integrating a global species spread risk assessment with a policy cost-effectiveness analysis. Specifically, we consider species spread risks and costs of port- and vessel-based strategies under both current organism concentration standards and stricter standards proposed by California. For each scenario, we estimate species spread risks and patterns using a higher-order analysis of a global ship-borne species spread model and estimate fleet costs for vessel- and barge-based ballast water treatment systems for each standard. We find that stricter standards may reduce species spread risk by a factor of 17 globally and would greatly simplify the complex network of ship-borne species spread. The current policy of IMO standards is most cost-effectively achieved through ship-based treatment, and that any additional risk reduction will be most cost-effectively achieved by port-based (or barge-based) technologies, particularly if these are strategically implemented at the top ports within the largest clusters. Barge-based ballast water management would require a shift in governance, and we suggest that this next level of policymaking could be feasible for special areas designated by the IMO, by State or multistate authorities, or by voluntary port applications.

Using Onboard-Produced Drinking Water to Achieve Ballast-Free Management

Based on the International Convention for the Control and Management of Ships’ Ballast Water and Sediments (the Ballast Water Management Convention, or BWM Convention) of the International Maritime Organization, from 8 September 2017, all ships must have an approved Ballast Water Management Treatment System (BWTS) to prevent the invasion of alien species through the discharge of ballast. Generally speaking, the need for an approved BWTS is limited to large vessels, as they are too large or too expensive for small vessels to install. This study aims to propose a simple ballast-free approach for small vessels (e.g., tugs, workboats, research vessels) that require ballast to compensate for the weight loss of fuel when sailing. Our approach involves refitting the dedicated ballast tank of these small vessels to be drinking water tanks and filling the tanks with onboard-generated distilled or reverse osmosis water to adjust the stability of the ships. We assessed our approach using three vessels. Two ships using our proposed method were certified by the American Bureau of Shipping as containing no ballast water tank, and not being subject to the BWM Convention. This study provides an environmentally harmless, easy to use, and economical approach for small vessels to comply with the BWM Convention.

Building on gAMBI in ports for a challenging biological invasions scenario: Blue-gNIS as a proof of concept

The status of aquatic ecosystems has historically been monitored by the use of biotic indices. However, few biotic measures consider the presence of non-indigenous species as a sign of anthropogenic pollution and habitat disturbance even when this may seriously affect the metric scores and ecological status classifications of an environment. Today, biological invasions are currently one of the greatest threats to biodiversity and sustainable blue economies around the world. In this work, environmental assessments were conducted in the Port of Gijon, Northern Spain, using eDNA metabarcoding, and the gAMBI (genetics based AZTI Marine Biotic Index) was estimated. Results indicate a high/good ecological status within the port. However, nine non-indigenous species and five invasive species were found, and a modification of the gAMBI that includes species invasiveness was proposed: Blue-gNIS. The index was preliminary tested against existing validated indices such as gAMBI, BENTIX (based on the ecology of macroinvertebrates) and ALEX (based on the invasiveness of the species). Blue-gNIS classified the port in a good ecological status and showed its potential usefulness to achieve more complete water quality assessments of ports.

Electrokinetic detection and separation of living algae in a microfluidic chip: implication for ship's ballast water analysis

Detecting living algae from treated ship's ballast water is an important task for port state control (PSC) under the requirement of the International Ballast Water Convention. In this paper, electrokinetic detection and separation of living algae from NaClO- and UV-treated ship's ballast water in a microfluidic chip are presented. The electrokinetic movement of algae in a straight poly ethylene glycol (PEG)-modified PDMS microchannel filled with 10% PEG solution was measured by using an optical microscope. The experimental results show that the moving velocity of dead algae is lower by more than 80% in comparison with living algae. The decreased velocity is larger for larger dead algae and the velocity is decreased to zero for dead algae larger than 6 μm in diameter. A curve was obtained to evaluate the vitality of algae with similar moving velocity but different sizes. Electrokinetic separation of living algae from a mixture sample in a straight channel was also achieved. The method presented in this paper provides a moving velocity-based approach for quickly evaluating the living status of algae in treated ship's ballast water.

Non-indigenous species in marine and coastal habitats of the South China Sea

The South China Sea (SCS) sustains and is a regional center of high marine and coastal biodiversity. It is also one of the most important mariculture and marine fisheries regions in the world. Many non-indigenous species (NIS) were introduced into the SCS as artifacts of increasing mariculture production and fishery harvests. Little information exists about NIS in the SCS. In this study, research examining NIS and their threats in the SCS are reviewed. Current NIS conditions assessed include their status, threat to native biodiversity, contribution to mariculture and fisheries harvest, management, and the need for future research in specific areas are identified. A total of 90 NIS including 17 algae, 6 vascular plants, 3 bryozoans, 23 molluscs, 6 crustacea, 3 ascidians, and 32 fishes were introduced into the SCS from 1600 to the present. The primary pathways of introduction are through aquaculture, followed by shipping, ecological restoration, and biocontrol. The main introduced country is China. Some NIS have caused negative impacts on the environment and economy. Some NIS are potential threats to humans as well as biodiversity in the SCS. More research focused upon monitoring and managing NIS in the SCS is needed.

Biosecurity implications of drifting marine plastic debris: Current knowledge and future research

The introduction and spread of marine non-indigenous species (NIS) and pathogens into new habitats are a major threat to biodiversity, ecosystem services, human health, and can have substantial economic consequences. Shipping is considered the main vector for marine biological invasions; less well understood is the increased spread of marine NIS and pathogens rafting on marine plastic debris (MPD). Despite an increasing research interest and recent progress in characterizing the plastisphere, this manuscript highlights critical knowledge gaps and research priorities towards a better understanding of the biosecurity implications of MPD. We advocate for future research to (i) investigate plastisphere community succession and the factors influencing NIS propagules and pathogens recruitment through robust experimental investigations; (ii) combine microscopy and molecular approaches to effectively assess the presence of specific taxa; (iii) include additional genetic markers to thoroughly characterize the biodiversity associated with MPD and explore the presence of specific marine pests.

Species delimitation integrative approach reveals three new species in the Nemertopsis bivittata complex

The presence of cryptic species is fairly frequent in many invertebrate groups and even more so among invertebrates with simple morphology, such as nemerteans. Consequently, the use of molecular methods for species delimitation has become a needed tool to complement morphological analyses to better recognise such species. Nemertopsis bivittata is one example of species with subtle morphological variation, but ample geographic distribution, being a good candidate for a species complex study. Here we applied two mitochondrial genes, and 2903 single nucleotide polymorphism (SNP) variants in addition to morphological characters to investigate the presence of cryptic species among specimens previously identified as N. bivittata along the Brazilian Coast. To do so, specimens were collected at 15 different sites in the north-east, south-east and southern regions. Three new species of Nemertopsis are described based on morphological and molecular analyses: Nemertopsis caete sp. nov., Nemertopsis pamelaroeae sp. nov. and Nemertopsis berthalutzae sp. nov. The species N. pamelaroeae and N. berthalutzae present broad distributions from north-east to south-east; N. caete, however, is restricted to the north-east coast. This is the first study to use this combined approach in nemerteans and shows the advantages of integrating genomic markers with classical taxonomy, and applying objective approaches to delimiting species as independently evolving entities.

Spatial heterogeneities of human-mediated dispersal vectors accelerate the range expansion of invaders with source-destination-mediated dispersal

Rapid range expansions of invasive species are a major threat to ecosystems. Understanding how invasive species increase their habitat ranges and how environmental factors, including intensity of human activities, influence dispersal processes is an important issue in invasion biology, especially for invasive species management. We have investigated how spatially heterogeneous factors influence range expansion of an invasive species by focusing on long-distance dispersal, which is frequently assisted by human activities. We have developed models varying two underlying processes of a dispersal event. These events are described by source and destination functions that determine spatial variations in dispersal frequency and the probability of being a dispersal destination. Using these models, we investigated how spatially heterogeneous long-distance dispersal influences range expansion. We found that: (1) spatial variations in the destination function slow down late population dynamics, (2) spatial variations in the source function increase the stochasticity of early population dynamics, and (3) the speed of early population dynamics changes when both the source and the destination functions are spatially heterogeneous and positively correlated. These results suggest an importance of spatial heterogeneity factors in controlling long-distance dispersal when predicting the future spread of invasive species.

Network analysis of ballast-mediated species transfer reveals important introduction and dispersal patterns in the Arctic

Rapid climate change has wide-ranging implications for the Arctic region, including sea ice loss, increased geopolitical attention, and expanding economic activity resulting in a dramatic increase in shipping activity. As a result, the risk of harmful non-native marine species being introduced into this critical region will increase unless policy and management steps are implemented in response. Using data about shipping, ecoregions, and environmental conditions, we leverage network analysis and data mining techniques to assess, visualize, and project ballast water-mediated species introductions into the Arctic and dispersal of non-native species within the Arctic. We first identify high-risk connections between the Arctic and non-Arctic ports that could be sources of non-native species over 15 years (1997-2012) and observe the emergence of shipping hubs in the Arctic where the cumulative risk of non-native species introduction is increasing. We then consider how environmental conditions can constrain this Arctic introduction network for species with different physiological limits, thus providing a tool that will allow decision-makers to evaluate the relative risk of different shipping routes. Next, we focus on within-Arctic ballast-mediated species dispersal where we use higher-order network analysis to identify critical shipping routes that may facilitate species dispersal within the Arctic. The risk assessment and projection framework we propose could inform risk-based assessment and management of ship-borne invasive species in the Arctic.

Perspectives on the marine environment and biodiversity in recreational ports: The marina of Gijon as a case study

Recreational ports are known to be sources of pollution to the coastal marine environment due to the pouring of pollutants or the transfer of invasive species to neighboring areas. Nonetheless, the responsibility of protecting the marine environment does not lie solely on the users of the ports, but also affects the rest of citizens. Thus, an effective communication is necessary between scientists and citizens to avoid the lack of knowledge and boost cooperation against these environmental problems. In this study, (focused on the marina of Gijon, Northwestern Spain) citizens set education and social media as the main sources of information, rarely considering science outreach. Also, their environmental knowledge showed to be based on a visual perception, rather than on a cognitive one, as marine litter was considered a great environmental problem, while invasive species and biofouling went unnoticed, remarking the lack of an effective communication from scientific sources.

Information sharing may impede the success of environmental projects

A major challenge in ecosystem management is to promote cooperation among the multiple agents that manage the ecosystem. In particular, sharing information among the agents is often essential for reaching a desirable collective treatment. However, it is unclear how the sharing of information affects the incentives of selfish agents to cooperate and contribute to the common environmental project. Here, we consider a harmful species population that migrates across lands and causes damages to multiple agents, each of which aims to minimize her/his own costs due to both treatment and damages over time. We use game-theoretical models and compare the resulting collective treatment in three scenarios that differ in the information that agents have about (1) the true contribution of their neighbors to the treatment and (2) the true damages inflicted on their neighbors by the harmful species. We demonstrate that sharing such social information may incentivize the agents to free ride on their neighbors' contributions, thereby reducing the efficiency of the collective treatment. This implies that monitoring and sharing information may have negative consequences, and the extent to which information should be shared in joint projects necessitates a careful examination.

What and where? Predicting invasion hotspots in the Arctic marine realm

The risk of aquatic invasions in the Arctic is expected to increase with climate warming, greater shipping activity and resource exploitation in the region. Planktonic and benthic marine aquatic invasive species (AIS) with the greatest potential for invasion and impact in the Canadian Arctic were identified and the 23 riskiest species were modelled to predict their potential spatial distributions at pan-Arctic and global scales. Modelling was conducted under present environmental conditions and two intermediate future (2050 and 2100) global warming scenarios. Invasion hotspots-regions of the Arctic where habitat is predicted to be suitable for a high number of potential AIS-were located in Hudson Bay, Northern Grand Banks/Labrador, Chukchi/Eastern Bering seas and Barents/White seas, suggesting that these regions could be more vulnerable to invasions. Globally, both benthic and planktonic organisms showed a future poleward shift in suitable habitat. At a pan-Arctic scale, all organisms showed suitable habitat gains under future conditions. However, at the global scale, habitat loss was predicted in more tropical regions for some taxa, particularly most planktonic species. Results from the present study can help prioritize management efforts in the face of climate change in the Arctic marine ecosystem. Moreover, this particular approach provides information to identify present and future high-risk areas for AIS in response to global warming.

Higher-order patterns of aquatic species spread through the global shipping network

The introduction and establishment of nonindigenous species (NIS) through global ship movements poses a significant threat to marine ecosystems and economies. While ballast-vectored invasions have been partly addressed by some national policies and an international agreement regulating the concentrations of organisms in ballast water, biofouling-vectored invasions remain largely unaddressed. Development of additional efficient and cost-effective ship-borne NIS policies requires an accurate estimation of NIS spread risk from both ballast water and biofouling. We demonstrate that the first-order Markovian assumption limits accurate modeling of NIS spread risks through the global shipping network. In contrast, we show that higher-order patterns provide more accurate NIS spread risk estimates by revealing indirect pathways of NIS transfer using Species Flow Higher-Order Networks (SF-HON). Using the largest available datasets of non-indigenous species for Europe and the United States, we then compare SF-HON model predictions against those from networks that consider only first-order connections and those that consider all possible indirect connections without consideration of their significance. We show that not only SF-HONs yield more accurate NIS spread risk predictions, but there are important differences in NIS spread via the ballast and biofouling vectors. Our work provides information that policymakers can use to develop more efficient and targeted prevention strategies for ship-borne NIS spread management, especially as management of biofouling is of increasing concern.

Multiple agents managing a harmful species population should either work together to control it or split their duties to eradicate it

The management of harmful species, including invasive species, pests, parasites, and diseases, is a major global challenge. Harmful species cause severe damage to ecosystems, biodiversity, agriculture, and human health. In particular, managing harmful species often requires cooperation among multiple agents, such as landowners, agencies, and countries. Each agent may have incentives to contribute less to the treatment, leaving more work for other agents, which may result in inefficient treatment. A central question is, therefore, how should a policymaker allocate treatment duties among the agents? Specifically, should the agents work together in the same area, or should each agent work only in a smaller area designated just for her/him? We consider a dynamic game-theoretic model, where a Nash equilibrium corresponds to a possible set of contributions that the agents could adopt over time. In turn, the allocation by the policymaker determines which of the Nash equilibria could be adopted, which allows us to compare the outcome of various allocations. Our results show that fewer agents can abate the harmful species population faster, but more agents can better control the population to keep its density lower. We prove this result in a general theorem and demonstrate it numerically for two case studies. Therefore, following an outbreak, the better policy would be to split and assign one or a few agents to treat the species in a given location, but if controlling the harmful species population at some low density is needed, the agents should work together in all of the locations.

Stronger regional biosecurity is essential to prevent hundreds of harmful biological invasions

Biological invasions often transcend political boundaries, but the capacity of countries to prevent invasions varies. How this variation in biosecurity affects the invasion risks posed to the countries involved is unclear. We aimed to improve the understanding of how the biosecurity of a country influences that of its neighbours. We developed six scenarios that describe biological invasions in regions with contiguous countries. Using data from alien species databases, socio-economic and biodiversity data and species distribution models, we determined where 86 of 100 of the world's worst invasive species are likely to invade and have a negative impact in the future. Information on the capacity of countries to prevent invasions was used to determine whether such invasions could be avoided. For the selected species, we predicted 2,523 discrete invasions, most of which would have significant negative impacts and are unlikely to be prevented. Of these invasions, approximately a third were predicted to spread from the country in which the species first establishes to neighbouring countries where they would cause significant negative impacts. Most of these invasions are unlikely to be prevented as the country of first establishment has a low capacity to prevent invasions or has little incentive to do so as there will be no impact in that country. Regional biosecurity is therefore essential to prevent future harmful biological invasions. In consequence, we propose that the need for increased regional co-operation to combat biological invasions be incorporated in global biodiversity targets.

Confirmation of the shell-boring oyster parasite Polydora websteri (Polychaeta: Spionidae) in Washington State, USA

Invasions by shell-boring polychaetes such as Polydora websteri Hartman have resulted in the collapse of oyster aquaculture industries in Australia, New Zealand, and Hawaii. These worms burrow into bivalve shells, creating unsightly mud blisters that are unappealing to consumers and, when nicked during shucking, release mud and detritus that can foul oyster meats. Recent findings of mud blisters on the shells of Pacific oysters (Crassostrea gigas Thunberg) in Washington State suggest a new spionid polychaete outbreak. To determine the identity of the polychaete causing these blisters, we obtained Pacific oysters from two locations in Puget Sound and examined them for blisters and burrows caused by polychaete worms. Specimens were also obtained from eastern oysters (Crassostrea virginica Gmelin) collected in New York for morphological and molecular comparison. We compared polychaete morphology to original descriptions, extracted DNA and sequenced mitochondrial (cytochrome c oxidase I [mtCOI]) and nuclear (small subunit 18S rRNA [18S rRNA]) genes to determine a species-level molecular identification for these worms. Our data show that Polydora websteri are present in the mud blisters from oysters grown in Puget Sound, constituting the first confirmed record of this species in Washington State. The presence of this notorious invader could threaten the sustainability of oyster aquaculture in Washington, which currently produces more farmed bivalves than any other US state.

Replicated anthropogenic hybridisations reveal parallel patterns of admixture in marine mussels

Human-mediated transport creates secondary contacts between genetically differentiated lineages, bringing new opportunities for gene exchange. When similar introductions occur in different places, they provide informally replicated experiments for studying hybridisation. We here examined 4,279 Mytilus mussels, sampled in Europe and genotyped with 77 ancestry-informative markers. We identified a type of introduced mussels, called "dock mussels," associated with port habitats and displaying a particular genetic signal of admixture between M. edulis and the Mediterranean lineage of M. galloprovincialis. These mussels exhibit similarities in their ancestry compositions, regardless of the local native genetic backgrounds and the distance separating colonised ports. We observed fine-scale genetic shifts at the port entrance, at scales below natural dispersal distance. Such sharp clines do not fit with migration-selection tension zone models, and instead suggest habitat choice and early-stage adaptation to the port environment, possibly coupled with connectivity barriers. Variations in the spread and admixture patterns of dock mussels seem to be influenced by the local native genetic backgrounds encountered. We next examined departures from the average admixture rate at different loci, and compared human-mediated admixture events, to naturally admixed populations and experimental crosses. When the same M. galloprovincialis background was involved, positive correlations in the departures of loci across locations were found; but when different backgrounds were involved, no or negative correlations were observed. While some observed positive correlations might be best explained by a shared history and saltatory colonisation, others are likely produced by parallel selective events. Altogether, genome-wide effect of admixture seems repeatable and more dependent on genetic background than environmental context. Our results pave the way towards further genomic analyses of admixture, and monitoring of the spread of dock mussels both at large and at fine spacial scales.

Marine stepping-stones: Connectivity of Mytilus edulis populations between offshore energy installations

Recent papers have suggested that epifaunal organisms use artificial structures as stepping-stones to spread to areas that are too distant to reach in a single generation. With thousands of artificial structures present in the North Sea, we test the hypothesis that these structures are connected by water currents and act as an interconnected reef. Population genetic structure of the blue mussel, Mytilus edulis, was expected to follow a pattern predicted by a particle tracking model (PTM). Correlation between population genetic differentiation, based on microsatellite markers, and particle exchange was tested. Specimens of M. edulis were found at each location, although the PTM indicated that locations >85 km offshore were isolated from coastal subpopulations. The fixation coefficient FST correlated with the number of arrivals in the PTM. However, the number of effective migrants per generation as inferred from coalescent simulations did not show a strong correlation with the arriving particles. Isolation by distance analysis showed no increase in isolation with increasing distance and we did not find clear structure among the populations. The marine stepping-stone effect is obviously important for the distribution of M. edulis in the North Sea and it may influence ecologically comparable species in a similar way. In the absence of artificial shallow hard substrates, M. edulis would be unlikely to survive in offshore North Sea waters.

Contrasting seasonal and spatial distribution of native and invasive Codium seaweed revealed by targeting species-specific eDNA

AIM

Codium fragile, an invasive seaweed, has spread widely during the last century, impacting on local seaweed communities through competition and disturbance. Early detection of C. fragile can help on its control and management. Environmental DNA (eDNA) has proved successful for early detection of aquatic invasive species but its potential use for seaweed remains understudied. We used a species-specific eDNA qPCR approach to investigate the spatial distribution, abundance, and coexistence of the invasive C. fragile and three native Codium species (Codium vermilara, Codium tomentosum, and Codium decorticatum) in the Cantabrian Sea.

LOCATION

Bay of Biscay, Northern Atlantic Coast of the Iberian Peninsula; two ports, a beach and a rocky cliff.

METHODS

We designed species-specific primers in barcoding regions targeting short fragments of the rbcL gene for the invasive Codium species, and the elongation factor Tu (tufA) gene for the native species, to assess their spatial and seasonal distributions using quantitative real-time PCR in samples collected during summer, autumn, and winter.

RESULTS

We found seasonal differences in the presence of the invasive Codium fragile and two of the native Codium species, but did not detect C. decorticatum at any point. Species distribution patterns produced with qPCR targeting species-specific eDNA coincided with the known distribution based on previous conventional sampling, with a seasonal alternance of C. fragile and C. vermilara, and a marked dominance of invasive C. fragile in ports, which are known hotspots for invasive species.

MAIN CONCLUSIONS

Our results demonstrate the utility of using eDNA for early detection and monitoring of invasive seaweed. Native and invasive Codium spp. displayed significant seasonal and spatial differentiation that needs to be taken into account in risk management. Regular monitoring of ports and adjacent areas using eDNA should help to assess the potential expansion of invasive Codium and the need for management interventions to avoid the displacement of native seaweed.

Unravelling the origin and introduction pattern of the tropical species Paracaprella pusilla Mayer, 1890 (Crustacea, Amphipoda, Caprellidae) in temperate European waters: first molecular insights from a spatial and temporal perspective

Paracaprellapusilla Mayer, 1890 is a tropical caprellid species recently introduced to the Eastern Atlantic coast of the Iberian Peninsula and the Mediterranean Sea. In this study, we used direct sequencing of mitochondrial (COI and 16S) and nuclear (28S and ITS) genes to compare genetic differences in presumed native and introduced populations in order to infer its introduction pattern and to shed light on the native range of this species. The temporal pattern of genetic diversity at the westernmost limit of the geographic range of P.pusilla in Europe (the Atlantic coast of southern Spain) over an eight-year period was also investigated. Our results confirm P.pusilla as a neocosmopolitan species and suggest that the species is native to the Atlantic coast of Central and South America. Paracaprellapusilla seems to have been introduced into European waters from multiple introduction pathways and source populations, which are likely to include populations from coastal waters of Brazil. Multiple introduction pathways may have been involved, with the most important being commercial shipping through the Strait of Gibraltar. While this tropical species appears to be expanding in the Mediterranean, populations from the westernmost limit of its geographic range in Europe showed a temporal instability. This study constitutes the first molecular approach focused on this species, but it is also the first study of temporal change in genetic diversity of any introduced marine amphipod. Additional intensive sampling of this species, including both native and non-native populations, and detailed temporal studies are still necessary to properly understand how genetic diversity influences the introduction and survival of P.pusilla in invaded areas.

Ecological risk assessment of predicted marine invasions in the Canadian Arctic

Climate change is impacting environmental conditions, especially with respect to temperature and ice cover in high latitude regions. Predictive models and risk assessment are key tools for understanding potential changes associated with such impacts on coastal regions. In this study relative ecological risk assessment was done for future potential introductions of three species in the Canadian Arctic: periwinkle Littorina littorea, soft shell clam Mya arenaria and red king crab Paralithodes camtschaticus. These species occur in locations connected to Canadian Arctic ports through shipping and have the potential to be introduced via ballast water discharge. The methodology proposed in this study is unique in the sense that it considers not only ballast water origin, but also the distribution of the species being assessed and the sensitivity of the receiving habitat. It combines detailed information (ballast water source of each tank, transit time, time of the year when the water is released, environmental suitability of receiving habitat, impact, and habitat sensitivity) in order to assess ecological risk. Through the use of this approach it is highlighted that domestic discharge events pose a higher relative overall risk on a vessel-specific and cumulative annual bases than international discharges. The main ports of Deception Bay and Churchill were classified as being at moderate to high relative risk for L. littorea and M. arenaria, especially from domestic vessels, while relative overall risk for P. camtschaticus was low for international vessels and null for domestic vessels due to few ships transiting from its range of distribution to Canadian Arctic ports. This work can serve as an approach to help build a list of potential high risk species–a “grey” watch list–for the Canadian Arctic, and provides useful information for consideration in future decision making actions such as the identification of high risk pathways, species and ports.

Different approaches and limitations for testing phytoplankton viability in natural assemblies and treated ballast water

Shipping is recognised as an unintentional efficient pathway for spreading non-native species, harmful organisms and pathogens. In 2004, a unique IMO Convention was adopted to control and minimize this transfer in ship's ballast water. This Convention entered into force on 8th September 2017. However, unlikely the majority of IMO Conventions, the Ballast Water Management Convention requires ships to comply with biological standards (e.g. concentration of organisms per unit of volume in ballast water discharges). This study aimed to apply different techniques developed to measure concentrations of viable phytoplankton in natural and treated ballast water samples and compare them with the established flow cytometry method and vital staining microscopy. Samples were collected in the English Channel over one year and on-board during ballast water shipboard efficacy tests. Natural abundance of live phytoplankton varied from 23% to 89% of the total, while for cells larger than 10 μm (a size defined by the BWM Convention) the percentage varied from 3% to 60%. An overall good correlation was seen between the measurements taken with the two fluorometers and in comparison with the flow cytometry analysis, as found in previous studies. Analysis of treated ballast water samples showed a large variation in the number of viable cells, however indicating a low level of risk on all occasions for regulatory purposes. One of the key aspects to bear in mind when sampling and analysing for compliance is to be aware of the limitations of each technique.

DNA barcodes of Antipode marine invertebrates in Bay of Biscay and Gulf of Lion ports suggest new biofouling challenges

Marine biological invasions threaten global biodiversity nowadays. In this article, we have studied fouling communities from 10 port areas of south Bay of Biscay (Atlantic Ocean) and Gulf of Lion (Mediterranean Sea). A total of 834 individuals were genetically barcoded and corresponded to 95 different species. A total of 76 native species 8 genera and 1 family were identified, 58 from the Bay of Biscay and 23 from the Gulf of Lion. Furthermore, 19 species were identified as non-indigenous or cryptogenic (18 from the Bay of Biscay and 4 from the Gulf of Lion). We found a high proportion of Antipode non-indigenous species (NIS) that represented the 19.3% of all sampled individuals and the 54.21% of NIS specimens of this study. A framework for inference of donor regions based on a phylogenetic screening of genetic sequences was proposed as a proof of concept and tested, as well as models for the relationship between NIS introductions, maritime imports and distance to NIS native range and inferred donor areas. Consistent generalized linear models (GLM) with positive association between NIS genetic diversity and distance, not with maritime growth weight imports, strongly suggest that distant NIS could pose higher invasion risk than closer species. Selection for wider tolerance ranges during the long travel -direct or stepwise, as well as environmental similarity between donor and receiving regions, may explain these results.

Risk factors for fouling biomass: evidence from small vessels in Australia

Invasive non-indigenous species (NIS) are a threat to marine biodiversity and marine reliant industries. Recreational vessels are recognised as an important vector of NIS translocation, particularly domestically. This paper reports on a novel application of multilevel modelling and multiple imputation in order to quantify the relationship between biofouling biomass (wet weight) and the vessel-level characteristics of recreational and fishing vessels. It was found that the number of days since the vessel was last cleaned strongly related to the biofouling biomass, yet differed dependent on vessel type. Similarly, the median number of trips undertaken was related to the biofouling biomass, and varied according to the type of antifouling paint (AF) used. No relationship was found between vessel size and biofouling biomass per sample unit. To reduce the spread of NIS, vessel owners should use an AF paint suitable to their vessel's operational profile, and follow a maintenance schedule according to the paint manufacturer's specifications.

Big data analysis for evaluating bioinvasion risk

Background

Global maritime trade plays an important role in the modern transportation industry. It brings significant economic profit along with bioinvasion risk. Species translocate and establish in a non-native area through ballast water and biofouling. Aiming at aquatic bioinvasion issue, people proposed various suggestions for bioinvasion management. Nonetheless, these suggestions only focus on the chance of a port been affected but ignore the port’s ability to further spread the invaded species.

Results

To tackle the issues of the existing work, we propose a biosecurity triggering mechanism, where the bioinvasion risk of a port is estimated according to both the invaded risk of a port and its power of being a stepping-stone. To compute the invaded risk, we utilize the automatic identification system data, the ballast water data and marine environmental data. According to the invaded risk of ports, we construct a species invasion network (SIN). The incoming bioinvasion risk is derived from invaded risk data while the invasion risk spreading capability of each port is evaluated by s-core decomposition of SIN.

Conclusions

We illustrate 100 ports in the world that have the highest bioinvasion risk when the invaded risk and stepping-stone bioinvasion risk are equally treated. There are two bioinvasion risk intensive regions, namely the Western Europe (including the Western European margin and the Mediterranean) and the Asia-Pacific, which are just the region with a high growth rate of non-indigenous species and the area that has been identified as a source for many of non-indigenous species discovered elsewhere (especially the Asian clam, which is assumed to be the most invasive species worldwide).

Optimal treatment allocations in space and time for on-line control of an emerging infectious disease

A key component in controlling the spread of an epidemic is deciding where, when and to whom to apply an intervention. We develop a framework for using data to inform these decisions in realtime. We formalize a treatment allocation strategy as a sequence of functions, one per treatment period, that map up-to-date information on the spread of an infectious disease to a subset of locations where treatment should be allocated. An optimal allocation strategy optimizes some cumulative outcome, e.g. the number of uninfected locations, the geographic footprint of the disease or the cost of the epidemic. Estimation of an optimal allocation strategy for an emerging infectious disease is challenging because spatial proximity induces interference between locations, the number of possible allocations is exponential in the number of locations, and because disease dynamics and intervention effectiveness are unknown at out-break. We derive a Bayesian on-line estimator of the optimal allocation strategy that combines simulation-optimization with Thompson sampling. The estimator proposed performs favourably in simulation experiments. This work is motivated by and illustrated using data on the spread of white nose syndrome, which is a highly fatal infectious disease devastating bat populations in North America.