Modeling the risk of aquatic species invasion spread through boater movements and river connections.

Aquatic invasive species (AIS) are one of the greatest threats to the functioning of aquatic ecosystems worldwide. Once an invasive species has been introduced to a new region, many governments develop management strategies to reduce further spread. Nevertheless, managing AIS in a new region is challenging because of the vast areas that need protection and limited resources. Spatial heterogeneity in invasion risk is driven by environmental suitability and propagule pressure, which can be used to prioritize locations for surveillance and intervention activities. To better understand invasion risk across aquatic landscapes, we developed a simulation model to estimate the likelihood of a waterbody becoming invaded with an AIS. The model included waterbodies connected via a multilayer network that included boater movements and hydrological connections. In a case study of Minnesota, we used zebra mussels (Dreissena polymorpha) and starry stonewort (Nitellopsis obtusa) as model species. We simulated the impacts of management scenarios developed by stakeholders and created a decision-support tool available through an online application provided as part of the AIS Explorer dashboard. Our baseline model revealed that 89% of new zebra mussel invasions and 84% of new starry stonewort invasions occurred through boater movements, establishing it as a primary pathway of spread and offering insights beyond risk estimates generated by traditional environmental suitability models alone. Our results highlight the critical role of interventions applied to boater movements to reduce AIS dispersal.

Modelo del riesgo de la invasión de especies acuáticas dispersadas por movimiento de botes y conexiones entre ríos Resumen Las especies acuáticas invasoras (EAI) son una de las principales amenazas para el funcionamiento de los ecosistemas acuáticos a nivel mundial. Una vez que una especie invasora ha sido introducida a una nueva región, muchos gobiernos desarrollan estrategias de manejo para disminuir la dispersión. Sin embargo, el manejo de las especies acuáticas invasoras en una nueva región se complica debido a las amplias áreas que necesitan protección y los recursos limitados. La heterogeneidad espacial de un riesgo de invasión es causada por la idoneidad ambiental y la presión de propágulo, que puede usarse para priorizar la ubicación de las actividades de vigilancia e intervención. Desarrollamos una simulación para estimar la probabilidad de que un cuerpo de agua sea invadido por EAI para tener un mejor entendimiento del riesgo de invasión en los paisajes acuáticos. El modelo incluyó cuencas conectadas a través de una red multicapa que incluía movimiento de botes y conexiones hidrológicas. Usamos como especies modelo a Dreissena polymorpha y a Nitellopsis obtusa en un estudio de caso en Minnesota. Simulamos el impacto de los escenarios de manejo desarrollado por los actores y creamos una herramienta de decisiones por medio de una aplicación en línea proporcionada como parte del tablero del Explorer de EAI. Nuestro modelo de línea base reveló que el 89% de las invasiones nuevas de D. polymorpha y el 84% de las de N. obtusa ocurrieron debido al movimiento de los botes, lo que lo estableció como una vía primaria de dispersión y nos proporcionó información más allá de las estimaciones de riesgo generadas por los modelos tradicionales de idoneidad ambiental. Nuestros resultados resaltan el papel crítico de las intervenciones aplicadas al movimiento de los botes para reducir la dispersión de especies acuáticas invasoras.

Assessing the performance of four indicative analysis devices for ballast water compliance monitoring, considering organisms in the size range ≥10 to <50 µm.

To minimize the global transfer of harmful aquatic organisms and pathogens, the International Maritime Organization (IMO) has introduced the standard in Regulation D-2 to limit the number of viable organisms in ballast water discharged by ships. To meet the standard, many ships are installing ballast water management systems. Concurrently, regulators are looking for indicative analysis devices able to assess compliance with Regulation D-2, producing rapid, accurate and reliable results while being easy to operate. The purpose of this research is to compare four indicative analysis devices against detailed microscopy for measuring the size class of organisms ≥10 to <50 µm in minimum dimension (e.g., phytoplankton, including autotrophs, heterotrophs or mixotrophs), using field and laboratory tests. Comparisons were conducted on (treated) ballast water discharge samples collected across Canada during three consecutive years (2017-2019). During seven tests in 2019, paired ballast water uptake samples were also obtained, facilitating measurements before and after treatment was applied. Indicative analysis devices also were challenged with natural environmental samples containing different organism abundance levels, ranging from low (nominally <10 cells mL-1) to high (nominally >150 cells mL-1) during laboratory tests. While the indicative analysis devices examined during this research produced numeric estimates having weak correlations with the standard reference method, categorical outcomes (above/below the D-2 standard) had high agreement (89% or better) when assessing ballast water samples, but lower agreement (67% or poorer) during laboratory tests. There was a relatively high rate of false negative results measured by all devices during laboratory tests. Results provided by indicative analysis devices had higher uncertainty when organism abundances in ballast samples are below and close to the D-2 standards.

AIS explorer: Prioritization for watercraft inspections-A decision-support tool for aquatic invasive species management.

Invasions of aquatic invasive species have caused significant economic and ecological damage to global aquatic ecosystems. Once an invasive population has established in a new habitat, eradication can be financially and logistically impossible, motivating management strategies to rely heavily upon prevention measures to reduce the introduction and spread. To be productive, on-the-ground management of aquatic invasive species requires effective decision-making surrounding the allocation of limited resources. Watercraft inspections play an important role in managing aquatic invasive species by preventing the overland transport of invasive species between waterbodies and providing education to boaters. In this study, we developed and tested an interactive web-based decision-support tool, AIS Explorer: Prioritization for Watercraft Inspections, to guide AIS managers in developing efficient watercraft inspection plans. The decision-support tool is informed by a network-based algorithm that maximized the number of inspected watercraft that move from AIS infested to uninfested lakes within and between counties in Minnesota, USA. It was iteratively built with stakeholder feedback, including consultations with county managers, beta-testing of the web-based application, and workshops to educate and train end-users. The co-development and implementation of data-driven decision support tools demonstrate how interdisciplinary methods can be used to connect science and management to support decision-making. The AIS Explorer: Prioritization for Watercraft Inspections application makes optimized research outputs accessible in multiple dynamic forms that maintain pace with discovery of new infestations and local needs. In addition, the decision support tool has supported improved and closer communication between AIS managers and researchers on this topic.

Managing aquatic invasions: Optimal locations and operating times for watercraft inspection stations.

Aquatic invasive species (AIS) cause significant ecological and economic damages around the world. A major spread mechanism for AIS is traffic of boaters transporting their watercraft from invaded to uninvaded waterbodies. To inhibit the spread of AIS, Canadian provinces and American states often set up watercraft inspection stations at roadsides, where potentially infested boats are screened for AIS and, if necessary, decontaminated. However, since budgets for AIS control are limited, watercraft inspection stations can only be operated at specific locations and daytimes. Though theoretical studies provide managers with general guidelines for AIS management, more specific results are needed to determine when and where watercraft inspections would be most effective. This is the subject of this paper. We show how linear integer programming techniques can be used to optimize watercraft inspection policies under budget constraints. We introduce our approach as a general framework and apply it to the prevention of the spread of zebra and quagga mussels (Dreissena spp.) to the Canadian province of British Columbia. We consider multiple scenarios and show how variations in budget constraints, propagule sources, and model uncertainty affect the optimal policy. Based on these results, we identify simple, generally applicable principles for optimal AIS management.

Testing Emphasis Message Frames and Metaphors on Social Media to Engage Boaters to Learn about Preventing the Spread of Zebra Mussels.

Message frames are often used to communicate about invasive species due to the additional meaning they provide. They appear in calls to action like "join the battle against invasive species," "unwelcome exotics," or "Stop Aquatic Hitchhikers." However, little is known about how stakeholders respond to these message frames. This research tested five common message emphasis frames used in invasive species communication. These message frames were placed in social media advertisements about zebra mussels to determine the impact each message frame had on user online behavior. For cost-per-click (CPC), ANOVA showed effects for framing and gender. Model coefficients revealed that Hitchhiker and Protective had significantly higher CPC than Science, and that women had a higher CPC. For comments, ANOVA showed effects for framing and gender. Model coefficients revealed that no frame had a significantly different effect on comments than Science, and that women commented on posts less. For shares, ANOVA showed effects for framing. Model coefficients revealed that Hitchhiker was shared more than Science. It is important to note that neither Militaristic nor Nativist outperformed Science on any measured outcome. Coupled with ethical considerations, our results suggest the use of Nativist and Militaristic frames are not necessary to influence online behavior. Message frames without ethical issues can be used to achieve the outcomes we tested without compromising message effectiveness. Within this article, we provide background on commonly used invasive species message frames, explain our methods for testing how they impact user behavior, and suggest limitations and applications of this work.

Climate warming moderates the impacts of introduced sportfish on multiple dimensions of prey biodiversity.

Human-assisted introductions of exotic species are a leading cause of anthropogenic change in biodiversity; however, context dependencies and interactions with co-occurring stressors impede our ability to predict their ecological impacts. The legacy of historical sportfish stocking in mountainous regions of western North America creates a unique, natural quasiexperiment to investigate factors moderating invasion impacts on native communities across broad geographic and environmental gradients. Here we synthesize fish stocking records and zooplankton relative abundance for 685 mountain lakes and ponds in the Cascade and Canadian Rocky Mountain Ranges, to reveal the effects of predatory sportfish introduction on multiple taxonomic, functional and phylogenetic dimensions of prey biodiversity. We demonstrate an innovative analytical approach, combining exploratory random forest machine learning with confirmatory multigroup analysis using multivariate partial least-squares structural equation models, to generate and test hypotheses concerning environmental moderation of stocking impacts. We discovered distinct effects of stocking across different dimensions of diversity, including negligible (nonsignificant) impacts on local taxonomic richness (i.e. alpha diversity) and trophic structure, in contrast to significant declines in compositional uniqueness (i.e. beta diversity) and body size. Furthermore, we found that stocking impacts were moderated by cross-scale interactions with climate and climate-related land-cover variables (e.g. factors linked to treeline position and glaciers). Interactions with physical morphometric and lithological factors were generally of lesser importance, though catchment slope and habitat size constraints were relevant in certain dimensions. Finally, applying space-for-time substitution, a strong antagonistic (i.e. dampening) interaction between sportfish predation and warmer temperatures suggests redundancy of their size-selective effects, meaning that warming will lessen the consequences of introductions in the future and stocked lakes may be less impacted by subsequent warming. While both stressors drive biotic homogenization, our results have important implications for fisheries managers weighing the costs/benefits of stocking-or removing established non-native populations-under a rapidly changing climate.

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.

Risk of invasive species spread by recreational boaters remains high despite widespread adoption of conservation behaviors.

The spread of non-native aquatic species among waterbodies has become a major social, environmental, and economic concern. An important mechanism of this spread is the inadvertent transport of organisms on recreational boats as they are moved among waterbodies. Organisms can survive on the exterior of the boat, the interior, attached to fishing tackle, and can be intentionally moved by boaters. In response, local, state, and federal U.S. agencies have invested in outreach campaigns to educate boaters about the impacts of invasive aquatic species and the ways that boaters can reduce the risk of spread. We surveyed boaters in the U.S. state of Illinois to determine their travel patterns and how frequently they clean different parts of their boats. A majority of boaters reported that they always take recommended actions to clean their boat exterior (72% of respondents), boat interior (78%), and fishing tackle (55%), and only 4% reported that they intentionally move organisms. We used network methods to analyze the movement of recreational boaters and found strong connections among 28 highly visited waterbodies. When we removed the 38% of respondents who Always take recommended actions to reduce risk of species spread by all four mechanisms this network was minimally altered and still contained all 28 waterbodies. This indicates that despite high adoption of conservation behaviors there is a continuing risk of non-native species transport among all waterbodies. This work shows that further action is necessary if the impacts of invasive aquatic species are to be reduced in the future.

Broad shifts in the resource use of a commercially harvested fish following the invasion of dreissenid mussels.

Dreissenid mussels, including the zebra (Dreissena polymorpha) and quagga (Dreissena rostiformus bugensis) mussel, are invasive species known for their capacity to act as ecosystem engineers. They have caused significant changes in the many freshwater systems they have invaded by increasing water clarity, reducing primary productivity, and altering zooplankton and benthic invertebrate assemblages. What is less clear is how their ecosystem engineering effects manifest up the food web to impact higher trophic levels, including fish. Here, we use a biological tracer (stable isotopes of carbon and nitrogen) to analyze long-term and broad-scale trends in the resource use of benthivorous lake whitefish (Coregonus clupeaformis) in the Laurentian Great Lakes, where dreissenid mussels have become established in each lake except Lake Superior. We measured stable isotope ratios from archived material (fish scale samples) collected over several decades by multiple agencies and from 14 locations around the Great Lakes. In the majority of locations, the δ13 C of lake whitefish increased following the establishment of dreissenid mussels. Trends in δ15 N were less clear, but significant breakpoints in the time series occurred within 5 yr of dreissenid establishment in several locations, followed by declines in δ15 N. In contrast, isotopic signatures in Lake Superior locations did not show these trends. Our results provide evidence that lake whitefish shifted toward greater reliance on nearshore benthic production, supporting the theory that fundamental energy pathways are changed when dreissenid mussels become established. Importantly, these effects were noted across multiple, large, and complex ecosystems spanning a broad geographic area. Our study underscores the potential for aquatic invasive species to alter key ecosystem services as demonstrated here through their impacts on energy pathways supporting a commercially harvested fish species.

Coupling ecological and social network models to assess "transmission" and "contagion" of an aquatic invasive species.

Network analysis is used to address diverse ecological, social, economic, and epidemiological questions, but few efforts have been made to combine these field-specific analyses into interdisciplinary approaches that effectively address how complex systems are interdependent and connected to one another. Identifying and understanding these cross-boundary connections improves natural resource management and promotes proactive, rather than reactive, decisions. This research had two main objectives; first, adapt the framework and approach of infectious disease network modeling so that it may be applied to the socio-ecological problem of spreading aquatic invasive species, and second, use this new coupled model to simulate the spread of the invasive Chinese mystery snail (Bellamya chinensis) in a reservoir network in Southeastern Nebraska, USA. The coupled model integrates an existing social network model of how anglers move on the landscape with new reservoir-specific ecological network models. This approach allowed us to identify 1) how angler movement among reservoirs aids in the spread of B. chinensis, 2) how B. chinensis alters energy flows within individual-reservoir food webs, and 3) a new method for assessing the spread of any number of non-native or invasive species within complex, social-ecological systems.

Assessing the success of invasive species prevention efforts at changing the behaviors of recreational boaters.

Aquatic invasive species (AIS) pose major conservation challenges in freshwater ecosystems. In response, conservation organizations invest considerable resources in outreach to encourage AIS prevention behaviors among recreational boaters. Despite this, remarkably little is known about whether these efforts catalyze significant changes in boaters' perceptions, or whether they cause changes in behaviors that reduce AIS risk. We interviewed managers at the 14 Illinois organizations active in AIS outreach to determine regional priorities for, and investment in, AIS outreach. The results show a network of collaboration that reinforces a limited set of conservation messages. Next, we surveyed 515 recreational boaters to evaluate access to outreach, knowledge of AIS, and consistency of prevention behavior. Boater recognition of prevention slogans and knowledge of AIS and AIS prevention behavior was similar across Illinois regions despite large regional differences in investment in outreach. Most boaters (94%) report never intentionally moving organisms among waterbodies. Fewer reported that they Always perform recommended actions to reduce risk of AIS spread on their boat interior (68%), boat exterior (63%), or fishing tackle (47%). Recognition of prevention slogans and the number of AIS recognized were significantly, positively, associated with Always performing AIS prevention behavior on the vectors of the boat exterior, and fishing tackle, respectively. Our results suggest that increasing knowledge may be a necessary condition for higher adoption of AIS prevention behaviors, but that this alone may not be sufficient. Instead, efforts targeted at boaters who do not currently practice the recommended actions are likely to be necessary.

Carbon Dioxide Toxicity to Zebra Mussels (Dreissena polymorpha) is Dependent on Water Chemistry.

Carbon dioxide (CO2) is gaining interest as a tool to combat aquatic invasive species, including zebra mussels (Dreissena polymorpha). However, the effects of water chemistry on CO2 efficacy are not well described. We conducted five trials in which we exposed adult zebra mussels to a range of CO2 in water with adjusted total hardness and specific conductance. We compared dose-responses and found differences in lethal concentration to 50% of organisms (LC50) estimates ranging from 108.3 to 179.3 mg/L CO2 and lethal concentration to 90% of organisms (LC90) estimates ranging from 163.7 to 216.6 mg/L CO2. We modeled LC50 and LC90 estimates with measured water chemistry variables from the trials. We found sodium (Na+) concentration to have the strongest correlation to changes in the LC50 and specific conductance to have the strongest correlation to changes in the LC90. Our results identify water chemistry as an important factor in considering efficacious CO2 concentrations for zebra mussel control. Additional research into the physiological responses of zebra mussels exposed to CO2 may be warranted to further explain mode of action and reported selectivity. Further study could likely develop a robust and relevant model to refine CO2 applications for a wider range of water chemistries. Environ Toxicol Chem 2024;43:1312-1319. Published 2024. This article is a U.S. Government work and is in the public domain in the USA. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Review and Development of Best Practices for Toxicity Tests with Dreissenid Mussels.

Since their introduction to North America in the 1980s, research to develop effective control tools for invasive mussels (Dreissena polymorpha and D. rostriformis bugensis) has been ongoing across various research institutions using a range of testing methods. Inconsistencies in experimental methods and reporting present challenges for comparing data, repeating experiments, and applying results. The Invasive Mussel Collaborative established the Toxicity Testing Work Group (TTWG) in 2019 to identify "best practices" and guide development of a standard framework for dreissenid mussel toxicity testing protocols. We reviewed the literature related to laboratory-based dreissenid mussel toxicity tests and determined the degree to which standard guidelines have been used and their applicability to dreissenid mussel testing. We extracted detailed methodology from 99 studies from the peer-reviewed and gray literature and conducted a separate analysis for studies using presettlement and postsettlement mussels. We identified specific components of methods and approaches that could be refined or standardized for dreissenid mussels. These components included species identification, collection methods, size/age class distinction, maintenance practices, testing criteria, sample size, response measures, reporting parameters, exposure methods, and mortality criteria. We consulted experts in the field of aquatic toxicology and dreissenid mussel biology on our proposed. The final recommendations contained in the present review are based on published standard guidelines, methods reported in the published and gray literature, and the expertise of TTWG members and an external panel. In addition, our review identifies research needs for dreissenid mussel testing including improved methods for early-life stage testing, comparative data on life stages and between dreissenid mussel species, inclusion of a reference toxicant, and additional testing of nontarget species (i.e., other aquatic organisms). Environ Toxicol Chem 2023;42:1649-1666. © 2023 His Majesty the King in Right of Canada. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. Reproduced with the permission of the Minister of Environment and Climate Change Canada. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

DNA assays for genetic discrimination of three Phragmites australis subspecies in the United States.

Premise: To genetically discriminate subspecies of the common reed (Phragmites australis), we developed real-time quantitative (qPCR) assays for identifying P. australis subsp. americanus, P. australis subsp. australis, and P. australis subsp. berlandieri. Methods and Results: Utilizing study-generated chloroplast DNA sequences, we developed three novel qPCR assays. Assays were verified on individuals of each subspecies and against two non-target species, Arundo donax and Phalaris arundinacea. One assay amplifies only P. australis subsp. americanus, one amplifies P. australis subsp. australis and/or P. australis subsp. berlandieri, and one amplifies P. australis subsp. americanus and/or P. australis subsp. australis. This protocol enhances currently available rapid identification methods by providing genetic discrimination of all three subspecies. Conclusions: The newly developed assays were validated using P. australis samples from across the United States. Application of these assays outside of this geographic range should be preceded by additional testing.

A comparison of survey method efficiencies for estimating densities of zebra mussels (Dreissena polymorpha).

Abundance surveys are commonly used to estimate plant or animal densities and frequently require estimating detection probabilities to account for imperfect detection. The estimation of detection probabilities requires additional measurements that take time, potentially reducing the efficiency of the survey when applied to high-density populations. We conducted quadrat, removal, and distance surveys of zebra mussels (Dreissena polymorpha) in three central Minnesota lakes and determined how much survey effort would be required to achieve a pre-specified level of precision for each abundance estimator, allowing us to directly compare survey design efficiencies across a range of conditions. We found that the required sampling effort needed to achieve our precision goal depended on both the survey design and population density. At low densities, survey designs that could cover large areas but with lower detection probabilities, such as distance surveys, were more efficient (i.e., required less sampling effort to achieve the same level of precision). However, at high densities, quadrat surveys, which tend to cover less area but with high detection rates, were more efficient. These results demonstrate that the best survey design is likely to be context-specific, requiring some prior knowledge of the underlying population density and the cost/time needed to collect additional information for estimating detection probabilities.

Round Goby (Neogobius melanostomus) impacts on benthic fish communities in two tributaries of the Great Lakes.

Numerous fish species in the Laurentian Great Lakes have been negatively impacted by the establishment of the invasive Round Goby (Neogobius melanostomus). However, limited understanding exists as to how Round Goby has impacted small-bodied native benthic fishes after its secondary invasion into tributaries of the Laurentian Great Lakes. To investigate Round Goby impacts on darter species (family Percidae) in tributary ecosystems, catch per unit area (CPUA) of native and non-native fishes from two riverine ecosystems in Southwestern Ontario (Ausable River, Big Otter Creek) were analyzed. Spatial analyses indicated Round Goby CPUA was highest proximate to the Great Lakes, with a sharp decline in CPUA at sites upstream from each lake (Round Goby CPUA approached zero after 18 and 14 km in the Ausable River and Big Otter Creek, respectively). There was some evidence of a negative relationship between the CPUA of Round Goby and several darter species along the tributary gradients, with moderately negative co-occurrence between Round Goby and Rainbow Darter in the Ausable River and Johnny Darter and Percidae species overall in Big Otter Creek. However, overwhelming evidence of negative associations between Round Goby and all darter species was not found. The negative relationship between the CPUA of Round Goby and some darter species was observed over similar time periods since establishment but greater spatial scales than in previous studies, and therefore has important implications for understanding the ecological impacts of Round Goby in tributary ecosystems.

Effects of shipping on non-indigenous species in the Baltic Sea.

Shipping is regarded as an important vector for aquatic non-indigenous species (ANIS) worldwide. Less attention has been paid to its role in relation to environmental and economic causes of introduction and establishment, the knowledge of which is necessary to assess effects of changes in regulations on shipping. The purpose of this study was to estimate the impact of shipping on the incidence of ANIS in the Baltic Sea compared with environmental and economic factors. To this end, a production function was estimated with count data on ANIS (response variable) and shipping, environmental and economic factors as explanatory variables. Regression results from different regression models showed that shipping has a significant impact on ANIS incidence and can account for up to 38% of the number of ANIS in the sea. Predictions of the impact of measures implementing the Convention for the Control and Management of Ships' Ballast Water and Sediment indicated a reduction by 17% in the number of ANIS, which was counteracted by an expected increase in shipping traffic.

First evaluation of ballast water management systems on operational ships for minimizing introductions of nonindigenous zooplankton.

Ballast water is a leading pathway for the global introduction of aquatic nonindigenous species. Most international ships are expected to install ballast water management systems (BWMS) by 2024 to treat ballast water before release. This study examines if ballast water discharges managed by BWMS are meeting standards for organisms ≥50 µm in minimum dimension (i.e., <10 organisms per m3; typically zooplankton). Representative samples of ballast water were collected from 29 ships (using 14 different BWMS) arriving to Canada during 2017-2018. Fourteen samples (48 %) had zooplankton concentrations clearly exceeding the standard (ranging from 18 to 3822 organisms per m3). Nonetheless, compared to earlier management strategies, BWMS appear to reduce the frequency of high-risk introduction events. BWMS filter mesh size was an important predictor of zooplankton concentration following treatment. Greater rates of compliance may be achieved as ship crews gain experience with operation and maintenance of BWMS.

Title: Low concentrations of glyphosate in water and sediment after direct over-water application to control an invasive aquatic plant.

When an invasive wetland grass degrades a Ramsar wetland and Important Bird Area, decisive management action is called for. To limit the extent and spread of European Phragmites australis, the Ontario government began the first, large-scale application of glyphosate (Roundup CustomⓇ) over standing water to control an invasive species in Canadian history. Between 2016 and 2018, over 1000 ha of marsh were treated. To assess the concentration, movement and longevity of this herbicide in treated marshes, we measured the concentration of glyphosate, its primary breakdown product aminomethylphosphonic acid (AMPA), and the alcohol ethoxylate-based adjuvant AquasurfⓇ in water and sediments in areas of the highest exposure and up to 150 m into adjacent bays. The maximum observed concentration of glyphosate in water was 0.320 mg/L, occurring within 24 hr of application. The maximum glyphosate concentration in sediment was 0.250 mg/kg, occurring within about 30 days of application. AMPA was detectable in water and sediment, indicating microbial breakdown of glyphosate in the marsh, but at low concentrations (maxwater = 0.025 mg/L, maxsed = 0.012 mg/kg). The maximum distance from the point of application that glyphosate was detected in the water was 100 m, while AMPA was detectable only at the edge of where glyphosate was applied (0 m). Concentrations in water returned to pre-treatment levels (0.005 mg/kg) for over one year but less than two years. Concentrations of alcohol ethoxylates were variable in space and time, following a pattern that could not be attributed to AquasurfⓇ use. The direct, over-water application of Roundup CustomⓇ with AquasurfⓇ to control invasive P. australis did not reach concentrations deemed to pose toxicological concern to aquatic biota by the Canadian Council of Ministers of the Environment.

A Framework for Aquatic Invasive Species Surveillance Site Selection and Prioritization in the US waters of the Laurentian Great Lakes.

Risk-based prioritization for early detection monitoring is of utmost importance to prevent and mitigate invasive species impacts. The Great Lakes Water Quality Agreement, a binational commitment between the United States and Canada to restore and protect the waters of the Laurentian Great Lakes, identifies aquatic invasive species (AIS) as one of ten priority issues (annexes) that must be addressed to ensure the chemical, physical, and biological integrity of the Great Lakes. The Agreement calls out the need for a comprehensive strategy for detecting and tracking new and potentially invasive species. Yet, with a surface water area of 95, 000 square miles (246, 049 square km) and shoreline length of 10, 210 miles (16, 431 km), the Great Lakes represent a daunting challenge for prioritizing where AIS surveillance activities should occur. Our goal was to develop a spatially-explicit and quantitative approach for identifying the highest risk sites for AIS introduction into the US waters of the Great Lakes based on the cumulative risk of new introductions (including range expansions) from a range of pathways and associated taxa. We estimate "invasion risk" scores for nearly 6,000 sites (9 km x 9 km) across the Great Lakes basin using proxy measures for propagule pressure weighted by the proportion of taxa associated with each proxy variable. Proxy variables include human population, number of ship visits, marina size, number of ponds, and number of natural or artificial aquatic connections. In total, we identify more than 1,800 sites with invasion risk scores >0. A small subset of these 1,800+ sites accounts for a majority of predicted propagule pressure and are therefore logical targets for future surveillance and AIS prevention efforts. Many of the highest risk sites are located in western Lake Erie, southern Lake Michigan, and the St. Clair-Detroit River System.