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Invasive species are often assumed to have measurable impacts throughout their potential range, but this is not always true. This study evaluated whether zebra mussels (Dreissena polymorpha) were causing an increase in water clarity near the southern edge of their North American expansion using a 40+ year dataset. We looked for abrupt shifts and long-term trends in water clarity and compared these to the estimated zebra mussel invasion date for 7 reservoirs in Missouri, USA. We also looked at water clarity in 26 non-invaded reservoirs to evaluate whether zebra mussel impacts were being masked by variation in environmental factors. Collectively, our analyses provide a weight of evidence based on a lack of consistent shifts in water clarity corresponding with zebra mussel invasions. Mussel establishment did not increase water clarity, likely because densities were too low to result in a measurable impact. The highest zebra mussel density we observed was 65 mussels m−2, an order of magnitude less than in systems where they have had a sustained impact. Low densities could be due to a combination of sublethal environmental conditions such as warm water temperatures, suspended inorganic particulates, fluctuating water levels, and reduced oxygen concentrations, as well as limited hard substrata or predation by fish. While additional study is required to understand which, if any, of these factors may be limiting zebra mussel establishment in Missouri, our study shows that dreissenids are not having an impact as elsewhere throughout their range, suggesting that how an invader alters ecosystem functions is critical to determining its impact. [ABSTRACT FROM AUTHOR]

The ecological impact of dreissenid mussel (e.g., quagga and zebra) populations and their empty shells on native fauna in large rivers and lakes has been extensively studied. However, there is limited information on their effects in small wadable streams. Although established mussel populations in these systems are uncommon, their shells are found in high densities in benthic environments and may adversely impact stream communities. Shell densities were quantified using quadrats in two wadable streams to assess impacts on native benthic macroinvertebrates and fish. Eight reaches of each river were sampled, four with dreissenids and four without, totaling 16 locations. Macroinvertebrate and fish communities were characterized using diversity and environmental tolerance indices. Shell densities were significantly higher in dreissenid-invaded sites compared to sites with only native bivalves in both rivers. Dense shell beds had degraded biological conditions with fewer sensitive macroinvertebrates, but bed density did not affect overall macroinvertebrate or fish diversity. These findings differ from lake and large river studies, which found a greater impact of dreissenid shell deposition on macroinvertebrate and fish diversity than we observed in small wadable streams. Thus, a different approach to management and restoration may be necessary to maintain a natural community composition in wadable streams. [ABSTRACT FROM AUTHOR]

Diatom-based paleolimnological studies conducted ~25 years ago on five lakes (i.e., Big Rideau, Upper Rideau, Lower Rideau, Indian and Otter lakes) within the Rideau Canal system (Ontario, Canada) tracked extensive catchment disturbances related to canal construction (starting ca. 1828). Over the past three decades, these lakes have experienced additional environmental stressors including invasive zebra mussels and accelerated climate warming, warranting a paleolimnological re-assessment. We examine diatom compositional changes and visible range spectroscopy-inferred chlorophyll-a (VRS-Chla) trends over the past >200 years from sediment cores collected in 2019-2020 from these same lakes, with the aim of assessing environmental changes registered in these records since the original studies were undertaken ~25-30 years ago. Despite large-scale cultural disturbances, including extensive deforestation and flooding for canal construction, the most ecologically notable diatom changes in all sediment records occurred in the past ~25-30 years, and coincided with increases in VRS-Chla. During this recent period, small cyclotelloid and elongate planktonic diatoms increased in relative abundance, while large-celled Aulacoseira taxa declined. Exceptions to this trend include Upper Rideau Lake, where planktonic diatoms were scarce throughout the core and shifts occurred among benthic taxa, and Big Rideau Lake, which has a large littoral zone, where epiphytic diatoms became prominent in the past decade. These recent diatom changes could not be explained by nutrient enrichment, as measured total phosphorus (TP) concentrations have declined significantly since the 1970s. Increases in small planktonic taxa in some of the lakes also pre-date the ca. 1990 arrival of zebra mussels. We conclude that these recent changes were best explained by regional warming and declining wind speed resulting in new lake physical regimes. Such climate-driven changes are also consistent with the recent development of cyanobacterial blooms in these lakes, despite declining nutrient levels.

Early detection and rapid response represent cornerstones of effective management of biological invasions, and development of methods that increase the sensitivity and efficiency of species detection directly benefit such efforts. We compared environmental DNA (eDNA) and canine scent detection of Dreissena polymorpha (Pallas, 1771), the Eurasian zebra mussel, in lakes of central Texas, USA. Environmental DNA analysis has become routinely incorporated as a component of D. polymorpha management programs; however, canine scent detection has typically been limited to inspection for adult mussels on watercraft. Thus, our work represents the first attempt to evaluate detection of D. polymorpha veligers (i.e., free-swimming larval stages) and other microscopic traces in environmental samples with canine scent detection. The specific objectives of this study were to: 1) evaluate whether canines can detect D. polymorpha in environmental samples; 2) quantify and compare limits of detection of canine scent detection and eDNA analysis; and 3) assess the performance of detection technologies through blind screening of ten lakes. In order of objective, our major findings include: 1) canines can be trained to detect D. polymorpha veligers in water samples; 2) eDNA detection is 2-100x more sensitive than canine scent detection; and 3) canine scent detection and eDNA both appear to outperform microscopy for D. polymorpha detection in environmental water samples. However, more work is needed to understand the conditions dictating when canine scent detection or eDNA outperforms the other. [ABSTRACT FROM AUTHOR]

The Rideau Canal (Ontario, Canada) was constructed in the early 1830s, primarily as a means to transport military personnel, but now is primarily recreational. The construction of the canal and associated flooding, as well as other land-use changes, likely impacted lakes within the system, however, long-term monitoring data are not available. Furthermore, recent environmental changes, including accelerated climate warming, are affecting lake ecosystems. Shallow, macrophyte-dominated Lake Opinicon, which is part of the canal system, has been impacted by other various catchment disturbances over the past ~ 200 years. A previous diatom-based paleolimnological study conducted on the lake, examining a core collected in 1995, found that the diatom responses to a host of large-scale catchment disturbances were moderate compared to nearby deeper lakes. A more recent diatom-based study conducted on a 2019 core (the same core used in the present study) found similar results; however, over the most recent ~ 25–30 years a striking shift in diatom assemblage composition was documented, coinciding with increased regional climate warming. Nothing is known concerning long-term changes within the primary consumers linked to the array of disturbances. Here, we examined changes in cladoceran assemblages over the past ~200 years, using the 2019 sediment core, to track their response to various environmental stressors including climate warming. We found that pelagic Bosmina and Daphnia species began to increase in the early nineteenth century, consistent with the flooding of the lake during canal construction. The most ecologically notable changes in the cladoceran record, however, occurred in the most recent sediments. These were characterized by marked declines (often to trace abundances) in several littoral taxa, concurrent with a further increase in the relative abundance of small, pelagic Bosmina spp. This most recent compositional shift was consistent with accelerated regional climate warming and associated limnological changes, decreased total phosphorus (TP) concentrations, and changing food sources. These changes in primary consumers will likely cascade throughout the food web. [ABSTRACT FROM AUTHOR]

Understanding how to control macroorganisms in source water and during treatment can help operators suppress their proliferation in the distribution system and prevent customer complaints. [ABSTRACT FROM AUTHOR]

Zebra Mussels (Dreissena polymorpha) were introduced into the US in the 1980s and have since spread throughout the country with concomitant impacts on aquatic ecosystems. We placed 20 m transects in a variety of sediment types and collected data on sediment size, mussel coverage (the percent of the bottom covered by mussels), and the presence of macrophytes within 0.25 m2 quadrats in White Bear Lake, MN. To assess the degree of Zebra Mussel aggregation, we calculated Morisita's index of dispersion (Iδ) at four levels of spatial scale − 0.25 m2, 1 m2, 4 m2, and 40 m2. Understanding the pattern of aggregation in Zebra Mussels is crucial in detecting early invasions, monitoring populations, and attempting to eradicate them. There was greater Zebra Mussel coverage within quadrats with coarser substrates (gravel/cobble and mixed sediment – including rock and boulders) compared to those with finer substrates (silt and sand). Macrophyte coverage did not significantly influence Zebra Mussel coverage on the lake bed sediments. Spatial scale had a large impact on the measure of mussel aggregation. Zebra Mussels in sand and silt had the highest degree of aggregation and high levels of macrophytes resulted in greater degrees of aggregation on the lake bed sediments. Zebra mussel coverage measured at larger spatial scales generally resulted in lower aggregation values, across both sediment types and levels of macrophyte coverage. The appropriate selection of spatial scale for sampling or observation is critical when upscaling local density to lake populations. Zebra Mussels have spread throughout the US and significantly alter aquatic ecosystems. Zebra mussels are often aggregated on the bottom of aquatic systems and are found preferentially on lake beds with coarser material at the bed (gravel and rock). Using the correct spatial scale to assess mussel coverage is crucial for accurate population estimates. Zebra Mussel infestations might be managed by partial-lake treatment options; however, treatment areas need to be chosen based on Zebra Mussel density and distribution patterns. Knowledge of the relationship between spatial scale, sediment type, macrophyte availability and population coverage and aggregation is needed for these types of treatment programs. [ABSTRACT FROM AUTHOR]

The impacts of species invasions can subside over time as ecosystems 'adapt' and invaders decline or increase over time as additional species invade. The character and timescales of invasion impacts provide important insights into ecosystem dynamics and management. Yet long-term studies of invasion impacts remain rare and often confound invasive species impacts with coincident environmental change. One way to address this challenge is to ask: what ecological changes over time since invasion are recapitulated in ecosystems that span a range of conditions, are located in different regions, and were invaded in different decades? We synthesize many-decade time series across seven ecosystems to resolve shared changes in seven key ecosystem features following invasion by zebra mussels and subsequent invasion by quagga mussels. These two congeners are among the most widespread invasive species that re-engineer and increasingly co-invade freshwater ecosystems. Seven polymictic shallow lakes with long-term data sets reveal remarkably similar trends, with the strongest ecosystem impacts occurring within 5–10 years of zebra mussel invasion. Surprisingly, plankton communities then exhibited a partial, significant recovery. This recovery was absent, and impacts of initial invasion amplified, in four lakes where quagga mussels outcompeted zebra mussels and more completely depleted phytoplankton. Thus, we show that the ecosystem impacts of invasive species can subside over time but amplify with serial introductions of competing, even closely similar, taxa. [ABSTRACT FROM AUTHOR]

A pioneering, quantitative study published in Journal of Animal Ecology in 1966 on freshwater mussel populations in the River Thames, UK, continues to be cited extensively as evidence of the major contribution that mussels make to benthic biomass and ecosystem functioning in global river ecosystems.Ecological alteration, as well as declines in freshwater mussel populations elsewhere, suggest that changes to mussel populations in the River Thames are likely to have occurred over the half century since this study.We resurveyed the site reported in Negus (1966) and quantified the changes in mussel population density, species composition, growth patterns and productivity.We found large declines in population density for all unionid species. The duck mussel Anodonta anatina decreased to 1.1% of 1964 density. The painter's mussel Unio pictorum fell to 3.2% of 1964 density. The swollen river mussel Unio tumidus showed statistically nonsignificant declines. In contrast to 1964, in 2020 we found no living specimens of the depressed river mussel Pseudanodonta complanata (classified as Vulnerable by the IUCN Red List) but found new records of the invasive, nonnative zebra mussel Dreissena polymorpha and Asian clam Corbicula fluminea. Additionally, we found strong decreases in size‐at‐age for all species, which now grow to 65–90% of maximum lengths in 1964. As a result of reduced density and size, estimated annual biomass production fell to 7.5% of 1964 levels.Since mussels can be important to ecosystem functioning, providing key regulating and provisioning services, the declines we found imply substantial degradation of freshwater ecosystem services in the River Thames, one of the UK's largest rivers. Our study also highlights the importance to conservationists and ecologists of updating and validating assumptions and data about wild populations, which in the present era of anthropogenic ecosystem alteration are undergoing significant and rapid changes. Regular population surveys of key species are essential to maintain an accurate picture of ecosystem health and to guide management. [ABSTRACT FROM AUTHOR]

Long-term changes in diatom community composition provided important insights into how multiple stressors affected shallow, macrophyte-dominated Lake Opinicon, Ontario (Canada) over the past ~ 200 years. A previous paleolimnological study of a sediment core collected in 1995 found that diatom responses to numerous large-scale cultural disturbances since the early nineteenth century were moderate in comparison to pronounced diatom responses to similar disturbances in nearby deeper lakes within the Rideau Canal system. The abundance of macrophytes in shallow and previously polymictic Lake Opinicon likely played an important role in maintaining a stable, clear-water equilibrium state. We examined diatom assemblages from a sediment core collected in 2019 to re-assess whether Lake Opinicon maintained its resistance to change over the past ~ 25 years. Despite numerous, intense early nineteenth and twentieth century cultural disturbances in Lake Opinicon's catchment (complete deforestation, flooding with the construction of the Rideau Canal), the highest rate of diatom compositional change occurred only in the past ~ 25 years, when planktonic diatoms became prevalent for the first time in the lake's postglacial history. This recent shift in assemblage composition is not explained by nutrient enrichment, as total phosphorus concentrations, measured since the 1970s, have declined significantly. The first appearance of zebra mussels (~ 1990s) and significant increases in Secchi depth broadly co-occurred with the diatom assemblage shift, but precipitous declines in mussel populations since 2013 and a continued increase in planktonic diatom taxa suggest the impact of this invasive species was modest. Instead, changes in diatom assemblage composition were strongly related to increasing regional air temperatures. Limnological monitoring indicated that, over the past few decades, previously polymictic Lake Opinicon has experienced increasingly longer and more stable periods of thermal stratification that are consistent with observed trends in regional warming and reduced wind speed. These water column changes, which accompanied reduced ice cover duration, would have provided favourable conditions for planktonic diatom growth. We conclude that the nature and high rate of diatom compositional change over the past ~ 25 years signifies that an ecological threshold was crossed in response to warming and changes in lake thermal structure. [ABSTRACT FROM AUTHOR]

10 sites were selected for investigating zebra mussels in the Tigris River for the study that was conducted for the period from January to December 2020. The results of this investigation showed that zebra mussels were recorded in the Tigris at Taji on sites 7, 8, 9 and 10, while it was not found in the Tigris at Kut on sites 1, 2, 3, 4, 5 and 6. This is the first time that this species was ever recorded in the Tigris. It was found that the sites where zebra mussels appeared had a clear impact on the decrease in the total organic carbon %age and turbidity (NTU). High dissolved oxygen values were observed in the sites where zebra mussels were recorded, and the appearance of zebra mussels in these sites caused a clear decrease in the appearance and total density of benthic invertebrates, in addition to a clear increase in the total density of epiphytic algae. Zebra mussels caused the disappearance of the local species of the phylum Mollusca and crustaceans in the sites where it appeared. [ABSTRACT FROM AUTHOR]

Early detection of dreissenid mussels (Dreissena polymorpha and D. rostriformis bugensis) is crucial to mitigating the economic and environmental impacts of an infestation. Plankton tow sampling is a common method used for early detection of dreissenid mussels, but little is known about the sampling intensity required for a high probability of early detection using the method. We used implicit dynamic occupancy models to estimate plankton tow detection probabilities of dreissenid mussels from a long-term data set containing plankton tow samples collected across central and western United States. We fit models using a) the entire data set, including water bodies with unknown occupancy status in addition to heavily infested water bodies, b) a data subset that included water bodies with paired water temperature data, and c) a data subset that included water bodies with lower dreissenid densities. For the entire data set, we found that estimated detection probabilities varied by water body size and ranged from approximately 0.10 to 0.86. For the water temperature subset, we observed the same pattern between detection probability and water body size as we did for the full data but additionally found that the estimated detection probabilities were much higher when water temperatures were above 12 °C. For the lower dreissenid density subset, we found that the estimated probability of detecting dreissenid mussels with a single aggregated plankton tow sample was near zero. Given these estimates, we conclude that the number of aggregated plankton tow samples taken per water body in the data is far fewer than the number needed to ensure a high probability of detecting dreissenid mussels, especially if they are at low densities. We summarize the analyses with a discussion of plankton tow sampling protocol changes needed to improve estimates of dreissenid detection probabilities. [ABSTRACT FROM AUTHOR]

Drinking water treatment plants in the Great Lakes often protect their intake structures against dreissenid biofouling by prechlorinating when water temperatures exceed 12 °C. This temperature threshold is based on the reproduction characteristics of zebra mussels. However, in recent years, zebra mussels have largely given way to quagga mussels in the region. These mussels reportedly reproduce at temperatures as low as 5 °C. The objective of this study was to determine if the current 12 °C trigger point for prechlorination remains appropriate. A 3-year monitoring program using bioboxes recorded mussel veliger concentrations and settlement potential in water drawn from the intakes of three drinking water treatment plants on Lake Ontario. Water temperature was a poor predictor of veliger presence and settlement. Reproduction and settlement were observed outside of the traditional temperature thresholds. Furthermore, no relationship was found between the number of veligers in the water column and those settling, suggesting that there are complex environmental factors that influence mussel activity. Nevertheless, it was observed that settlement occurred consistently between the months of July and November in the 3 years of the study. Therefore, a calendar-based approach to trigger prechlorination, as opposed to a temperature-based approach, is suggested. HIGHLIGHTS Settlement was observed at temperatures

Over the past three decades, the Rideau River (Ontario, Canada) watershed has experienced a land-use change from rural and agricultural land towards urban land, and the introduction and expansion of invasive species. This study examined spatial and temporal patterns of periphyton biomass (chlorophyll-a and ash-free dry mass) collected from riffle zones in 1995 and 2019 along a 66-km stretch of the Rideau River. This study also examined long-term changes in water nutrient and chloride concentrations collected through the Provincial Water Quality Monitoring Network between 2000 and 2018. Declines in total nitrogen between 2000 and 2018 occurred in areas that have not experienced urbanization since the 2000s. In contrast, declines in total phosphorus and increases in chloride between 2000 and 2018 occurred at midstream and downstream sites that have undergone urbanization during the same time period. Conductivity also showed an increase with distance downstream similarly in both 1995 and 2019. Average total phosphorus and total Kjeldahl nitrogen concentrations were lower in 2019 compared to 1995 but did not increase with distance downstream as seen in many river systems, including the Rideau River, in earlier years. Periphyton biomass did not change along the length of the river between 1995 and 2019, despite the declines in nutrient concentrations. These findings highlight the persistence of riverine periphyton in a multi-use watershed experiencing ongoing anthropogenic changes.

Siloxane-polyurethane hybrid coatings were assessed for biofouling control caused by freshwater mussels. Invasive species such as zebra (Dreissena polymorpha) and quagga (Dreissena bugensis) mussels have rapidly spread through the waterways in the United States causing major concerns in reservoir infrastructure and freshwater lakes. Current coating solutions such as biocidal anti-fouling coatings are not suitable given the released biocides which may accumulate in reservoirs. Biocide free fouling release coatings based on silicone elastomers do not have adequate mechanical durability. The siloxane-polyurethane (SiPU) coatings were evaluated using model organism laboratory assays and real-life performance was evaluated in the freshwater field environment. Two coating compositions displayed excellent performance in field trials for up to 2+ years. The surface analysis experiments of the coatings indicate that the morphology of the coatings is affected by the formulations' solvent choice. These coatings show great promise in mitigating biofouling predominated by freshwater mussels. [ABSTRACT FROM AUTHOR]

The transfer pathways of organic matter and elements from phytoplankton to zooplankton in freshwater ecosystems are important for understanding how aquatic ecosystems function. We conducted a mesocosm experiment to determine how fish and zebra mussels altered the transfer efficiencies of essential substances including carbon (C), polyunsaturated fatty acids (PUFAs), total fatty acids (FAs), phosphorus (P), and nitrogen (N) from phytoplankton to zooplankton. We assessed the transfer efficiencies of the essential substances from phytoplankton to zooplankton as the ratio of their zooplankton production (P) per unit of biomass (B) to that of phytoplankton to exclude grazing or predation effects. We hypothesized that zebra mussels and fish would affect the transfer of materials from phytoplankton to zooplankton by altering the contents of essential elements and FAs in phytoplankton and zooplankton communities and/or due to shifts in the planktonic community structure mediated by grazing and/or predation. Fish increased the transfer efficiencies of eicosapentaenoic acid 20:5 ω-3 (EPA), docosahexaenoic acid 22:6 ω-3 (DHA), and P relative to the control. We speculated that fish weakened the control of zooplankton over algal assemblage by selectively feeding on larger cladocerans such as Daphnia. Therefore, fish can increase the relative proportion of high-quality food for zooplankton, improving food conditions for the available zooplankton. In contrast, zebra mussels reduced the transfer efficiencies of EPA and DHA relative to the control treatment likely due to competition with zooplankton for PUFA-rich food particles. However, zebra mussels did not have any impact on the transfer efficiencies of C, total FAs, N, and P. EPA, DHA, and P were transferred more efficiently than C from phytoplankton to zooplankton, while total FAs, which are commonly used as an energetic source, were transferred as efficiently as C. The enrichment of consumers with the most important substances relative to their basal food sources creates the potential for the successful transport of these substances across aquatic trophic webs.

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. [ABSTRACT FROM AUTHOR]

Zebra mussels (Dreissena polymorpha) filter feed phytoplankton and reduce available pelagic energy, potentially driving fish to use littoral energy sources in lakes. However, changes in food webs and energy flow in complex fish communities after zebra mussel establishment are poorly known. We assessed impacts of zebra mussels on fish littoral carbon use, trophic position, isotopic niche size, and isotopic niche overlap among individual fish species using δ13C and δ15N data collected before (2014) and after (2019) zebra mussel establishment in Lake Ida, MN. Isotope data were collected from 11 fish species, and from zooplankton and littoral invertebrates to estimate baseline isotope values. Mixing models were used to convert fish δ13C and δ15N into estimates of littoral carbon and trophic position, respectively. We tested whether trophic position, littoral carbon use, isotopic niche size, and isotopic niche overlap changed from 2014 to 2019 for each fish species. We found few effects on fish trophic position, but 10 out of 11 fish species increased littoral carbon use after zebra mussel establishment, with mean littoral carbon increasing from 43% before to 67% after establishment. Average isotopic niche size of individual species increased significantly (2.1-fold) post zebra mussels, and pairwise-niche overlap between species increased significantly (1.2-fold). These results indicate zebra mussels increase littoral energy dependence in the fish community, resulting in larger individual isotopic niches and increased isotopic niche overlap. These effects may increase interspecific competition among fish species and could ultimately result in reduced abundance of species less able to utilize littoral energy sources. [ABSTRACT FROM AUTHOR]

The distribution, density, biomass and size-structure of the zebra mussel (Dreissena polymorpha) population in Lake Winnipeg were examined between 2017 and 2019. Zebra mussels have colonized most of the available hard substrate in the south basin and Narrows region, but colonization of the north basin remains low at present, even on suitable substrate. Numerical densities and shell free biomass peaked at 5530 ± 953 m−2 and 64.7 ± 57.9 g shell free dry mass m−2 respectively. The distribution appeared to be strongly limited by substrate type and availability, with further limitations on the distribution imposed by physical disturbance in shallow waters and unsuitable substrate in deeper areas of the lake. Zebra mussels <1 year old dominated the populations, and individuals >18 mm were exceedingly rare. Poor recruitment was observed at sites along the eastern side of the south basin compared to elsewhere in the lake. The proximate causes of these differences in colonization success and recruitment are not clear, but may be in part due to heterogeneous patterns of key physico-chemical environmental conditions such as calcium concentrations required for successful development of juvenile mussels and colder water temperatures in the north basin. This study provides a baseline of information on which to track further expansion of zebra mussels in Lake Winnipeg and assist efforts to develop an understanding of how zebra mussels may affect the ecology of Lake Winnipeg. [ABSTRACT FROM AUTHOR]

Host-associated microbiota play a critical role in host fitness by providing nutrition, enhancing digestion capabilities, and by providing protection from pathogens. Here, we investigated the effects of two environmental stressors, temperature, and salinity, on the microbiota associated with zebra mussels (ZMs), a highly invasive bivalve in North America. To examine this in detail, lake-collected ZMs were acclimated to laboratory conditions, and subjected to temperature and salinity stress conditions. The impact of these stressors on the diversity, composition, and dynamics of ZM-associated microbiota were assessed by using amplicon- and shotgun-based sequencing, and qPCR-based approaches. Elevated temperature was found to be the primary driver of ZM mortality, although salinity alone also increased its likelihood. Stressor-induced ZM mortality, which ranged between 53 and 100%, was concomitant with significant increases in the relative abundance of several genera of putative opportunistic pathogens including Aeromonas. These genera were only present in low relative abundance in ZMs obtained from the control tank with 0% mortality. Shotgun sequencing and qPCR analyses indicated that the relative and absolute abundances of pathogenic Aeromonas species (particularly A. veronii) were significantly greater in temperature-induced dead ZMs. Taken together, our results show that environmental stress, especially elevated temperature (> 25 °C), is associated with the rapid mortality of ZMs as well as the proliferation of putative opportunistic bacterial pathogens. [ABSTRACT FROM AUTHOR]

Ecosystems across the United States are changing in complex and unpredictable ways and analysis of these changes requires coordinated, long‐term research. This paper is a product of a synthesis effort of the U.S. National Science Foundation funded Long‐Term Ecological Research (LTER) network addressing the LTER core research area of "populations and communities." This analysis revealed that each LTER site had at least one compelling "story" about what their site would look like in 50–100 yr. As the stories were prepared, themes emerged, and the stories were group into papers along five themes: state change, connectivity, resilience, time lags, and cascading effects. This paper addresses the cascading effects theme and includes stories from the Bonanza Creek (boreal), Kellogg Biological Station (agricultural and freshwater), Palmer (Antarctica), and Harvard Forest (temperate forest) LTER sites. We define cascading effects very broadly to include a wide array of unforeseen chains of events that result from a variety of actions or changes in a system. While climate change is having important direct effects on boreal forests, indirect effects mediated by fire activity—severity, size, and return interval—have large cascading effects over the long term. In northeastern temperate forests, legacies of human management and disturbance affect the composition of current forests, which creates a cascade of effects that interact with the climate‐facilitated invasion of an exotic pest. In Antarctica, declining sea ice creates a cascade of effects including declines in Adèlie and increases in Gentoo penguins, changes in phytoplankton, and consequent changes in zooplankton populations. An invasion of an exotic species of lady beetle is likely to have important future effects on pest control and conservation of native species in agricultural landscapes. New studies of zebra mussels, a well‐studied invader, have established links between climate, the heat tolerance of the mussels, and harmful algal blooms. Collectively, these stories highlight the need for long‐term studies to sort out the complexities of different types of ecological cascades. The diversity of sites within the LTER network facilitates the emergence of overarching concepts about trophic interactions as an important driver of ecosystem structure, function, services, and futures. [ABSTRACT FROM AUTHOR]

Diporeia spp. were a key component of the Great Lakes benthos, converting the pelagic algal rain to secondary production, which is critical for Great Lakes fishes. However, Diporeia declines since the 1980s have been rapid and widespread. While there are temporal relationships between Diporeia declines and spread of zebra and quagga mussels, establishing a mechanistic link has been difficult. Diporeia declines may result from competition for food resources with dreissenid mussels; however, conflicting evidence suggests food limitation may not be the direct link. To test food limitation, we analyzed gut contents of Diporeia collected between the 1980s and 2009 from two deep (>100 m) and one nearshore station (~50 m depth) in southern Lake Michigan. We further analyzed sediment cores from the same stations to resolve relationships among food resources, Diporeia diet, and diet selectivity during pre- and post-dreissenid invasion. In spring, pre-dreissenid Diporeia fed selectively and exclusively on large (Stephanodiscus) and filamentous centric diatoms (Aulacoseira). Diporeia diets showed significant shifts during the 2000s to greater proportions of small centric and araphid diatoms, coincident with Diporeia declines and offshore expansion of quagga mussels. Sediment cores recorded declines in Aulacoseira and large Stephanodiscus from 1960 to 2009 and increases in small centrics after dreissenid introduction. Accounting for high selectivity in springtime Diporeia diets, community changes in sediment records are consistent with changes observed in Diporeia diets and suggest Diporeia declines have been exacerbated by a shift from more nutritious and highly preferred diatom species to less nutritious and negatively selected species. [ABSTRACT FROM AUTHOR]

Due to the potential hazard of diclofenac on aquatic organisms and the lack of higher-tier ecotoxicological studies, a long-term freshwater mesocosm experiment was set up to study the effects of this substance on primary producers and consumers at environmentally realistic nominal concentrations 0.1, 1 and 10 µg/L (average effective concentrations 0.041, 0.44 and 3.82 µg/L). During the six-month exposure period, the biovolume of two macrophyte species (Nasturtium officinale and Callitriche platycarpa) significantly decreased at the highest treatment level. Subsequently, a decrease in dissolved oxygen levels was observed. High mortality rates, effects on immunity, and high genotoxicity were found for encaged zebra mussels (Dreissena polymorpha) in all treatments. In the highest treatment level, one month after the beginning of the exposure, mortality of adult fish (Gasterosteus aculeatus) caused effects on the final population structure. Total abundance of fish and the percentage of juveniles decreased whereas the percentage of adults increased. This led to an overall shift in the length frequency distribution of the F1 generation compared to the control. Consequently, indirect effects on the community structure of zooplankton and macroinvertebrates were observed in the highest treatment level. The No Observed Effect Concentration (NOEC) value at the individual level was

The main characteristics of the population of Dreissena polymor­pha (Pallas, 1771) in Lake Pleshcheyevo in 2014–2016 are dis- cussed, and two different sampling methods for D. polymorpha are compared. The lack of mass reproduction of D. polymorpha in 2015 is possibly related, among other causes, to climate change and alterations in the temperature regime of the lake. Dreissena is shown to be one of the main benthic suspension feeders in Lake Pleshcheyevo.

Zebra mussels (Dreissena polymorpha) are pistachio-sized freshwater bivalves native to the regions around the Black and Caspian seas. Since their discovery in Lake St. Clair, Michigan, in the late 1980s, they have spread distressingly fast through the Great Lakes and Mississippi River basin, as well as to other lakes and rivers in the eastern United States and Canada.

This paper presents a GIS-based tool named Arc-BEST (Bioaccumulation Evaluation Screening Tool) to perform spatially distributed bioaccumulation risk analyses. Estimating bioaccumulation risk is important to help predict potentially adverse effects from contaminants on ecosystems and human health, which are key factors in the development of sound public policy. Arc-BEST is based on the BEST model in the U.S. Army Corps of Engineers BRAMS (Bioaccumulation Risk Assessment Modeling System) software, released in 2012. It predicts concentration of concern contaminants in predators’ tissues from concentrations in organisms at the bottom of the food chain, and corresponding bioaccumulation factors. Additionally, it estimates carcinogenic and non-carcinogenic risks for humans that consume those species. The greatest contribution of Arc-BEST is that it enables the automated use of digital spatial data sets, which improves model creation speed, analysis and visualization of results, and comparison and cross-referencing with other geographic datasets. Furthermore, the model was improved to consider up to four trophic levels. The code is written in Python and is open-source. In this work Arc-BEST is used as part of a screening-level risk assessment process in order to identify hot spots where further studies and monitoring should be performed to ensure humans and ecosystems health. The tool is successfully applied to a case study in the Laurentian Great Lakes, where long-term effects of polychlorinated biphenyls (PCBs) is performed, based on measured concentrations in zebra mussels (Dreissena polymorpha), and local bioaccumulation factors from previous studies. Zebra mussels have a great filtration capacity and high bioconcentration rates, increasing the bioavailability of contaminants for predator species. PCBs concentrations in different-level predators are predicted. Furthermore, health risks for humans that consume sport fish are estimated for various exposure scenarios. The distribution of the risks in the lakes is analyzed, and critical areas are identified.

The non-indigenous round goby (Neogobius melanostomus) entered the Flint River, Michigan, USA around 1996 while zebra mussels (Dreissena polymorpha) invaded in late 1998. We wanted to identify if there were round goby or darter (Etheostoma/Percina spp.) diet or density alterations by comparing 1998 data with our 2002 data after mussel colonization. Chironomids dominated the round goby’s pre-zebra mussel diet in August 1998 (89% by number), followed by hydropsychids (10%). After zebra mussels arrived, diets diversified; chironomids declined to 52%, hydropsychids stayed the same, gastropods were more prominent (22%) and 4% were zebra mussels. Data from a site upriver (with no round gobies or zebra mussels) showed darters consumed mostly chironomids (49%), mayflies (11%) and hydropsychids (9%), suggesting reliance on chironomid prey and other interactions compromised the ability of darters to coexist with round gobies downstream, since only one of three species present during 1998 was collected in 2002. Benthic assemblages on rocks changed dramatically (R-values =0.95) from 1998 to 2002. Blackside darter (Percina maculata) density in the presence of round gobies increased eightfold compared with 1998. We hypothesized zebra mussels fostered the growth of macrophytes, resulting in odonates composing 42% by volume of blackside darter diets in 2002 compared with 10% in 1998. Diet overlaps between small and large round gobies and blackside darters were high (Schoener Index =0.55–0.59, R-values =0.11–0.24), suggesting potential negative competitive interactions. Zebra mussel-mediated ecosystem changes may have decreased interspecific competition for food with blackside darters, allowing coexistence with round gobies. Native darters with varied diets feeding in mid-water, are most likely to coexist with round gobies, especially where dreissenids potentially mediate competitive interactions.

A liquid formulation of acid-stabilized ionic copper called EarthTec QZ was used in an effort to eradicate invasive quagga mussels (Dreissena rostriformis bugensis) from an entire 12-hectare lake in Pennsylvania in fall of 2017. The treatment consisted of three separate applications of ionic copper delivered over a period of 37 days with the intent to minimize likelihood of spreading invasive mussels during a one-time water transfer event planned for later that year, from the treated lake to an adjacent river. Mussel mortality was estimated through use of caged adult mussels that were suspended at different locations and depths throughout the lake. Adult mussels began to die within 3 days of the initiation of treatment, particularly in the top 6 meters of the water body. The death of the last caged mussel was confirmed 40 days after the initiation of treatment, in a cage that had been placed in the metalimnion at a depth of 9 meters below the surface. Both biological and physicochemical data collected during the treatment period revealed that there was a pronounced thermocline at 8-11 meters depth. The layer of water in the thermocline resisted mixing, suggesting an explanation for why mussels located above and below this metalimnion were eradicated quickly, yet those within the metalimnion required targeted treatment techniques and 40 days to succumb to 100% mortality. Visual inspection of the shoreline after partial pump-down of the quarry in early November revealed high densities of empty shells from dead adults, and no live adults were found. Analysis of eDNA samples taken in December of 2017 and again in July 2018 concluded no mussel eDNA was detectable. Plankton tows collected and analyzed by microscopy in July, August and September 2018 were rich with zooplankton but no live mussel veligers were found. The cumulative sum of product applied throughout the entire course of treatment totaled 13,500 liters, which is equivalent to 0.44 mg/L as copper as calculated on the full volume of the lake -- noteworthy because it is less than half the concentration EPA allows (1.0 mg/L) in a single algaecide treatment. This experience illustrates that low doses of acid-stabilized ionic copper can have profound effects on invasive mussel populations and are a viable management tool. If future sampling confirms that this eradication effort was successful, it will be the first recorded instance of eradicating quagga mussels from an entire lake. [ABSTRACT FROM AUTHOR]

Sampling water for environmental DNA (eDNA) is an emerging tool for documenting species presence without direct observation, allowing for earlier detection and faster response than conventional sampling methods in aquatic ecosystems.However, current understanding of how eDNA is transported in streams and rivers remains imprecise, with uncertainty of how the unique transport properties of eDNA may influence the interpretation of a positive detection. To test the utility of eDNA sensing in flowing waters, we compared quantitative eDNA analyses to zebra mussel density surveys in a Danish river.Although flowing water complicates the relationships between eDNA production, transport, and removal, we found weak but positive relationships between eDNA concentration, zebra mussels, and biophysical parameters. For example, while zebra mussel densities were only moderately predicted by eDNA concentrations, eDNA was most strongly influenced by nutrient concentrations and water velocity. These results may be used to inform future sampling strategies, where hydrological variables could better constrain eDNA fate.We also modelled estimates for net eDNA transport, retention, and degradation to estimate the relative importance of these processes for removing eDNA from the water column. In our study system, physical retention accounted for c. 70% of removal when compared to degradation alone, making it an important process to consider when assessing downstream eDNA transport. [ABSTRACT FROM AUTHOR]

Economists are increasingly interested in causally interpretable estimates of environmental health externalities, particularly on infant health. This paper focuses on a specific case by investigating microcystin, a toxin produced by freshwater blue-green algal blooms. We exploit a natural experiment caused by a zebra mussel die-off in a large lake located in the state of Michigan, USA to identify changes in microcystin-related infant outcomes surrounding the lake. Using both the synthetic control method and a difference-in-differences strategy, we find that instances of low birth weight around the lake fell by 1.4 percentage points after lake water quality improved. Along the intensive margin, birth weight and length of gestation increased by 17.1 g and 0.47 weeks, respectively. Improvements to low birth weight result in $768,500 in average annual hospitalization cost savings. Many robustness and falsification tests are performed including using both annual and monthly data and accounting for possible weather confounders and seasonality. Results suggest that microcystin can affect infant health at levels below current water advisory guidelines. [ABSTRACT FROM AUTHOR]

Aquatic invasive species (AIS) threaten ecosystem health, serving as a major challenge for conservation efforts worldwide. Invasive species easily move across jurisdictional boundaries that may each have diverse management approaches, leading to management mosaics in which each manager's actions impact those of neighboring jurisdictions. Here, we investigate the potential impact of collaborations between counties in Minnesota in managing four aquatic invasive species (Eurasian watermilfoil, spiny waterflea, starry stonewort, and zebra mussels), with a focus on evaluating the efficiency of county-led prevention programs. We aimed to identify potential collaboration networks, each representing a group of counties with a relatively high number of potentially infested boats moving between them and describe the connections within those groups using social network analysis. We found that collaboration networks formed by ranking reciprocal connections amongst counties yielded efficiency gains over a non-collaborative or county-focused approach but were still less efficient than a state-wide approach. This study presents an analytical framework for identifying collaborations based on AIS dispersal pathways that may increase the efficiency of inter-jurisdictional prevention efforts. [ABSTRACT FROM AUTHOR]

Zebra mussels (Dreissena polymorpha) are an aquatic invasive species that plague much of North America and are difficult to impossible to eradicate once they become established. Therefore, prevention and monitoring are key elements in the control of these organisms. Traditional microscopy is commonly used in monitoring but requires the presence of larval veligers. This limits the times when resource managers can monitor for the presence in northern lakes. A new monitoring tool, environmental DNA (eDNA), may allow for a more efficient and cost-effective monitoring program for zebra mussels. We developed and tested an environmental DNA assay in the fall and spring for zebra mussels in two Minnesota lakes, one heavily infested and another newly infested. We found that DNA copy numbers tended to be higher near the lake bottom and DNA was more concentrated in softer substrates. We also found that the amount of zebra mussel DNA sampling in winter resulted in similar results to when sampled in fall. This suggests that one could collect and analyze eDNA for zebra mussels during winter months to help inform future efforts in monitoring and control. [ABSTRACT FROM AUTHOR]

Purpose: Zebra mussels (Dreissena polymorpha) alter the transport dynamics and fate of particulate matter in aquatic systems by intercepting, retaining, and recycling suspended materials. This study examines the effect of particle processing by dressenids on the nature (grain size distribution, settling velocity, porosity  and density) and transport properties (critical shear stress for erosion, erosion rates, and bed stability) of suspended particulate matter in lakes.Materials and methods: The bed stability, erosion rate, and critical shear stress for erosion of dreissenid biodeposits were measured in an annular flume. The particle size distribution, settling rate, density, and porosity were measured to characterize the physical nature of the biodeposits. Materials studied in the flume include (1) a combination of biodeposits and surface sediments collected from dreissenid beds and (2) biodeposits harvested in a weir box populated with dreissenids.Results and discussion: The settling rates of both biodeposit/sediment mixtures and pure biodeposits were lower than natural sediment in lacustrine environments. Erosion characteristics and transport properties of biodeposits were strongly influenced by bed age and the presence of mussels. Bed stability increased after 7 days, with a τcrit of 0.26 Pa compared to the 2- and 14-day consolidation periods (τcrit = 0.13 and 0.15 Pa), respectively. The observed changes in bed stability with bed age will modify the transfer of particulate materials to the offshore profundal zone as well as the rates and magnitudes of sediment-associated nutrients in the near shore zone.Conclusions: Biostabilization of surficial lake-bottom sediments impacted by mussel biodeposits may increase bed stability and reduce the export of particulate matter to the offshore environment. Further, well-developed communities of dreissedid mussels have an armoring effect on deposited sediment, which reduces remobilization of sediment and biodeposits. However, once eroded, the dreissedid modified deposits will likely be transported further due to their low-settling velocity. [ABSTRACT FROM AUTHOR]

The non-indigenous round goby (Neogobius melanostomus) entered the Flint River, Michigan, USA around 1996 while zebra mussels (Dreissena polymorpha) invaded in late 1998. We wanted to identify if there were round goby or darter (Etheostoma/Percina spp.) diet or density alterations by comparing 1998 data with our 2002 data after mussel colonization. Chironomids dominated the round goby's pre-zebra mussel diet in August 1998 (89% by number), followed by hydropsychids (10%). After zebra mussels arrived, diets diversified; chironomids declined to 52%, hydropsychids stayed the same, gastropods were more prominent (22%) and 4% were zebra mussels. Data from a site upriver (with no round gobies or zebra mussels) showed darters consumed mostly chironomids (49%), mayflies (11%) and hydropsychids (9%), suggesting reliance on chironomid prey and other interactions compromised the ability of darters to coexist with round gobies downstream, since only one of three species present during 1998 was collected in 2002. Benthic assemblages on rocks changed dramatically (R-values =0.95) from 1998 to 2002. Blackside darter (Percina maculata) density in the presence of round gobies increased eightfold compared with 1998. We hypothesized zebra mussels fostered the growth of macrophytes, resulting in odonates composing 42% by volume of blackside darter diets in 2002 compared with 10% in 1998. Diet overlaps between small and large round gobies and blackside darters were high (Schoener Index =0.55-0.59, R-values =0.11-0.24), suggesting potential negative competitive interactions. Zebra mussel-mediated ecosystem changes may have decreased interspecific competition for food with blackside darters, allowing coexistence with round gobies. Native darters with varied diets feeding in mid-water, are most likely to coexist with round gobies, especially where dreissenids potentially mediate competitive interactions. [ABSTRACT FROM AUTHOR]

Gaskill JA, Woller-Skar MM. 2018. Do invasive dreissenid mussels influence spatial and temporal patterns of toxic Microcystis aeruginosa in a low-nutrient Michigan lake? Lake Reserv Manage. 00:00-00. Invasive dreissenid mussels enable harmful Microcystis blooms in low-nutrient lakes not historically accustomed to high cyanobacteria densities. Here, we examined patterns in Microcystis and microcystin spatially across Little Traverse Lake, Michigan, and temporally over the course of the lake's bloom. Because Microcystis spends part of its life cycle in the sediment, we included benthic and surface densities in our study. We also looked at the spatial relationship between dreissenid biomass and Microcystis density using local and global statistics and found that the clear relationship previously demonstrated to exist between these 2 taxa on the lake scale does not seem to be maintained on a finer, site scale. Distributions of Microcystis (surface and benthic) and microcystin in the lake were largely random and we observed no link between dreissenid biomass and Microcystis density. This suggests that either these taxa are not related on the site scale, or that environmental factors have a greater influence on localized Microcystis distributions than the location of dreissenid beds. Finally, we observed highest densities of surface Microcystis during mid-summer and highest densities of benthic Microcystis in the fall. This is consistent with Microcystis's life history in many temperate lakes: densities increase to their highest levels in late summer and decline into autumn as temperatures drop and colonies sink to the sediment. As invasive dreissenids continue to spread, knowing how they will affect harmful algae will be vital to bloom mitigation. [ABSTRACT FROM AUTHOR]

Long time series data can provide insights into dynamics of large lakes. We use the USEPA-GLNPO biological monitoring dataset (phytoplankton, benthos, zooplankton and water quality), collected from 1996 through 2016, to identify whether there is evidence of concordant linear or non-linear trends in community composition, density/biomass/biovolume and major environmental parameters. We show changes in biotic assemblages and water quality variables, particularly in Lakes Michigan and Huron. These include changes in phytoplankton biovolume and zooplankton biomass, increasing invasive Dreissena abundance and decreasing densities of other benthos. Biotic changes are accompanied by pronounced changes in water quality and nutrient ratios. Species change-points, identified using threshold indicator taxon analysis, are often less abrupt, but there are clear shifts in a large proportion of species in each assemblage. The concordance of breakpoints among assemblages or lack thereof provides valuable insight into potential drivers of ecosystem change. [ABSTRACT FROM AUTHOR]

The environmental fate, persistence, and non-target animal impacts of traditional molluscicides for zebra, Dreissena polymorpha, and quagga, D. bugensis, mussel control led to the development of the biomolluscicide Zequanox. Although previous research has demonstrated the specificity of Zequanox, one study indicated sensitivity of salmonids and lake sturgeon, Acipenser fulvescens, following non-label compliant exposures to Zequanox. This study was conducted to evaluate sublethal and lethal impacts of Zequanox exposure on juvenile lake sturgeon and lake trout, Salvelinus namaycush, following applications that were conducted in a manner consistent with the Zequanox product label. Fish were exposed to 50 or 100 mg/L of Zequanox as active ingredient for 8 h and then held for 33 d to evaluate latent impacts. No acute mortality was observed in either species; however, significant latent mortality was observed in lake trout that were exposed to the highest dose of Zequanox. Statistically significant but biologically minimal differences were observed in the weight (range 20.17 to 21.49 g) of surviving lake sturgeon at the termination of the 33 d post-exposure observation period. Statistically significant and biologically considerable differences were observed in the weight (range 6.19 to 9.55 g) of surviving lake trout at the termination of the 33 d post-exposure observation period. Histologic evaluation of lake trout gastrointestinal tracts suggests that the mode of action in lake trout is different from the mode of action that induces zebra and quagga mussel mortality. Further research could determine the sensitivity of other salmonid species to Zequanox and determine if native fish will avoid Zequanox treated water. [ABSTRACT FROM AUTHOR]

Dreissenid mussels are aggressive invasive species that are continuing to spread across North America and co-occur in the same waterbodies with increasing frequency, yet the outcome and implications of this competition are poorly resolved. In 2009 and 2015, detailed (700 + sample sites) surveys were undertaken to assess the impacts of invasive dreissenid mussels in Lake Simcoe (Ontario, Canada). In 2009, zebra mussels were dominant, accounting for 84.3% of invasive mussel biomass recorded. In 2015, quagga mussels dominated (88.5% of invasive mussel biomass) and had expanded into profundal (> 20 m water depth) sites and onto soft (mud/silt) substrates with a mean profundal density of 887 mussels/m 2 (2015) compared to ~ 39 mussels/m 2 in 2009. Based on our annual benthos monitoring, at a subset of ~ 30 sites, this shift from zebra to quagga mussels occurred ~ 2010 and is likely related to a population decline of zebra mussels in waterbodies where both species are present, as recorded elsewhere in the Great Lakes Region. As the initial invasion of dreissenid mussels caused widespread ecological changes in Lake Simcoe, we are currently investigating the effects this change in species dominance, and their expansion into the profundal zone, will have on the lake; and our environmental management strategies. Areas of future study will include: changes in the composition of benthos, fish, or phytoplankton communities; increased water clarity and reduction of the spring phytoplankton bloom; energy/nutrient cycling; and fouling of anthropogenic in-lake infrastructures (e.g. water treatment intakes) built at depths > 25 m to avoid previous zebra mussel colonization. [ABSTRACT FROM AUTHOR]

It takes time before a defensive phenotype can be effectively developed, which handicaps sessile bivalves exposed to acute predation risks. In a laboratory experiment, we examined whether predation threats induce zebra mussels to limit metabolic rates, serving as a fast-response defence that reduces the chances of chemical detection by predators. We measured the respiration rate of mussels exposed to predation treatments (fish fed zebra mussels, fish fed chironomids, crushed zebra mussels) and to predation-free conditions, and we tested the effect of these treatments on attachment strength and aggregation. Compared with the predation-free controls, all mussels in the predation treatments tended to initially have suppressed metabolic rates. The rate of metabolism increased over time in all treatments, but only in the presence of fish fed chironomids was the increase significantly greater than in the control. Attachment strengths and aggregation rates were similar for all treatments after 7 days. Our results provide the first evidence of predation-induced changes in zebra mussel metabolic rates. We suggest that mussels respond differently to different types of predation threats. Immediately after receiving predation cues, they react promptly by lowering their production of metabolites, but over time, they re-adjust their response to the actual predation threat present. [ABSTRACT FROM AUTHOR]

Aquatic invasive species (AIS) are of concern in North America due to their devastating impacts on ecosystems and economies. The Great Lakes region is particularly vulnerable to AIS introduction and establishment with at least 184 nonindigenous species reported in this region from a large number of taxa including viruses, bacteria, diatoms, protozoa, arthropods, mollusks, fish, and plants. Representative species from these groups were explored, describing the features of their natural history and current efforts in prevention and control. Specifically, five AIS that are expected to spread to novel areas in the region are discussed: viral hemorrhagic septicemia virus and heterosporis (pathogens affecting fish), starry stonewort (an alga), zebra mussels (a bivalve), and carps (fishes). Novel strategies for AIS control include next-generation sequencing technologies, gene editing, mathematical modeling, risk assessment, microbiome studies for biological control, and human-dimension studies to address tensions related to AIS management. Currently, AIS research is evolving to adapt to known technologies and develop novel technologies to understand and prevent AIS spread. It was found that AIS control in this region requires a multidisciplinary approach focusing on the life history of the species (e.g., pheromones), adaptive management of anthropogenic structures (e.g., bubble curtains), and the integration of human dimensions to develop efficient management plans that integrate local citizens and management agencies. [ABSTRACT FROM PUBLISHER]