Research Interests: Mathematics and Biology
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Bithynia tentaculata is an invasive aquatic snail that was first discovered in the upper Mississippi River (UMR) in 2002 and has subsequently expanded throughout a number of Navigation Pools in the region. In addition to being a threat to... more
Bithynia tentaculata is an invasive aquatic snail that was first discovered in the upper Mississippi River (UMR) in 2002 and has subsequently expanded throughout a number of Navigation Pools in the region. In addition to being a threat to native benthos, the snail ...
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ABSTRACT Non-indigenous species (NIS) are well-recognized as threats to biodiversity worldwide. Yet the interaction between NIS and disease emergence in native habitats remains poorly understood. Bithynia tentaculata is an invasive... more
ABSTRACT Non-indigenous species (NIS) are well-recognized as threats to biodiversity worldwide. Yet the interaction between NIS and disease emergence in native habitats remains poorly understood. Bithynia tentaculata is an invasive aquatic snail which is now found in the Upper Mississippi River (UMR). A key concern with this snail is that it harbors trematode parasites (such as Sphaeridiotrema spp.) that have been associated with waterfowl mortality in the region. In this study, we used a combination of field collections and laboratory experiments to better understand the roles that infection competency and host life-history responses play in disease transmission in the UMR. Results from the field and laboratory showed that B. tentaculata infected with Sphaeridiotrema spp. grew to a larger size than uninfected individuals. Although infection was not observed in a number of native species, results from this study suggest that they may still suffer exposure costs (such as reduced growth). Moreover, variability in infection competency between NIS and native snails may dilute or amplify host infection risk. This study reinforces the importance of considering both host life-history responses and competency in systems involving NIS, and provides insight into the factors potentially modulating waterfowl disease in the UMR.
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Bithynia tentaculata is an invasive snail that was discovered in the Upper Mississippi River (UMR) in 2002. In addition to being a threat to native benthos, the snail also harbors parasite associated with annual outbreaks of waterfowl... more
Bithynia tentaculata is an invasive snail that was discovered in the Upper Mississippi River (UMR) in 2002. In addition to being a threat to native benthos, the snail also harbors parasite associated with annual outbreaks of waterfowl mortality in the UMR. Trophic transmission of parasites between snails and birds occurs during seasonal waterfowl migrations, which can depend intimately on temperature. We developed an annual model for waterfowl disease in the UMR where transmission depends on water temperatures gleaned from empirical studies. By running simulations from annual temperature profiles selected randomly from a normal distribution, we quantified the association between the number of infected hosts and annual average temperatures. Model output demonstrated that as annual average temperatures rise, infected host populations initially increase and then decay after temperatures exceed a certain threshold. Results from this work suggest that increasing temperatures in the region may have a negative effect on parasites, decreasing their transmission and reducing infected host populations.
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ABSTRACT Background/Question/Methods Bithynia tentaculata is an invasive snail that was discovered in the upper Mississippi River in 2002. In addition to being a threat to native benthos, the snail harbors two parasite species that kill... more
ABSTRACT Background/Question/Methods Bithynia tentaculata is an invasive snail that was discovered in the upper Mississippi River in 2002. In addition to being a threat to native benthos, the snail harbors two parasite species that kill thousands of migrating waterfowl when infected snails are consumed. Both parasite species exhibit temperature-dependent transmission patterns with no transmission occurring when temperatures either fall below or exceed certain thresholds. The transmission window overlaps the waterfowl's seasonal migrations. The inclusion of temperature into disease models has been very important for better predicting infection outcomes across a number of host-parasite systems including trematode parasites such as human schistosomes. Using data collected from our empirical work, we developed an annual model for the host-parasite system in which transmission depends on water temperatures. Results/Conclusions The size of the infected host populations display a sensitivity on the range of the transmission window. We quantify the dependence of the number of infected hosts to the annual average temperature with three variance scenarios (low, medium, and high variance). As the annual average temperature increases, the prediction intervals for infected populations initially increase, reaching a threshold, after which they decay. Results suggest that warming trends in water temperature may have a positive effect on future uninfected populations.
Farm ponds in southeastern Minnesota are primarily constructed to prevent off-site soil erosion and to provide wildlife habitat in this predominantly agricultural landscape. Consequently, these ponds are subject to a variety of... more
Farm ponds in southeastern Minnesota are primarily constructed to prevent off-site soil erosion and to provide wildlife habitat in this predominantly agricultural landscape. Consequently, these ponds are subject to a variety of disturbances from agriculture, especially sedimentation and eutrophication. Natural ponds are rare and are located primarily at low elevations along tributaries to the Mississippi River. We examined chironomid richness, community structure and size-frequency distribution in response to a gradient of land use and water quality in 40 randomly selected ponds. Ponds were classified as natural or constructed; constructed ponds were further classified based on land use adjacent to the pond. Chironomid larvae and water quality were sampled 3 times in summer 2001. Chironomid generic richness significantly differed among pond type and community composition was strongly associated with adjacent land use. Size-frequency distributions were analyzed for the 10 most ubiquitous taxa: Polypedilum, Glyptotendipes, Chironomus, Tanytarsus, Procladius, Endochironomus, Ablabesmyia, Cricotopus, Dicrotendipes and Cladopelma. In general, slopes of normalized size-spectra for these taxa co-varied along the land use/water quality gradient. These results suggest that chironomid-body size may be a useful metric in biological assessments to evaluate the ecological integrity of constructed-pond ecosystems.
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ABSTRACT Background/Question/Methods Bithynia tentaculata is an invasive aquatic snail that has recently spread to the upper Mississippi River from the Great Lakes region. The invasive capacity of this species often leads to its dominance... more
ABSTRACT Background/Question/Methods Bithynia tentaculata is an invasive aquatic snail that has recently spread to the upper Mississippi River from the Great Lakes region. The invasive capacity of this species often leads to its dominance within the mollusk community. Moreover, B. tentaculata harbors a number of parasitic trematodes that have rippling effects throughout the ecosystem due to their detrimental impacts on thousands of migrating waterfowl every year. Unfortunately, even though these organisms are directly disrupting general ecosystem stability and economics in the upper Midwest, little is actually known about the factors responsible for successful snail colonization and subsequent parasite transmission to hosts. To address these shortcomings, we have utilized a number of complimentary approaches (field collections, and experimental manipulations) to 1) investigate the processes underlying distributions of B. tentaculata and its parasites, and 2) generate biologically relevant parameters for developing mathematical models to predict future patterns of disease. Results/Conclusions Through quantitative field sampling and experimentation we have documented extensive spatial and temporal variability in snail distributions which may be dictated, in part, by substrate size and water velocity. In addition, we have shown through both field collections and experimentation that the parasites are specific for particular snail species at the first stage of the life cycle but can infect a number of host species during subsequent stages. Not only have these empirical results helped us to better understand this particular system, they have also provided us with parameters for use in mathematical models aimed at predicting disease persistence in the upper Mississippi River.
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Glossosoma intermedium are efficient grazers of periphyton and are often found in high densities (10,000 individuals/m 2 ). These insects are keystone herbivores, locally regulating periphyton biomass. The combination of high densities... more
Glossosoma intermedium are efficient grazers of periphyton and are often found in high densities (10,000 individuals/m 2 ). These insects are keystone herbivores, locally regulating periphyton biomass. The combination of high densities and grazing efficiency limits available periphyton for grazing macroinvertebrates, including G . intermedium . We observed in the field and in preliminary laboratory studies that larvae mount the cases of conspecifics. We hypothesized that the frequency of this behavior varies inversely with the level of periphyton available on stream substrates. This hypothesis was tested by a series of laboratory experiments. Larvae were collected from a local stream and placed in artificial flumes containing unglazed quarry tiles that were either colonized with periphyton or bare (uncolonized). We observed mounting behavior with time-lapse video photography. Larvae encountered conspecifics at the same rate on colonized and uncolonized tiles. However, on colonized t...
Laboratory experiments were undertaken to assess the effects of three levels of cobble embeddedness on the microdistribution of the sculpin Cottus beldingi and its stonefly prey, Skwala americana. Experiments were conducted separately and... more
Laboratory experiments were undertaken to assess the effects of three levels of cobble embeddedness on the microdistribution of the sculpin Cottus beldingi and its stonefly prey, Skwala americana. Experiments were conducted separately and together as predator and prey in temperature- and flow-controlled artificial streams. When tested either separately or together, both the predator sculpin and its stonefly prey occurred in significantly greater numbers on substrata having unembedded cobbles than substrata having half- or completely embedded cobbles. Stonefly densities were greater in substrate having unembedded cobbles even though predator densities within the more embedded cobble patches were significantly lower. These findings support the hypothesis that higher predator densities influence prey densities less than the structural habitat quality of unembedded-cobble patches.
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Larval Glossosoma spp. construct portable mineral cases, which they carry while grazing on benthic diatoms in cold water streams. Diatoms also colonize Glossosoma cases. Under certain conditions, Glossosoma larvae mount the cases of... more
Larval Glossosoma spp. construct portable mineral cases, which they carry while grazing on benthic diatoms in cold water streams. Diatoms also colonize Glossosoma cases. Under certain conditions, Glossosoma larvae mount the cases of conspecifics and appear to be grazing. Consequently case microhabitats may at times serve as a refugium for diatoms from grazers and at other times an alternative grazing surface for Glossosoma . During 1999 and 2000, we seasonally sampled two streams with high populations of the keystone herbivore Glossosoma intermedium in southwestern Wisconsin. We examined diatom community composition on G. intermedium cases and the substrata from which the cases were removed. In general, diatom community structure changed seasonally on both microhabitats. Achnanthes minutissima and Amphora pediculus were present both on cases and substrate in all sample periods although their relative abundances fluctuated significantly. On both surfaces temporal trends in the benthi...
Native freshwater mussels are a diverse, but imperiled fauna and may be especially sensitive to increasing water temperatures because of their patchy distribution, limited mobility, limited dispersal, larval dependence on a host fish, and... more
Native freshwater mussels are a diverse, but imperiled fauna and may be especially sensitive to increasing water temperatures because of their patchy distribution, limited mobility, limited dispersal, larval dependence on a host fish, and the fact that they already inhabit fragmented landscapes. Recent research suggests that many mussel species may currently be living near their upper thermal limits. We tested the hypothesis that elevated water temperatures (20, 25, 30, and 35°C) will adversely affect the survival and physiology of juvenile and adult mussels in laboratory tests. In juveniles, the 28-d LT50’s (lethal temperature affecting 50% of the population) ranged from 25.3 to 30.3°C across 3 species. Mortality of 4 species of adults was minimal. In general, heart rate, but not growth rate, was significantly affected by temperature in juveniles, but the magnitude of these effects was small. Preliminary analyses suggest that metabolic processes (i.e., rates of oxygen consumption a...
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As part of the endangered humpback chub (HBC; Gila cypha ) Adaptive Management Program, a parasite survey was conducted from 28 June to 17 July 2006 in 8 tributaries and 7 adjacent sections of the main stem of the Colorado River, U.S.A.... more
As part of the endangered humpback chub (HBC; Gila cypha ) Adaptive Management Program, a parasite survey was conducted from 28 June to 17 July 2006 in 8 tributaries and 7 adjacent sections of the main stem of the Colorado River, U.S.A. In total, 717 fish were caught, including 24 HBC. Field necropsies yielded 19 parasite species, 5 of which (Achtheres sp., Kathlaniidae gen. sp., Caryophyllaidae gen. sp., Myxidium sp., and Octomacrum sp.) are new records for Grand Canyon, Arizona, U.S.A. Spearman's correlation coefficient analyses showed no correlations between parasite burden and fork length for various combinations of fish and parasite species. Regression analyses suggest that no parasite species had a strong effect on fish length. The most diverse parasite community (n = 14) was at river kilometer (Rkm) 230, near the confluence of Kanab Creek. The most diverse parasite infracommunity (n = 12) was found in the non-native channel catfish (CCF; Ictaluris punctatus). Overall parasite prevalence was highest in CCF (85%) followed by that in HBC (58%). The parasite fauna of humpback chub was mainly composed of Bothriocephalus acheilognathi and Ornithodiplostomum sp. metacercariae.
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We assessed the utility of larval burrowing dragonflies (Odonata: Anisoptera: Gomphidae) as biosentinels of methylmercury (MeHg) contamination. Gomphids were the most abundant family of dragonflies sampled during 2008-2010 from 17 lakes... more
We assessed the utility of larval burrowing dragonflies (Odonata: Anisoptera: Gomphidae) as biosentinels of methylmercury (MeHg) contamination. Gomphids were the most abundant family of dragonflies sampled during 2008-2010 from 17 lakes in four national parks of the northwestern Laurentian Great Lakes region. Ten species of burrowing gomphids were sampled; 13 lakes contained 3 or more species, and 2 species of Gomphus co-occurred in 12 lakes. Most of the total Hg (THg) in whole, late-instar larvae was MeHg, with mean percent MeHg exceeding 60% in 16 lakes. Mean MeHg in larvae of a given species varied greatly among lakes, ranging from 4 to 109 ng g(-1) dry weight. Methylmercury levels in larvae, however, were much less variable within a given lake and species. The mean concentration of MeHg in burrowing gomphids was positively correlated with mean MeHg concentration in unfiltered lake water. Mean concentrations of THg and MeHg in multispecies assemblages of Gomphus were also positively correlated with mean THg in coexisting prey fish and game fishes. We recommend-and provide guidance on-the application of burrowing gomphids as biosentinels of MeHg contamination, which can extend the bioassessment of MeHg to fishless fresh waters.
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Bithynia tentaculata is an aquatic invasive snail first detected in the upper Mississippi River (UMR) in 2002. The snail harbors a number of parasitic trematode species, including Sphaeridiotrema pseudoglobulus, that have been implicated... more
Bithynia tentaculata is an aquatic invasive snail first detected in the upper Mississippi River (UMR) in 2002. The snail harbors a number of parasitic trematode species, including Sphaeridiotrema pseudoglobulus, that have been implicated in waterfowl mortality in the region. We assessed the capacity of S. pseudoglobulus cercariae to infect B. tentaculata and native snails found in the UMR. Four snail species (one invasive and three native) were individually exposed to S. pseudoglobulus larvae and all were successfully infected. A subsequent experiment examining infection patterns in invasive and native hosts exposed singly or in mixed treatments revealed no difference in parasite establishment among snail species. Our results add to our understanding of S. pseudoglobulus transmission and provide insight into processes underlying waterfowl disease in the UMR.
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Research Interests: Zoology and Malacologia
Research Interests: Earth Sciences, Wetlands, Water quality, Eutrophication, Environmental Change, and 15 moreBiological Sciences, Cattle Grazing, Aquatic Ecosystem, Environmental Sciences, Land Cover, Nutrient Enrichment, Land Use, Community Structure, Species Diversity, Species Richness, Agricultural land use change, Water Quality, Turbidity, Aquatic Animals, and Total Nitrogen
Farm ponds in southeastern Minnesota are primarily constructed to prevent off-site soil erosion and to provide wildlife habitat in this predominantly agricultural landscape. Consequently, these ponds are subject to a variety of... more
Farm ponds in southeastern Minnesota are primarily constructed to prevent off-site soil erosion and to provide wildlife habitat in this predominantly agricultural landscape. Consequently, these ponds are subject to a variety of disturbances from agriculture, especially sedimentation and eutrophication. Natural ponds are rare and are located primarily at low elevations along tributaries to the Mississippi River. We examined chironomid richness, community structure and size-frequency distribution in response to a gradient of land use and water quality in 40 randomly selected ponds. Ponds were classified as natural or constructed; constructed ponds were further classified based on land use adjacent to the pond. Chironomid larvae and water quality were sampled 3 times in summer 2001. Chironomid generic richness significantly differed among pond type and community composition was strongly associated with adjacent land use. Size-frequency distributions were analyzed for the 10 most ubiqui...