Cephalopods provide forage to a wide range of predators in marine food-webs. Despite their ecological importance, a basic understanding of the mechanisms controlling predation risk and demand is lacking. This is true of one of the most common species of squid found in the northwest Atlantic, the longfin inshore squid (Loligo pealeii). In this dissertation, I address this shortcoming by investigating the role that size and behavior play in influencing squid’s vulnerability to predation. I used long-term food habits, population survey, and commercial landings data, to quantify size-based patterns of predation respective to 25 species of predators. Additionally, I estimated the amount of overlap between predatory consumption and the fishery catch for squid by size. I found that finfish and elasmobranchs generally consumed juvenile and sub-adult squid, while marine mammals primarily targeted adults. Consequently, marine mammals had the highest overlap with the fishing industry for squid size resources. Although large squid were not common in predator diets, predators did not appear to be gape-limited when feeding on squid. This suggested that other factors, including behavior, were important in shaping size-based patterns of predation. I used a laboratory-based approach to quantify attack and capture behaviors towards squid by two predators representing contrasting foraging tactics. Bluefish (Pomatomus saltatrix) and summer flounder ( Paralichthys dentatus) were chosen as cruising and ambush predators, respectively. Patterns in attack rates suggested that size-selection on squid was constrained by passive processes rather than active choice in both predators. Size-dependent profitability functions were calculated by combining capture success rates, handling times, and relative prey mass, and determined that bluefish was the more efficient predator of squid. Lastly, I evaluated the occurrence and effectiveness of anti-predator responses used by squid in the presence of bluefish and flounder. Squid behavior depended on the type of predator present, and the survival value of primary and secondary defense behaviors differed during interactions with each predator. The results of this project are intended to improve the quality of management of squid and their predators by providing a better understanding of predator-prey interactions in the northwest Atlantic.

<p dir="ltr">Physical traits and the hydrologic setting of lake and wetland environments strongly affect the biogeochemical signature of aquatic ecosystems and their structure and function in the landscape. Natural freshwater ecosystems have a high propensity for carbon capture and storage through aerobic production, sedimentation, and sequestration, yet differing physical characteristics including water depth, lake surface area, and watershed size likely influence the extent to which these processes occur. Anthropogenically modified ecosystems also demonstrate complex function regarding carbon cycles, where the influence of human disturbance heightens nutrients and carbon loads into aquatic systems and leads to unique biochemical regimes. Across Indiana, agricultural practices currently affect around 65 percent of the state’s landscape, while urban development and population growth are expected to expand throughout the state. This trend is modeled throughout the midwestern United States, where the impacts of urban development on aquatic environments is further heightened by expected changes in climate, as storm intensity strengthens, and rainfall increases during certain times of the year. While understudied, there is good reason to believe that Indiana’s lakes and wetlands have incredible variability in carbon processing and carbon quality within and between systems. This variation is influenced by the wide variety of drivers including hydrology, geomorphology, water chemistry, metabolic processes, and redox conditions. The interactive influence of each of these drivers, however, is poorly understood across wide scale gradients. Predicting ecosystem productivity and its relationship with carbon dynamics is therefore an important tool for understanding freshwater ecosystems’ contributions to global fluxes of carbon. The variability within and across midwestern ecosystems creates a challenging, yet critical paradigm to understand the complexities of carbon dynamics in aquatic ecosystems, emphasizing the importance for direct data collection across a stratified gradient of ecosystems. This research shows that 1) human-assigned classifications of system type, including lake, reservoir, and wetland, are useful tools in classifying the metabolic and nutrient regimes of lentic systems, and 2) morphological features including lake depth and watershed area influence the structure of carbon quality throughout the water column. Findings provide valuable information to watershed and lake managers on the importance of different physical drivers in determining water quality across a range of lentic systems.</p>

Freshwater fungi are vital to the aquatic food web, essential for nutrient cycling, energy flow, and ecosystem regulation. Their distribution is particularly contingent upon agricultural runoff, which can carry agrochemicals capable of influencing the freshwater mycobiota and potentially impacting the ecosystem services which they provide. While such impacts are well documented for freshwater bacterial communities, fungal communities are critically understudied. Here, we address this research gap by assessing the impact of anthropological and environmental perturbations on the freshwater mycobiota in the agriculturally dominated South Nation River basin in Eastern Ontario, Canada. We undertook biweekly water sampling from 2016-2021, complemented by rich ancillary data including water properties, hydrology, weather conditions, and fungal ITS2 metabarcoding. Our study yielded 6,571 Operational Taxonomic Units from 503 water samples, spanning 15 fungal phyla, dominated by Ascomycota, Basidiomycota, and Chytridiomycota. Agricultural land use decreased the mycobiota alpha diversity and distinct fungal communities were observed at agricultural ditch and mixed-use sites compared to the forested site. Notably, river discharge emerged as a predominant influencer of both alpha and beta diversity, likely transporting fungi via precipitation, especially from plant-rich catchment basins. Intriguingly, environmental data only explained a fraction of fungal community variation, underscoring the significance of unmeasured factors such as fungicide application, alongside stochastic community assembly processes. This work highlights the complex interplay of factors influencing the freshwater fungal community in agriculturally impacted watersheds and shows the need for further investigation for a more comprehensive understanding of the freshwater fungal ecology.

Movement is a core mechanism through which animals interact with their environment. A popular approach for investigating animal movement involves the use of GPS telemetry, which provides insights into both the spatial and temporal patterns exhibited by an individual or population. While many approaches for evaluating movement data have often analyzed intensity of use, most studies focused on a single property of use: the total duration an animal spent in a location. While this can provide insight into which landscape and habitat characteristics an individual may be selecting for, it does not fully account for how that space is being used. Therefore, it could be beneficial to combine more than one aspect of intensity of use to evaluate the behavioral mechanisms leading to patterns in space use, and by extension the drivers of home range structuring. As a territorial, central-place forager, the North American beaver (Castor canadensis) presents an ideal system for investigating drivers of home range structuring. However, while some species are easily tracked through traditional GPS attachment methods (such as GPS collars or backpacks), other species such as beavers present unique challenges given their fusiform shape and tapered neck. The overall objective of my thesis was to better understand fine-scale movement of beavers and the drivers of home range structuring. To do so, in chapter 1, I first developed and tested three different GPS transmitter attachment methods to determine which was most effective in terms of retention time (RT, total number of days a transmitter remains attached) and GPS fix success rate (FSR, % of successful fixes vs. attempted) and investigated to what degree various factors (season, sex, and age class) affected these results. In chapter 2, I analyzed space use in relation to four intensity of use metrics with machine learning to define homogenous types of space use. These metrics included the total number of visits, total and mean duration of visits, and mean interval between visits. GPS transmitters glued to the lower back of beavers provided up to two months of fine-scale data, as well as producing the highest FSR. In addition, longer retention times were found for transmitters attached to males versus females, and for transmitters deployed in the fall versus the spring. Using these data, I was able to capture five distinct population level intensity of use types including, low use – irregular, low use – regular, medium use – short duration, medium use – long duration, and lodge use. These types of use were all generally observed towards the core of the home range. In addition, all types of use were characterized by low intervals between visits except for the low use – irregular cluster. These results suggest highly structured, regular movements occurring in the core of beaver home ranges related primarily to shelter, foraging patches, and the movement paths used to link these locations. Overall, this approach allowed me to delineate between two distinct low use and medium use types and provided insight into the different behavioral mechanisms that may be driving these similar types of use. Capturing these different types of use was only possible by specifically combining multiple movement metrics at once to evaluate space use, as opposed to strictly using the number of GPS fixes to evaluate a location.

Lower back pain (LBP) is a medical condition that will affect most of us at some point in our lives. Several medical causes have been identified for LBP, yet the large majority of LBP patients do not receive a specific diagnosis. These patients use up a large majority of health care resources, and accumulate billions of dollars in medical costs in countries throughout the globe. In recent years, an increasing focus has been placed on the idea that aquatic therapy may be an effective therapy for LBP patients. Exercise therapy has already proven itself as an effective means for treating LBP. Thus, combined with the unique properties of water, experts believe that aquatic therapy is the future of LBP treatment. This thesis aims to explore the efficacy of aquatic therapy as a treatment for LBP. Through the analysis of controlled peer-reviewed studies, scholarly information databases, and historical data on LBP treatment, this thesis evaluates the relationship between aquatic therapy and LBP in its entirety. Scientific properties of water have shown its many uses in rehabilitative therapy treatments. Water, in theory, is able to manipulate the exercise environment to allow for more substantial progress to be made. In studies where aquatic therapy was tested versus no treatment, aquatic therapy proved to be a more efficient and effective option. Still, when placed against other therapies, aquatic therapy did not always prove more effective. While the analyzed studies support the idea that aquatic therapy is an effective treatment for LBP, further research is needed to determine how aquatic therapy holds up against other forms of treatment.

Metformin is the most common first-line oral therapeutic agent used in the treatment of type-2 diabetes. Because of its widespread use, metformin has been increasingly detected in wastewater effluent. It is partially bio-transformed into guanylurea is subsequently released into aquatic environments. Since the literature concerning the effect of metformin and guanyl urea on early life stage of fish is scant, the aim of this research was to understand the potential influence of metformin and guanylurea on developmental, cardiometabolic and behavioral responses in zebrafish embryos, from the 4 cell stage (3 hours post fertilization, hpf) to first feed (120 hpf). To this end, embryos were exposed to environmentally relevant (0.4, 4, 40 μg·L−1) and supra-environmental (400 and 4000 μg·L−1) concentrations of the two chemicals. Metformin caused an increased mortality and spinal abnormalities in all concentrations compared to controls. and increased pericardial and yolk sac edema at the highest tested concentration. Metformin did not cause alterations in hatch or heart rate over the examined developmental stages. In addition, metformin did not cause alterations in general swimming, light-dark movement, startle response or thigmotaxis, irrespective of exposure concentration. Exposure to guanylurea over the same developmental stages caused a significant difference in mortality at 40 μg·L−1 only. Guanylurea did not cause alterations to any of the other tested endpoints. Our data suggests that metformin and guanylurea caused modest impacts to embryonic development of zebrafish at these concentrations. / Thesis / Master of Science (MSc) / Pharmaceuticals have been detected at the ng to µg L-1 range in aqueous environments for decades. These compounds are designed to be biologically active at low concentrations and can cause elicit adverse effects in non-target species. Among the more recently detected compounds are the antihyperglycemic drug metformin and its biotransformation product (guanylurea), which have been the focus of few studies in fish. This thesis addresses multiple knowledge gaps by examining the potential impacts of metformin and guanylurea during the embryonic and early larval zebrafish period (3-120 hours post-fertilization). Exposure to metformin resulted in increased mortality and abnormalities. Guanylurea exposure increased mortality at one dose. We suggest that metformin and guanylurea cause modest effects in developing larval zebrafish.

Flowering rush (Butomus umbellatus L.) is a perennial wetland/aquatic plant that is native to Eurasia but has invaded North America and spread across Southern Canada and the Northern U.S. where it thrives along wetlands, shallow shorelines, and in submersed habitats of lakes, ponds, streams, rivers, and reservoirs. Little is known about the life cycle of flowering rush in its invaded range as only one study has investigated flowering rush phenology in Minnesota, USA. As flowering rush continues to expand its range southward in the U.S. it is imperative that resource managers 1) better understand the plants life cycle, 2) identify more aggressive and 3) selective herbicide strategies, and 4) utilize adaptive management protocols. In a mesocosm experiment, flowering rush grown in southern climates produced less overall biomass but produced more buds than recorded in northern populations. A second mesocosm study using one to four biweekly sequential diquat (0.37 mg L-1) treatments reduced flowering rush biomass and rhizome bud density by 62 to 100% one year after treatment. Additionally, there were no differences among diquat treatments suggesting that more aggressive diquat protocols may not be useful. In field trials, flowering rush was selectively reduced 92 to 99% by diquat treatments over two years, while hardstem bulrush was not affected. In mesocosms, flowering rush and hardstem bulrush were exposed to the contact herbicides diquat, endothall, copper, carfentrazone-ethyl, and flumioxazin; endothall (3.0 mg L-1) selectively reduced aboveground biomass of flowering rush by 69% and diquat (0.19 mg L-1) selectively reduced belowground biomass by 77%. None of the other herbicides affected flowering rush. In a Minnesota field project to identify adaptive control strategies, treatment sites were designated as having very-low, low, or high flowering rush prevalence with each receiving no, one, or two diquat treatments (0.37 mg L-1), respectively. Flowering rush did not increase after single diquat applications in low prevalence sites while prevalence declined in high prevalence sites. This suggests that single diquat applications are suitable to maintain control of sites with low flowering rush prevalence allowing resource managers to allocate unused resources elsewhere.

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