Marine ecosystems contain both highly abundant and diverse communities of vertebrates and invertebrates; however anthropogenic activity has drastically altered the species composition and diversity of these ecosystems. Specifically, human activity has targeted high trophic level species and degraded much of the biogenic habitat that faunal communities rely upon. These alterations have resulted in the loss of many marine predators and overall declines of marine biodiversity. To investigate the consequences of marine predator loss and community level species decline, I use a combination of large-scale data synthesis and in situ field observations of marine fish communities. I first use a meta-analysis approach to synthesize the consequences of marine predator loss in benthic marine ecosystems worldwide. From this synthesis, I was able to determine some of the biotic and abiotic factors that regulate the response of marine herbivores and primary producers to predator loss. Specifically, I show that marine predators have the strongest effect on populations of marine herbivores when predators and herbivores were similar in size and when larger herbivores were involved. Conversely the factors that best explained the response of the primary producer populations were related to the abiotic environment. The results show that primary producers respond the most positively to the presence of predators in high nutrient environments. While I found no link between the magnitude of change in the herbivore population and the magnitude of change in the producer population, I was able to demonstrate that primary producers are under the strongest top-down controls when nutrient concentrations are high, sea surface temperatures are low, and when the predator is larger in size than the herbivore. Finally, I use the data related to marine reserves to show that reserves are an effective tool to help reverse the trophic consequences of marine predator loss and that they are most effective when they are older in age. The third chapter examines the links between community diversity and community biomass within fish communities in eelgrass ecosystems in Northern British Columbia. After controlling for environmental variation, I found that it was the dominance of certain species within a community that resulted in the highest ecosystem function. This finding was demonstrated by both the taxonomic and functional metrics of diversity used. While previous work on this topic has shown that richness is positively correlated to function, my results are to the contrary, and suggest that further investigation into which aspects of community diversity drive ecosystem function is required. In conclusion, my results provide a new synthesis of the consequences of marine predator loss across the world and show how species diversity is linked to ecosystem function in local eelgrass fish communities. / Graduate / 2018-12-17

Worldwide declines in populations of large elasmobranchs and the potential cascading effects on marine ecosystems have garnered considerable attention. Far less appreciated are the potential ecological impacts of changes in abundances of small to medium bodied elasmobranchs mesopredators. Crucial to elucidating the role of these elasmobranchs is an understanding of their habitat use and foraging ecology in pristine conditions. I investigated the trophic interactions and factors driving spatiotemporal variation in abundances of elasmobranch mesopredators in the relatively pristine ecosystem of Shark Bay, Australia. First, I describe the species composition and seasonal habitat use patterns of elasmobranch mesopredator on the sandflats of Shark Bay. Juvenile batoids dominated this diverse community and were extremely abundant in nearshore microhabitats during the warm season. Stomach content analysis and stable isotopic analysis revealed that there is a large degree of dietary overlap between common batoid species. Crustaceans, which tend to be found in seagrass habitats, dominated diets. Despite isotopic differences between many species, overlap in isotopic niche space was high and there was some degree of individual specialization. I then, investigated the importance of abiotic (temperature and water depth) and biotic (prey and predator abundance) factors in shaping batoid habitat use. Batoids were most abundant and tended to rest in shallow nearshore waters when temperatures were high. This pattern coincides with periods of large shark abundance suggesting batoids were seeking refuge from predators rather than selecting optimal temperatures. Finally, I used acoustic telemetry to examine batoid residency and diel use of the sandflats. Individual batoids were present on the sandflats during both the warm and cold seasons and throughout the diel cycle, suggesting lower sandflat densities during the cold season were a result of habitat shifts rather than migration out of Shark Bay. Combined, habitat use and dietary results suggest that batoids have the potential to seasonally impact sandflat dynamics through their presence, although foraging may be limited on the sandflats. Interestingly, my results suggest that elasmobranch mesopredators in pristine ecosystems probably are not regulated by food supply and their habitat use patterns and perhaps ecosystem impacts may be influenced by their predators.

京都大学 / 新制・課程博士 / 博士(地球環境学) / 甲第23351号 / 地環博第209号 / 新制||地環||40(附属図書館) / 京都大学大学院地球環境学舎地球環境学専攻 / (主査)教授 德地 直子, 教授 柴田 昌三, 准教授 西川 完途 / 学位規則第4条第1項該当 / Doctor of Global Environmental Studies / Kyoto University / DGAM

Context: Inferior vena cava (IVC) anomalies have a 0.5% incidence rate and could be associated with other congenital abnormalities. In later stage of the disease, trophic ulcers with or without deep vein thrombosis (DVT) is consistent finding.Case Report: A 29-year-old male patient presented with recurrent lower extremity ulcers. Further workup revealed an absent infrahepatic inferior vena cava, prominently dilated azygos and hemiazygos veins with enlarged retroperitoneal collaterals without DVT.Conclusion: IVC anomaly should be suspected in a young patient presenting with unexplained venous thrombosis and recurrent ulcers of a lower extremity. IVC anomaly would inherently lead to blood flow stasis and endothelial injury. Thus per Virchow's triad, other risk factors for hypercoagulability such as physical inactivity, smoking tobacco, oral contraceptive pills should be avoided and when hereditary thrombophilias or other irreversible risk factors are present, lifelong anticoagulation should be considered.

The Sacramento River watershed provides important rearing habitat for key aquatic species, including juvenile Chinook salmon (Oncorhynchus tshawytscha). Salmon rearing in the watershed may inhabit the mainstem river channel or a corresponding floodplain, the Yolo Bypass, before migrating to the ocean. Studies of juvenile salmon have indicated that floodplain rearing may be beneficial in terms of growth and survival, likely related to different trophic pathways of the river and floodplain. However, fish also encounter many anthropogenic stressors in these habitats, such as pesticides, which have well-documented use and environmental presence in the region. Rearing individuals are potentially exposed to pesticides via trophic transfer, which may vary based on utilized food webs due to hydrophobic pesticide fate and transport. To examine the food web structure of each system and the potential for pesticide exposure through dietary routes, a two-year field study was completed. First, to characterize dietary contributions, a three-tiered approach incorporating stable isotopes (δ13C, δ15N and δ34S), essential fatty acids and gut content analyses was employed. Subsequently, pesticides were extracted from prey items and salmon and analyzed to determine contaminant residues. Stable isotope analyses indicated that critically important components of juvenile Chinook diet were amphipoda and adult diptera in 2019 and 2020, respectively. Amphipoda groups had higher concentrations of the fatty acid docosahexaenoic acid (DHA), an important component for fish development, than juvenile diptera or oligochaeta. Diptera (larvae and adults) were frequently found in juvenile Chinook stomachs from both areas and years. Throughout the pesticide examination, organochlorines including the DDT group (p,p’-DDT, p,p’-DDD and p,p’-DDE) were prevalent in all examined biota. There were a significantly greater number of pyrethroid and phenylpyrazole detections and concentrations in zooplankton as compared to macroinvertebrates (Poisson regression, p < 0.05) across regions and years. Additionally, significantly higher concentrations of organochlorines were exhibited in floodplain rearing fish as compared to the Sacramento River (ANOVA, p < 0.05). These findings suggest that juvenile Chinook feeding primarily on zooplankton may be exposed to a greater range of pesticides than those exhibiting benthic feeding, but these pelagic prey were not demonstrated as a major dietary item during the two-year study. Additionally, the previously inferred benefits of floodplain rearing may come at a cost of increased organochlorine exposure. This research has allowed for a robust assessment of potential trophic transfer of pesticides to juvenile salmon, which may help inform future floodplain restoration efforts.

Non-native macrophytes structurally impact aquatic assemblages, yet little is known regarding how they influence energy pathways in freshwater ecosystems. Allelopathy in Eurasian watermilfoil- Myriophyllum spicatum has been shown to target basal epiphytic organisms resulting in differences in assemblage structure of colonizing epiphyton between M. spicatum and native M. sibiricum. I conducted a growth chamber experiment to investigate the hypothesis that differences in assemblage structure of colonizing epiphyton between these two macrophytes influence trophic dynamics within aquatic systems. My data suggest M. spicatum produces higher concentrations of allelochemicals, resulting in a more diverse epiphytic assemblage compared to M. sibiricum. This could result in potential transformation of trophic dynamics by decoupling carbon as it flows from primary producer to primary consumer. This work identifies a contributing mechanism responsible for M. spicatum invasiveness and provides new insight in its ecology and management of this non-native macrophyte.

The Hutchinsonian niche is the n dimensional hyper volume that allows for the persistence of a species. Castor canadensis, a large semi-aquatic rodent, is an ecosystem engineer and often a keystone species for many ecosystems. I examined the effect of multiple spatial scales on hierarchical habitat selection byC. canadensis using presence-only modeling techniques. I also determined individual trophic niche specialization in C. canadensis utilizing stable isotope analysis. I concluded that C. canadensis displayed scale independent habitat selection when comparing landscape and fine spatial scales. Individual trophic niche specialization occurred in colonies of the same resource availability. Also, individual trophic niches varied substantially between wetlands. These results have implications for the management of “generalist” species because populations can be composed of specialized individuals. Studies of niche across spatial and organizational scales are required for successful conservation and management strategies.

Eutrophication is of interest in the field of water quality. Eutrophic lakes, when used as sources for drinking water, can cause problems during the treatment process, for example algae blooms can clog filters, requiring more water and energy to be used during the cleaning and backwashing of the filters. Excess nutrient loading and eutrophication can also harm fish and aquatic life habitats. Certain species of algae and cyanobacteria can be toxic to humans as well. Since 1998, Dr. A. Woodruff Miller has collected water samples from 46 lakes and ponds in Yellowstone National Park. The Carlson Trophic State Index, the Vollenweider Model, the Larsen Mercier Model, the Burns Trophic Level Index, and the Naumann Trophic Scale were then used to assign each lake or pond to a trophic state classification (Oligotrophic, Mesotrophic, Eutrophic, and Hyper-Eutrophic). Of the 46 total lakes and ponds that have been tested over the past 14 years, five lakes are classified as slightly oligotrophic, implying that the waters are relatively clear and free from nutrient pollution. Of the 46 lakes, 19 are classified as slightly mesotrophic, mesotrophic, or strongly mesotrophic. These classifications imply that the waters are moderately clear and contain some nutrient pollution. Of the 46 lakes, 14 are classified as slightly eutrophic, eutrophic, or strongly eutrophic. This implies that the waters have high turbidity and nutrient content. Of the 46 lakes, 8 are classified as slightly hyper-eutrophic or hyper-eutrophic. These lakes are noticeable for their high algae content with very high nutrient content. These classifications are based on the most recent year sampled.

Grassland birds are the most rapidly declining bird guild in North America, due in large part to extensive loss and fragmentation of grassland habitat resulting from the spread of agriculture and other human-dominated landscapes. Over the past several decades, grassland birds have increasingly become a guild of high conservation and management interest as their populations continue to decline and suitable grassland habitat becomes continually scarcer. Although studies investigating grassland bird responses to management actions and habitat structure are common, few studies are concerned with clarifying the mechanisms through which habitat structure may affect grassland birds. Filling this knowledge gap is critical for increasing our understanding of grassland bird ecology and improving the effectiveness of management and restoration actions for grassland birds. To address this knowledge gap, I took a uniquely holistic approach to traditional grassland bird-habitat studies by concurrently gathering data on multiple wildlife taxa that may interact with birds to examine how these different taxa respond to habitat characteristics across multiple spatial scales, and how those responses may in turn impact grassland birds. Research was conducted on 10 grassland sites at Burning Star State Wildlife Management Area in northeast Jackson County, Illinois, during the bird breeding season (May-July) from 2018 to 2021. My first five objectives were to determine the grassland habitat characteristics that were most highly associated with the following taxa: arthropods, an important food source for adult and nestling grassland birds; small mammals, which are occasional nest predators and an alternate prey source for more prolific nest predators; snakes; raccoons; and grassland birds. My final objective was to estimate the extent to which grassland bird habitat associations were mediated through nest predator abundance, alternate prey abundance, and food availability. In Chapter 2, I examined associations between grassland arthropod communities and habitat characteristics representing three spatial scales: local (within-patch vegetation structure and composition), patch (size, shape, edge composition), and landscape (landcover composition within a 400 m buffer). In addition to their relevance for grassland birds, arthropods play important functional roles in grasslands and are useful indicators of grassland health. I collected arthropod samples using pan traps in grassland patches at Burning Star, and used generalized linear mixed models to relate variation in arthropod biomass and diversity to habitat predictor variables. I found that arthropod biomass increased with vegetation height at the local scale and proportion of forest/shrub edge at the patch scale, while arthropod diversity responded only to local-scale variables, including a negative association with vegetation height and woody vegetation cover, and a positive association with forb cover. I conclude that local vegetation structure and composition are the main drivers shaping arthropod communities at Burning Star, and that limiting woody encroachment and increasing forb cover and variation in vegetation height within grassland patches may encourage arthropod abundance and diversity in tallgrass prairies. In Chapter 3, I estimated associations between small mammal abundance and habitat variables, again representing three spatial scales. I surveyed small mammal communities using a grid of 100 Sherman traps set out for three nights at each study site. I identified all captured individuals to genus, individually marked them with ear tags, and estimated abundance using a combination of Huggins P and C models in Program Mark and generalized linear mixed models in Program R. I found that small mammal abundance was positively related to vegetation density and negatively related to plant diversity, though variation in plant diversity affected Microtus voles more strongly than Peromyscus mice. At the landscape scale, small mammal abundance was positively associated with the amount of water surrounding a patch, and negatively associated with the amount of grassland surrounding a patch. Variation in small mammal community composition (proportions of Microtus vs Peromyscus) was mostly governed by differences in habitat structure at the landscape scale, rather than differences in vegetation structure at the local scale. I suggest that managers interested in influencing small mammal abundance in grasslands encourage dense vegetation growth by limiting disturbance if increased small mammal abundance is desired, or reduce vegetation density by increasing disturbance frequency to reduce small mammal abundance. Additionally, increasing plant diversity by sowing a high diversity of seeds may be an effective way to control Microtus vole populations. In Chapter 4, I estimated the habitat associations of snakes at Burning Star, focusing on the relative abundance of snakes among different grassland sites, as well as snake diversity and species-specific occupancy. Although snakes are prolific nest predators of grassland birds, they are also integral components of grassland systems, and there may be instances where managers and decision-makers wish to increase, rather than decrease, their abundance in grasslands. I found that snake community metrics were strongly and positively related to an increase in woody plant cover at the local (within-patch) scale. Snake relative abundance was also positively related to an increase in grass cover and a decrease in forb cover, though my occupancy results suggest that this was primarily driven by an increase in black kingsnakes (Lampropeltis nigra). At the patch scale, snake relative abundance and diversity were both positively related to the proportion of patch edge composed of roads. Habitat structure at the landscape scale had the smallest impact on snakes in this study, though the proportion of trees in the landscape was positively related to snake diversity. I suggested that managers and conservationists interested in manipulating snake abundance in grasslands focus on within-patch vegetation structure and composition. Decreasing woody cover in grasslands, or increasing the ratio of forbs to grasses, may reduce the presence of snakes, while maintaining a woody component could encourage both snake abundance and diversity. In Chapter 5, I estimated the habitat characteristics that were most strongly associated with raccoon abundance estimates in grassland patches at Burning Star. Raccoons have become increasingly important avian nest predators in midwestern grasslands due to rampant habitat fragmentation. I estimated raccoon abundance using an occurrence index from a series of baited trail cameras located in grassland sites. I found no convincing evidence of raccoon abundance being influenced by local scale habitat structure, beyond a weak association with vegetation height. At the patch scale, raccoon abundance was positively related to the proportion of patch edge composed of roads. At the landscape scale, raccoon abundance was negatively related to grassland, and positively related to water, within 400 meters of a grassland patch. I recommended that managers concerned with minimizing the presence of raccoons in grasslands should limit roads along grassland perimeters, maximize the proportion of grassland in the landscape surrounding a grassland patch, and avoid planning a grassland restoration in close proximity to open water if possible. In Chapter 6, I estimated the habitat characteristics that were most strongly associated with daily nest survival, nest density, and abundance of Dickcissels (Spiza americana), Field Sparrows (Spizella pusilla), and Common Yellowthroats (Geothlypis trichas), but also considered responses of all grassland bird species combined. I considered habitat characteristics representing four spatial scales: nest site, within-patch, patch, and landscape, though the nest site scale was only considered for nest survival analyses. I found that Dickcissels, an obligate grassland species, exhibited the strongest response to fire, as nest density drastically improved after previously undisturbed grasslands were burned. Dickcissel abundance was positively related to agriculture at the landscape scale and negatively related to woody cover. Field sparrows demonstrated a preference for woody cover and proximity to forests and shrublands, and Common Yellowthroats were positively associated with forb cover. Both Field Sparrow and Common Yellowthroat nest survival increased with greater distance from an edge, though no edge effect was detected for Dickcissel nest survival. All bird species benefitted from increased plant diversity and greater patch size. All species also responded negatively to vegetation height or litter depth, suggesting that fire, which reduces vegetation biomass and litter, may indirectly benefit the facultative grassland birds of Burning Star in addition to Dickcissels. In Chapter 7, I used structural equation models and data gathered in the previous five chapters to estimate whether the effects of habitat structure on breeding Field Sparrows is mediated through changes in predator (snake and raccoon) abundance, alternate prey availability, or arthropod biomass. I used Field Sparrows as the focal species for this chapter because they were the most common grassland bird in my dataset. I found no evidence of nest survival or nest density of Field Sparrows being directly influenced by nest predator abundance, alternate prey, or arthropod biomass, although habitat characteristics associated with increased nest survival were also associated with greater arthropod biomass and reduced predator abundance. I suggested that habitat structure at Burning Star may primarily impact breeding Field Sparrows through direct means, such as influencing nest concealment or foraging efficiency. These results also suggest that nest success and nest density are decoupled in this study area, so Field Sparrows may be preferentially selecting nest sites with structural characteristics that do not increase nest survival. Ultimately, my findings from this study indicate that while predator avoidance and food provisioning likely play an important role in determining nest survival for grassland birds, predator abundance and arthropod biomass may not necessarily predict predation risk and foraging efficiency to the extent that is often assumed.

No description available.