Food Web Ecology of Coastal Wetlands in Alaska and the Laurentian Great Lakes Under Global Change

Coastal wetlands are among the most productive and biologically diverse ecosystems on the planet, providing an array of ecological and societal benefits. Unfortunately, more than half of the global area of wetlands has been lost, primarily due to human activities on the landscape. In my dissertation, I use a multidisciplinary approach to assess how freshwater coastal wetlands are responding to various threats from anthropogenic activities, including land-use change, invasive species, and climate change. To do so, I use a combination of fieldwork, laboratory analyses, and data science to assess biodiversity, understand food web structure, and forecast water temperatures. First, I reviewed the role of algal communities in freshwater coastal wetland ecosystems, by conducting a meta-analysis of the published literature on the roles of phytoplankton, periphyton, and metaphyton in coastal wetlands of the world’s large lakes, with a focus on the Laurentian Great Lakes. Second, I assessed the spatial diversity of invertebrate communities in the Great Lakes and explored how wetland vegetation and surrounding land use influence these communities using random forest models. This study highlighted the distinct negative impacts of agricultural development and urbanization on these interface ecosystems. Third, in southcentral Alaska (USA), I used stable isotopes of carbon and nitrogen to explore how the invasive macrophyte Elodea canadensis has impacted food web structure of wetlands in the Copper River Delta. I found that Elodea occupies a distinct isotopic space compared to native vegetation and is minimally consumed and incorporated into the aquatic food web. Fourth, I used high-frequency air and water temperature data from two regions of southcentral Alaska to train Bayesian statistical models to forecast projected changes in water temperature of Alaskan coastal wetland ponds. My analysis suggests significant warming of ponds based on future climate scenarios provided by the International Panel on Climate Change, which could threaten Pacific salmon populations dependent on these ecosystems. Finally, in a social science chapter, I analyzed trends in STEM attitudes using four nationally representative, longitudinal surveys of high school cohorts conducted from 1980 to 2009. This chapter ties together my interests in ecology with how researchers can create more positive experiences for society when they engage with STEM education. The ecological and economic importance of freshwater coastal wetlands highlights the need to evaluate and mitigate threats and long-term impacts of human disturbance. I found commonalities and differences between wetlands of the Great Lakes and those of Alaska in that wetlands in both regions are being reshaped by anthropogenic activities but that the relative importance of stressors differs by region. Overall, my dissertation integrates physical, chemical, and biological elements of coastal wetlands in Alaska and in the Great Lakes region to reveal the impacts of land use change, invasive species, and climate change on these vital ecosystems.