Do Cyanobacteria Blooms Enhance Parasite Loads in Lake Erie Yellow Perch?

Harmful Algal Blooms composed of cyanobacteria (HABs) are a major concern globally, especially in ecosystems that support commercial and recreational fisheries. Although HABs have been shown to negatively affect the services provided by ecosystems (e.g., safe water for drinking and recreation), their influence on fish populations, and fish health in particular, remains largely unknown. Given that Lake Erie has been experiencing large HABs during the past 15 years and supports important commercial and recreational fisheries, I sought to help Lake Erie agencies understand if HABs are posing a health risk to their valued fish populations. To this end, I explored the relationship between parasite loads in yellow perch (Perca flavescens), which supports Lake Erie’s largest commercial fishery and second largest recreational fishery, and cyanobacteria concentration. Specifically, I tested the hypothesis that parasite loads in the liver of young-of-year yellow perch would increase with increasing cyanobacteria concentration, as cyanotoxins associated with HABs (e.g., microcystin) have been shown to cause liver damage and physiological stress in other fish species. To answer this question, I measured parasite loads in 519 individuals captured from 54 sites across the western basin of Lake Erie during 2011-2019. My results were opposite of my expectations with mean liver parasite loads being negatively correlated with HAB severity. This finding, which was supported by other non-fish studies, suggests that HABs may actually benefit yellow perch by reducing parasite infections. Ultimately, my research points to the need for more research, if fisheries management agencies are truly to understand the net effect of HABs on their valued fishery resources.No embargoAcademic Major: Neuroscienc

A review of the stable isotope bio-geochemistry of the global silicon cycle and its associated trace elements

Silicon (Si) is the second most abundant element in the Earth’s crust and is an important nutrient in the ocean. The global Si cycle plays a critical role in regulating primary productivity and carbon cycling on the continents and in the oceans. Development of the analytical tools used to study the sources, sinks, and fluxes of the global Si cycle (e.g., elemental and stable isotope ratio data for Ge, Si, Zn, etc.) have recently led to major advances in our understanding of the mechanisms and processes that constrain the cycling of Si in the modern environment and in the past. Here, we provide background on the geochemical tools that are available for studying the Si cycle and highlight our current understanding of the marine, freshwater and terrestrial systems. We place emphasis on the geochemistry (e.g., Al/Si, Ge/Si, Zn/Si, d13C, d15N, d18O, d30Si) of dissolved and biogenic Si, present case studies, such as the Silicic Acid Leakage Hypothesis, and discuss challenges associated with the development of these environmental proxies for the global Si cycle. We also discuss how each system within the global Si cycle might change over time (i.e., sources, sinks, and processes) and the potential technical and conceptual limitations that need to be considered for future studies