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Access Type
WSU Access
Date of Award
January 2025
Degree Type
Dissertation
Degree Name
Ph.D.
Department
Biological Sciences
First Advisor
Donna Kashian
Abstract
Harmful algal blooms are a growing threat to freshwater habitats around the globe. The causative agents, cyanobacteria, may or may not release deadly toxins as they take over. These toxins are known to cause illness and even death in fish, birds, and mammals including humans; however, little is known about their impact on keystone, semiaquatic amphibian species. In this work I holistically evaluated species vulnerability, spatial and temporal interactions, and developmental effects of HABs and native amphibians in Michigan through a series of theoretical, field, and laboratory experiments. Using a novel trait-based ecological risk assessment framework, I identified trends in individual, population, and species level HAB vulnerability across Michigan’s 23 native amphibians. Most low-risk taxa scored consistently across individual, population, and species scales; whereas higher risk taxa scores were more volatile and often strongly influenced by species-level measures of high resiliency. I then evaluated historic and ongoing interactions between these species by comparing spatial and temporal overlap from state HAB surveys, amphibian community science records, and simple field surveys. I identified August and September as periods of major overlap in HAB occurrence and amphibian observation and development. Spatial hotspots for toxic HABs and amphibian observation were limited, but I recorded signs of Rana clamitans breeding activity in 52% of historic HAB lakes including 3 lakes with ongoing toxic blooms. Finally, I designed a repeat exposure experiment to determine the impact of cyanotoxins on embryonic and larval R. clamitans growth and development. After field collecting frog eggs and cyanobacteria cultures, I observed accelerated hatch rates in animals exposed to the high concentration of cyanobacteria extracts after 2 days. Animals were retained and maintained in non-toxic media with regular husbandry to allow for standard development. After this holding period, tadpoles were re-exposed to cyanobacteria solutions that were the same or slightly modified from the primary exposure. In these cases, previous exposure to low levels of microcystin as embryos limited growth as tadpoles, but other carry over effects from high concentration exposures were not observed. In all tadpoles exposed to 100 µg/L microcystins, accelerated growth and development was measured. Across all embryonic and larval exposures, fewer than 5% of animals died, which suggests that microcystins may not be lethal over high, chronic exposures in developing R. clamitans. Results from this research collectively suggest that HABs pose a risk to many species of amphibians in early stages of development and that more research is needed to elucidate the mechanisms and eventual trade-offs of the developmental plasticity observed in my final experiments. My research contributes novel methodologies for risk assessment and experimental assays that may be used by other scientists to responsibly fill the large gap in understanding this stressor. These findings support some previous work that indicate HABs as sublethal stressors in developing amphibian species. This collective work can be used to predict, quantify, and respond to growing threat of HABs in freshwater habitats to protect vulnerable populations.
Recommended Citation
Friday, Brenna, "Quantifying The Ecotoxicological Effects Of Harmful Algal Blooms On Vulnerable Native Amphibians" (2025). Wayne State University Dissertations. 4156.
https://digitalcommons.wayne.edu/oa_dissertations/4156