Master of Science, The Ohio State University, 1961, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science (MS), Bowling Green State University, 2021, Biological Sciences

Aquaculture is one of the fastest growing food sectors of the world economy and reached a record high of 178.5 million tonnes in 2018. Saprolegnia sp. is a fish pathogen with a wide range of hosts including all salmonids. It is responsible for millions of dollars of damage annually to aquaculture. It is estimated that roughly ten percent of all hatched salmon succumb to Saprolegnia infections. The resulting economic losses range in the tens of millions of dollars. Early detection in large bodies of water can prove difficult with current capture methods. This study was conducted to determine if Daphnia magna, a filter feeder could be used as a biocontrol agent and as an indicator for the presence of small amounts of Saprolegnia zoospores in water. Time-lapse images of zoospores were documented at different time points (0-, 30-, 60-, and 90-minutes) after the introduction of Daphnia magna and plates were allowed 48 hours for encysted zoospores to germinate. By 90 minutes, number of visual zoospores had declined significantly compared to controls. After 48-hour incubation control had mycelial growth while Daphnia exposed plates did not, indicating that Daphnia magna did consume zoospores and could be used as a biocontrol agent to control Saprolegnia spp.. To determine if Daphnia magna can be used for detection of Saprolegnia spp., quantitative PCR (qPCR) with Saprolegnia specific primers targeting a cytochrome oxidase subunit I gene, was utilized. In Daphnia magna that had consumed zoospores at different times (5,10, 30, 40, and 50 minutes), qPCR failed to detect Saprolegnia spp.. This study indicates Daphnia magna does intake zoospores, indicating that it has potential to be used as a biocontrol agent against Saprolegnia infection. However, the DNA of Saprolegnia degrades too quickly once were inside Daphnia magna and cannot be used as an indicator for the presence of Saprolegnia spp.

Committee: Vipaporn Phuntumart PhD (Advisor); Raymond Larsen PhD (Committee Member); Paul Morris PhD (Committee Member) Subjects: Biology

Master of Science, Miami University, 2020, Biology

Shifts in forest composition could have significant effects on freshwater zooplankton due to changes in quality of inputs of terrestrially-derived Dissolved Organic Matter (DOM). DOM has been shown to have concentration dependent effects on primary production, but no consistent concentration dependent effects on zooplankton growth rates, raising questions about the potential importance of DOM source. Red maple (Acer rubrum), a native tree, and Amur honeysuckle (Lonicera maackii), an invasive shrub, were used to test the effects of DOM source on juvenile Daphnia ambigua. Amur honeysuckle-derived DOM was expected to have greater negative effects. Bioassays were conducted in the presence or absence of algae with no additional DOM, or red maple or Amur honeysuckle-derived DOM. Both Amur honeysuckle and red maple had negative effects on growth rates in the presence of algae with red maple inducing significantly lower growth rates. Red maple-derived DOM also had negative effects on survival. The negative effects seen in the presence and absence of algae provided evidence for both indirect effects likely due to phytotoxicity and direct negative effects respectively. Future studies accounting for DOM source could enhance our understanding of the complex roles of DOM in regulating consumers in aquatic ecosystems.

Committee: Craig Williamson (Advisor); Maria Gonzalez (Committee Member); Karsten Mauer (Committee Member) Subjects: Biology; Ecology; Freshwater Ecology; Limnology

Bachelor of Science, Ashland University, 2019, Biology/Toxicology

Plastic pollution has been a growing global issue since the production and widespread consumption of plastic began more than 60 years ago. Over time, detrimental impacts on ter-restrial and aquatic organisms have been observed. Microplastics are plastic pieces or fibers (less than 5 mm) that contaminate aquatic systems and may impact zooplankton, aquatic ani-mals that naturally ingest phytoplankton and other food particles of a similar size. Zooplankton are consumed by fish, so organisms higher in the food web are expected to be impacted by zo-oplankton ingestion of microplastics as those plastics consumed by zooplankton are trans-ferred to the predatory fish and thus bioaccumulate through the trophic food web. This study investigated the potential of the model zooplankton, Daphnia magna, to ingest microplastic spheres and microfibers through concentration and extended exposure experiments. D. magna are a large species and were found to readily ingest polystyrene spheres 50µm in size. Since D. magna demonstrated an affinity for sphere ingestion, animals were exposed to the more com-mon contaminant, microfibers, to determine if ingestion occurred and if there were impacts on survival and reproduction. Despite a lack of fiber ingestion, Daphnia exposure to low levels of microfibers over twenty days showed a reduction in the number of eggs generated in a clutch, reduction in the viability of neonates that gestate to term, and reduction in the overall number of neonates. Microplastics may pose a harm not only to organisms such as D. magna but also to organisms higher in the trophic system through bioaccumulation and reduction in available zooplankton as a food source if reproductive success is decreased when exposed. Further stud-ies of native organisms are necessary to establish the effects of microplastic pollution on freshwater systems and the organisms that rely on them.

Committee: Jenna Dolhi Binder Ph.D. (Advisor); Patricia Saunders Ph.D. (Advisor); Jeffrey Weidenhamer Ph.D. (Advisor) Subjects: Biology

Doctor of Philosophy, Miami University, 2017, Ecology, Evolution and Environmental Biology

Food chain efficiency (FCE) is an important ecological phenomenon, and previous work has demonstrated that the light and nutrient supply into an aquatic system affects FCE via changes in algal quantity and quality. However, less work has focused on how carnivore characteristics influence FCE. My dissertation research examines how bottom-up and top-down effects interact to constrain FCE. Aquatic ecosystems are often phosphorus (P) limited; therefore, consumers with high body P content may suffer decreased growth. In chapter 1, I report on an experiment conducted to test the effects of light and nutrient supply and carnivore identity on FCE using two carnivores with differing body P content. I found that FCE was constrained by different factors in food chains with different carnivores, indicating that carnivore identity impacts FCE. P limitation may be a more important driver of FCE in early vertebrate carnivore ontogeny, as many larval fish undergo a dramatic increase in body P content as they develop bones. Chapter 2 describes a mesocosm experiment in which I found that even in the larval stage bluegill are highly sensitive to food quantity. I also found that FCE increased with increased abundance of basal resources, further emphasizing the importance of energy limitation in constraining FCE. Not only are the rates of nutrient supply important for FCE, but the ratio of N to P supply (N:P) can also influence the quantity and quality of algae as a food resource. In chapter 3 I evaluated how light, P supply, and N:P supply affected FCE. I found that N:P supply did not affect FCE, suggesting that algal communities may be able to buffer the effects of high or low N:P supply. The algae – herbivore link is the most important trophic coupling in determining FCE due to a greater mismatch between producer and herbivore stoichiometry. If herbivore growth decreases due to energy or nutrient limitation, overall FCE also decreases. In chapter 4 I used Daphnia growt (open full item for complete abstract)

Committee: Maria Gonzalez (Advisor); Michael Vanni (Committee Member); Thomas Crist (Committee Member); Michelle Boone (Committee Member); M.H.H. Stevens (Committee Member) Subjects: Aquatic Sciences; Ecology

Doctor of Philosophy, The Ohio State University, 1987, Graduate School

Committee: Not Provided (Other) Subjects: Biology

Master of Science (MS), Ohio University, 2004, Environmental Studies (Arts and Sciences)

Laboratory bioassays using Ctenodaphnia magna (Order: Cladocera) were performed to test the toxicity of acid mine drainage (AMD) contaminated sediments at four heavily impacted streams around Athens with reduced mean pH, visible metal precipitates and elevated water column concentrations of iron, aluminum and manganese. Bioassays showed that sediments from all of the AMD impacted sites were highly toxic to Daphnia. Toxicity was correlated to reduced pH but not with any specific metal content. In another experiment, AMD contaminated sediments were placed in baskets and transplanted into the bed of a healthy stream for five days. They were collected on the second and fifth day and tested for toxicity. After five days in the clean stream, aluminum and iron-contaminated substrates were no longer toxic to the Daphnia. These results suggest that sediments at these sites will not retain toxicity after remediation of the AMD input.

Committee: Kelly Johnson (Advisor) Subjects:

Master of Science, Miami University, 2009, Zoology

Many polycyclic aromatic hydrocarbons (PAHs) can cause acute toxicity to aquatic organisms (e.g. fish, zooplanktons, etc) through photodynamic activation in the presence of environmentally relevant intensities of ultraviolet radiation. My research focused on the impact of different food quality on the physiological performance of Daphnia magna, and impact of nanoparticles on the UV-induced toxicities. In the studies of food quality, I hypothesized that different diet type may lead to varied carotenoid production, which was related to different UV tolerance. Studies indicated that food quality has a significant effect on the carotenoid production and physiological performance of Daphnia, however, no proportional relationship between carotenoid production and physiological performance was observed. In addition, long-term exposure (21 d) of low-level C60 caused significant cellular damage in the Daphnia magna alimentary canal. This study highlighted the importance of examining the interactions between existing stressors and nanoparticles in the aquatic environment.

Committee: James T. Oris PhD (Advisor); Craig E. Williamson PhD (Committee Member); Maria J. Gonzalez PhD (Committee Member); Kathleen A. Killian PhD (Committee Member) Subjects: Zoology

Doctor of Philosophy, Miami University, 2007, Zoology

Freshwater ecosystems are especially susceptible to climatic change, including anthropogenic-induced changes, as they are directly influenced by the atmosphere and terrestrial ecosystems. A major environmental factor that potentially affects every element of an ecosystem, directly or indirectly, is ultraviolet radiation (UVR). UVR has been shown to negatively affect the DNA of aquatic organisms by the same mechanism, formation of photoproducts (cyclobutane pyrimidine dimers; CPDs), as in humans. First, the induction of CPDs by solar UVR was quantified in four aquatic and terrestrial temperate ecosystems. Data show significant variation in CPD formation not only between aquatic and terrestrial ecosystems but also within a single ecosystem and between seasons. Second, there is little quantitative data on UV-induced DNA damage and the effectiveness of DNA repair mechanisms on the damage induced in freshwater invertebrates in the literature. The rate of photoproduct induction (CPDs) and DNA repair (photoenzymatic and nucleotide excision repair) in Daphniafollowing UVR exposures in artificial as well as two natural temperate lake systems was tested. The effect of temperature on the DNA repair rates, and ultimately the organisms' survival, was tested under controlled laboratory conditions following artificial UVB exposure. The results of these studies suggest a significant interaction of UVR and temperature on individual survival and ultimately population dynamics in freshwater systems. Lastly, freshwater human pathogens have negative effects ranging from gastrointestinal distress in otherwise healthy individuals to death in the immunocompromised and elderly. The control of infectious pathogens in water treatment is imperative. The abiotic and biotic environmental stressors of human pathogens are not well understood. Herein, solar radiation and artificial UVB are shown to significantly decrease the infectivity of Cryptosporidium parvum in vitro. The generalist filter feed (open full item for complete abstract)

Committee: Craig Williamson (Advisor) Subjects:

Doctor of Philosophy, Miami University, 2007, Zoology

Herbicides and reservoirs are ubiquitous in the Midwestern United States. Reservoirs can act as storage units, slowly releasing herbicides into outflowing stream(s). Atrazine is the most widely used herbicide in the world. Previous studies yielded conflicting results regarding its ability to stimulate male production by Daphnia, an effect hypothesized to lower population growth rates. In this study, atrazine consistently flushed into Acton Reservoir during spring. The reservoir had positive and negative effects on atrazine exposure times: occasionally diluting atrazine below 10 µg L-1 but always extending exposure times to 5 and 3 µg L-1 thresholds. Release of atrazine-laden water by the reservoir also extended exposure times in the outflowing stream. Reservoir Daphnia exhibited excess male production during high atrazine exposure in 2003. However, in laboratory studies, Daphnia did not increase male production in response to atrazine, regardless of food availability, population growth phase, or exposure history. Laboratory populations of D. parvula invested in sexual reproduction while conditions were favorable for population growth, and returned to asexual reproduction under unfavorable conditions. Males were produced across a wide range of environmental conditions whereas ephippial females appeared only briefly. There was a cost to male production in terms of reduced carrying capacity, but not population growth rate. There were also windows within which Daphnia could increase male production without producing fewer parthenogenetic neonates. Increased male production seemed a significant disadvantage between clones only when level of investment in male production was high, and populations were at or near carrying capacity. Excess male production may be a common strategy of D. parvula clones rather than an indicator of endocrine disruption. Unlike atrazine, JHA (juvenile hormone analog) insecticides enhance male production by Daphnia and are likely to have other de (open full item for complete abstract)

Committee: Maria Gonzalez (Advisor) Subjects:

PHD, Kent State University, 2009, College of Arts and Sciences / Department of Biological Sciences

A recent invader to Ohio is the cladoceran, Daphnia lumholtzi which was first reported in the state in 1993. A survey of 93 lakes and reservoirs was used to investigate the current distribution of D. lumholtzi in Ohio. Analysis of these samples revealed that D. lumholtzi has established in 19 of the waterbodies surveyed. Surface area was the only abiotic characteristic that exhibited a significant difference between invaded and non-invaded localities, thus it seems unlikely that local environmental conditions prohibit the invasion of D. lumholtzi. Additionally, it was found that D. lumholtzi is associated with smaller sized zooplankton communities. These results suggest that interactions with the native species, rather than abiotic characteristics, may be responsible for controlling the establishment of D. lumholtzi. Sediment cores were processed for cladoceran remains and sedimentary pigments to determine community types that are vulnerable to invasion and the potential impact that D. lumholtzi may have on native communities. The paleolimnological study determined that lakes invaded by D. lumholtzi are characterized by lower species diversity and communities comprised of smaller sized zooplankton species. These results were supported in an experimental mesocosm study. A resource overlap study investigated the utilization of food resources by D. lumholtzi in comparison to native cladoceran species. This study concluded that there is minimum food resource overlap between D. lumholtzi and small bodied zooplankton species, while larger species consume larger particles and exhibit higher grazing rates than D. lumholtzi. Each of the investigations suggests that communities with larger sized species may inhibit the establishment of D. lumholtzi as a result of high resource overlap. Communities dominated by smaller species may be more susceptible to invasion as D. lumholtzi does not appear to be in direct competition with these species. Further, the elongated spines of (open full item for complete abstract)

Committee: Robert Carlson (Committee Chair); Mark Kershner (Committee Member); James Blank (Committee Member); Alison Smith (Committee Member) Subjects: Biology; Ecology; Environmental Science; Freshwater Ecology; Paleoecology