PHD, Kent State University, 2023, College of Arts and Sciences / Department of Biological Sciences

Over the past few decades, the massive anthropogenic increase in PPCP consumption and their subsequent release, ubiquitous distribution, and pseudo-persistence in the environment have compelled many people to monitor PPCPs in rivers, lakes, drinking water, groundwater, and sediments. PPCPs can also enter drinking water treatment plants via either surface water or sometimes through groundwater. Despite their widespread distribution, PPCP monitoring is not mandatory in DWTPs according to federal or state regulations in the US, thereby limiting our understanding of PPCP occurrence, distribution, and subsequent removal in DWTPs. The removal of PPCPs in DWTPs also depends on the specific treatment processes (conventional or advanced) and the molecular structures of the removed compounds. Despite some studies focusing on PPCP occurrence and removal from DWTPs, there is still a significant knowledge gap regarding compound-specific removal of PPCPs both seasonally and treatment-wise (conventional vs. advanced). There is also insufficient knowledge about the removal of mixed PPCPs in sand-anthracite biofilters, particularly for drinking water. Moreover, their effects (microbial and biochemical) on benthic aquatic invertebrates are not well investigated. The overall goal of this dissertation was to understand the distribution of PPCPs in the surface and drinking water, their chemical and biological removal from water, and their effects on benthic aquatic invertebrates. Specifically, I aimed to understand how PPCPs are distributed in the surface and drinking waters of Northern Ohio, how they are removed from the finished waters in water treatment plants, how microbial community changes with the removal and/or interactions of PPCPs from drinking water in sand-anthracite biofilters and finally how PPCPs induce microbial and biochemical changes in freshwater crayfish.

Committee: Xiaozhen Mou Ph.D (Advisor); Laura Leff Ph.D (Advisor) Subjects: Chemistry; Ecology; Microbiology

PHD, Kent State University, 2022, College of Arts and Sciences / Department of Biological Sciences

Freshwater ecosystems serve as habitats for an array of macroinvertebrates and microorganisms. Macroinvertebrates are an integral part of freshwater ecosystems and their guts serve as habitats for various microorganisms, including bacteria. However, the role of freshwater macroinvertebrates and their gut microbiomes in performing ecosystem functions, including (but not limited to) biogeochemical processes, are relatively less explored than free-living microbiomes. The overall goal of this dissertation is to understand the contribution of freshwater macroinvertebrates towards nitrogen dynamics (denitrification in particular), antibiotic resistance, and the connection of these processes to bacterial community composition and function. Hence, I examined differences in antibiotic resistance gene (ARG) abundances and bacterial community composition among macroinvertebrate guts, sediment, and water microbiomes in an urban Northeast Ohio stream, looked at connection between denitrification functional genes and denitrification rates in crayfish guts, and effect of bioturbation on dissolved inorganic nitrogen, denitrification and bacterial abundance and community composition. Overall, the results showed that macroinvertebrate guts may serve as potential reservoirs of ARGs, however, we did not find evidence to show that macroinvertebrates serve as vectors of ARGs. Furthermore, we found that crayfish guts support both incomplete and complete denitrification while bioturbation by macroinvertebrates having different modes of burrowing influenced dissolved inorganic nitrogen concentration and bacterial community composition differently. Future studies need to focus on extensive sampling to draw generalizations about the role of macroinvertebrates in antibiotic resistance and denitrification in aquatic ecosystems. Additionally, such results when tested in field experiments can have implications on restoration and management decisions, and connect the effect of anthropogenic activi (open full item for complete abstract)

Committee: Laura Leff PHD (Advisor) Subjects: Ecology

PHD, Kent State University, 2022, College of Arts and Sciences / Department of Biological Sciences

Microplastics are a global concern in aquatic ecology and are readily colonized by bacteria in the environment. There is a lack of information on bacterial colonization of eroded and un-eroded microplastics in freshwater. In this study, six types of microplastics were incubated for 8 weeks in microcosms with water from Lake Erie. Microcosms were inoculated with one of three species: Acinetobacter (A.)calcoaceticus, Burkholderia (B.)cepacia, and Escherichia (E.)coli. These bacterial species are ubiquitous in water bodies associated with human populations. Bacterial surface coverage was determined using electron and fluorescent microscopy. Quantifications of EPS and surface roughness were performed by confocal microscopy and measuring contact angles (θw) of water droplets on microplastics, respectively. Analyses revealed surface coverage differed among bacterial species and plastic types after 8 weeks. As the study progressed, E.coli remained the most abundant while A.calcoaceticus gradually decreased on most surfaces. Analyses of microcosms revealed polypropylene disks had lower bacterial abundance. Conversely, eroded polypropylene disks had highest bacterial abundance, indicating importance of surface roughness (lower θw values) and surface physicochemical properties of microplastics in bacterial colonization. Our results demonstrated that bacterial colonization of microplastics is affected by both the physicochemical properties of microplastics and the physiological properties of colonizing bacteria.

Committee: Laura G. Leff (Advisor); Christopher Blackwood (Committee Member); Daniel Holm (Committee Member); Tara Smith (Committee Member); Xiaozhen Mou (Committee Member) Subjects: Materials Science; Microbiology; Molecular Biology; Plastics