Aspects of bacterial community ecology within the American oyster (Crassostrea virginica), and surveillance of post-harvest Vibrio vulnificus occurrence

La Valley, Kenneth John University of Rhode Island 2005 해외박사(DDOD)

This dissertation research addressed the fundamental question of what the general microbial flora within the oyster is and what influence depuration and relay have on bacterial communities in the oyster. Comparisons of bacterial community profiles were made using culture-dependent and culture-independent isolation techniques and a nested PCR-DGGE (Denaturing Gradient Gel Electrophoresis) approach. Differences in the composition of the bacterial community between culture-dependent and culture-independent profiles were detected. The effect of culture-based techniques is significant and results in a biased representation of community structure. This bias may be minimized for the oyster compared to the large differences typically detected between culturable and total microbial communities from a sample, since external and internal surfaces of the oyster supply a nutrient rich micro-environment not unlike an enrichment broth. These micro-environments may allow proliferation of the majority of bacterial species who specialize in these environments, thus inhibiting many of the transient non-specialist bacterial species inadvertently ingested during respiratory and feeding mechanisms. Using API 20E test strips, dominant culturable species were identified as members of the genera Vibrio. Approximately 60% of Vibrio isolates were V. parahaemolyticus. Additional Vibrio species included, V. alginolyticus, V. cholerae, and V. vulnificus. The remaining isolates identified by the API system were Aeromonas and Photobacterium species. Oyster-associated bacterial community profiles generated from depurated and relay samples were compared using the same nested PCR-DGGE approach. Oyster-associated profiles between replicate samples within a harvest area and treatment only showed minor variations. Depuration significantly altered the relative species diversity and abundance of dominant ribotypes. Cluster analysis identified groups of ribotypes that persisted or disappeared following depuration. Relay was shown to significantly increase both relative ribotype diversity and relative abundance measures. Post-harvest surveillance for Vibrio vulnificus by a commercial processing facility was conducted from May 2001 to September 2003. Harvest areas included Delaware Bay, Long Island Sound, and Prince Edward Island. Occurrence followed a seasonal distribution. Low densities were observed in June, increased through August, and became rare by September. Post-harvest handling was identified as a critical control point for elevated pathogen densities.

A four-year retrospective study of domestic violence and police response in Asians using the Rhode Island Domestic Violence/Sexual Assault Police Reporting Forms

Ngo, Tu Anh University of Rhode Island 2005 해외박사(DDOD)

Problem. Domestic violence (DV) results in the death of four women daily in the US and affects all racial/ethnic groups. Due to immigration, cultural values, and attitude toward authority, there may be unique factors influencing the DV experience for Asian victims that are not well understood due to a paucity of research. Objective. This study examined DV homicide and arrests, victims' reporting, violence severity, and police response to DV calls for Asian victims compared to African American, Hispanic, and White victims. Method. This was a cross-sectional, retrospective study (2001-2004) of DV incidents in Rhode Island based on secondary data analysis of responses from the Domestic Violence/Sexual Assault Reporting Forms. Cases were included if they met the following criteria: arrest cases, female victims, heterosexual intimate (former or current) relationships between victim and suspect. Based on 130 Asian victims, the same number of African American, Hispanic, and White cases were randomly selected to equalize the number in each group (total n = 520). Results. Victims' average age was 32. There were 24 DV homicides during the time under study, 1 of which was Asian. Asians and Whites had lower percentages and African Americans and Hispanics had higher percentages of arrests resulting from DV calls relative to their respective percentage representation in the RI population. Chi square analyses showed that Asians had more physical assault than Non-Asians except for Hispanics. Logistic regression results showed that Asians were 2.32 times more likely to have been physically assaulted than Whites. Chi square analyses showed that police were less likely to give Temporary Restraining Order information and less likely to check for Restraining Order No Contact Order (RONCO) for Asian victims than for White victims. In logistic regression, Asians were 0.44 times as likely as Whites to have the police check for a RONCO and 0.43 times as likely as Whites to have the police take crime scene photos. Conclusion. Study findings support ethnic differences in DV experience and police response to DV. These unique characteristics for Asians and other minorities warrant further investigation. Implications include earlier intervention for Asian victims and improved police response for minorities.

Native and exotic Phragmites australis in Rhode Island: Distribution and differential resistance to insect herbivores

Lambert, Adam Matthew University of Rhode Island 2005 해외박사(DDOD)

In this research, I studied an introduced strain of Phragmites australis (Cav.) Trin. Ex. Steudel that is displacing native P. australis in the United States and altering ecological processes of native environments. The purpose of this study was to determine the distribution of native and exotic P. australis in Rhode Island and determine if there is a difference in resistance to native and exotic insect herbivores among the various P. australis haplotypes. I also studied possible factors that may cause these differences. I conducted experiments using field surveys and field and laboratory insect feeding experiments. All exotic insects tested fed on both native and exotic P. australis ; the native insect I tested in the laboratory fed on native and exotic haplotypes, but only completed development on the exotic haplotype. The implications for haplotype specific biological control of exotic P. australis are discussed.

Assessing Treatment Performance of Advanced Nitrogen-Removal Onsite Wastewater Treatment Systems

Ross, Bianca Noelle University of Rhode Island ProQuest Dissertations 2020 해외박사(DDOD)

Wastewater is a major source of nitrogen (N) to groundwater and coastal waterbodies, threatening both environmental and public health. Advanced N-removal onsite wastewater treatment systems (OWTS) are used to reduce effluent N concentration through biological N removal (BNR). Despite the important role that these systems play in treating nutrient- and pathogen-rich wastewater, few studies have targeted the mechanisms involved in N removal, their capacity to produce effluent to meet regulatory standards, or their impact on the atmosphere.I evaluated effluent total N (TN) concentration, the structure and composition of N-removing microbial communities, and greenhouse gas fluxes of advanced N-removal OWTS in the town of Charlestown, Rhode Island, USA. To assess N outputs from advanced OWTS and compliance with the 19 mg N/L state regulatory standard for advanced-treated effluent, in Manuscript 1 I quantified TN concentration of effluent from 50 advanced N-removal OWTS between March 2017 and December 2019, and evaluated differences as a function of N-removal technology, home occupancy pattern (systems used seasonally vs. those used year-round), and various wastewater properties. Four N-removal OWTS technologies were included in this study: (i) Orenco Advantex® AX20 (n = 33), (ii) Orenco Advantex® RX30 (n = 9), (iii) BioMicrobics MicroFAST® (n = 3), and Norweco Singulair® (models TNT, 960, and DN; n = 5). RX30 systems produced the lowest median TN concentration (mg N/L) (13.2), followed by FAST (13.4), AX20 (14.9) and Norweco (33.8). Compliance with the state standard varied among technologies, with compliance rates of 78%, 73%, 67%, and 0% for RX30, AX20, FAST, and Norweco systems, respectively. Effluent TN concentration did not vary as a function of occupancy pattern. Ammonium and nitrate were identified as predictors for effluent TN in all technologies; temperature and pH were also part of best-fit models for FAST and Norweco systems, respectively. Systems used year-round produced a significantly higher median daily (5.3 g N/d) and annual (2.3 kg N/yr) N load than did seasonally-used systems (3.7 g N/d and 0.41 kg N/yr), likely due to differences in home usage patterns, demographics, and associated differences in system flow.Assessment of treatment capabilities of advanced N-removal OWTS requires fast, accurate methods of monitoring performance. Regular monitoring of OWTS using in situ rapid tests can provide an inexpensive option for assessing treatment performance. In Manuscript 2 I assessed the ability of a portable photometer to accurately measure ammonium and nitrate concentrations in final effluent from 46 advanced N-removal OWTS in 2017. By comparing measurements made using the photometer with values determined by standard laboratory methods, I determined that photometer-based analysis reliably estimates inorganic N (ammonium and nitrate) concentration in field and laboratory settings. Photometer-based analysis of the sum of inorganic N species also consistently approximated the total N concentration in the final effluent from the systems. A cost-benefit analysis indicated that the photometer is a more cost-effective option than having samples analyzed by commercial environmental testing laboratories after analysis of 8 to 33 samples. These results suggest that a portable photometer can be used to provide reliable, cost-effective measurements of ammonium and nitrate concentrations, and estimates of total N levels in advanced N-removal OWTS effluent in a way that helps to identify underperforming systems.Advanced N-removal OWTS remove N from effluent via microbial nitrification and denitrification. Despite the important role that microorganisms play in N removal, few studies have investigated the nitrifying and denitrifying microbial communities in advanced N-removal OWTS. In Manuscript 3, I used high-throughput sequencing to evaluate the structure and composition of nitrifying and denitrifying bacterial communities in 44 advanced N-removal OWTS. I sampled effluent from these systems in June and September 2017, targeting the genes encoding ammonia monooxygenase (amoA) and nitrous oxide reductase (nosZ), and assessed differences in the diversity and taxonomy of nitrifying and denitrifying communities as a function of technology, occupancy pattern, and season. Alpha diversity (species diversity at a local scale) and beta diversity (differences in species diversity among communities/sites) for amoA varied strongly as a function of season. Differences in beta diversity for nosZ were also influenced by season, although to a lesser extent than for amoA. Alpha diversity for nosZ varied among technologies. Nitrosospira and Nitrosomonas were the main genera of nitrifying bacteria in advanced N-removal OWTS. The predominant genera of denitrifying bacteria included Zoogloea, Thauera, and Acidovorax. Differences in taxonomy for each gene generally mirrored patterns observed in alpha and beta diversity, highlighting the important role that season and technology play in shaping communities of amoA and nosZ, respectively.Microbial activity is required for the removal of N, pathogens, and organic C in advanced N-removal OWTS. However, these processes produce greenhouse gases (GHGs) including carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). In Manuscript 4 I measured GHG emissions from 27 advanced N-removal OWTS in the towns of Jamestown (2016) and Charlestown (2018), Rhode Island, USA, and assessed differences in flux based on technology, occupancy pattern, and zone within the system (oxic vs. anoxic zone), as well as various wastewater properties. Flux values for CO2, CH4, and N2O fluxes ranged from -0.44 to 61.8, -0.0029 to 25.3, and -0.02 to 0.23 µmol m-2 s-1, respectively. CO2 and CH4, but not N2O, fluxes were significantly higher in the anoxic/hypoxic zone than the oxic zone. CO2 and CH4 fluxes from the anoxic/hypoxic zone were positively correlated with 5-day biochemical oxygen demand, and negatively correlated with dissolved oxygen and nitrate, suggesting that anaerobic respiration contributes significantly to CO2 and CH4 flux. CO2 and CH4 fluxes peaked at ~22 to 23oC, as expected for microbial processes. CH4 flux was positively correlated with ammonium concentration in the anoxic/hypoxic zone, likely due to inhibition of methane oxidation by ammonium. N2O flux was not significantly correlated to any wastewater parameter. I estimated that advanced N-removal OWTS contribute approximately 347 g CO2 equivalents capita-1 day-1, comparable to emissions from conventional OWTS.My findings show that advanced N-removal OWTS in Rhode Island vary in their compliance with the state’s standard for final effluent TN, in the structure and composition of their N-cycling microbial communities, and in their contribution of GHGs to the atmosphere. Continued monitoring of effluent TN from these systems could be easily achieved using rapid tests such as a field photometer, which we found to be a reliable and cost-effective predictor of effluent TN concentrations.

The relationship between school and independent educational evaluations: Issues in identification and eligibility for students with learning disabilities

Lynch, Marie A University of Rhode Island 2005 해외박사(DDOD)

There has been a significant rise in the number of students identified with learning disabilities, and consequently determined eligible to receive special education services since 1980. Some have argued that there has been an under- and over-identification of children with learning disabilities, and that the criteria in which to judge whether a learning disability exists is particularly faulty. This investigation examined the relationship between 50 school-based and independent educational evaluations (IEEs) regarding the identification of children with learning disabilities. The reason for referral, assessment processes used, and the overall criteria employed in these evaluations were reviewed using mixed methodological approaches. The level of agreement was also studied between school and agency evaluations. Unsatisfactory agreement was found when comparing learning disabilities identification specifically. Results, however, indicate satisfactory agreement between evaluations when they consider a broader spectrum of disability categories. Paired t-tests indicate that the independent agency employed almost twice as many informal and formal measures as schools did. A smaller sample was further analyzed using content analyses noting particular issues with report specificity and quality. The lack of information about school team-based decision was cited as a limitation. Overall access to IEEs, the need for definitive LD identification criteria, and the need for more collaboration among evaluators to enhance student achievement and family understanding of need were noted as implications.

Induction of embryonic diapause in the calanoid copepod Acartia hudsonica

Avery, David Edward University of Rhode Island 2000 해외박사(DDOD)

The copepod <italic>Acartia hudsonica</italic> grows and reproduces in Narragansett Bay in winter and spring, spending summers as dormant eggs. I investigated the change in egg types from immediately-hatching eggs to dormant eggs. Temperature and length of day were hypothesized to act as the cues inducing this population to produce dormant eggs, and the variation in the dormant-egg responses of individual females was quantified. <italic> A. hudsonica</italic> produced some dormant eggs early in the spring, but most of the switch to dormant eggs occurred in June. Experiments showed that temperatures above about 16°C increased the proportion of dormant eggs produced whereas increased length of day did not. In several experiments between 42% and 85% of the variance in the fraction of dormant eggs produced was attributed to variance among individuals. In estuaries in the northern part of its range, <italic>A. hudsonica </italic> populations are present year-round and may not express diapause. This difference may be genetic or phenotypic. Using a full-sib rearing design and analysis of variance, I assessed the relative importance of these two sources of variation in two populations, northern and southern. Both populations showed phenotypic plasticity in fraction of dormant eggs produced. Further, both populations showed significant sibship-environment interactions. Both populations also revealed a significant amount of genetic variation in the fraction of dormant eggs produced. It has been hypothesized that a storage bank of viable embryos in diapause can act to maintain genetic variation in a population by harboring genotypes that were successful in the past. If so, we may be able to detect changes in gene frequencies that correspond to diapause induction or termination. I hypothesized that allozyme allele frequencies would reflect changes in the genetic variability of two copepod populations in relation to the induction of seasonal diapause or the seasonal emergence of nauplii from eggs in diapause. <italic> Acartia tonsa</italic> and <italic>A. hudsonica</italic> had distinct patterns of enzyme migration at common loci. Further, <italic>A. tonsa</italic> showed significant changes in allele frequencies at all loci examined, while <italic> A. hudsonica</italic> showed changes at <italic>Mpi</italic> only. However, there were no systematic temporal or allelic patterns to the allele frequency changes.

The effect of solar ultraviolet radiation on marine planktonic ciliate survival and the penetration of ultraviolet irradiance on Georges Bank

Martin-Webb, Elena Berneita University of Rhode Island 1999 해외박사(DDOD)

This study is the first to examine the penetration of UV radiation on Georges Bank, investigate the effect of both ultraviolet-B (UVB: 280–320 nm) and ultraviolet-A (UVA: 280–320 nm) on the survival of marine planktonic ciliates, and compare results between estuarine and off-shore populations. Planktonic ciliates play an important functional role in marine and freshwater ecosystems as grazers, nutrient regenerators, and a link between the microbial food-web and higher trophic levels. Global increases in UVB due to stratospheric ozone depletion may impact their survival. Natural assemblages of microplankton on Georges Bank (Spring 1995, 1997) and the Pettaquamscutt Estuary (Summer, 1996) were exposed to ambient solar irradiance with and without UVB and with and without UV (280–380 nm) for two days. UVB (305 nm, 320 nm) and UVA (340 nm, 380 nm) exposure was measured. Water column UV irradiance on Georges Bank and the Pettaquamscutt Estuary was also measured. Wavelength specific diffuse attenuation coefficients (K_dλ) were calculated for 305, nm, 320 nm, 340 nm, 380 nm, and PAR. Ciliate abundance and chlorophyll concentration decreased in the presence of UVB and UVA. The greatest losses occurred due to UVB in April on Georges Bank, with a 657o decrease in mean ciliate abundance and a 52% decrease in mean chlorophyll. UVA caused decreases as great as 36% in ciliate abundance and a 32% in chlorophyll. A dose-response threshold appeared to occur between 600 and 800 Joules/m<super>2</super> of 305 nm UVB. Results suggest that the effect of UVB on ciliate survival may be indirect as well as direct. K_d305 averaged 1.04 m<super>−1</super> (SD, ±0.14 m<super>−1</super>) on Georges Bank and varied little over space or time. UV attenuation was significantly higher on the Crest region compared to the Southern Flank of Georges Bank, possibly due to phytoplankton-derived DOM. Penetration of UVB relative to mixed depth suggests that ciliates may be impacted by environmental UV on Georges Bank. K_d305 in the Pettaquamscutt Estuary (12.59 m<super>−1</super>) was an order of magnitude greater than on Georges Bank, indicating that near-shore microplankton are exposed to less environmental UV than off-shore communities.

Experiences of White Women Graduate Students in a Diversity and Inclusion Badge Program at a Predominantly White Institution in a Time of Whitestream Racial Reckoning

Argus, Stefanie University of Rhode Island ProQuest Dissertations 2023 해외박사(DDOD)

The purpose of this study was to explore how white women engaged with interrogating whiteness, race, and racism after completing a multi-session diversity program designed for graduate students. This qualitative research project tends to the following research question: What are the lived experiences of white women who complete a diversity and inclusion program for graduate students? For this research project, white women who are graduate students participated in-depth, semi-structured interviews. Using critical whiteness theory, a feminist research framework, and Interpretive Phenomenological Analysis, this study identified commonalities in experiences among participants (Creswell & Poth, 2018; van Manen, 2014). As is common in phenomenology and feminist research, participant narratives illustrated the parts constituting the whole picture of the phenomenon. The five elements describing the essence of the white women graduate students’ experiences in the diversity and inclusion program were: motivation, participation, racial literacy, agreement, and reflection. Each of these superordinate themes had component subthemes. Research results were represented in prose and also in the form of two composite poems. Finally, I present study limitations and synthesize recommendations on how institutions of higher learning can intentionally structure (un)learning spaces for white students to further their anti-racism work.

Nucleic acids as indicators of growth rates and nutritional condition of Calanus finmarchicus (Copepoda: Calanoida)

Wagner, Melissa M University of Rhode Island 2000 해외박사(DDOD)

Measuring growth rates of zooplankton is essential to studies of secondary production of pelagic food webs. Ribonucleic acid (RNA) content offers a simple way to estimate growth rates of natural populations of zooplankton without incubating animals or repeatedly sampling cohorts. I investigated the relationship of RNA concentration of the copepod <italic>Calanus finmarchicus</italic> to food availability, temperature, and growth rates and developed several models for estimating growth rates from RNA. Growth rates were measured in terms of carbon, nitrogen, protein, and DNA content. RNA:DNA ratios of stages N6-adult were affected by food concentration and were inversely related to temperature. RNA:DNA ratios increased with stage in all food and temperature treatments. To account for the effects of stage and temperature on RNA:DNA and its relation to growth, I developed the Relative RNA:DNA Index (RRD), which was strongly related to relative protein and carbon growth rates (r<super> 2</super> = 0.70). Growth rates were a direct function of RNA:protein and the interaction Temperature × RNA:protein (r<super>2</super> = 0.63–0.83). Both the RRD and the RNA:protein ratio are useful indices of growth for <italic> C. finmarchicus</italic>. The RRD method requires less laboratory work but more extensive data manipulation. I used the Relative RNA:DNA Index (RRD) to evaluate the nutritional status of natural populations of <italic>C. finmarchicus </italic> in relation to growth rates, egg production rates, and phytoplankton biomass (chl <italic>a</italic>). In the Georges Bank region of the NW Atlantic Ocean, during winter–spring 1995 and spring 1997, RRD was related to rates of growth and egg production. For stages C1–C5, high RRD was associated with higher relative growth rates (carbon and nitrogen, r<super>2</super> = 0.13–0.19, <italic>P</italic> < 0.05). RRD of adult females was strongly related to egg production rates (eggs female<super>−1</super> day<super>−1</super>, r<super>2</super> = 0.70). RRD was hyperbolically related to chl <italic>a</italic> during stages N6–C4, but not related during C5 and C6. Phytoplankton biomass may limit the growth of the younger stages, which experience their highest growth rates during the spring diatom bloom, whereas the late juvenile and adult stages are less dependent on phytoplankton concentration and can maintain high growth rates in some areas until as late as mid-June.

Mechanisms, ecology, and toxicology of zooplankton feeding processes in the presence of harmful algae (Alexandrium spp.)

Teegarden, Gregory Joseph University of Rhode Island 1999 해외박사(DDOD)

The role of grazers in the population dynamics of toxic <italic>Alexandrium spp</italic>., and specific mechanisms of feeding responses of zooplankton to toxic prey, have not been well studied. I had three main objectives in this study: to determine whether copepods could recognize and selectively avoid toxic <italic>Alexandrium</italic> spp. prey; to assess whether selective grazing in natural field bloom conditions could affect <italic>Alexandrium </italic> spp. bloom dynamics; to quantify toxin uptake, retention, and detoxification in copepods that fed upon <italic>Alexandrium</italic> spp. dinoflagellates. Experiments with fluorescently labeled toxic and non-toxic strains of <italic> Alexandrium</italic> spp. demonstrated that copepods could distinguish cell types on the basis of toxin content. Feeding trials with mixtures of <italic> Alexandrium</italic> spp. and non-toxic alternate dinoflagellate species demonstrated that non-toxic <italic>Alexandrium</italic> spp. were selectively ingested, and toxic <italic>Alexandrium</italic> spp. were selectively avoided. Experiments were conducted with field collected copepods and water samples containing natural concentrations of toxic <italic>Alexandrium fundyense</italic>. Results demonstrated that at the low levels of <italic>Alexandrium</italic> spp. abundance typical of the southwestern Gulf of Maine (∼1000 cells liter<super>−1</super>), toxic cells were neither selectively avoided nor ingested, but were consumed at rates comparable to those of ambient phytoplankton. The low density of toxic cells, and the fact that toxicity is not a perfect defense against grazers, probably contributed to the observed feeding behavior. Thus, in the southwestern Gulf of Maine, blooms of toxic <italic>Alexandrium </italic> spp. may experience significant grazing pressure from zooplankton. When copepods fed on toxic <italic>Alexandrium</italic> spp., toxins were accumulated in the tissues. A minor fraction of the calculated ingested toxin was retained in tissues or recovered in fecal pellets (≤5% each). The remaining toxin (∼90%) was lost to the environment, and literature evidence suggests that regurgitation and sloppy feeding contributed to this loss. The presence of alternate non-toxic prey did not affect retention efficiency. Toxin accumulation occurred in two phases; the first (exponential) phase corresponded closely to models of gut filling, while the second (linear) phase suggested toxin incorporation into tissues. Detoxification was rapid in most species of copepod tested.