Donald J Snodgrass

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Recent documents in Master's Theses
  1. Elevated surface temperatures exacerbate the threat of hypoxia within coastal ecosystems. These two primary stressors likely interact as they elicit opposing physiological responses from marine organisms. Metabolic depression is typically associated with hypoxia, while metabolic rates increase with temperature. Moreover, physiological effects of combined stressors may not be additive. In light of increasing pressures from hypoxia, elevated ocean temperatures, and other stressors within coastal regions, studies need to examine effects of multiple stressors on physiology of coastal organisms.

    Mass-specific aerobic respiration (VO2) was characterized as a proxy for metabolic cost of Streblospio gynobranchiata, at combined levels of dissolved oxygen and temperature relative to body size. Also, changes in VO2 during acclimation to hypoxia and respiratory recovery following hypoxia exposure were examined. Overall, oxyregulatory abilities were maintained with decreasing dissolved oxygen levels and increasing temperatures except at the highest temperature treatment, indicating the critical temperature was reached within the treatment range. Over a 12 hour period of hypoxia exposure, this species showed an initial acclimation period, followed by a decreased VO2for the remainder of the exposure. After returning to aerated conditions following acclimation to hypoxia, VO2 appeared to increase and decrease in two cycles over a 12 hour period, possibly reflecting energy cycling in terms of ATP usage. VO2peaked at 10 hours, overshooting reference normoxia readings, perhaps indicating an oxygen debt. Streblospio gynobranchiata exhibited a high tolerance to these combined stressors, however, further challenges by decreasing oxygen and increasing temperatures may surpass this species’ ability to meet energy demands.

  2. In her lifetime, Lois Lenski wrote, illustrated, and otherwise contributed to more than one hundred books for children and preteens. This study focuses on Lenski’s regional books for preteens, novels that Lenski claimed were written from real life. Using interpretive narrative analysis, this study evaluates two of Lenski’s regional novels: Strawberry Girl (1945), the 1946 Newbery award-winner and second installment in the American Regional series, and High-Rise Secret (1966), the eleventh installment in the Roundabout America series, focusing specifically on Lenski’s creative process. The analysis of Lenski’s works was contextualized using literature focusing on the concepts of character representation, authority, power, and agency. As such, this study also addresses children’s books as cultural artifacts alongside issues of socialization and identity creation. Historically, the focus of the period in which Lenski was writing her regional novels is on the creation of a national unity and identity following such events as World War II. However, this national identity is inherently biased in favor of the ethnically White considering its development prior to the period of social change inspired by the Civil Rights movement. While the study found that there was little to no difference between character and environment representation when comparing the real-life situations and the novels, the narrative structure, content construction, and predominance of ethnically White characters demonstrate that both the books and their author were products of their time.

  3. This research examines the duality of the roles of American women during World War II. The research draws upon oral histories, newspaper accounts and advertisements, music and films of the time, letters and family scrapbooks, and primary and secondary sources. Most prior research focuses on either women in the workforce or women in the home. This research synthesizes all aspects of the lives of women as they navigated the hostile terrain of the male workforce and continued to perform the duties assigned to them by society. This research highlights the multiple roles that women successfully executed as they cared for their families and their country.

  4. Red Drum, Sciaenops ocellatus, are highly sought after by sport fishermen in Mississippi coastal waters. In 2016, Mississippi anglers made over 180,000 fishing trips targeting Red Drum, making it the second most targeted marine species. The current Fishery Management Plan of the Gulf of Mexico Fishery Management Council, prohibits harvest of Red Drum in federal waters. Monitoring of the stock in Mississippi state waters occurs at sites that are almost exclusively estuarine, using gear types selective for juvenile fish. Additional samples come from the for-hire-industry that typically targets larger Red Drum. This project’s goal was to target age three to five-year-old Red Drum to investigate any bias in some precautionary reference point estimates potentially introduced by relatively small numbers of samples in that age range. A sensitivity analysis was conducted to determine if estimates of Spawning Stock Biomass Per Recruit (SSBPR) and Escapement Rate (ER) were impacted by the addition of length-at-age data for Red Drum collected by additional methods. Estimates of SSBPR and ER made with model parameters determined from previously collected data were compared to these estimates that include the additional data. I found that the mean SSBPR estimates were significantly lower (p < 0.05) prior to the inclusion of the additional data, while the ER estimates from the existing data were significantly greater (p < 0.05) than the new estimates. These findings attest to the value of resampling techniques and sensitivity analysis when choosing appropriate precautionary reference points and investigating the integrity of data collection methods.

  5. Overweight and obesity during adolescence is a primary public health concern as these conditions are associated with several chronic health conditions (cardiovascular disease, Type II Diabetes, etc.) that can affect individuals into adulthood. The purpose of this study was two-fold: 1) to examine the prevalence of overweight and obesity among adolescents with chronic health conditions; and 2) To examine the odds of physical activity and sedentary behaviors in adolescents with chronic health conditions, viewing whether the presence of chronic health conditions impact PA and sedentary behaviors.

    Analyses included 28,778 adolescents aged 10-17 from the 2011-12 National Survey of Children’s Heath. Adolescents were grouped into one of nine different groups based on body mass index classification (normal weight, overweight, obese) and the presence of chronic health conditions (no chronic health conditions, one chronic health condition, or two or more chronic health conditions). Outcomes included the prevalence of overweight and obesity among chronic health conditions group, as well as regular physical activity, sports participation, club participation, television viewing time, and computer usage. Approximately 15% of adolescents with no secondary chronic health conditions were classified as overweight, and 13% were classified as obese. Of those with one secondary chronic health condition, 17% overweight, and 16.5% were classified as obese. For adolescents with two or more secondary chronic health conditions, 17.9% were classified as overweight, and 22.6% were classified as obese. Adolescents classified as overweight with two or more chronic health conditions were 26% less likely to engage in regular physical activity (p=0.015), 47% less likely to have participated in a sport within the past 12 months (ppp

    

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