Showing 421 - 430 of 681 Items
The Relationship between Nitrate Concentration and Phytoplankton Blooms in Harpswell Sound
Date: 2014-08-01
Creator: Sasha Kramer
Access: Open access
- Phytoplankton require certain essential nutrients for growth. The Redfield ratio (Redfield, 1934) dictates an ideal element proportion of 106 carbon: 16 nitrogen: 1 phosphorus in order to maintain balanced phytoplankton growth through photosynthesis (Li et al., 2008). Under typical conditions, the concentration of nutrients present in the water directly controls the attainable phytoplankton yield (i.e. one inorganic nitrogen from nitrate yields one organic nitrogen in cellular form). While plankton that are starved of nutrients tend to die off quickly, plankton that are simply nutrient limited can adjust to constant but low levels of nutrient concentration (Cullen et al., 1992), often by adjusting their Redfield ratio. As an essential nutrient, nitrogen is a limiting factor for phytoplankton growth in the ocean (Dugdale, 1967). In oceanic and coastal ecosystems, dissolved nitrate (NO3-) is the most commonly available form of nitrogen (Zielinski et al., 2011). The formation of nutrients through microbial processes such as denitrification in deep water creates a source of nitrogen in the deep ocean (Arrigo, 2005). Phytoplankton growth is limited by both light and nutrients: therefore, the transport of nitrate into the euphotic zone controls the rate of primary production. In the Gulf of Maine, nitrate concentration varies with depth and season. Water density is determined by temperature and salinity; these qualities in turn control the depth of mixing and stratification, and thus the depth of the nitracline, the depth at which the high-nutrient deep waters are found (Townsend, 1998). An instrument known as the In Situ Ultraviolet Spectrophotometer (ISUS by Satlantic, Inc.) offers the ability to quantify nitrate concentrations based on optical properties. The instrument specifically measures the magnitude of absorption of ultraviolet light by dissolved nitrate molecules in the water. The concentration is determined from the ratio of the measured absorption coefficient to the molar absorption coefficient of nitrate. The ISUS is placed directly into the water at a site of specific interest—it measures the absorption and computes the nitrate concentration at this site every hour. This method of analysis gives superior stability, precision, and accuracy in data compared to a typical water sample analysis in a laboratory setting (Johnson & Coletti, 2002). For the past 4 years, an ISUS sensor has been deployed on the Bowdoin Buoy in Harpswell Sound collecting hourly observations of nitrate concentration concurrent with hourly observations of chlorophyll fluorescence (which can be used as a proxy for phytoplankton biomass). Once per week between May 21, 2014 and June 18, 2014, measurements of the depth distribution of salinity, temperature, density, chlorophyll fluorescence, and dissolved oxygen content were taken at the Bowdoin Buoy. Water samples were collected at five discrete depths each week, and were returned to the lab for analysis of chlorophyll concentration on the Turner fluorometer and nutrient concentration on the SmartChem. These laboratory analyses were used to calibrate and validate the buoy- and boat-based optical observations. The analysis of nitrate observations was performed in two phases. First, the variability in nitrate measured on the buoy since 2007 along with co-located discrete water samples was compared to a published historical dataset in order to place Harpswell Sound in the broader context of the Gulf of Maine. Second, the timeseries buoy observations of nitrate and chlorophyll were analyzed to determine temporal covariability. The historical nutrient and water quality data for the Gulf of Maine gathered by Rebuck et al. 2009 for 1990-2009 (in addition to unpublished data from 2010-2012) provided a broader spatial and temporal range for comparison with data from the Bowdoin Buoy in Harpswell Sound, Maine from 2007-2012. The historical nutrient data for the Gulf of Maine were measured in the lab; the nutrient data for Harpswell Sound was measured by the ISUS. There are relatively few match-ups for validation, but these points did show the correlation between the two methods. However, the similarity of the distribution of measured nitrate from water samples in lab and the in situ temperature and salinity characteristics of the sampled waters were very coherent with those measured by the ISUS, providing some quantitative validation. Future analysis of the ISUS data from summer 2014, in comparison to nutrient data from the water samples taken over the course of this summer, will further justify the validity of the ISUS data. A clear relationship between nitrate concentration and water temperature and nitrate concentration and salinity for both the Gulf of Maine and Harpswell Sound emerged (Figure 1). The highest concentrations of nitrate are found in the saltiest water (between 30-34 psu) and coldest water (between 3 and 12 degrees Celsius). This pattern was observed both generally in the Gulf of Maine and more specifically in Harpswell Sound, indicating that processes observed in Harpswell Sound are connected to broader scale oceanographic processes. These results also indicate that nutrients generated by deep ocean processes are dominant and river sources are negligible, a result that is not found in most areas. For both chlorophyll data and ISUS nitrate data, 2010 proved to be a model year with a clear and thorough timeseries from early February to late November. After analysis, the relationship between nitrate and chlorophyll showed a strong preliminary correlation of chlorophyll concentration (once again, as a proxy for phytoplankton biomass) increasing as nitrate concentration decreases (Figure 2). The low levels of phytoplankton consume the high levels of nitrate and therefore, as the bloom grows, the concentration of nitrate decreases proportionally. The expected dependence of chlorophyll concentration on nitrate concentration becomes incredibly clear through these results, similar to the results presented in Li et al., 2010. The ISUS data from 2007-2012 requires further processing in order to fully explore the relationship between chlorophyll and nitrate concentration on a pertinent timescale to bloom growth dynamics. While it is possible to construct a full time-series from the newly manipulated ISUS dataset after this summer work, it would be important and interesting to further examine the relationship between chlorophyll concentration and nitrate concentration in Harpswell Sound on daily, weekly, seasonal, and yearly timescales. This next step of investigation will require more time for data processing, but the work done this summer to validate the ISUS data and show the correlation between Harpswell Sound and the Gulf of Maine is incredibly promising for future work. Final report of research funded by the Doherty Coastal Studies Research Fellowship.
“How the World Could Be in Spite of the Way That It Is”: Broadway as a Reflection of Contemporary American Sociopolitical Life
Date: 2020-01-01
Creator: Isabel Thomas
Access: Open access
- Drawing on the plays and musicals of the 2018-2019 Broadway season, this thesis examines how theatre responds to the sociocultural, economic, and political conditions of society. Sociologists have largely overlooked theatre’s cultural influence, but Broadway productions act as social reflection by reproducing the conversations and inequalities of their context. Access to Broadway is limited, in various manners, by socioeconomic class, race, gender, ability, and age. As conversations about equity expand and audiences increasingly demand diversified representation, Broadway begins to shed the restraints of its conventions. In many regards, the recent changes fail in meaningfully transforming the Broadway institution. Those who control the stories on Broadway stages—producers, directors, writers—are disproportionately white and men, and the stories themselves predominantly uphold white privilege and heteronormativity. Economic pressures keep Broadway producers focused on high profit and cultural capital, at the expense of artistic and political risk. Broadway has particular affective power, employing the uniquely provocative effect of live theatre for unparalleled numbers of people. This influence is accompanied by responsibility to contribute to society’s progress rather than its stagnation, a responsibility which Broadway falls behind in fulfilling.
Advanced Mammals Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2020-01-01
Creator: Emma Bezilla
Access: Access restricted to the Bowdoin Community
The role of the ROG1 protein in pectin perception Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2014-05-01
Creator: Divya Hoon
Access: Access restricted to the Bowdoin Community
Determination of the Relationship Between Peptoid Catalyst Oligomeric Length and Catalytic Enantioselectivity of Trifluoromethylation of Aldehydes Access to this record is restricted to members of the Bowdoin community. Log in here to view.
- Restriction End Date: 2025-06-01
Date: 2020-01-01
Creator: Katharine Toll
Access: Access restricted to the Bowdoin Community
Role of SR-like RNA-binding protein 1 (Slr1) in hyphal tip localization of She3-transported mRNA in Candida albicans This record is embargoed.
- Embargo End Date: 2025-05-13
Date: 2020-01-01
Creator: Emma Beane
Access: Embargoed
From Left to Right? White Evangelical Politicization, GOP Incorporation, and the Effect of Party Affiliation on Group Opinion Change
Date: 2013-05-01
Creator: Devon B Shapiro
Access: Open access
- While most white evangelicals in America have advocated moral, cultural, and social conservatism since the Founding, the group’s fiscal and social welfare preferences have been more volatile. Early 20th century evangelicals tended to be socially conservative, fiscally liberal, and, to the extent that they were politicized, mostly Democratic partisans. Since that time, not only have white evangelicals abandoned the Democratic Party, but also they have largely become fiscal and social welfare conservatives. I attempt to explain that transformation. I first examine the dynamics of white evangelical politicization and GOP incorporation, providing social and historical context to the political and partisan calculations of white evangelicals since the 1970s. Further, I propose a party affiliation effect that helps to explain white evangelical fiscal and social welfare conservatism. This effect asserts that partisanship penetrates individual conceptions of political issues. In the case of white evangelicals, I argue that the group affiliated with the GOP largely on the basis of socio-moral issues and concerns. Partly as a result of that affiliation, group opinion on fiscal policy began to drift to the right, toward the Republican Party status quo. Consistent with this claim, I provide longitudinal analyses of ANES and GSS data that shed light on the timing of opinion changes. As we would expect, white evangelical opinion on economic issues was closer to Democratic partisans during the 1960s and moved moved toward Republicans during the 1980s-1990s.
Systemic Risk in the Airline Industry: Investigating the Effects of Network Interconnectedness on MES Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2020-01-01
Creator: Angela Goldshteyn
Access: Access restricted to the Bowdoin Community
Human Today, Posthuman Tomorrow in Margaret Atwood's MaddAddam Trilogy
Date: 2020-01-01
Creator: Benjamin Bousquet
Access: Open access
- Human Today, Posthuman Tomorrow explores the relationship between the human and the nonhuman in Margaret Atwood’s MaddAddam trilogy through the lens of posthuman theory. Atwood’s trilogy depicts a dystopian, anthropocentric world that hinges upon an apocalyptic, man-made epidemic known as the Waterless Flood. Through posthuman theory, this thesis looks at ways to reconcile the oppositional and hierarchical relationship between the human and the nonhuman. The thesis is split into three main chapters, each of which engages a different posthuman theory. The first chapter addresses the concept of hybridity as it is elaborated by Rosi Braidotti’s The Posthuman. Next, the thesis turns to Donna Haraway’s “The Companion Species Manifesto” to address the ways human-animal relations in the trilogy are imagined as mutual and non-hierarchical. The last chapter turns to the pigoon/human relationship through Gilles Deleuze and Félix Guattari’s concept of becoming to understand the ways in which humans and pigoons build a new, non-oppositional relationship. In all, this thesis works to understand the stakes of the trilogy through posthumanism to argue that only through a posthuman understanding of the world are we able to erode oppositional differences between humans and nonhumans and create a future inhabitable for all.
Narrative, Identity, and Holocaust Memorialization in the United States
Date: 2020-01-01
Creator: Alexander Noah Kogan
Access: Open access
- Narratives at Holocaust memorials and museums in the United States connect the Holocaust to present-day identities and weave the Holocaust into American history. Holocaust narratives––whether at the universal, national, or local level––draw moral lessons from the past. These narratives and their moral lessons redefine what constitutes the Holocaust and are determined by the needs and sentiments of the present. The sites of remembrance in this thesis at once show the significance of the Holocaust in American identities at both national and local levels, as well as encourage an active remembrance of the past that restructures these identities. The type of active remembrance and its purpose differs at each site, but each encourages a reconsideration of the past to find potentially applicable lessons for the present.