Filtering by
- All Subjects: Sargasso Sea
- All Subjects: Zooplankton
- Creators: Neuer, Susanne
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The biological carbon pump acts as part of the global carbon cycle through the photosynthetic fixation of inorganic carbon into dissolved and particulate organic carbon by phytoplankton. Previously, the biological carbon pump was attributed to large aggregates and zooplankton fecal pellets since their size and density results in faster sinking rates, efficiently exporting organic carbon to deeper depths in the ocean. However, recent studies have indicated that small cells, known as picoplankton, contribute significantly to the formation of sinking particles. The presence of exopolymeric substances (EPS), among them sticky transparent exopolymeric particles (TEP) and proteinaceous coomassie stainable particles (CSP), serve as influential factors of export flux and aggregation. The presence of heterotrophic bacteria can also affect aggregation and sinking velocity, as seen in previous studies, and is likely attributed to their EPS and TEP production. The staining and visualization of TEP and CSP allow for the qualitative determination of these types of EPS from bacteria isolated from sinking particles collected with particle interceptor traps at various depths in the Sargasso Sea. I study the presence of TEP and CSP in particle-associated bacteria. Cultures of picocyanobacteria, consisting of xenic Synechococcus and axenic Prochlorococcus, were used to establish positive and negative controls for stained isolate analysis. Marinobacter adhaerens served as a tertiary control for an axenic culture that stains positive for TEP. I chose six isolates of bacteria isolated from sinking particles to be stained and visualized to test for the secretion of TEP and CSP. Four of the isolates stained positive for both TEP and CSP, including Pseudoalteromonas sp., Erythrobacter sp., and Marinobacter sp., while one isolate, Micrococcus sp., stained positive only for TEP, and the last isolate, another Marinobacter sp., stained positive for only CSP. These results are important in understanding the role of plankton organisms in the formation of sinking particles.
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The first chapter demonstrates the capability of two strains of Scenedesmus acutus to grow in ultra-high-density (>10 g L-1 dry weight biomass) cultures in flat panel photobioreactors for year-round production in the desert Southwest with record volumetric biomass productivity. The advantages and efficiency of high-density cultivation are discussed. The second chapter focuses on uptake and utilization of the volatile components of wastewater: ammonia and carbon dioxide. Scenedesmus acutus was cultured on wastewater from both municipal and agricultural origin and was shown to perform significantly better on flue gas as compared to commercial grade CO2 and just as well on waste nutrients as the commonly used BG-11 laboratory culture media, all while producing up to 50% lipids of the dry weight biomass suitable for use in biodiesel. The third chapter evaluates the feasibility of using gravity sedimentation for the harvesting of the difficult-to-separate Scenedesmus acutus green algae biomass followed by microfluidization to disrupt the cells. Lipid-extracted biomass was then studied as a fertilizer for plants and shown to have similar performance to a commercially available 4-6-6 fertilizer. Based on the work from these three chapters, a summary of modifications are suggested to help current and future microalgae companies be more competitive in the marketplace with traditional agricultural commodities.
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A literature review demonstrated that municipal sewage sludge produced by wastewater treatment plants around the world contains detectable quantities of microplastics. Application of sewage sludge on land was shown to represent a mechanism for transfer of microplastics from wastewater into terrestrial environments, with some countries reporting as high as 113 ± 57 microplastic particles per gram of dry sludge.
To address the notable shortcoming of inconsistent reporting practices for microplastic pollution, this thesis introduced a novel, online calculator that converts the number of plastic particles into the unambiguous metric of mass, thereby making global studies on microplastic pollution directly comparable.
This thesis concludes with an investigation of a previously unexplored and more personal source of plastic pollution, namely the disposal of single-use contact lenses and an assessment of the magnitude of this emerging source of environmental pollution. Using an online survey aimed at quantifying trends with the disposal of lenses in the US, it was discovered that 20 ± 0.8% of contact lens wearers flushed their used lenses down the drain, amounting to 44,000 ± 1,700 kg y-1 of lens dry mass discharged into US wastewater.
From the results it is concluded that conventional and medical microplastics represent a significant global source of pollution and a long-term threat to ecosystems around the world. Recommendations are provided on how to limit the entry of medical microplastics into the built water environment to limit damage to ecosystems worldwide.