Date of Award

8-16-2024

Document Type

Open Access Dissertation

Department

Chemistry and Biochemistry

First Advisor

Michael Myrick

Abstract

Phytoplankton are microscopic unicellular organisms, and they are ubiquitous in marine and freshwater environments across the globe. They play a critical role in primary production, carbon fixation, and O2 production through photosynthesis. Phytoplankton comprise an abundant variety of genera and species, and the taxonomic makeup of a community can be an important indicator of environmental health. Phytoplankton are spatially and taxonomically diverse; they change in size and cellular content throughout their lifetime, and they can also alter their pigmentation in response to environmental factors, so it is important to understand the variability in size and pigmentation between individuals of the same species, as well as the variability for a single individual at different points in time. To determine the net impact of phytoplankton on global carbon, both the rate of photosynthesis, which is directly related to the rate at which carbon dioxide is removed from the atmosphere, and the rate of biomass sedimentation, which determine how that carbon is exported to the ocean floor, must be monitored. Therefore, efficient methods of collecting environmental water samples, analyzing single cells with high temporal resolution, and monitoring carbon flux are needed. This work describes the design and construction of novel optical instruments to address these needs. For targeted field sampling of phytoplankton, we developed a lightweight, low-power fluorometer capable of detecting chlorophyll at levels of 02 µg/L at a sampling frequency of 10 Hz that was deployed on a small Uncrewed Aircraft System (sUAS) with an onboard water sampling system. This fluorometer was controlled using an Arduino Nano 33 BLE Sense, which also handled data processing and storage. For laboratory analysis of single cells, we developed a fluidic control system for trapping and repeat analysis of individual cells that was controlled using a Red Pitaya single board computer. For monitoring carbon flux, we developed a scintillation detector for quantifying 234Th and 234Pam flux in the ocean as a proxy for net carbon removal, also based on a Red Pitaya single-board computer, taking advantage of the embedded field programmable gate array (FPGA) and publicly available software to perform pulse height analysis to discriminate weak signals from the solar radiation background.

Rights

© 2024, Zechariah Kitzhaber

Available for download on Saturday, May 31, 2025

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