Thesis--University of Wisconsin. / Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 164-169). Photocopy of typescript. Ann Arbor, Mich. : University Microfilms, 1972.-21 cm.

Thesis (Ph. D.)--University of California, Santa Barbara, 1987. / Vita. Includes bibliographical references (leaves 155-164).

Tesis--Universidad Autonoma de Baja California, Escuela Superior de Ciencias Marinas, 1975. / Includes bibliographical references (leaves 75-82).

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references (leaves 170-195). Also available in electronic version.

Thesis (Ph.D. (Zoology & Entomology)) - Rhodes University, 2007.

University, Diss., 2003--Kiel.

University, Diss., 2003--Bremen. / Enth. 5 Sonderabdr. aus verschiedenen Zeitschr. und Publ.

No description available.

Monitoring phytoplankton species composition and their abundance are routine tasks in marine ecological research and environmental monitoring. As phytoplankton populations are highly heterogeneous in terms of size, morphology, and most significantly, their abundance can change drastically in a very short time, it is extremely difficult to quantify and monitor them and there are demands on the instrumentation. Conventional optical microscopy and flow cytometry are the main tools to enumerate and identify phytoplankton, but they have a compromise between spatial information and acquisition speed. While imaging flow cytometry has the potential to integrate the benefit of high spatial resolution from optical microscopy and the advantage of high throughput from flow cytometry, two intrinsic blur sources, motion blur and out-of-focus blur, prevent imaging flow cytometers from obtaining high spatial resolution images with high throughput. To address these limitations, in this work, a novel light sheet based fluorescence imaging flow cytometer has been proposed, constructed, and tested for phytoplankton analysis. Both 2D and 3D imaging mode of the light sheet based fluorescence imaging flow cytometer have been investigated. In the 2D imaging mode, the instrument can screen untreated costal water samples at a volumetric throughput up to 1 ml/min. The instrument demonstrated shows a high immunity to motion blur, and all-in-focus fluorescence images are captured with a lateral resolution of 0.75 ± 0.06 µm for a wide size range ~ 1 µm to ~ 200 µm that includes pico-, nano-and microphytoplankton. This is made possible by suppressing the out-of-focus blur using thin light sheet illumination and image deconvolution, and by precluding the motion blur with a unique flow configuration. With these abilities, the instrument demonstrated has high potential as a practical field instrument for monitoring phytoplankton. In the 3D imaging mode, the instrument can scan a large number of phytoplankton cells in a short time with spatial resolution as achieved by light sheet microscopy. The lateral resolution is 0.81 ± 0.07 µm, and axial resolution in terms of FWHM of the axial scattering PSF is 1.42 ± 0.15 µm. The volumetric throughput of the instrument is 0.5 µl/min. This is benefitted from the improvement that 3D images can be acquired without the need of sample immobilization, in contrast to existing 3D imaging approaches, such as confocal fluorescence microscopy. Preliminary results from untreated coastal water samples and cultured samples show promising potentials of the instrument for phytoplankton monitoring and scientific research.

In this thesis, I present a unique temporal study of phytoplankton, nutrient and environmental dynamics that focussed on the transitional period between sea-ice cover conditions and open waters in a coastal inlet of the Canadian Arctic during 2016. I also compared the 2016 experimental data with continuous observations made by the Ocean Networks Canada (ONC) underwater observatory. Surface seawater sampling was conducted in Cambridge Bay with high temporal resolution from June 16 to August 3, to measure phytoplankton carbon and nitrate utilisation, silica production, phytoplankton biomass, phytoplankton taxonomy and dissolved nutrients. Throughout the study period, nitrate concentrations averaged 0.67  0.08 µmol L-1, and chlorophyll a and primary production were low at 0.11  0.005 µg L-1 and 0.25  0.02 µmol C L-1 d-1, respectively. The presence of sea-ice reduced physical mixing, which resulted in low surface nitrate concentrations. Phytoplankton assemblages, production rates and biomass were dominated by small flagellated cells (<5 µm) until late July, yet increases in temperature and nitrate later in the season enabled larger Chaetoceros spp. diatoms to bloom. The Chaetoceros bloom coincided with a peak in silica production (0.429 µmol Si L-1 d-1), which was otherwise low, but variable. The time series was divided into three phases based on changes in environmental conditions, these phases were used to evaluate changes in biological dynamics. Phase I was characterised by sea-ice, low nitrate and increasing phytoplankton biomass and primary production. Phase II was a transitional period, with calm water conditions a drop in phytoplankton biomass, however, an increase in the mean nitrate concentration enabled more consistent carbon fixation. PIII had greater environmental variability driven by mixing events. The mixing of the water column in PIII enabled larger Chaetoceors spp. to become prevalent in the surface waters contributing increasingly to the biomass and carbon utilisation. Overall, the nutrient concentrations, levels of biomass and production rates in Cambridge Bay were more reflective of those from oligotrophic regions. When comparing experimental data with observations made by the ONC observatory, a strong relationship between carbon utilisation and apparent oxygen utilisation became evident. This finding suggests that long-term in situ observations can potentially be used to monitor biological rates in the Arctic. The temporal resolution of this field study adds a seasonal perspective to our understanding of Arctic ecosystems, complements studies with greater spatial and interannual coverage, and can contribute to future numerical modelling of Arctic change. Furthermore, this study provides a first-time comparison between experimentally-measured phytoplankton production and cabled observations in the Arctic. / Graduate / 2019-09-07