title: Thermal source Fourier transform infrared microtomography applied to Arctic sea ice diatoms.
abstract: We have used thermal source Fourier Transform Infrared (FTIR) microtomographic imaging to compare sea ice diatoms growing under different light conditions. A prototype tomography accessory was designed to have sufficient degrees of freedom to align any tilted cylindrical sample relative to the axis of rotation, minimizing the off-axis path traced during rotation. The lightweight device rests on the motorized stage to position the sample in the field-of-view and enable mosaic imaging. Reconstruction routines were tested with simulated and real phantoms, to assess limitations in the Radon back-projection method employed. The distribution and abundance of biochemicals is analysed for targets larger than a single FPA tile. Two and three dimensional (2D and 3D) FTIR spectrochemical images were obtained with a Focal Plane Array (FPA, nominal 1.1 μm pixel edges) for phantoms (polystyrene beads in polyvinyl alcohol matrix) and diatom cells harvested from land fast, first-year ice sites in Resolute Passage (74 43.628'N; 95 33.330'W) and Dease Strait (69° 1.11'N; 105° 21.29'W), Nunavut, Canada. The analysis of relative concentrations of organic matter within the encapsulating silica frustules of diatoms is important for a better understanding of both the physiological state and the individual cellular response to environmental pressures. Analysis of 3D FTIR images of Nitzschia frigida collected from beneath high (17-19 cm) and low (3-7 cm) snow depth revealed higher concentrations of lipids in diatoms collected under low snow cover, uniquely based on spectroscopically determined total 3D cell volume and biochemical content.
authors.affiliation: Department of Chemistry, University of Manitoba, Winnipeg, Canada. Kathleen.Gough@umanitoba.ca.
authors.forename: Catherine
authors.initials: C
authors.lastname: Findlay
authors.forename: Jason
authors.initials: J
authors.lastname: Morrison
authors.forename: C J
authors.initials: CJ
authors.lastname: Mundy
authors.forename: Julia
authors.initials: J
authors.lastname: Sedlmair
authors.forename: Carol J
authors.initials: CJ
authors.lastname: Hirschmugl
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Gough