Applications of planar oxygen optodes in biological aquatic systems

Abstract

The work presented in this thesis investigates two-dimensional (2D) oxygen distribution and dynamics in biological aquatic systems with the help of recently developed porphyrin-based planar oxygen optodes and the modular luminescence lifetime imaging (MOLLI) system. The general characteristics of the used optodes were determined in experiments described in chapter 5. It is shown that planar optodes cannot easily be used to determine highly accurate oxygen distributions and dynamics, when very high spatial (< 15 µm) and temporal (< 3 s) resolutions are required (chapter 5 and 6). Major problems are the light guidance effect, relatively noisy oxygen data and the slow response time of the optodes. The oxygen data measured with porphyrin-based planar optodes are robust enough to visualise 2D oxygen heterogeneities and dynamics qualitatively in various biological systems. Porphyrin-based oxygen optodes proved to be powerful tools in aquatic systems where qualitative determination and visualisation of the heterogeneity and dynamics of 2D oxygen distributions are the focus of interest. One of the most appreciatory applications for planar optodes are permeable sediments (chapters 2, 3, 4 and 6 ).