OPTICAL MEASUREMENT OF OXYGEN AND TEMPERATURE IN MICROSCALE - STRATEGIES AND BIOLOGICAL APPLICATIONS

Sediments, microbial mats, biofilms and other microbial communities ar e characterized by steep gradients of physical and chemical parameters . Microsensors are powerful tools to measure these parameters with a s ufficient spatial resolution and with a small disturbance of the micro -environment in natural systems. Recently, fiber-optical microsensors have been introduced in the field of aquatic biology as an alternative to existing electrochemical microsensors. Such micro-optodes have alr eady been developed for high-resolution measurement of dissolved oxyge n and for temperature measurements. They are easy to fabricate and sho w an improved long-term and storage stability. An overview is given on the development and characterization of different types of micro-opto des for oxygen and temperature. A luminescence lifetime-based device h as been developed which is portable and enables microsensing both in t he laboratory and under field conditions. Limitations in practical wor k with optical microsensors are demonstrated, and strategies to overco me them briefly discussed. A micro-optode array as well as a method fo r high-resolution oxygen imaging in sediments are presented as two dif ferent ways to investigate the two-dimensional oxygen distribution in heterogeneous living systems. Future applications and developments in micro-optode research will be discussed briefly.