The dissertation applies laser thermal lens spectrometry (TLS) to the analysis of pigments in marine samples. This optical analytical technique offers a new approach in the ecophysiological and chemotaxonomical studies of marine phytoplankton through its main charactersictics such as high sensitivity, small sample requirements and low limits of detection (LOD). The dissertation describes in detail a novel TLS method and its application to the on-line monitoring of cell lysis, and the determination of chlorophylls and carotenoids in phytoplankton species following HPLC (High Performance Liquid Chromatography) separation. Six species of phytoplankton and one higher plant were investigated.

The on-line method detects the total amount of released pigments into the media using a specially constructed double dual beam TLS spectrometer. The device was tested on a cultured phytoplankton population with a density in the order of 5*10^8 cells/L, without any pretreatment steps. Lysis of Skeletonema costatum was induced by different concentrations of poly-APS (polymeric 3-octylpyridinium salts) and monitored for 13 hours. Treated cultures responded immediately to a concentrations of poly-APS greater than 0.6 mg/L, while in the cultures, shocked by concentrations of poly-APS less than 0.15 mg/L, there is a substantial increase in the release of pigments after nine hours. The LOD for released pigments in the culture media was from 0.6 to 1.0 ng/mL.

The pigment fingerprints of the phytoplankton species were studied using isocratic HPLC – TLS. Compared to conventional UV-Vis detectors the present technique resulted in an 80 fold decrease in the LOD i.e., 27 pg/mL (27 fg), for diatoxanthin. Majority of pigments shows the dynamic response to variable light conditions. An important finding was the confirmation of the existence of a parallel xanthophyll cycles in diatoms and suggests the presence of more xanthophyll cycles in other phytoplankton groups. Some minor and trace pigments were recognized as potentially taxonomically significant. The capability of TLS to distinguish between the two diatoms suggests that it is possible using TLS to extend chemotaxonomy to the level of order within the same class of phytoplankton.

Improvements in experimental conditions make the gradient HPLC system compatible with TLS detection, and significantly extends the applicability of the TLS detector for determination of phytoplankton pigments. The addition of mixing coils into the HPLC system diminished the effect of incomplete mixing of solvents and the LOD are from 0.28 to 0.36 ng/mL (5.6 – 7.2 pg), which are 1.3 to 28 times lower than the LOD of commercially available HPLC UV-Vis detectors.