Chlorophyll

Aged unispecific cultures and environmental samples have been analyzed using HPLC-PDA in order to reveal chlorophyll-a degradation processes. Unispecific aging studies showed that alteration of chlorophyll occurred during senescence, and revealed that chlorophyll-a breakdown differs amongst various groups (i.e. species specificity). Sediment trap and sediment studies reveal that a variety of precursor chlorophyll-a derivatives are present, and that senescence and geochemistry, per se, overlap strongly. Many of the reactions in the Treibs' scheme occur before and during deposition. Intracellular senescence and diagenetic pathways have been examined in this work. Comparison of aged unispecific cultures and environmental samples strongly suggests major in puts from the senescence pathway. The results further supports the concept "pyro" reaction (loss of the carbomethoxy group) fates chlorophyll diagenesis towards true DPEP compounds.

Fresh and aged unispecific samples have been analyzed using IP-RPHPLC and PDA in order to reveal the chlorophylls and carotenoids alterations during senescence and death. Aging studies showed that cyanobacterial chlorophyll- a was destroyed faster than carotenoids in room oxic conditions. The reverse was found for the other eukaryotic species. Species with high chlorophyllase activity produced phytol free chlorophyll derivatives during death. The rate of chlorophyll-a destruction was; room oxic > room anoxic > cold anoxic. Pyropheophorbide-a was often the final product of type-I chlorophyll-a degradation. The conversion from fucoxanthin to fucoxanthinol was observed. Chlorophyll-c was found to be destroyed faster than chlorophyll-a. The quantitative relationship of certain "biomarker" pigments (e.g. fucoxanthin, zeaxanthin) to chlorophyll-a was found not to change significantly during the first 1--2 months senescence-death scenarios. This aids the field of chemotaxonomy in that valid estimations may still be made when phytoplankton populations contain senescent individuals.