CHLOROPHYLL-A AND CHLOROPHYLL-B AND DIVINYL CHLOROPHYLL-A AND CHLOROPHYLL-B IN THE OPEN SUBTROPICAL NORTH-ATLANTIC OCEAN

Divinyl chlorophyll a (Chl a2) and divinyl chlorophyll b (chl b2) are chemotaxonomic tracers for the marine photooxytrophic procaryote Prochlorococcus marinus. Here we report the complete separation of chlorophyll a (chl a1) and chl a2 on a reverse-phase high-pressure liquid chromatography system that also achieves good separation of most other chemotaxonomically important pigments. Chlorophyll b (chl b1) and chl b2 are partially resolved, and their relative abundances are estimated with an on-line spectrophotometric method. Using these methods, we determined that chl a2 and chl b2 contributed up to 40 % to total chl a (the sum of chl a1 and a2) and up to 95 % to total chl b, respectively, in samples from the subtropical North Atlantic. The results suggest that Prochlorococcus represented a significant fraction of the total phytoplanktonic biomass. A comparison of chl b/a ratios observed in the field and chl b/a ratios measured in cultures of P marinus suggests the presence of 2 strains of this organism in the subtropical North Atlantic. The spectroscopic differences between chl a1 and chl a2 would have led to small underestimates of total chl a in these samples had these been analyzed by spectrophotometric methods. However, the standard fluorometric method would have underestimated total chl a on the average by 8 % with maximum values of 20 %.