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 Proch lorococcus marinus. Here we report the complete separation of chloroph yll a (chl a1) and chl a2 on a reverse-phase high-pressure liquid chro matography system that also achieves good separation of most other che motaxonomically important pigments. Chlorophyll b (chl b1) and chl b2 are partially resolved, and their relative abundances are estimated wi th an on-line spectrophotometric method. Using these methods, we deter mined that chl a2 and chl b2 contributed up to 40 % to total chl a (th e sum of chl a1 and a2) and up to 95 % to total chl b, respectively, i n samples from the subtropical North Atlantic. The results suggest tha t Prochlorococcus represented a significant fraction of the total phyt oplanktonic biomass. A comparison of chl b/a ratios observed in the fi eld and chl b/a ratios measured in cultures of P marinus suggests the presence of 2 strains of this organism in the subtropical North Atlant ic. 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 fl uorometric method would have underestimated total chl a on the average by 8 % with maximum values of 20 %.