ANALYSIS OF PHYTOPLANKTON OF THE AUSTRALIAN SECTOR OF THE SOUTHERN-OCEAN - COMPARISONS OF MICROSCOPY AND SIZE FREQUENCY DATA WITH INTERPRETATIONS OF PIGMENT HPLC DATA USING THE CHEMTAX MATRIX FACTORIZATION PROGRAM

A new matrix factorization program 'CHEMTAX' was used to interpret hig h-performance liquid chromatography (HPLC) pigment data from a transec t between Prydz Bay, Antarctica, and Australia during March 1987. The program calculated the abundance of diatoms, dinoflagellates, haptophy tes resembling Emiliania huxleyi, haptophytes resembling Phaeocystis a ntarctica, cyanobacteria, prasinophytes, chlorophytes and cryptophytes along the transect. The results were compared with those of microscop y and particle size analysis. The transect was dominated by small cell s: particle size analysis showed that particles <2 mu m represented 27 to 44% of the total by number while particles 2 to 20 mu m represente d 55 to 68%. Particles >20 mu m never represented more than 3% by numb er but constituted 57 to 93% of the total volume. Microscopic analysis showed that small flagellates were the most abundant cells along the transect, with a 5-fold increase in abundance at 47 degrees S. Numbers of diatoms (most <20 mu m in size) increased markedly south of the Po lar Front, correlating with the concentration of silica. Dinoflagellat e numbers were relatively constant along the transect, although somewh at higher north of 50 degrees S. Those <20 mu m in size were most nume rous and accounted for most of the latitudinal variation. interpretati on of HPLC pigment data using the CHEMTAX program was consistent with microscopical analysis. The computed abundances of diatoms and dinofla gellates correlated more strongly with the numbers of small (<20 mu m) diatoms and dinoflagellates, respectively, than with large ones. Comp uted cyanobacterial abundances correlated well with microscopical obse rvations except for small errors where cyanobacteria were absent, prob ably due to misallocation of zeaxanthin from chlorophytes and prasinop hytes. The program was able to distinguish 2 populations of haptophyte s along the transect, representing Phaeocystis antarctica and coccolit hophorids, even though their pigment compositions were qualitatively ( though not quantitatively) identical. It also indicated the separate d istributions of chlorophytes and prasinoxanthin-containing prasinophyt es, and showed the presence of cryptophytes where none were observed b y microscopy.