TAXONOMIC AFFINITIES OF MARINE COCCOID ULTRAPHYTOPLANKTON: A COMPARISON OF IMMUNOCHEMICAL SURFACE ANTIGEN CROSS-REACTIONS AND HPLC CHLOROPLAST PIGMENT SIGNATURES1

Immunological grouping, determined by affinities of polyclonal antibodies to surface antigens of intact cells, was used to characterize 19 clones of marine coccoid ultraplankton. The resulting cross-reactive antigen groups corresponded to pigment-groups as defined by HPLC analysis of chloroplast pigments (carotenoids and chlorophylls). Because immunological cross reactions are specific at the species level in groups of algae having well defined morphological criteria, we suggest that immunological methods can be used to recognize algae presently indistinguishable by standard morphological criteria, and especially in oceanographic applications involving qualitative cell enumerations of the ultraplankton.