ALGAL CHLOROPLASTS IN THE PROTOPLASM OF 3 SPECIES OF BENTHIC FORAMINIFERA - TAXONOMIC AFFINITY, VIABILITY AND PERSISTENCE

The ultrastructure and pigment content of algal chloroplasts (derived from Bacillariophyceae or Chrysophyceae) are described from 3 benthic species of brackish-water foraminiferans. Elphidium williamsoni Haynes contains 4×106 chloroplasts mg-1, whereas the contents of Nonion germanicum (Ehrenberg) and E. excavatum (Terquem) are about 10% of this value. The two former contain chlorophylls a and c and fucoxanthin, but these pigments were not detectable in the latter. E. williamsoni and N. germanicum had a net uptake of14C-HCO3-, proportional to their content of chlorophyll and number of chloroplasts, increasing linearly up to approximately 10 Klux. At light saturation the former assimilates 2.3x10-3 mg C mg-1 h-1 and the latter only about 20% of this value. Dark uptake was insignificant in all cases. Uptake could not be demonstrated in E. excavatum. The photosynthesis effected by these species is trivial in terms of the total benthic carbon fixation effected by the microflora. The chloroplasts survived longer in forminiferans kept in the dark than in light/dark adapted individuals. To keep a steady state population of chloroplasts under light/dark conditions, E. williamsoni must eat at least 65 chloroplasts individual-1 h-1, whereas the minimum consuption rate in N. germanicum is 20. © 1979 Springer-Verlag.