RETENTION OF CHLOROPLASTS AND BATHYMETRIC DISTRIBUTION IN THE SUBLITTORAL FORAMINIFERAN NONIONELLINA-LABRADORICA

The distribution of Nonionellina labradorica was studied with the help of bottom samples collected in the 1920's, 1930's and 1980's from soft bottoms at the Swedish west coast. It was found only below the pycnocline where the water is relatively cold (4-14-degrees-C) and has a salinity of more than 30 parts-per-thousand. It had roughly the same bathymetric distributional pattern in the 1980's as in the 1920's and 1930's. Microscopical and ultrastructural studies showed that its protoplasm contains symbiotic or sequestered chloroplasts down to 300 m depth. Specimens with chloroplasts from 45 m depth were incubated with C-14 in the laboratory and were able to photosynthesize. During the winter, the foraminiferan has a low feeding activity, a reduced chloroplast content, and a slow growth.