REGENERATION AND ABNORMALITY IN BENTHIC FORAMINIFER ROSALINA LEEI: IMPLICATIONS IN RECONSTRUCTING PAST SALINITY CHANGES

A laboratory culture experiment has been conducted to assess the response of marginal marine benthic foraminifer Rosalina leei to salinity and associated pH changes. Live specimens of Rosalina leei were subjected to a range (10-35 psu) of salinity. It was observed that hyposaline condition leads to dissolution of the calcareous tests. However, if the hyposaline condition persists only for a short period, then even after considerable dissolution, specimens were able to regenerate the dissolved part of the test. Additionally, in all the specimens subjected to lower than normal salinity, the regenerated chambers were abnormal. The abnormalities included smaller or larger chambers and addition of new chambers in planes different than the normal plane of the tests. The regenerated specimens, however, attained a final size almost equal to that of control specimens that were not subjected to hyposaline conditions. The differential response of R. leei was attributed to decreased seawater pH under hyposaline condition. The findings can help understand the increased abundance of abnormal specimens under ecologically stressed environments.

EXPERIMENT TO DECIPHER THE EFFECT OF HEAVY METAL CADMIUM ON COASTAL BENTHIC FORAMINIFER PARAROTALIA NIPPONICA (ASANO)

ABSTRACT The response of benthic foraminifer Pararotalia nipponica to heavy metal cadmium is observed in laboratory experiment. The results indicate that under a given set of conditions, heavy metal cadmium is deleterious to benthic foraminifera. Gradual increase in cadmium (Cd) concentration mainly affected normal growth and caused morphological abnormalities which were consistent from 4 µg/l to 14 µg/l. The intensity of deformation was severe exhibiting a peculiar change in coiling direction with increase in cadmium concentration. The presence of >50% deformed specimens at the lowest cadmium concentration (2 µg/l) indicates that the threshold of Cd concentration which is detrimental to P. nipponica is <2 µg/l