Relation of Calcium Uptake to Photosynthetic Activity as a Factor Controlling Calcification in Marine Algae.

Publisher Website
Google Scholar
Abstract
For the elucidation of relationship between photosynthesis and calcium carbonate deposition in marine algae, the rates of calcium-45 uptake and calification were investigated. The rate of calcium-45 uptake increased in the light by two to five times greater than that in the dark. A remarkable calcification gradient from the marginal part to the basal part was observed in the vegetative frond of Padina japonica. In the sporogenous frond, the uptake rate was greatly reduced even in the light especially at the sporogenous part. The amount of calcium taken up by calcareous algae was from ten to a hundred times larger than that by non- calcareous algae, while no significant difference was observed among the rates of their photosynthesis. In all species of calcareous and non-calcareous algae so far used in this work, the inhibitors of carbonic anhydrase caused a marked depression in the uptake rate even in the light, and the inhibitors of photosynthesis also made a cessation of measurable increase. Among four fractions from the algal fronds in which calcium-45 was incorporated, acid-soluble fraction which consists mainly of calcium carbonate showed higher radioactivity, while such fractions as ethanol soluble and alkali soluble ones contained lesser activities. Moreover, it was found that when the experiments were carried out in the light, the radioactivity incorporation into the acid-soluble fraction became greater as compared with that into the other fractions.