Premium
NO MECHANISTIC DEPENDENCE OF PHOTOSYNTHESIS ON CALCIFICATION IN THE COCCOLITHOPHORID EMILIANIA HUXLEYI (HAPTOPHYTA) 1
Author(s) -
Leonardos Nikos,
Read Betsy,
Thake Brenda,
Young Jeremy R.
Publication year - 2009
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.1529-8817.2009.00726.x
Subject(s) - emiliania huxleyi , photosynthesis , biology , coccolith , calcification , botany , total inorganic carbon , biophysics , carbon dioxide , phytoplankton , ecology , nutrient , chemistry , carbonate , medicine , organic chemistry , pathology
There is still considerable uncertainty about the relationship between calcification and photosynthesis. It has been suggested that since calcification in coccolithophorids is an intracellular process that releases CO 2 , it enhances photosynthesis in a manner analogous to a carbon‐concentrating mechanism (CCM). The ubiquitous, bloom‐forming, and numerically abundant coccolithophorid Emiliania huxleyi (Lohmann) W. W. Hay et H. Mohler was studied in nutrient‐replete, pH and [CO 2 ] controlled, continuous cultures (turbidostats) under a range of [Ca 2+ ] from 0 to 9 mM. We examined the long‐term, fully acclimated photosynthesis‐light responses and analyzed the crystalline structure of the coccoliths using SEM. The E. huxleyi cells completely lost their coccosphere when grown in 0 [Ca 2+ ], while thin, undercalcified and brittle coccoliths were evident at 1 mM [Ca 2+ ]. Coccoliths showed increasing levels of calcification with increasing [Ca 2+ ]. More robust coccoliths were noted, with no discernable differences in coccolith morphology when the cells were grown in either 5 or 9 mM (ambient seawater) [Ca 2+ ]. In contrast to calcification, photosynthesis was not affected by the [Ca 2+ ] in the media. Cells showed no correlation of their light‐dependent O 2 evolution with [Ca 2+ ], and in all [Ca 2+ ]‐containing turbidostats, there were no significant differences in growth rate. The results show unequivocally that as a process, photosynthesis in E. huxleyi is mechanistically independent from calcification.