![Sample our Bioscience journals, sign in here to start your access, Latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5925/TOC-Subject-Sample-2021-Bioscience.jpg"})
Abstract
High-calcifying cells of Emiliania huxleyi were grown on a synthetic seawater medium and the effect of nitrate (NO- 3) concentration on growth, calcite accumulation, calcification rate and DIC (dissolved inorganic carbon) utilisation determined. The stoichiometry between NO- 3 utilisation and calcite production was 1:6·5 (mol/mol). Calcification and growth were tightly coupled: calcite production ceased when cultures entered the stationary phase due to NO- 3 depletion, but by adding a pulse of NO- 3 growth and calcification were restored. The initial C/N ratio in the medium was important in relation to calcification rate. At 20 µM NO- 3 the total DIC (2 mM) was rapidly depleted, the calcification rate subsequently declining, whereas at 5 and 10 µM NO- 3 rates of calcification were constant at 20 g carbon cell-1 × 1014·h-1 throughout culture growth, excess DIC being present relative to the available NO- 3. Calcite production per unit NO- 3 was similar for isolates of E. huxleyi from neritic, oligotrophic and nitrate-rich waters. In laboratory cultures, where the photon flux density is optimised for growth, the initial NO- 3 concentration is a reliable indicator of final calcite yield.
Keywords: