Dissolved inorganic carbon utilization in relation to calcite production in Emiliania huxleyi (Lohmann) Kamptner

Abstract

SUMMARYThe relationship between caleite production and dissolved inorganic carbon (DIC) utilization was investigated using high-and low-calcifying strains of Emiliania huxleyi aerated with either air (0-03 % v/v CO^) or COj-free air. With cultures grown on air, calcite production was eight-fold greater in the high-calcifying eulture, but growth rates for high-and low-calcifying cultures were similar. Growth and caleite production were accompanied by a concomitant decrease in DIC and free CO^ in the high-calcifying culture, showing that HCO3" provides inorganic carbon for calcite synthesis. In low-calcifying cultures DIC and free CO.^ were relatively constant, confirming that cells acquire inorganic carbon mainly by the diffusive entry of free CO,.When cultures were aerated with CO^-free air the free CO^ concentration was below tbe /^^^[COJ for high-and low-calcifying cells and the low-calcifying cells were unable to grow. Growth of high-calcifying cells was observed, and the calcite yield was little changed from cultures gassed with air (003 °o v/v CO^). At tbese minimal COj eoncentrations HCO3" may provide inorganic carbon for calcite synthesis and CO^ for photosynthesis, allowing growth to oeeur. Calcite synthesis by E. huxleyi decreases DIC and carbonate alkalinity in cultures not in equilibrium with the gas phase.

Calcification rate and temperature effects on Sr partitioning in coccoliths of multiple species of coccolithophorids in culture

“…However, ''instantaneous'' calcification rate determinations (via 14 C incorporation) and determinations of integrated calcite production in previous culture experiments with E. huxleyi are consistent and suggest rather continuous calcite production during the photoperiod (e.g. Nimer and Merrett, 1992;Dong et al, 1993).…”

Constraints on the vital effect in coccolithophore and dinoflagellate calcite by oxygen isotopic modification of seawater

“…Indeed, the δ 18 O offset seen for G. oceanica in this study is +1.27 ‰ (± 0.01 ‰) from equilibrium whereas Dudley et al (1986) and Ziveri et al (2003) obtained values between +2.4 and +2.9 ‰, respectively. It remains difficult to explain the "heavy group" thermodynamically for oxygen isotopes assuming a calcification substrate of HCO 3 -, as suggested by the experiments of Nimer and Merrett (1993) and Sekino and Shiraiwa (1944).…”

“…There have been several studies demonstrating a large CO 2 diffusive supply to E. huxleyi relative to its carbon requirement owing to its small size and high area-to-volume ratio of the cell (Dong et al, 1993;Nimer et al, 1997;Nimer and Merrett, 1996;Bach et al, 2013). CO 2 has the heaviest oxygen isotope composition of all DIC species and water (Usdowski et al, 1991).…”

Blooms of Emiliania huxleyi are sinks of atmospheric carbon dioxide: A field and mesocosm study derived simulation

“…The delay is introduced because calcification continues after photosynthesis becomes nutrient limited. In cultures, this delay was 2 -3 days [Dong et al, 1993;Paasche, 1998]. In the mesocosm study, calcification rates were still 41% of the average rates 4 days after the peaks of E. huxleyi [van der Wal et al, 1994], possibly because nutrients were added daily during this study.…”