Mechanisms for the uptake of inorganic carbon by two species of symbiont-bearing foraminifera

B. ter Kuile*, J. Erez, E. Padan

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

85 Scopus citations

Abstract

The mechanisms for uptake of inorganic carbon (Ci) for photosynthesis and calcification of a perforate foraminifer, Amphistegina lobifera Larsen, and an imperforate species, Amphisorus hemprichii Ehrenberg, from the Gulf of Eilat, Red Sea were studied in 1986-1987 using 14C tracer techniques. Total Ci uptake of A. lobifera and photosynthetic carbon uptake of A. hemprichii fit the Hill-Whittingham equation that describes the overall rate of enzymatic reactions that are provided with their substrate through a diffusion barrier. This suggests that diffusion is the rate limiting step for total Ci uptake in A. lobifera. Photosynthesis by the isolated symbionts and uptake of CO32- for calcification obey Michaelis-Menten kinetics indicating that enzymatic reactions determine the rate of the separate processes. Both photosynthesis and calcification can be inhibited without affecting each other. Calcification rates in A. lobifera were optimal at Ca levels around normal seawater concentration and were sensitive to inhibitors of respiratory adenosine triphosphate (ATP) generation and Ca-ATP-ase. This indicates that Ca uptake is also active. Calcification rates of A. hemprichii increased linearly as a function of external Ci concentration over the entire experimental range (0 to 4 m M Ci). In contrast, photosynthetic rates showed Hill-Whittingham type kinetics. The dependence of calcification on the CO32- concentration was also linear, suggesting that its diffusion is the rate limiting step for calcification in A. hemprichii. Increasing Ca concentrations yielded higher calcification rates over the entire range measured (0 to 40 m M Ca). Calcification in A. hemprichii was less sensitive to inhibitors of ATP generation than in A. lobifera, suggesting that in A. hemprichii energy supply is less important for this process.

Original languageEnglish
Pages (from-to)241-251
Number of pages11
JournalMarine Biology
Volume103
Issue number2
DOIs
StatePublished - Jun 1989

Fingerprint

Dive into the research topics of 'Mechanisms for the uptake of inorganic carbon by two species of symbiont-bearing foraminifera'. Together they form a unique fingerprint.

Cite this