Table I.

Comparison of intracellular and extracellular inorganic carbon concentration of Symbiodinium sp. and A. carterae calculated using silicone oil centrifugation at differing pH values

Species	Culture Conditions	External pH	Ci External	Cint/Cext	Estimated Cint/Cext for Passive Diffusiona	Cint/Cext
						Estimated Cint/Cext
			μm
Symbiodinium sp.	Freshly isolated	8.0	200	0.9 ± 0.3	0.41	2.2 ± 0.7
			400	1.9 ± 0.2	0.41	4.6 ± 0.5
			1,000	1.7 ± 0.2	0.41	4.1 ± 0.5
			2,000	1.3 ± 0.1	0.41	3.2 ± 0.2
	Freshly isolated	7.0	20	11.0 ± 1.0	3.47	3.2 ± 0.3
			40	7.1 ± 1.1	3.47	2.0 ± 0.3
			100	5.1 ± 0.6	3.47	1.5 ± 0.2
			200	8.4 ± 0.3	3.47	2.4 ± 0.1
	1-d-old Cultureb	7.0	20	24.2 ± 5.1	3.47	7.0 ± 1.5
			40	23.0 ± 4.5	3.47	6.6 ± 1.3
			100	16.5 ± 1.4	3.47	4.8 ± 0.4
			200	12.9 ± 1.2	3.47	3.7 ± 0.3
	5-d-old Cultureb	7.0	20	14.4 ± 2.4	3.47	4.1 ± 0.1
			40	11.8 ± 1.7	3.47	3.4 ± 0.5
			100	9.0 ± 0.9	3.47	2.6 ± 0.3
			200	6.8 ± 0.7	3.47	2.0 ± 0.2
A. carterae	Culturedc	7.0	20	7.3 ± 2.6	ND	ND
			40	26.4 ± 7.7	ND	ND
			100	17.4 ± 2.2	ND	ND
			200	20.5 ± 5.8	ND	ND

Assays were conducted in 25 mm BTP and 428 mm NaCl at a photon flux density of 500 μE m⁻²s⁻¹.

^aEstimated C_int/C_ext assuming only passive diffusion of CO₂ into the cell and an intracellular pH of 7.62. 

^bSymbiodinium sp. was isolated from T. gigas and maintained in filtered seawater (0.45 μm). 

^cA. carterae was grown in G media (Loeblich, 1975) and harvested in log phase growth.