Table 3. Specific C and N fixation by Trichodesmium incubated at different times of day (day vs night) and under different pCO₂ levels (ambient vs high pCO₂), measured by LG-SIMS (mean±s.d.).

	pCO2	C-specific C fixation (h−1)	N-specific N fixation (h−1)
Day	Ambient	0.0099±0.0027	0.0028±0.0021 (n=117)
	High	0.0100±0.0033	0.0047±0.0024 (n=135)
Night	Ambient	0.0015±0.0005	0.0004±0.0001 (n=66)
	High	0.0014±0.0006	0.0004±0.0002 (n=72)
Control		0.0014±0.0001	0.0004±0.0001 (n=32)

Abbreviations: C, carbon; LG-SIMS, large geometry secondary ion mass spectrometry; N, nitrogen; pCO₂, partial pressure of carbon dioxide.

Controls are measurements on Trichodesmium cells incubated without stable isotope tracer additions.