Table 2.

Carbon fixation rates for Crocosphaera watsonii grown under one of three treatment conditions at 2 °C increments from 20 to 34 °C.

Treatment condition	Maximum carbon fixation rate (pmol C/cell/h)	Calculated optimum temperature for carbon fixation (°C)	Experimental optimum temperature for carbon fixation (°C)	Calculated thermal niche width (°C)	Experimental thermal niche width (°C)	Correlation factor (R2)	Minimum carbon fixation temperature (°C)	Maximum carbon fixation temperature (°C)
Replete	0.025	28.69	28–30	17.72	20–34 (14)	0.96	20	34a
Iron limited	0.015	30.16	26–34	15.65	22–34 (12)	0.79	22	34a
Phosphorus limited	0.015	28.23	28	17.33	20–32 (12)	0.90	20	32

Maximum fixation rates, calculated optimum temperatures, and calculated thermal niche widths for carbon fixation were derived using Eppley–Norberg curves. Experimental optimum temperatures were determined using one-way ANOVA tests (p < 0.05). The experimental thermal niche width refers to the range of hospitable temperatures observed for C. watsonii during the carbon fixation experiments. Similarly, maximum and minimum survival temperatures refer to the highest and lowest temperatures, respectively, at which carbon fixation was observed. ^aReplete and iron-limited cultures survived 2 and a half weeks with measurable growth, carbon-fixation, and nitrogen-fixation.