TABLE 3.

Threshold levels of CO₂ (μatm) for a range of biological responses for phytoplankton separating results of studies on single species from those at a community level. Responses are either negative (red), no effect (gray), or uncertain/no data (blank)

Biological response	Single species	Community
Chlorophyll a	1,500	1,500
Growth rate	No effect	No effect
Gross primary productivity		500
Net primary productivity		Few studies
F v/F m	No effect	Highly variable
rETR	No effect	Highly variable
POC concentration	No effect	1,000
Fatty acid content	High variable
eCA activity	800	800