In seawater, most of the dissolved carbon dioxide is in the form of
the bicarbonate ion, rather than in the form of carbonate ion or
dissolved gas.

I'm trying to estimate the growth rate of a range of algae as a
function of dissolved CO2. Can algal photosynthesis use the HCO3- ion
directly? What about the CO3-- ion?

The basic biology books I've looked up only mention CO2, not the
dissolved ionic species, but it occurred to me that if algae had to
rely on CO2 gas then they'd starve to death.