EELGRASS
SURFGRASS
MANGROVES
BROWN ALGAE
DIATOMS
Figure 1. Images showing the broad diversity of diatom silica structures. (a) Bar = 1 µm, (b) bar = 5 µm, (c) bar = 10 µm,
(d) bar = 500 nm, (e) bar = 2 µm, (f) bar = 10 µm, (g) bar = 2 µm, (h) bar = 2 µm, (i) bar = 50 µm, (j) bar = 2 µm, (k) bar = 1
µm, (l) bar = 10 µm. Reprinted from [4] with permission from the American Chemical Society.
DINOFLAGELLATES
REDFIELD RATIO
FORMS OF NITROGEN
N2
NH3
NH4+
NH4NO3
NO2NO3-
Molecular Nitrogen
DiNitrogen
Nitrogen Gas
Atmospheric Nitrogen
Ammonia
Ammonium
Ammonium Nitrogen
Ammonium Nitrate
Nitrite
Nitrate
a, b, When atmospheric CO2 enters the sea surface (a), it undergoes a series of reversible chemical reactions
known as the seawater carbonate buffer system (b), which releases protons (H+) that acidify the sea water. c,
Coccolithophores and other algae assimilate CO2 to produce organic carbon through photosynthesis. d,
Coccolithophores also perform calcification reactions, in which two bicarbonate ions (HCO3−) are converted
into one calcium carbonate (CaCO3) and one CO2 molecule. The CaCO3 is incorporated into coccoliths in the
algal shell. The CO2 from calcification is released, and can either contribute to ocean acidification or degas back
to the atmosphere (e), contributing to global warming. f, Biogenic particles from coccolithophores and other
phytoplankton sink from the ocean surface. The ratio of CaCO3 to organic carbon in this 'rain' of biogenic
particles is a critical parameter in the marine carbon cycle. Coccolithophores produce less calcium carbonate at
higher seawater concentrations of CO2.