Most people think that the air we breathe
comes from plants on land, but actually at least
it comes from seaweed. Just like land plants,
seaweeds convert sunlight, carbon dioxide and
water into oxygen and energy through a process
called photosynthesis. The process is basically
the same on land and in the ocean, except
seaweeds have slightly different strategies for
capturing sunlight. Land plants absorb
sunlight through photosynthetic pigments called
“chlorophyll”. But different kinds of seaweeds
have different pigment cells optimized for
absorbing different wavelengths of light. This is
because as sunlight hits the water and goes
deeper, red light gets absorbed while blue and
green wavelengths reach deeper (this is why the
oceans look blue and green!).
Seaweeds have adapted different ways to take
advantage of these different wavelengths of light.
Different types of species (e.g., green algae,
brown algae and red algae) contain different
pigments that are responsible for creating their
different colors. Like land plants, green algae
primarily use chlorophyll pigments. Chlorophyll
absorb mostly shorter, red wavelengths of light
that have a tough time penetrating deeper
waters. Brown algae have some chlorophyll, but the
main photosynthetic pigment they use is called
“fucoxanthin” and it reflects yellow light. Red
algae have chlorophyll as well, but they also use
bluish “phycocyanin” and reddish
“phycoerythrin”. These pigments absorb
longer, bluish wavelengths of light. These different
types of seaweeds live at different depths so that
they can optimize how much sunlight they
absorb at the wavelength they’re adapted to use.
Once seaweeds absorb sunlight through these
pigments, they undergo photosynthesis. A
byproduct of this reaction is oxygen, which is
released into the atmosphere for us to breathe!
Seaweed gives us oxygen the same way that
green plants on land give us oxygen.r and
other foods, using the energy from light
[photons]. Plants make sugar and other foods from
Carbon Dioxide and Water.
Plants use 6 molecules each of CO2 +
H2O to make 1 molecule of sugar
[C6H12O6] and 6
molecules of water [H2O]. Can you
add up the atoms on each side to see if the
equation is balanced?
Wow - this website says 70% of the oxygen in our
atmosphere comes from plants in the ocean, and
only 28% comes from plants on land:
save the plankton
"Save the Plankton, Breathe Freely - National
Here's a link about seaweed:
"What is seaweed? - NOAA's National Ocean Service"