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Re: peat or soil as DIC (CO2) substitute

Steve Pushak wrote, July 7:

>.....I have some questions:
>     Are the products of the biogenic decalcification (or the agents which
>     are responsible for that chemical acitivity) actually liberating CO2
>     from the organic acids or organic materials from the peat?

No, I don't think so.  Biogenic decalcification is the process of taking up
the bicarbonate ion (HCO3-) and removing CO2, leaving behind the hydorxide
ion, OH-.  In strong light, plants with this capability can raise up the pH
to between 10 and 11. When calcium bicarbonate is present, calcium
carbonate is precipitated on the leaves of the plants.   Not all aquatic
plants can do this.

>     Can aquatic plants meet carbon or CO2 requirements from peat?

I would think that peat decomposes too slowly to release enough CO2 to
support very much growth.  The fish, snails, etc. living on the food put in
probably are the major source.  When the pH gets high, absorbtion of CO2
from the atmosphere through the water surface would also provide some CO2.
Plants like Eriocaulon septangulare (spelling?) and Lobelia dortmania,
which grow in very soft water lakes get the bulk of their CO2 from the
substrate via the air channels in their roots.  These are small, slow
growing plants with large root systems and they are not, to my knowledge
used as aquarium plants.  Probably all rooted aquatic plants get some CO2
via their roots, but how rapid a growth this source will support is an
unanswered question.

Back in March Roger Miller wrote that he had some crypts doing quite well
in a sunlit tank with Vallisneria, Ceratophyllum and Elodea and the pH over
9.  In this same tank, Hygrophila polysperma died.  This was a very
significant post for me, because I always assumed that Crypts were high CO2
plants. Possibly they were getting a lot of CO2 via their roots.  Maybe
they can compete successfully for CO2 in the water with Elodea et. al.
Definitely they have some arrows in their quiver that I never suspected.

Paul Krombholz                  Tougaloo College, Tougaloo, MS  39174, in
cooler Jackson, Mississippi.