Date: Wed, 23 Jun 1999 20:53:44 -0400 From: "chris" <drosera@CAM.ORG> To: cp@opus.hpl.hp.com Message-Id: <aabcdefg2297$foo@default> Subject: Barley Straw explanation
Chris,
Wow, love your explanation. Don't understand it all, so I hope you
won't mind clarifying a few things for me.
DOC = a mixture of several compounds? PAR = light? of certain
wavelengths? exogenous, heterotrophic, macrophyte = ?
Do floating plants still apply to a tank that gets light from the
side? (on windowsill) Does blackwater extract do the same (or
more/less) as peat or barley straw? You said that I might change
the water frequently, but wouldn't I risk adding more phosphorus (or
other things for that matter) if I do that? Seems to me that if I
leave the water as it is, the phosphorus would get used up. Also,
don't the plants themselves need that phosphorus? Or is that an
element they get from their prey?
Sorry about all these questions. This is quite interesting to me.
If you choose to reply, you can answer in point form to save
yourself some time typing.
Thanks.
Chris F.
P.S. Know any good chemistry books for the not completely stupid on
the subject kind of person like me?
Hi Chris,
When barley straw starts to decompose in water, it releases a
substance called dissolved organic carbon (DOC). One of the
fractions of DOC are humic substances (humic and fulvic acids)
which add the pale yellow colour to the water. Humic substances
do several things, first, they attenuate photosynthetically active
radiation (PAR), which basically reduces the amount of light
available for the algae. Second, they bind to phosphorus and to
exogenous enzymes secreted by algae for that bound phosphorus,
basically starving the algae of food. Finally, when they are
phtodegraded by UV-B radiation, they act as a substrate for
heterotrophic bacteria, which are competitors with algae for
limited P sources. The bacteria outcompete algae for the leftover
P, and reduce algal biomass. There's been at least a few
published reports looking at reduction of algal and macrophyte
biomass in golf course ponds through barley straw additions.
Can it be used for Aldrovanda and Utricularia? Well, I'd say a
tentative yes. However, peat also has DOC in it which is released
into the water (again, that yellowish colour). Since barley straw
may be of unknown origin, and may have been treated with
pesticides, herbicides, and fertilizers, I'd suggest against it.
My advice? Change the water frequently so as to avoid a build up
of algae, or, grow a surface cover of something like Wolffia (sp?)
or another floating plant.
Flexing my brain muscle,
Chris
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