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bga and toxin production
I'd like to comment about what Paul Krombholz said about BGA produced toxins
in APD # 619. Cyanobacteria can be poisonous to animal life, and cause
death if the exposure is substantial. This is through its elaboration of
various toxins. Four years ago in Brazil there was an epidemic of sickness
and death (26 patients) in a dialysis unit which was directly traced to the
contamination with cyanobacteria of water used to make dialysate. The
patients died of liver failure, and the causative toxin was a microcystin
(which is a cyclic peptide) known to be elaborated by cyanobacteria. The
patients were probably exposed to a large amount of the substance
parenterally (i.e. directly into the veins) which may have accounted for the
particular potency of this exposure. In humans the ingestion of this toxin
causes a variety of lesser disturbances, such as gastroenteritis, dizziness
and fatigue. The cyanobacteria also produce other toxins (e.g. anatoxin a
and nodularins) and have been reported to cause liver injury in animals that
ingest large quantities of contaminated water.
I am not sure whether these toxins are harmful to plant life or other animal
life. BGA certainly does not seem harmful to fish, and in this regard it is
notable that I have yet to find a fish which will eat the organism (probably
because it does not have an appealing taste or smell). If the organism were
ingested by fish in large amounts it very well might have a deleterious
effect.
I suspect the H2O2 is killing the bacteria through direct oxidation rather
than through oxidation of a DOC.
A take home point of the toxin story is that BGA in large amounts can be
harmful to humans and animals, and that care should be taken when siphoning
it, etc.
Rob Sirota
Huntingdon Valley, Pa.