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Subject:

Re: algae blooms and fish farms

From:

Michael Barreto <[log in to unmask]>

Reply-To:

Michael Barreto <[log in to unmask]>

Date:

Wed, 3 Jul 2002 05:11:31 +0200

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text/plain

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Bruce Burrows wrote:
So you are not interested in the studies of the positive effects of fish
farms on kelp ?

David Menne replied:
I have found that one can usually find SOME data appearing to support any
preconceptions; while the truth is swept under the table.

An example which springs to mind is the improved survival and growth rates
of adult salmon in the presence of around 100 ppb cyanide [Doudoroff].

More examples of benefit, relating to ultratrace levels [generally sub-100
ppb] of normally toxic metals might be found; albeit for other plant and
animal species on :

9.3 The true value of a comprehensive range of trace elements

Think of the astounding results achieved by applying fish metabolytes on
terrestrial phyto-productivity.

Then think again if your preconceived quest for knowledge is not merely
going to conceal it from you [another Janusian Paradigm].

You can always add too much [or too little] of everything; but the right
proportions of fish ploep etc could be very beneficial for phytobenthics.

***************************************************************************

The stimulation of growth by low concentrations of a substance, which at
higher concentrations is toxic, is called hormesis. There are many other
terms used to describe this phenomenon (e.g. paradoxical concentration
effect, biphasic growth). I've found that low concentrations (about 0.03
mg/ml) of macroalgal extracts stimulated fungal growth, but at higher
concentrations (10 mg/ml) growth was inhibited.

The effect has also been seen with other organisms (e.g. bacteria to humans)
with a wide range of toxicants (e.g. radiation to nicotine and ethanol).

Intuitively the effect doesn't make sense and I haven't come across a
satisfactory explanation for it.

What usually happens with concentration/response experiments is that the
results are assumed to be linear at the lower concentrations without testing
this assumption. I would call this "sweeping the truth under the table".

See http://www.BELLEonline.com for more information.

Regards,
Michael Barreto
Botany Dept.
University of Pretoria
Pretoria
South Africa

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