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Fortunately, I think Roger Miller and I have just about exhausted our
knowledge of the topic we have been discussing. Just a couple of additional
points and my head will be empty for sure! :-)

Roger:  "That fact [of Leibniz Law] is of rather trivial value because
excess nutrients aren't usually a problem." And also, "Um, if the plants
aren't growing well then probably nutrient excess isn't the problem."  So if
it is patently obvious that NOTHING IS MISSING (yesterday's note) and excess
nutrients are usually not a problem, what on earth are we talking about? Are
the conditions always "optimum" (uh-oh) and we either have algae or we
don't!  You're leading me by the nose in tautological circles. And it must
be Groundhog's Day! :-)

Roger:  "Some people have reported success with [limiting nutrients other
than nitrogen], and other people have not.  Where it does work the reduction
in algae growth is thought to be a secondary effect of causing some other
nutrient to become limiting, plus the tertiary effect of competition.  It
isn't a direct effect of adding nitrate."  Of course it's the direct affect
of adding nitrate.  No other variables are changed.  Nitrate is added and
the algae declines.  Let the nitrate drop to zero and stay there for a week
and algae increases, dramatically.  How much more direct could it be?  As to
why that happens, I suspect we don't know.  I have no idea what you mean by
secondary and tertiary effects.  If you know what is going on biologically,
please tell us.

Roger: "Actually, if [algae doesn't increase in growth when nitrogen is
added], then nitrogen wasn't growth limiting to start with."  I agree with
that; but why does the algae decline when we add nitrogen?

Roger: "With* the simplifications of Leibnitz' rule and *if* nutrients are
growth-limiting, and *if* the growth rate of algae is high enough to become
a nuisance then it's because the *limiting* nutrient -- not any excess
nutrient-is too readily available."  Sorry to be dense, but say what!  The
limiting nutrient is too readily available, but no nutrient is in excess!!!
I don't have a clue what you're trying to say here.

Regards, Steve Dixon