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[APD] Algae or macrophyte dominated, RE: Roger's post

> Message: 5
> Date: Sun, 8 Feb 2004 20:36:47 -0700
> From: Roger Miller <roger at spinn_net>
> Subject: [APD] algae population dynamics
> To: aquatic-plants at actwin_com

Roger et al, I would suggest that you look at a paper by
Bachmann, Canfield, Hoyer et al, "Relations between Trophic
State Indicators and Plant Biomass in Florida Lakes,
Hydrobiologia 470:219-234, 2002". 

The polymitic nature along with the wide variation in both
macrophyte, algal domination, and nutrients levels in Florida
lake(Very high PO4 to almost absent PO4 etc), gives a good
representation at the variabilty in lakes that are more similar
to our plant tanks than many other studies.

Basically they used large numbers of lakes, 300+ lakes which
gave them highly siginificant P values, but..................low
R^2 values(scatter all over).

So they dismissed much of the significance as useful for
predicting plant biomass in terms of trophic status.

A few things came out of this paper, what NOT to look for and

If you include the PO4/Nitrogen included in the plant's biomass
into your measurements of Total PO4/N per m^3 etc, instead of
simply measuring the water column without the plants, then the
relationship is teased apart.
See fig 8.

The data seems to support the notion of alternate stable states
but is a poor predictor in lakes in general.

I made some comments to several people, include a couple of the
authors. I think more research is needed to understand the
dynamics involved, particularly in NH4/NO3 dfferences in each
lake. They seemed excited about the ideas but I went a few step
beyond where they were at this point in time. It'll take a fair
amount of research to show this, but.......I believe this might
tease apart the predictions making the understanding of
alternate stable state theory more predictive.  

Also the substrate soil pore water nutrient concentrations and
SRP would be useful.

Determining the NH4 is tough for the same reason it is when
figuring out how much our tanks are actually getting in this
form.Labeling with N15 will hopefully get at some of these
questions more thoroughly with algae/macrophytes. This is one
reason why I'm using the N15 reseach, it has it's failings but
hopefully will be good enough to tell what is going on between
the two groups. 

So while planted tanks might seem so-so with science, the
observations made can contibute greatly to large scale theories
in Limnology and Aquatic Biology in undertsanding these
"alternate stable states".

We know much of the notions about PO4 concentrations in lakes
are NOT useful in determining whether or not a lake is going to
be algal or macrophyte dominated. There's a lot of variation
between lakes, each lake needs considered individually. Making
broad generalization by limnologist in the past about lakes
perhaps supported myths about PO4 in planted tanks as well.

Hope this helps,

Tom Barr



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