Re: exp design

[Thomas Barr <tcbiii at earthlink_net>]

> So, first, I want to make sure I'm not re-inventing the wheel.  Other than
> hobbyist publications, are there any academic journals which may have
> already published some of the techniques we use?

Plenty of stuff out there on these topics. TAG is about best hobby level
publication floating around.

Journal of FW ecology, Aquatic Botany(I spoke with the editor of this one
today, he asked me about my project), Journal of Phycology, Ecology, Plant
Physiology, the database at the Center for Invasive and Aquatic plants(these
folks have everything published about aquatic plants!) etc.

  (CO2 fert, N/P/K 
> dosing)  Secondly, I was wondering if someone could describe or give some
> references about how to accurately measure plant "health" (dissolved oxygen
> levels to measure photosynthesis perhaps?)

DO is a common measure of production but it doesn't specifically tell you
which plant or algae, just the total O2 produced and you can/will need to
find the O2 consumed(respiration) for gross vs total O2.
This is the common measure for algae productivity. Submersed plants would be
similar. Carbon uptake and O2 evolved is a good measure. There are some
issues but many go with this measurement.
Chl a is another used in aquatic sciences but is not suitable so much for
aquatic plants but I suppose you could find a way to use that one.
Then there are indirect methods. NO3 uptake etc.
And then there are isotopes but that's pricey.


> What analytical lab techniques
> exist to put a number on "plant growth"?

RGR is about the best "gauge". (Relative growth rate). Mooney, Peacery,
Ehleringer, Rundel's book is quite good for lab stuff.
You'll need adapt it to submersed plants but it should work well. There are
some relatively good books out there. FW ecology, limnology etc are good
places to look under.

 Specifically, I am interested in
> watching plant response to various nutrient levels.  For example, I wish to
> investigate NO3/PO4/K levels and generate a response surface.

Different plants will respond differently, and you'll have to do the RGR for
each plant. How do plan to test the nutrient uptake from the substrate for
example? There are a number of ways to approach these questions.

>  I am 
> imagining two tanks, under the same light, substrate, with separate
> filters, 10 6" lengths of my favorite stem plant in each tank.  Other than
> dry weight, are there any other ways to quantify and compare the growth in
> these tanks?

Sacrifice a few stem plants to get a relative correlation between the dried
live weight and the dry weight or leaf area to plant mass etc, some method
that gives a reasonable measure of biomass.
> 
> I am starting graduate school and will be in a position to beg for some
> time on very good equipment (FTIR, AA, Mass Spec/GC, Analytical balances)
> and would really like to do a few good experiments and give something back.

Start digging in the literature then:-)
A stat's class and exp design class is always a good worthwhile class to
take. Figure out a way to answer your question. Will what I'm doing really
allow me me to say something about this question?

 You can change your question to suit what you _can_ answer since often
times you cannot answer the question you really want because it's beyond
your ability/funding/is not possible or or or.....  isolation and lab set
ups without gravel/fish etc might not be realistic either. So then after you
isolate things, then you'll need to go back with an idea of the model from
the lab exercise and see if it matches the real tank. Then try to do the
same thing in nature etc find evidence etc.
Pick a specific question, not a general one. It often helps to imagine what
a graph of your results will look like and write this down.

I'm using 8 tanks for my experiment. It's far more involved and narrows down
more than you think. You have to address many questions to answer
one........ maybe......... if you are lucky.......then you might be able to
say something about the results......
 Then your prof's will pick on you about the project till your blue in the
face tossing cans of spam at your fragile glass like ego repeatedly....try
and predict what they will ask you and be prepared. Leave no stone unturned.
Enjoy.

Regards, 
Tom Barr

> 
> Cheers,
> Jeff Ludwig
> Newark, DE
>