Zapins

Since others might want to read primary literature about aquatic plants, growth rates, deficiencies, and toxicities here are a few good sources of information that I have found and used in the past.

This resource is free (as far as I have seen), it will allow you to download publications. I've used it to read up on metal toxicity and some other plant issues:
http://www.plantphysiol.org/

Using my login ID I logged into www.sciencedirect.com and then selected one of the journals: Aquatic Botany, Aquatic Toxicology, or Plant Physiology and Biochemistry. Then typed in my search criteria like "CO2 assimilation," "iron toxicity," etc.

These three journals have articles written on the toxicity of nutrients like heavy metals, ammonia, CO2, and basically anything else you can think of. The information is specific to aquatic plants and is extremely valuable. You will need a login ID from an institution to access it. Sometimes if you have an old university or college library ID that still works you can navigate to sciencedirect from your university's library page after you log in to your library's site.

Zapins

Here is another seemingly free database where you can search for free scientific papers:

http://onlinelibrary.wiley.com/journ...SN%291469-8137

The above link takes you to the journal called "New Phytologist" which you can search for terms of interest on the right side.

Zapins

Another database with many open access articles. Just use the search bar at the top right:
http://www.intechopen.com/books/crop...crops-a-review

Zapins

This book is fantastic. It has a lot of very technical and interesting information about aquatic plants and nutrients for them. You may be able to download it from the following link.

Title: Aquatic Photosynthesis
Subtitle: (Second Edition)
Edition: STU - Student edition
Author(s): Paul G. Falkowski and John A. Raven
Publisher(s): Princeton University Press (October 2013)
Stable URL: http://www.jstor.org/stable/j.ctt4cgbxs