Are there, for example, guilds of sea plants and fish that naturally grow well together and offer each other cumulative benefits? Do seascapes experience succession is the same way that dry land forests do? Are there distinct layers? I know that some people are using 3D vertical systems incorporating seaweeds, fish and shellfish, but does this also naturally occur in nature?

Marine Biologist/Mariculturist/Microbial Ecologist/Bioorganic chemist here:

It absolutely wouldn't let me comment on the link in a previous post. Here it is: http://www.cbsnews.com/stories/2006/11/02/health/webmd/main2147223.shtml

So here is some good news:

www.nmfs.noaa.gov/stories/2013/05/05_02_13status_of_stocks_2012.html