They feed off carbohydrates both simple and complex. They convert ammonium nitrogen into ammonium nitrate which is the form the plants can use. I still do not know what it is. I would guess the slit from plant material on the bottom of the sea. Perhaps some bromine which is only found in ocean water which is a main component of the tryptophans that inturn produce the growth hormones known as auxins. Though I may be off. Let me check some thing on GorillaGrow.org(anic) Home of Organic Chemistry Homepage

Post thoughts. I am thinking Br produces D vitamins or cytokinins. as the atomic wieght is about 79 to 80.

Auxins are the blue b vitamins and cytokinins are the yellow or d vitamins.

I get the current atomic wieghts from here Chemistry: WebElements Periodic Table