Azam agreed, noting that bacteria seem to munch selectively on the exuded polysaccharides, consuming a bit here, a bit there. Most, however, is either ignored or tossed aside, becoming new material in the gel meshwork. Both Azam and Alldredge are quick to caution that these descriptions are tentative. Carbon, of course, is elemental to life on Earth. Disassemble any living creature into its organs, break those organs down into cells and the cells into molecules and you will find chains and rings of carbon atoms.
Carbon is the stuff of which life is made.
The carbon cycle is the circular process by which life traps and uses the sun' s energy. Other organisms eat the plants, then get eaten themselves. Carbon moves through the system, some of it released back into the atmosphere through respiration. Until relatively recently, the carbon cycle was finely balanced, with just the right amounts of the element existing in organic matter, surface rocks, the atmosphere or dissolved in the ocean. Over the last two centuries, however, that equilibrium has become threatened by humans burning prodigious amounts of coal, oil and natural gas, releasing into the atmosphere massive quantities of carbon from fossil fuels.