BIOGEOCHEMICAL CYCLES• It is a well known fact that there is only a limitedamount of essential elements that are present on earth.Most people would think, because of that fact, weshould have run out of these essential elements agesago. This would be true if it wasn’t forthe biogeochemical cycles. This “recycles” essentialchemical elements within the earth’s atmosphere. It isable to do this by sending these elements throughbiotic or abiotic (living and non-living) pathways.
• Carbon is a major part of the framework for theoriginal molecules essential to all organisms.Carbon is released into the atmosphere by twomain processes; these can be recognized as theburning of fuel as well a cellular transpiration byproducers and consumers. What removes vastamounts of CO2 from the atmosphere is a processknown as photosynthesis by plants, algae, andcyanobacteria. What has been adding even moresubstantial CO2 into the atmosphere is the burningof fossil fuels which has been connected to globalwarming.
• Phosphorus is a major element within energy storingmolecules (for ATP, Phospholipids, and Nucleicacids). Phosphate is added gradually added to the soilby the weathering of rocks. Some finds its way intothe bodies of water while others are eventually eatenby consumers and travels within the food chain.Decomposition returns Phosphate into the soil. Onlyrelatively small amounts of phosphate are presentwithin the atmosphere because there are nosignificant phosphorous containing gases; it usuallytravels as dust or spray.
• Compared to CO2 and N2 naturally occuring sulfur is "alreadyfixed". Sulfur occurs in nature as sulfate, e.g. gypsum (CaSO4),(FeS2) and elemental sulfur. The sulfate concentration in the oceanis 2.4 g/L. In anearobic waters, sedimentary organisms generatehydrogen sulfide. The atmospher contains SO2 gas (released byvolcanic activity). Sulfate is reduced to organic sulfur compounds(R-SH) by plants, fungi and bacteria. Sulfate reducing bacteriagenerate hydrogen sulfide (H2S) from sulfate and photosyntheticgreen and purple sulfur bacteria as well as some chemolithotrophsoxidize hydrogen sulfide to elemental sulfur. Organic sulfurcompounds such a dimethyl sulfide are released into the ocean byalgae.