4.The Phosphorous,Calcium,and Silica Cycles ©Phosphorous Cycle Organic and inorganic phosphates e Cycles through living organisms,water,and soil Calcium Cycle Reservoirs are rocks and oceans o Marine phototrophic microorganisms use Ca2+to form exoskeleton 9 Microbiology,Shanghai Jiao Tong University9 Microbiology, Shanghai Jiao Tong University 4. The Phosphorous, Calcium, and Silica Cycles Phosphorous Cycle • Organic and inorganic phosphates • Cycles through living organisms, water, and soil Calcium Cycle • Reservoirs are rocks and oceans • Marine phototrophic microorganisms use Ca2+ to form exoskeleton