1. Aquatic Plants and the Environment (SWES, ECOL, WFSc 474/574) Nutrient Cycles in Wetlands Dr. Kevin Fitzsimmons Professor – University of Arizona

2. Carbon Cycle C 6 H 12 O 6 6 H 2 O + 6 CO 2 C 6 H 12 O 6 + 3O 2 sugars and other organics digestion and respiration + 3O 2 Photosynthesis sugars and other organics and oxygen water and carbon dioxide CH 3 CH 2 OCOOH (lactic acid) other acids (humic and tannic) CH 4 + CO x anaerobes, fermentation, and methanogens

3. Carbonate Cycle CO 2 + H 2 O H 2 CO 3 H + + HCO 3 - H + + CO 3 2- carbon dioxide dissolved in water carbonic acid bicarbonate ion carbonate ion

4. Carbonate cycle

5. Calcium, Silica, Carbon cycles

6. Nitrogen cycle Nitrogen is often a limiting element in freshwater aquatic system Adding nitrogen will cause rapid increase in primary productivity Nitrogen in anaerobic sediments - denitrification (reduction to NH 3 or N 2 gas)

7. Nitrogen cycle in aquatic systems

8. Phosphorus cycle Phosphorus and orthophosphate. Organic P decomposes and releases PO4, taken up by algae and plants or adsorbs to clay particles and precipitates. Anaerobic conditions can re-release P to water.

9. Sulphur cycle Organic sulphur, digested to sulphates, then reduced to sulphur dioxide, elemental sulphur or hydrogen sulfide

10. Saturated Soils Bacteria decompose organics, quickly use available DO Anaerobic conditions, anaerobes scavenge O release H + Reducing conditions Redox reactions in sediments / soils Oxidized Form Reduced Form Eh (mV) O2O2 H 2 O (CO 2 )350Aerobic respirationoxidizing conditions NO 3 - N2N2 250Denitrification Mn 4+ Mn 2+ 250 Fe 3+ Fe 2+ 160Fe Reduction Gray (gley) SO 4 2- H2SH2S-150Sulfate Reduction Rotten Eggs CO 2 CH 4 -250Methanogenesisreducing conditions

11. Hydric Soils Wetland Ecosystem Management