1. REDOX: IRON, SULFUR, & SILICA

2. Redox Potential pE = -log free electrons When corrected to pH 7 (H + = OH - ), called E h When E h positive – oxidizing environment When E h negative – reducing environment

3. Redox vs. pH

4. Redox (mv) of common liquids

5. Example of Redox data

6. pH and ORP in Lake Skiennungen

10. Fe & Mn in oligotrophic and eutrophic lakes

11. Iron and Manganese in a Productive Lake

12. Redox: Sulfur and Iron

13. Particulate Fe and Fe (II) through the year

14. Sulfur and Iron in Mud

15. Fe & Mn in Crooked lake (mesotrophic)

16. Fe & Mn in Little Crooked lake (eutrophic)

17. Transport of Fe in a lake

18. Iron Oxidizing Bacteria Gallionella (an iron-oxidizing bacterium) 4Fe (HCO 3 ) 2 + O 2 + 6H 2 O 4Fe (OH) 3 + 4H 2 CO 3 + 4CO 2 + 58 kcal

19. Ferrobacillus iron bacteria 4FeCO 3 + O 2 + 6H 2 O Fe(OH) 3 + 4CO 2

20. Mn cycling relative to O 2

22. REDOX and Sulfur

23. S in oligotrophic and eutrophic lakes

24. SO 4 in a mesotrophic hardwater lake

25. SO 4 budget for Linsley Pond

26. ORP, pH, and Sulfur bacteria

27. Autotrophic Sulfur-Oxidizing Bacteria and Iron Transformations Thiobacillus Some of the reactions that it can mediate FeS 2 + 3½O 2 +H 2 O FeSO 4 + H 2 SO 4 2FeSO 4 + ½O 2 + H 2 SO 4 Fe 2 (SO 4 ) 3 + H 2 O

28. Bacterial Transformations of Sulfur Sulfate-Reducing Bacteria (heterotrophic and anaerobic) Sulfur-Oxidizing Bacteria – Chemosynthetic – Pigmented Autotrophic

29. Sulfate-Reducing Bacteria Ex: Desulfovibrio Heterotrophic and anaerobic H 2 SO 4 + 2(CH 2 O) 2CO 2 2H 2 O + H 2 S H 2 SO 4 + 4H 2 H 2 S + 4H 2 O

30. Chemosynthetic Sulfur-Oxidizing Bacteria Ex: Beggiatoa Deposit elemental S inside cell H 2 S + ½O 2 S + H 2 O S + 1½O 2 + H 2 O H 2 SO 4 Ex: Thiobacillus Deposit elemental S outside 2Na 2 S 2 O 3 + O 2 2S + 2Na 2 SO 4

31. Green Sulfur Bacteria Ex: Chlorobium Uses a pigment similar to chlorophyll CO 2 + 2H 2 S LIGHT Food + H 2 O + 2S 2CO 2 + 2 H 2 O + H 2 S LIGHT Food + H 2 SO 4

32. Purple Sulfur Bacteria Ex: Chromatium They deposit sulfur intracellularly Same reactions as Chlorobium

33. Purple Non-Sulfur Bacteria Ex: Rhodobacter Na 2 S 2 O 3 +2CO 2 +3H 2 O LIGHT Food + Na 2 SO 4 +H 2 SO 4

34. Microbial-mediated Sulfur cycle in a lake

35. Sulfate reduction in Lake Gek Gel and the Black Sea

36. Distribution of sulfur in meromictic Lake Belovod

37. Abandoned Mine Drainage

38. Microbial Oxidation of Pyrite

39. AMD Discharges

40. Acid Precipitation

41. Si in lakes

42. Some Common Diatoms

43. Si in oligotrophic Lawrence Lake

44. Si and diatom population dynamics in Lake Windermere

45. Dynamics of diatom periphyton and plankton

46. Green Algae and Diatoms