1. THE NITROGEN CYCLE IN SURFACE WATERS

2. PHYTOPLANKTON ELEMENTAL COMPOSITION O53% C27% K6.2% H5.5% N4.6% Ca1.0% S0.7% Na0.7% P0.5% Fe0.4% Mg0.4% Zn0.3% Cu0.02% B0.01% Mn0.009% Co0.0006% V0.0006% Mo0.0001% Si0.1%; DIATOMS 20%

3. N2N2

4. FIGURE 12-1; N 2 IN GREEN LAKE AND BELOIE LAKE

5. N-FIXATION

6. CYANOBACTERIA AND N-FIXATION

7. OTHER MICROBIAL NITROGEN FIXERS Azotobacter

8. MEROMICTIC LAKES AND N-FIXATION

9. SYMBIOSIS N-FIXATION OFTEN THROUGH SYMBIOSIS WITH VASCULAR PLANTS e.g. – Alders (wetland plants) – Legumes – Azolla (aquatic fern)

10. AMMONIUM AND NITRATE

11. AMMONIUM BY-PRODUCT OF DEAMINATION NH 4 + and NH 4 OH (see p233) pHNH 4 + : NH 4 OH 63000:1 7300:1 830:1 9.51:1

12. NITROGEN CYCLE

13. NITRIFICATION NH 4 + NO 2 - Nitrosomonas – Requires O 2 ; wide range of temperature and pH NO 2 - NO 3 - Nitrobacter – Requires O 2 ; warm temperatures and low pH

14. DENITRIFICATION C 6 H 12 O 6 + 12NO 3 - 12NO 2 - + 6CO 2 +6H 2 O C 6 H 12 O 6 + 8NO 2 - 4N 2 + 2CO 2 + 4CO 3 -- + 6H 2 O

16. REDUCTION IN AN ANOXIC ENVIRONMENT

17. NITRIFICATION AND DENITRIFICATION

18. ORGANIC NITROGEN DISSOLVED ORGANIC NITROGEN (DON) PARTICULATE ORGANIC NITROGEN (PON) DON:PON INCREASES WITH EUTROPHICATION

19. NITRATE AND PON

21. INORGANIC NITROGEN IN WINTERGREEN LAKE

23. NITROGEN CYCLE

24. NITROGEN IN STREAMS

25. NUTRIENT SPIRALLING

26. NITROGEN LOADING

28. NITRATE IN THE CHESAPEAKE BAY

29. Dead Zone summer 2011, USEPA