1. Nutrient Cycles Eutrophication Nitrogen –Chemical Forms in the Aquatic Environment –Chemical Transformations –Cycle f-ratio Carbon

2. Nutrient Cycles and Eutrophication Light penetration with depth Mixing and stratification Phytoplankton nutrient use Ocean circulation

3. Eutrophic Refers to areas that contain high nutrient concentrations and support high biological productivity Eastern Boundary Currents Upwelling

4. Eutrophication An increase of nutrients in a system (N or P) which promotes excessive plant growth (and decay) and is likely to cause severe reductions in water quality Increase in nutrient loading

5. Experimental Lakes Area

7. Point and Nonpoint sources of chemical inputs

8. Algal Bloom in Lake

9. BeforeAfter

10. Adverse effects of eutrophication on lakes, reservoirs, rivers and coastal marine waters Increased biomass of phytoplankton Toxic or inedible phytoplankton species Increases in blooms of gelatinous zooplankton Increased biomass of benthic and epiphytic algae Changes in macrophyte species composition and biomass Decreases in water transparency Taste, odor, and water treatment problems Dissolved oxygen depletion Increased incidences of fish kills Loss of desirable fish species Reductions in harvestable fish and shellfish Decreases in perceived aesthetic value of the water body

12. New species invasion Eutrophication may cause competitive release - nutrient normally limiting ↑↑. ↑ nitrogen might allow new, competitive species to invade and outcompete original inhabitant species

13. The changes in nutrient levels and biology can directly affect humans: The water can be injurious to health The amenity value of the water may decline Increased vegetation may impede water flow and navigation Commercially important species of fish may disappear Treatment of drinking water may be difficult and supply can have an unacceptable taste or odor

14. Prevention of eutrophication

15. The main effects caused by eutrophication: 1. Species diversity decreases and the dominant biota changes 2. Plant and animal biomass increase 3. Turbidity increases 4. Rate of sedimentation increases, shortening the lifespan of the lake 5. Anoxic conditions may develop

16. Gulf of Mexico

17. Caspian Sea

18. Algal Bloom

19. Oligotrophic LakeEutrophic Lake

21. Chemical Forms – Nitrogen

22. Chemical Forms – N NO 3 2- (Nitrate) NO 2 - (Nitrite) NH 4 + (Ammonium) CO(NH 2 ) 2 (Organic, Urea) N 2 (Dissolved gas) N 2 O (Nitrous Oxide)

23. Annual Surface Nitrate Concentration

24. The Marine Nitrogen Cycle

25. *

26. * *

27. * * *

28. Denitrification Nitrification NO 3 2- (Nitrate) → NO 2 - (Nitrite) → NH 4 + (Ammonia) Heterotrophic microbes (anerobic) NH4+ (Ammonia) → NO2- (Nitrite) → NO32- (Nitrate) Heterotrophic microbes (aerobic)

29. Nitrate Uptake into the Cell Reduction steps: Reduced forms of nitrogen are ‘preferred’ NO 3 NO 2 NH 4 Reduction steps Diffusional Gradient Proteins Phytoplankton other Autotrophs - Assimilatory N Reduction

30. Nitrate Phytoplankton Upwelling Mixing Vertical Flux N 2 Fixation Rivers Deposition PON DIN Euphotic Zone

32. f-ratio Upwelling Zone 0.8 Gyre 0.1 Global Average < 0.5 New Production New + Regenerated Production

33. Sediment traps to catch sinking particles

35. Sustainable yields

36. Nitrate Phytoplankton Upwelling Mixing Vertical Flux N 2 Fixation Rivers Deposition PON DIN Euphotic Zone Fishing

37. New Production Oligotrophic gyres Upwelling regions