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Before After

Eutrophication. Before After. Eutrophication – nutrient enrichment of waters Major nutrients - phosphorus and nitrogen Consequences - increased plant growth - decreased water quality.

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Before After

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  1. Eutrophication Before After

  2. Eutrophication – nutrient enrichment of waters Major nutrients - phosphorus and nitrogen Consequences - increased plant growth - decreased water quality

  3. Eutrophication of lakes, reservoirs and rivers ranks as one of the most widespread environmental problems. Eutrophication can have significant negative ecological, health, social and economic impacts on use of a primary and finite resource, water.

  4. Decreased water quality • Algal blooms • Decreased transparency • DOC and chlorination disinfection products • Toxic cyanobacteria and dinoflagellate • Growth of aquatic plants • Anoxia

  5. Effects of Eutrophication Source: Issues in Ecology #2 (1998)

  6. Laguna de Bay, Philippines

  7. Decreased water quality Elevated nitrate concentrations Species changes Increased incidence of water-related diseases

  8. Positive features of eutrophication - increased fish yield - increased plant production and nutrient reuse

  9. Indicators of eutrophication Secchi disk transparency Chlorophyll concentration Phosphorus concentrations Nitrogen concentrations

  10. Experimental Lakes Area Lake 227

  11. C, N C, N, P Eutrophic algal blooms Lake 226

  12. Effects of Eutrophication Source: Issues in Ecology #2 (1998)

  13. Source: Issues in Ecology #2 (1998)

  14. Classification of Lakes Source: Principles Env. Sci. & Eng. (Davis & Masten)

  15. Total P vs. Chlorophyll a Source: Principles Env. Sci. & Eng. (Davis & Masten)

  16. Meybeck, 1982

  17. N fixation • N2 reactive N • (e.g. NH3 , NH4+) • Mostly biological symbiotic free- living bacteria (asymbiotic)

  18. Synthetic fertilizer • production is considered • N fixation • takes N2, reacts it with • natural gas, producing NH3 • and CO2

  19. Agriculture…

  20. (Townsend et al. Frontiers Ecol. Environ. 2003)

  21. (Tilman et al. Nature, 2002)

  22. Percent Increase in Nitrogen Fluxes in Rivers Source: Millennium Ecosystem Assessment

  23. Gulf of Mexico Dead Zone Source: NOAA

  24. US East Coast Source: Issues in Ecology #2 (1998)

  25. Fish Kills and Anoxia in the Chesapeake

  26. (Townsend et al. Frontiers Ecol. Environ. 2003)

  27. Is N or P limiting? – Assessment Concentration ratios Experimental enrichments Supply and recycling ratios Physiological assays

  28. Gradient of Conditions Low Nutrient Supply Low N & P conc. in lake Low algae productivity Low chlorophyll a Lake more transparent Greater Secchi disc depth High Nutrient Supply High N & P conc. in lake High algae productivity High chlorophyll a Lake less transparent Smaller Secchi disc depth Toxic inflow High Flowrate High Sediment Analysis of Cause and Effect

  29. Within-lake factors which moderate degree of eutrophication * food web structure * sediment regeneration * basin morphology * hydrodynamics

  30. Technically effective control of eutrophication is possible but not always economically feasible

  31. Solutions… • Source Reduction • Eliminate excess fertilization • Wastewater treatment plants • In Lake Control: • Mechanical harvesting of aquatic plants • Chemical control (algaecides) • Biological control (increase grazing) • Flow augmentation • Deep water aeration • Selective removal of deep water • Sediment removal

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