1. ©2010 Elsevier, Inc. Chapter 14 Nitrogen,Sulfur, Phosphorus, and Other Nutrients Dodds & Whiles

2. ©2010 Elsevier, Inc. FIGURE 14.1 Streamers composed of the sulfur-oxidizing bacterium Thermothrix at Mammoth Terrace, Yellowstone National Park (courtesy of R. W. Castenholz) and a transmission electron micrograph of a heterocyst (the site of nitrogen fixation in Nostoc and other cyanobacteria) attached to a smaller dividing vegetative cell with a diameter of approximately 8 μm. (Micrograph courtesy of N. J. Lang).

3. ©2010 Elsevier, Inc. FIGURE 14.2 Nitrogen assimilation. This figure illustrates that nitrogen must be assimilated in the form of ammonium, and energy requirements for assimilation are N 2. NO 3 2. NO 2 2. NH 4 1.

4. ©2010 Elsevier, Inc. FIGURE 14.3 A diagram of cyanobacterial vegetative cells, a heterocyst, adaptations to protect nitrogenase from deactivation by O 2, and mode of N transport from the heterocyst into vegetative cells.

5. ©2010 Elsevier, Inc. FIGURE 14.4 Distribution of nitrate (A) and ammonium (B) in hypereutrophic Wintergreen Lake, Michigan, as a function of depth and time. Ice cover occurred from January to March. Darker colors represent higher concentrations. Contours are reported in μg liter 21. (Reproduced with permission from Wetzel, 1983).

6. ©2010 Elsevier, Inc. FIGURE 14.5 Concentrations of nitrate in groundwater flowing from undisturbed prairie (top, solid line), nitrate in Kings Creek, Kansas (middle, a stream influenced by groundwater that passes under cropland), and discharge in the same stream (bottom). High nitrate is related to input of groundwater from below fertilized cropland that dominates flow during periods of low discharge, and these concentrations are substantially greater than found in pristine groundwater. (Data courtesy of Konza Prairie Long-Term Ecological Research site).

7. ©2010 Elsevier, Inc. FIGURE 14.6 A conceptual diagram of the nitrogen cycle.

8. ©2010 Elsevier, Inc. FIGURE 14.7 Correlation between nitrate intake and rates of gastrointestinal cancer. (After P. E. Hartman. 1983. Reprinted by permission of Wiley–Liss, Inc., a subsidiary of John Wiley & Sons, Inc.).

9. ©2010 Elsevier, Inc. FIGURE 14.8 A conceptual diagram of the sulfur cycle. A 5 assimilation.

10. ©2010 Elsevier, Inc. FIGURE 14.9 A diagram of the phosphorus cycle.

11. ©2010 Elsevier, Inc. FIGURE 14.10 Concentration of silica as a function of depth and time in hypereutrophic Wintergreen Lake, Michigan (A), and oligotrophic Lawrence Lake, Michigan (B). Concentrations are given in mg liter 21, with darker contour fills corresponding to greater concentrations. (Reproduced with permission from Wetzel, 1983).

12. ©2010 Elsevier, Inc. FIGURE 14.11 The relationship between epilimnetic silicon and biomass of the diatom, Asterionella, in Lake Windermere, England. Note how decreases in dissolved silica correspond with high densities of diatoms. (Data from Lund, 1964).

13. ©2010 Elsevier, Inc. FIGURE 14.12 A conceptual diagram of the iron cycle.

14. ©2010 Elsevier, Inc. FIGURE 14.13 Relationship among redox gradients, dissolved oxygen, nutrient concentrations, and functional groups of microorganisms responsible for biogeochemical fluxes. This figure illustrates the steep gradients that occur at oxic/anoxic interfaces, and how such interfaces are a hot spot for biogeochemical activities.