Nitrogen fixation coral reefs

Yamamuro et al. (1995) were the first to use a N-natural abundance approach in a coral reef environment, surveying various components of the ecosystem and concluded that much of the nitrogen demand on the reef is met by N2 fixation. 

Similarly, in coral reef communities, N2 fixation in carbonate sands are a major source of N2 fixation, and the recent discovery of diazotrophic coccoid cyanobacteria living within the tissues of Montastrea corals suggests that there may well be more diazotrophic symbioses with corals. Many sponges harbor cyanobacteria symbioses, and these may also be important sources of fixed nitrogen. 

France, R., Holmquist, J., Chandler, M., and Cattaneo, A. (1998). delta N-15 evidence for nitrogen fixation associated with macroalgae from a seagrass-mangrove coral reef system. Mar. Ecol. Prog. Ser. 167, 297-299. 

Shashar, N., Feldstein, T., Cohen, Y., and Loya, Y. (1994b). Nitrogen-Fixation (Acetylene-Reduction) on a Coral-Reef. Coral Reefs. 13, 171—174. 

WiUe, N. (1904). Die schizophyceen der plankton expedition. Ergeb. Elumbolt-Stift. 4, 1—88. Williams, S. L., and Carpenter, R. C. (1998). Effects of unidirectional and oscillatory water flow on nitrogen fixation (acetylene reduction) in coral reef algal turfs, Kaneohe Bay, Hawaii. /. Exp. Mar. 

Figure 21.1 Microbial nitrogen cycling processes in sedimentary environments on a coral reef (A) nitrogen fixation (B) ammonification (C) nitrification (D) dissimilatory nitrate reduction and denitrification (E) assimilatory nitrite/nitrate reduction (F) ammonium immobilization and assimilation. Adapted from D Elia and Wiebe (1990). Anammox (the anaerobic oxidation of NH4" with NO2 yielding N2 ) is not represented, as it has not yet been shown to occur on coral reefs, but may be found to be important in reef sediments.

Nitrogen fixation also occurs in the lagoonal waters of coral reefs and this may contribute to the nitrogen economy of these systems as well. Biegala and Raimbault (2008) recently reported on the relatively high densities of diazotrophic coccoid cyanobacteria in coral lagoon waters of New Caledonia. 

Capone, D. G., Taylor, D. L., and Taylor, B. F. (1977). Nitrogen-fixation (acetylene-reduction) associated with macroalgae in a coral reef community in the Bahamas. Mar. Biol. 40, 29—32. 

Hanson, R. B., and Gundersen, K. (1977). Relationship between nitrogen fixation (acetylene reduction) and the C N ratio in a poUuted coral reef ecosystem, Kaneohe Bay, Hawaii. Estuar. Coast Mar. Sci. 5, 437-444. 

O Neil, J. M., and Capone, D. G. (1996). Effects of elevated nutrients (ENCORE) on benthic nitrogen fixation and denitrification. Proceedings of the 8th International Coral Reef Conference, Panama, June 21—29. 

Wilkinson, C. R., and Fay, P. (1979). Nitrogen fixation in coral reef sponges with symbiotic cyanobacteria. Nature. TVi, 527—529. 

Wilkinson, C. R., and Sammarco, P. W. (1983). Effects of fish grazing and damselfish territoriahty on coral-reef algae 2. nitrogen-fixation. Mar. Ecol. Prog. Ser. 13(1), 15—19. 

Wilkinson, C. R., Wflhams, D. M., Sammarco, P. W., Hogg, R. W., andTrott, L. A. (1984). Rates of nitrogen-fixation on coral reefs across the continental-shelf of the central Great Barrier-Reef Mar. Biol. 80(3), 255-262. 

Williams, S. L., and Carpenter, R. C. (1997). Grazing effects on nitrogen fixation in coral reef algal turfs. Mar. Biol. 130, 223-231. 

Marine sediments are an important compartment for N cycHng. Shelf sediments in particular are sites of active denitrification (Codispoti et al., 2001), and estuarine, coastal, and coral reef sediments can be important sites of nitrogen fixation (Burns et al, 2002 Capone, 1983 Capone et al., 1992). Despite extensive study of biogeochemical processes in sediments, the study of the microbial loop in this compartment has had considerably less attention, possibly due to difficulty in studying sediment microorganisms. There are two primary differences between water column and sediment microbial processes. The first of these is the presence... 

For the purpose of this text on symbioses as they relate to the marine nitrogen cycle, we wiU first emphasize the more common open ocean diatom-diazotrophic associations (DDAs), then summarize the recent advances in our understanding of sponge-nitrifying microbial associations, and provide brief introductions to a few other relevant symbioses. In addition, we recommend, the chapter by O Neil and Capone (Chapter 21) for details on algal-animal symbioses of Coral Reefs as they relate to the nitrogen cycle. Chapter 4 by Carpenter and Capone on Nitrogen Fixation and Chapter 5 by Ward on Nitrification. 

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