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Title: In situ nitrogen fixation associated with seagrasses in the Gulf of Elat (Red Sea)
Contributor(s): Pereg, Lily (author); Sar, N (author); Lipkin, Y (author)
Publication Date: 2002
DOI: 10.1023/A:1016566019208
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Abstract: In situ nitrogen fixation associated with the seagrass 'Halophila stipulacea', at the northern Gulf of Elat (Red Sea), is eight to ten times higher than that of nearby plant-free areas. A daily cycle of nitrogen fixation is evident, with rates during the day being seven times greater than during the night. Removal of seagrass leaves only from a patch within a seagrass bed gradually decreases nitrogen fixation activity, reaching the rates of plant-free areas after ten hours. A method devised for the in situ measurement of nitrogen fixation rates using belljars is described in detail. Nitrogen fixation rates in situ are higher than in the laboratory and lack the lag period typical to laboratory measurements. In laboratory experiments using intact plant samples, glucose enhances nitrogen fixation rates both in light and dark. Photosystem II inhibitor (3-3,4-dichloro-phenyl-1,1-dimethylurea) doubles nitrogen fixation rates in light. Both field and laboratory results indicate that light is essential for nitrogen fixation activity in the 'H. stipulacea' bed possibly through its effect on cyanobacterial population that occupy the aerobic niches of the phyllosphere and on photosynthetic Rhodospirillacean bacteria that inhabit the anaerobic ones. Nitrogen fixation rates evident in 'H. stipulacea' beds in situ account for a considerable portion of the biomass production by the seagrasses. The dependence of high nitrogenase activity by the diazotrophs on the presence of the seagrasses indicates the great importance of the seagrass community to the nitrogen cycle in its highly oligotrophic surroundings of the Gulf of Elat.
Publication Type: Journal Article
Source of Publication: Aquatic Ecology, 36(3), p. 387-394
Publisher: Springer Netherlands
Place of Publication: The Netherlands
ISSN: 1386-2588
Field of Research (FOR): 060205 Marine and Estuarine Ecology (incl Marine Ichthyology)
Peer Reviewed: Yes
HERDC Category Description: C1 Refereed Article in a Scholarly Journal
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