title: Rhizobacterial population density and nitrogen fixation in seagrass community of Gulf of Mannar, India.
abstract: Seagrass rhizosphere generally supports high bacterial population density which plays a major role in determining the nutrient cycles of the sea. Higher densities of total heterotrphic bacteria (26.3 x 10(6) CFU g(-1)), nitrogen fixing (27.3 x 10(3) CFUg(-1), ammonifying (44.66 x 10(6) MPN g(-1)) and nitrifying bacteria (42.33 X 10(6) MPN g(-1)) have been registered in the seagrass areas than the non seagrass area. In particular, all these rhizosphere microbial population was higher in Thalassia hemprichii. The rates of nitrogen fixation was recorded in the different species of seagrasses such as Enhalus acoroides (1.166 n mol g(-1) d(-1)), Halophila ovalis (0.166 n mol g(-1) d(-1)), Thalassia hemprichii(18.5 n mol g(-1) d(-1)), Cymodocea serrulata (10.5 n mol g(-1) d(-1)), Halodule uninervis (5.375 n mol g(-1) d(-1)) and Syringodium isoetifolium (0.666 n mol g(-1) d(-1)) using gas chromatography. The average nitrogen fixation by the seagrasses of Gulf of Mannar alone was estimated to be 7640.58 n mol m(-2) d(-1) and the contributions from the rhizosphere microbes will increase the quantity to many fold.
authors.affiliation: Centre of Advanced Studies in Marine Biology, Faculty of Marine Sciences, Annamalai University, Parangipettai-608 502, India.
authors.forename: S
authors.initials: S
authors.lastname: Raja
authors.forename: T
authors.initials: T
authors.lastname: Thangaradjou
authors.forename: K
authors.initials: K
authors.lastname: Sivakumar
authors.forename: L
authors.initials: L
authors.lastname: Kannan
mesh_terms: D007194:India; D009586:Nitrogen Fixation; D006109:Poaceae / Q000382:microbiology*; D012230:Rhizobiaceae / Q000254:growth & development / Q000502:physiology*