Macro and micro nutrients of tropical seagrasses, Halophila ovalis, H. spinulosa and Halodule uninervis in Johore, Malaysia

The present study determined and compared contents of macro- (Nitrogen-N, Phosphorus-P, Potassium-K, Calcium-Ca, Magnesium-Mg) and micro- (Zinc-Zn, Iron-Fe, Manganese-Mn, Cupper-Cu) nutrients in four seagrass species big-leaved (BL) Halophila ovalis (R. Br.) Hook. f., small-leaved (SL) H. ovalis (R. Br.) Ascherson, H. spinulosa (R. Br.) Aschers. in Neumayer and Halodule uninervis (Forssk.) Aschers from three locations Merambong shoal, Seluyong shoal-۱ and Seluyong shoal-۲, Johore, Malaysia on March ۲۰۱۳. Dried seagrass samples were subjected to wet digestion method and concentration determined using a Perkin Elmer ۵۱۰۰ PC atomic absorption spectrophotometer. Macro and micro-nutrients varied with species and locations. Observed macro-nutrient contents were high for N (۱۷۳۲۰ mg kg-۱) in big-leaved (BL) H. ovalis from Seluyong shoal-۲, P (۲۹۲۱.۳۳ mg kg-۱) in big-leaved (BL) H. ovalis from Seluyong shoal-۱, and for K (۱۰۹۴۲.۶۷ mg kg-۱) in H. uninervis from Merambong shoal and for Ca (۱۰۵۷۶ mg kg-۱) in small-leaved (SL) H. ovalis from Merambong shoal. Mg (۳۵۳۴.۶۷ mg kg-۱) was comparatively higher in H. spinulosa from Merambong shoal. Micro-nutrients such as Zn ranged from ۱۳۸.۶۷ mg kg-۱ to ۲۱۲ mg kg-۱ and Cu from ۱۳.۳۳ mg kg-۱ to۱۷.۳۳ mg kg-۱ with no discernible differences between species. Fe concentration was consistently higher in all species. Hierarchically macro and micro-nutrients contents did not show a consistent ordered pattern according to species and location. Based on biplots generated by Principle component analysis (PCA), there were clear separation of seagrass species based on the micro- and macro-nutrient contents with locations from Malaysia and other regions.