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-1 and Seluyong shoal-2, Johore, Malaysia on March 2013. Dried seagrass samples were subjected to wet digestion method and concentration determined using a Perkin Elmer 5100 PC atomic absorption spectrophotometer. Macro and micro-nutrients varied with species and locations. Observed macro-nutrient contents were high for N (17320 mg kg-1) in big-leaved (BL) H. ovalis from Seluyong shoal-2, P (2921.33 mg kg-1) in big-leaved (BL) H. ovalis from Seluyong shoal-1, and for K (10942.67 mg kg-1) in H. uninervis from Merambong shoal and for Ca (10576 mg kg-1) in small-leaved (SL) H. ovalis from Merambong shoal. Mg (3534.67 mg kg-1) was comparatively higher in H. spinulosa from Merambong shoal. Micro-nutrients such as Zn ranged from 138.67 mg kg-1 to 212 mg kg-1 and Cu from 13.33 mg kg-1 to17.33 mg kg-1 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.