Nutrient and mass allocation of South-east Asian seagrasses

Differences in ramet size (i.e, the mass of a shoot with its share of leave s, rhizome and roots) and allocation of mass and nutrients to different ram et components were quantified based on a comparative analysis of these prop erties in a large set of seagrass meadows under contrasting conditions of n utrient availability in the Philippines and Thailand. The ramet size differ ed by two orders of magnitude between the smallest species, Halophila ovali s (12 mg DW per ramet), and the largest, Enhalus acoroides (7.3 g DW per ra met). However, the pattern of mass allocation to different ramet components was similar among species. The vertical rhizome was the most variable rame t component, Compared to seagrasses in general, nitrogen concentrations in the leaves of these South-east Asian seagrasses were low (leaf N less than or equal to 2% DW), and the phosphorus concentrations high (leaf P > 0.2% D W). The amount of nutrients allocated to leaves was of the same magnitude a s that to rhizomes and roots. Seagrass ramet mass and the percentage of mas s allocated to roots were independent of total nitrogen or phosphorus in th e sediment far most species. The nutrient concentrations of seagrass tissue s differed among coexisting species which suggests that differences in the nutritional status among South-east Asian species are more dependent on spe cies-specific differences in nutrient acquisition or requirements than on n utrient availability in the sediment. (C) 1999 Elsevier Science B.V, All ri ghts reserved.