BIOMASS, LEAF GROWTH AND LOSS RATE OF THE SEAGRASS SYRINGODIUM-ISOETIFOLIUM ON DRAVUNI ISLAND, FIJI

We measured the biomass, patterns of growth and loss of Syringodium isoetifolium (Aschers.) Dandy, in a monospecific seagrass stand off Dravuni Island, Fiji. Shoot density was between 2831 and 7164 shoots m(-2); the leaf area index (LAI) ranged from 1.3 to 2.5 m(2) m(-2). Most (68%) of the plant biomass (519 g dry weight m(-2)) was below ground and consisted mainly of root material. The leaves were cylindrical (cross-section diameter, 2 mm) and very brittle, so increases (growth) and decreases (losses) in leaf length were measured from a tag positioned at the leaf base to the leaf tip. The specific growth rates (production/biomass (P/B) ratio) and loss rates of shoots were 0.028 day(-1) and 0.030 day(-1), respectively. The leaf productivity of 2.5 g dry weight m(-2) day(-1) and defoliation of 2.6 g dry weight m(-2) day(-1) were determined by multiplying the leaf biomass by the P/B ratio. The mean leaf length was 295 mm and the maximum time a leaf remained attached to a shoot (leaf longevity) was 56 days. These data result from a short-term study in October 1989. The data show that the standing crop was maintained in a steady state with rates of leaf production and defoliation of approximately 0.8 cm per shoot day(-1).