Ecological characteristics of tropical seagrasses, especially Enhalus acoroides

Abstract

Enhalus acoroides is a large and common species in tropical segrass beds and contributes significantly to total seagrass biomass. Fertile plants with male and female flowers or fruits are found throughout the year. Positive relationships were observed in the species number and total coverage of seagrsses, but negative relationships were observed in the species, number and coverage of E. acoroides. In terms of depth distribution, pattern in relation to tidal level was shown especially with respect the peduncle length of female flowers. There is a meristematic zone at the basal part of the leaf, and the meristematic potential decreased with age. The growth rate of young leaves ranged from 8-19mm day^-1 at the basal part, and about 5-7 weeks were required before attaining maximum length. On the fate of production in E. acoroides, the leaves contributed 85.7% of the total defoliation and 14.3% came from floating leaves. Conditions of the sediments were as follows: COD values ranged from 4-10 mgO•g^-1 DM and the ratio of mud contents (<33 μm grain size) ranged from 2.9-11.3%. These results suggest that individuals E. acoroides can survive in severe environmental conditions.