Seasonality and depth zonation of intertidal Halophila ovalis and Zostera japonica in Ha Long Bay (northern Vietnam)
Tu, Thi Lan Huong Nguyen, Van Tien Nguyen, Hoang Tri Seasonality and depth zonation of two common intertidal northern Vietnamese seagrass species, Halophila ovalisandZostera japonica, were investigated in a 50 m long intertidal transect from 1999 till 2001.Z. japonicaoccurred in the middle intertidal (1.2 m above mean chart datum to mean sea level at 2.1 m above chart datum).H. ovalisoccurred deeper in the intertidal (between 1.0 and 1.4 m above chart datum). Based on seasonally different sensitivity to reciprocal transplants, it is concluded that this zonation is most likely due to different tolerances to low light availabil-ity (less inZ. japonica) and desiccation (less inH. ovalis). Both species reached maximum shoot densities in September–October with total biomasses around 70 g DW m −2 . Flowering inZ. japon-icaoccurred in April only, whilstH. ovalisflowered in November after the rainy season and again in April. Seasonality in density and biomass was apparent and similar...