Diel variation and trophic structure in coral-reef zooplankton of Peninsular Malaysia

Biomass in zooplankton (>100μm) and particulate organic matter (POM) (0.7-100μm) was investigated every 3 hours for two days at the fringing reef of Redang and Tioman Island, the east coast of Peninsular Malaysia. The zooplankton was size-fractionated into three fractions (100-200μm, 200-335μm, and >335μm) and POM was divided into two size-fractions (0.7-35 and 35-100μm). The POM (0.7-100μm) accounted for more than 95% of the total biomass (POM+zooplankton) in the water column. The largest size fraction (>335μm) was the most dominant in zooplankton biomass during the two days at both islands. Nocturnal vertical migration also occurred most strongly in the largest size fraction (>335μm). The biomass of the largest fraction (>335μm) may be supported by high growth rate in the smaller size zooplankton (100-200 and 200-335μm) and the large amount of POM (0.7-100μm). The contribution of phytoplankton biomass was approximately 10% of the POM (0.7-100μm). The mean C/N ratio of the POM (0.7-100μm) at Redang and Tioman Islands were 5.9 and 6.6, respectively. Most of the diet of particle-feeders in both study areas would mainly originate from mucus which was produced by corals