Diel variation of zooplankton in the tropical coral-reef water of Tioman Island, Malaysia

Zooplankton was sampled at 3-h intervals for a 48-h period from a coral reef of Tioman Island, Malaysia. It was size-fractionated into three size classes: 100-200, 200-335, and > 335 mu m using different sieves with different mesh sizes. Total zooplankton (> 100 mu m) abundance and biomass in the water column were high later at night (0300 h), not just after sunset as previously described in other studies. Only the largest size-fraction (> 335 mu m) of zooplankton significantly differed in biomass and abundance between day and night. The increase in the large zooplankton later in the night is suggested to be caused by the advection of pelagic species into the reef. This work has provided a measurement of the variation of zooplankton community over coral reef that can exist on a scale of hours.