Abstract:
A study on diel variation was carried out in Bidong Island fringing reef to
understand coral-reed zooplankton ecology on diel basis, zooplankton abundance and
size composition. The samples were taken for 48 hours with 3 hours interval.
Zooplankton was collected vertically with 1 OOμm mesh size Kitahara net and sizefractionated
into 100-300 μm and >300 μm. Diel variation of the zooplankton showed
that abundance during night was always greater compared to day. Nocturnal increase
occurred most strongly in the large fraction (>300 μm). In Bidong Island, the peak of
zooplankton is late at night at 3a.m (22976 ± 1339 ind. m-3). Large size fraction
(>300μm) zooplankton show strong pattern of nocturnal migration which consist of
several species of zooplankton such as polychaetes, appendicularia, nauplius,
copepods, arrow worms and ra.diolarian. While for small fraction zooplankton (100-
300μm) most common zooplankton were polychaetes, appendicularia, copepods,
bivalvia, gastropodanauplius and ra.diolarian. The highest peak for small size
zooplankton was at 3a.m (11557 ± 355 ind. m-3). M-Whitney analysis shows that
there were differences in the night and day zooplankton population (p<0.05).
