Jellyfish abundance and composition were investigated at three-hour intervals for a 48-hour period from a fringing reef of Redang Island,... » More

Jellyfish abundance and composition were investigated at three-hour intervals for a 48-hour period from a fringing reef of Redang Island, Malaysia. The abundance of jellyfish in the water column was significantly higher during the night, being 2.2 times as high (90 ± 87 indiv. m-3) as during the day (40 ± 111 indiv. m-3). The jellyfish community was dominated by the calycophoran siphonophore Diphyes chamissonis, constituting 80.1% of the total jellyfish abundance, followed by Aglaura hemistoma (5.5%) and Liriope tetraphylla (4.8%). At night, abundances of D. chamissonis and L. tetraphylla peaked at 2100 h, while A. hemistoma was most abundant at 0300 h. The peaks in abundance at 2100 h coincided with the bottom of the tide during the study period, while at 0300 h the tide was rising towards its peak due to an inflow of offshore water into and over the reef. Diphyes chamissonis and L. tetraphylla may have occurred close to the reef bottom during the day and migrated into the water column at night, while A. hemistoma may undergo diel migration offshore and may have been advected inshore with the incoming tide because of their migration into surface waters in the nearby offshore water at night.

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