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Pakistan Journal of Biological Sciences
Year: 2001  |  Volume: 4  |  Issue: 12  |  Page No.: 1487 - 1489

Photosynthetic and Respiration Responses of Dugong Grass Thalassia hemprichii (Ehrenb) Aschers. at Teluk Kemang Seagrass Bed, Malaysia

M.K. Abu Hena, K. Misri, B. Japar Sidik, O. Hishamuddin and H. Hidir    

Abstract: Photosynthetic and respiration responses were measured in situ at different depths and under a variety of light regime for seagrass Thalassia hemprichii from coastal area of Teluk Kemang, Port Dickson, Malaysia. The photosynthesis and respiration rate was measured from evolution of oxygen from the seagrass enclosed in glass cuvet. The photosynthetic rate at 0.5 m was higher (0.429 ± 0.086 mg O2/hr/g fr wt.) than at 2.0 m depth (0.289 ± 0.034 mg O2/hr/g fr wt.). Respiration rate was not significantly different at two depths. In laboratory study, the light saturation of T. hemprichii was reached at 400-800 μmol/m2/sec, whereas, the compensation point was around 20 μmol/m2/s. The photosynthesis was relatively constant at light intensity up to 1600 μmol/m2/s. Comparing these results to in situ light measurement from the seagrass bed (1095.430±5.803 μmol/m2/s at surface water and 115.00±1.512 μmol/m2/s. at 2.0 m depth), this species depth distribution should not be light limited to a depth of about 2.0 m i.e. T. hemprichii could penetrate a depth of more than 2.0 m in this study area. However, the present field observation indicated that this species could only be found at intertidal area (1.5 - 2.0 m High Water Level) and assumed that other environmental factors i.e. current movement, water visibility and sediment status may affects the depth distribution of this seagrass in this costal water.

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