Abstract:
This study aims to measure net photosynthetic rate, chlorophyll-a and total phytoplankton biomass m Setiu Lagoon, Terengganu. Three samplings were conducted: 13th September 2006 (South-West monsoon), 12th October 2006 (Intermonsoon) and 14th December 2006 (North-East monsoon). Fourteen sampling stations were set at Setiu Lagoon. The methods applied in this study were Winkler's dissolved oxygen method and Light-dark bottles for determination of primary productivity, chlorophyll-a determination using UV spectrophotometer, and Lackey drop method for determination of total phytoplankton abundance. The changing of monsoon season was found to be the most significant factor that affects the water quality in Setiu Lagoon. Low level of net photosynthetic rate was found in North-East monsoon season. The mean values of net photosynthetic rate for 1st, 2nd and 3rd sampling were 180.00±67.50 mg.c.m·3.hr-1, 123.19±46.53 mg.c.m·3.hr-1 , and 68.06±26.07 mg.C.m-3.hr- 1 respectively. The light intensity may be the major limiting factor. Besides, the mean value of chlorophyll-a level in 151 , 2nd and 3rs sampling were 2.19±1.34 mg m · 3 , 0.94±0.81 mg m ·3 , and 0.60±0.46 mg m ·3 respectively. The increasing volume of freshwater input into the Lagoon during North-East monsoon was the factor that caused lower level of chlorophyll-a in Setiu Lagoon. Furthermore, nutrient may affect the chlorophyll-a level.
