Monsoon effects on primary productivity, chlorophyll-a and total suspended solids (TSS) in Setiu lagoon, Terengganu

Abstract

This study aims to determine net photosynthetic rate, chlorophyll-a and total suspended solids in Setiu lagoon. Three samplings were conducted: 81h September 2007 (South-West monsoon), 21 October 2007 (Inter-monsoon) and 291h Dicember 2007 (North-East monsoon). Fourteen sampling stations were set around the Setiu lagoon. The changing of monsoon was found to be the most important factor that affects the water quality in Setiu lagoon. Thus Winkler's dissolved oxygen method and Light-dark bottles were using to determine the primary productivity, spectrophotometer was use to measure the concentration of chlorophyll-a in water sample and filtration of water san1ple and the constant weight of residue that trap in filter paper to determine the total suspended solid. The mean values of net photosynthetic rate for 151 , 2nd and 3rd sampling were 103. 91 mg.C.m-3.hr- 1, 31.25 mg.C.m-3.hr- 1 and 36.72mg.C.m-3.hr-1 respectively. The light intensity is the major factor. Moreover the mean values of chlorophyll-a during 151 , 211d and 3rd sampling were 0.908mg.m-3, 0.938 mg.C.m-3.hr- 1 and 0.441 mg.C.m-3.hr- 1 respectively. It is due to the greater volun1e of freshwater during North-east monsoon, low salinity and dilution of nutrient of freshwater cause the lower chlorophyll-a level. Finally the mean values of total suspended solids for 151 , 211d and 3rd sampling were 25.1 Smg.L- 1 , 9.05mg.L - 1 and 27.Smg.L-1 respectively. The total suspended solids in Setiu lagoon didn't exceed the interim standard from DOE. Thus the TSS in Setiu lagoon still in the safety level.