Effect of monsoons on distribution of organic matter in sediment of Setiu lagoon, Terengganu

Abstract

The distribution of Total Organic Carbon (TOC) and Biological Oxygen Demand (BOD) in sediment of Setiu Lagoon was studied. Four sampling field trips were conducted at 14 stations. The mean and standard deviation values of TOC (total organic carbon) in sediment during the first, second, third and fourth sampling periods for the lagoon stations were 6.715±5.789 mg C/g, 7.149±5.589 mg C/g, 8.333±5.718 mg C/g and 8.269±0.049 respectively. The mean and standard deviation values of biological oxygen demand (BOD) in sediment samples during first, second, third and fourth sampling periods were 0.104±0.092 mg C/g, 0.500±0.118 mg C/g, 0.512±0.139 mg C/g and 0.466±0.121 respectively. While the mean and standard deviation values for biodegradable organic carbon in sediment samples were 0.041±0.037 mg C/g (first sampling), 0.200±0.047 mg C/g (second sampling), 0.205±0.056 mg C/g (third sampling) and 0.187±0.049 mg C/g (fourth sampling). The mean and standard deviation values for non biodegradable organic carbon in sediment samples was 6.674±5.753 mg C/g (first sampling), 6.949±5.547 mg C/g (second sampling), 8.128±5.665 mg C/g (third sampling) and 8.082±5.815 mg C/g (fourth sampling). TOC and BOD5 reading was increasing significantly during Inter monsoon and early northeast monsoon. But, there was slightly decreasing of TOC and BOD concentration during fourth sampling (late Northeast monsoon). This might be due to agricultural terrestrial run-off brought by inland rainfall during monsoon season Nevertheless, Setiu Lagoon is still considering as an unpolluted aquatic system with the organic matter.