Effect of monsoons on hydrological parameters in the Setiu lagoon, Terennganu

Abstract

This study was conducted at the Setiu Lagoon during Southwest Monsoon, Intermonsoon and Northeast Monsoon. The temperature, salinity, pH, dissolved oxygen and water current data were collected in situ while for the total alkalinity it was determined by titration method in laboratory. All the data were then analyzed in order to compare the effect of monsoons to each parameter recorded. Most of the hydrological parameters were significantly different to the monsoons (p<0.05). The mean for temperature during Southwest Monsoon, Inter-monsoon and Northeast Monsoon were 31.65 ± 0.03°C, 28.97 ± O. l 6°C and 28.17 ± 0.11 °C respectively. For the salinity, the mean were 26.94 ± 0.08 ppt, 22.79 ± 1.80 ppt and 14.79 ± 0.53 ppt respectively. As for the pH, the mean recorded were 7.75 ± 0.00, 7.68 ± 0.07 and 6.28 ± 0.08 respectively. The means for dissolved oxygen were 5.37 ± 0.07 mg/1, 3.85 ± 0.25 mg/1 and 3.74 ± 0.19 mg/1 respectively. As for total alkalinity, the means recorded were 118.05 ± 1.34 mgCaC03/l, 35.29 ± 0.80 mgCaC03/l and 30.76 ± 0.61 mgCaC03 /l respectively. However, the current movement was not significantly different to the sampling period (p>0.05), most probably because the current movement was influenced by tide. The means for the current flow were 0.123 ± 0.17 mis (Southwest Monsoon), 0.199 ± 0.19 mis (Inter-monsoon) and 0.220 ± 0.24 mis (Northeast Monsoon). For the stations at the Northwest part of the lagoon, the current direction was towards the Southeast and for the stations at the Southeast; the current direction was in the opposite direction. Since there is monsoon changes in the Setiu Lagoon, it can reduce the effect of wastes accumulation from the aquaculture, culture pond and river runoff.