Halocline Induced by Rainfall in Saline Water Ponds in the Tropics and Its Impact on Physical Water Quality

In saline water ponds in the tropics, a halocline may occur due to rainfall, especially in the rainy season. The critical impacts of haloclines in saline water ponds are heat insulation and the obstruction of vertical mixing. Considering the water quality in saline water ponds, the appearance of a halocline could have an impact on its variation, as the pond water quality may be impacted by both heat insulation and the obstruction of vertical mixing. Especially in saline water ponds with the purpose of aquaculture production, the appearance of a halocline may lead to dangerous risks, such as physiological stress on aquaculture products, increases in pathogenic micro-organisms, and deterioration of water quality. In the present study, the impact of the appearance of a halocline on physical water qualities was investigated by analyzing continuous on-site observation data obtained in Thailand. It was found that, after the appearance of the halocline, the heat was stored in the lower high-salinity layer, due to the heat insulation effect of the halocline. Furthermore, the halocline was also suggested to have an impact on the transportation of turbidity and to change the DO (dissolved oxygen) distribution in the vertical direction. These results are expected to provide information for assessment of the risk in saline water ponds and to contribute to a new approach for understanding deterioration problems in saline water aquaculture ponds.