Influence of human activity and monsoon dynamics on spatial and temporal hydrochemistry in tropical coastal waters (Sanya Bay, South China Sea)

Human activities and oceanic influences like mixing and/or upwelling define the hydrochemical and biological characteristics of coastal regions. In Sanya Bay, northern South China Sea, the balance between these two influences on spatial and temporal scales is poorly understood. The influence from human activities was due to discharge from Sanya River, whereas the most important marine influence was related to seasonal changes in hydrodynamics. Spatial differences (p < 0.05) in total nitrogen (TN) and chlorophyll-a (Chl-a) were observed. Seasonal differences were observed for temperature and nutrients. Human activities are the dominant factor influemcing hydrochemistry in the inner bay. This region exhibited the maximum influence of discharge from Saya River as estimated by higher nutrient levels. Oceanic influences like upwelling and mixing caused by monsoons are the dominant factors influencing hydrochemistry in the central and outer bay. Both human activities and oceanic influences play important roles in coastal ecosystems in Sanya Bay. This study has defined these characteristics so that better management policies can be enacted.