Two stations were visited in the western tropical Pacific Ocean: The South-East Asia Time-series Station (SEATS) in the northern South China Sea (SCS) and station F2 in the Philippine Sea, ~230 km to the northeast of the Luzon Strait. Water samples were taken aboard the R/V Dong-Fang-Hong 2 in July and August 2017 from 13 depths between 5 m and 3800 m at SEATS and 11 depths between 5 m and 3200 m at F2 using Niskin bottles mounted on a SeaBird 911 conductivity-temperature-depth (CTD) rosette sampler. A time-course dark incubation (50 days) with sampling time at 0, 3, 7, 11, 15, 23, 34 and 50 d was conducted for the bottommost sample from F2 with and without prior exposure to solar radiation. The value of different parameters was calculated as the ratio of the signal of property X at irradiation time t to that at time zero.