Sources of settling particulate organic carbon during summer in the northern Taiwan Strait

The settling of particulate organic carbon is significant for the vertical transfer and burial of organic carbon. Using time-series sediment traps, we collected settling particulate matter in the near-bottom layer (8 mab [meters above bed]) over eight continuous days in the continental shelf waters of the northern Taiwan Strait and analyzed the particulate organic carbon content. The observational results indicated that the deposition flux in the continental shelf waters during the summer in the north-eastern Taiwan Strait is 0.86 g/m2·d ∼10.68 g/m2·d; the corrected deposition flux is lower than the measured value by approximately 4.5%-30.6%. The particulate organic carbon (POC) content and δ13C org‰ value are 0.589%-0.741% and −20.74‰∼−22.61‰. The δ13C org‰ indicated that the settling particulate matter was primarily from marine sources at a contribution rate of 70%-88%. Settling particulate matter primarily came from the re-suspension of bottom sediment which accounted for 65%-85% of settling particulate matter. The rising thermocline and halocline near the bottom can strengthen the contribution of re-suspension to the settling particulate organic carbon.