1. Fig. 4. A framework configured to calculate a P budget. Shelf ( <200 m ) Upper slope ( 200-600 m ) Lower slope ( 600-1000 m ) Base of slope ( >1000 m ) PARTICULATE PHOSPHROUS INPUT AND BURIAL EFFICIENCY IN THE GAOPING COASTAL SEA Yu-ching Yeh 1, Jia-Jang Hung 1 and Chi-An Huh 2 1. Institute of Marine Geology and Chemistry, National Sun Yat-San University, Kaohsiung, Taiwan, ROC 2. Institute of Earth Science, Academia Sinica, Taiwan, ROC Objectives To understand the transport of particulate phosphorus from the Gaoping River to the Gaoping coastal sea. To realize the modification of receiving particulate phosphorus during sedimentation and burial processes in the Gaoping coastal sea. To construct preliminarily the budget of particulate phosphorus in the Gaoping coastal sea. Results and Discussion 2. Burial fluxes of particulate P in coastal sediments The burial fluxes of particulate P are determined from the sedimentation rates of sediments and concentrations of particulate P in sediments. The sedimentation rate of sediment ranges from 0.032 to1.62 g/cm 2 /yr in the GP coastal sea. The burial fluxes range from 0.02 to 0.85 mg/cm 2 /yr for TP, from 0.02 to 0.73 mg/cm 2 /yr for PIP, and from 0.002 to 0.124 mg/m 2 /yr for POP. The TP was approximately consisted of 87% PIP and 13% POP. The spatial pattern of burial fluxes shows a pair of depositional lobes located on the flank of GP canyon along the upper slope (200-600m) (Fig. 3). The result may be caused by sedimentation from turbidity flows overflowing the canyon (Huh et al., 2008). The total sedimentary flux was estimated to be 0.132 mg P/cm 2 /yr, but 4.7% of total P flux was recycled into the water column. The phosphorus budget was proposed according to Figs. 4 and 7. Fig. 5. Variations of total sedimentary P fluxes (a), diffusive DIP fluxes (b), diffusive DOP fluxes (c), burial PIP fluxes (d) and burial POP fluxes (e) as a function of location depth in the GP coastal sea. The phosphorus burial efficiency (PBE) was estimated by using the method of Ingall and Jahnke (1994) PBE (%) = 100 × A P / J P where A P is the burial rate of phosphorus species and J P is the total sedimentary phosphorus flux. The PBE is generally higher than 80% except for the Station 789-L3. The Station 791-L18 has a highest PBE, which is identical to the station with the highest sedimentation rate of sediments (Fig.6). The highest PBE is likely linked to the effect of typhoon event. 3. Benthic fluxes and burial efficiency of P The total sedimentary fluxes are the sum of diffusion fluxes and burial fluxes. Fig. 5 shows the variation of total sedimentary fluxes, diffusion and burial fluxes for sampling stations with various depths. The total sedimentary fluxes of TP decreased generally with the depth of sampling stations. The 791-L18 Station was the highest fluxes among the sampling stations. Fig. 6. The relation plot between phosphorus burial efficiency and the depth of sampling stations. Conclusions 1.The Gaoping River carried about 3.14×10 4 ton/yr particulate P into the GP coastal sea, the river particulate-P was consisted of 92% PIP and 8% POP. The particulate P was carried mainly in 10-63 µm particles in the wet season and 63-150 µm particles in the dry season. 2.The mean annual burial flux of particulate P is 0.13 mg/cm 2 /yr, corresponding to a total burial of 3.9×10 3 ton/yr (1.26×10 8 mol/yr) P in the study area. 3.The PBE was generally higher than 80%. The highest PBE is on the site identical to that of the highest sedimentation rate of sediment in the GP coastal sea 4.At present, only about 12% of river borne phosphorus was buried in the Gaoping coastal sea. Fig.1. The study site and location of sampling stations in the Gaoping River and coastal sea. Fig. 2. Temporal variations of river discharge and P-fluxes (left), and relationship between discharge and P-associated particle size (right). Fig. 3. Spatial contours of burial fluxes of PIP (a), POP (b), TP (c) and sedimentation rates (d) in the GP coastal sea. Fig. 7. A conceptual model showing the phosphorus budget in the GP coastal sea. Gaoping River input = 1.01 × 10 9 mol P/yr Total input (sedimentary flux) = 1.32 × 10 8 mol P/yr Sediment Primary Production Photic zone Diffusion flux (DIP+DOP) = 6.22 × 10 6 mol P/yr Burial Flux (PIP+POP) = 1.26 × 10 8 mol P/yr Water column 1. River transport of particulate P The GP River carried about 3.14×10 4 ton/yr (1.01×10 9 mol/yr ) particulate P into the GP coastal sea in 2007. The total P flux was primarily determined by the river runoff during the May-yu (monsoon) and typhoon seasons. The particulate P was approximately consisted of 92% PIP and 8% POP. Meanwhile, the particulate P existed mainly in 10-63  m particles during the wet season and in 63-150  m particles during the dry season (Fig. 2).