Shelf 200 m

1
PARTICULATE PHOSPHROUS INPUT AND BURIAL
EFFICIENCY IN THE GAOPING COASTAL SEA Yu-ching
Yeh1, Jia-Jang Hung1 and Chi-An Huh2 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

• River transport of particulate P
• The GP River carried about 3.14104 ton/yr
  (1.01109 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 mm particles during the
  wet season and in 63-150 mm particles during the
  dry season (Fig. 2).

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/cm2/yr in the GP
coastal sea. The burial fluxes range from 0.02 to
0.85 mg/cm2/yr for TP, from 0.02 to 0.73
mg/cm2/yr for PIP, and from 0.002 to 0.124
mg/m2/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/cm2/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.
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.
The phosphorus burial efficiency (PBE) was
estimated by using the method of Ingall and
Jahnke (1994) PBE
() 100 AP / JP where AP is the burial rate
of phosphorus species and JP 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.
Shelf ( lt200 m ) Upper slope ( 200-600 m ) Lower
slope ( 600-1000 m ) Base of slope ( gt1000 m )
Conclusions

• The Gaoping River carried about 3.14104 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.
• The mean annual burial flux of particulate P is
  0.13 mg/cm2/yr, corresponding to a total burial
  of 3.9103 ton/yr (1.26108 mol/yr) P in the
  study area.
• 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
• At present, only about 12 of river borne
  phosphorus was buried in the Gaoping coastal sea.