Title
Annual Cycle and Budgets of Nutrients in the Yellow Sea：a model study
1. Members’ names and affiliations
Zhao Liang, Tianjin University of Science and Technology
Zhang Jing, Tianjin University of Science and Technology
2. AimThis study aims to study the budgets and transformations of both DIN andPON in the Yellow Sea and quantify the spatial differences in the sources andsinks of nutrients in the area with an employment of three-dimensional coupledbiophysical model (ECSECOM). What’s more, it promotes cooperation andstudent exchange between Tianjin University of Science and Technology and theCenter for Marine Environmental Studies (CEMS) of Ehime University.
3. Procedure

A three-dimensional coupled biophysical model (ECSECOM) was establishedto study the annual cycles and budgets of both dissolved inorganic nitrogen (DIN)
and particulate organic nitrogen (PON) in the Yellow Sea,. We simulated the DIN
and PON cycles in the Yellow Sea, calculated the annual budgets of nitrogen andanalyzed the spatial distributions and seasonal variations of each sources andsinks of DIN and PON.
4. Results

Figure 1, and Figure 2 show horizontal distribution of simulated DIN and PON
at the surface (2m depth) and bottom layer, where January represents winter,
April represents spring, July represents summer, and November represents
Autumn; water depth of 2 m represents the surface layer, and the vertical 20thlayer of the model (the last layer of water column) represents the bottom layer.
Figure 1 and Figure 2 indicate that: The DIN concentration decreases throughspring and summer due to the spring blooms and reaches the lowest value in July,then increases greatly in autumn. The concentration of PON is low in winter andspring, and increases in summer and autumn following the growth of chlorophylla and peaks in November.
Figure 3 shows annual budgets of the nutrient in the Yellow Sea, while Atmos
represents atmospheric deposition, Rege represents regeneration from benthic
remineralization, Net prod represents net primary productivity, Dere represents
remineralization of the detritus, Mort represents mortality of phytoplankton,
Remi represents remineralization, Rsus and Sedi represents resuspend andsedimentation of PON. JJC means Jeju channel. ECS means East China Sea. BSmeans Bohai Sea. Regarding the budgets of DIN, primary production andrespiration of phytoplankton are the most important sink and source of DIN. The
remineralization of the detritus pool compensates 29.20% of the consumption ofDIN by the primary production process, while external input of DIN accounts for
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17.72%. There are 48.08% of PON converting to DIN, the most of the rest PON
deposit to the sediment. The transformation rate from DIN to PON is 29.20%.

Fig.1 Horizontal distribution of simulated DIN at the surface (2m depth) and bottom
layerFig.2 Horizontal distribution of simulated PON at the surface (2m depth) and bottom
layer

Fig.3 Annual budgets of the nutrients in the Yellow Sea (109gN/a)

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Figure 4-6 show the spatial distribution of internal processes of N nutrients, whichmeans net primary productivity, DIN from remineralization of the detritus, and PON
from mortality of phytoplankton, respectively, indicating that: Two high-value areasof net production in the South Yellow Sea move to the nearshore from spring tosummer. The remineralization of the detritus remained high values around the coastof the Korean peninsula. A wide range of low value areas along Shandong peninsulain winter and autumn. Mortality of phytoplankton occurs along the most areas ofYellow Sea except Subei shoal in spring and summer.

Fig. 4. Net primary productivity in the Yellow Sea

Fig. 5. DIN from remineralization of the detritus in the Yellow Sea

Fig. 6. PON from mortality of phytoplankton in the Yellow Sea

Figure 7-9 show the spatial distribution of external N nutrients, which means DIN
from atmospheric deposition, DIN regeneration from benthic remineralization, and Netsedimentation of PON through the sediment-water interface. The figures indicate that:(1) Atmospheric deposition: Gradient from the coast to the open sea in the south Yellow
Sea- mainly wet deposition. Homogeneous in the north yellow sea- mainly dry

3 / 5deposition.
(2) Regeneration from benthic remineralization: High values in the central muddy areaof the south Yellow Sea and the northern part of Shandong peninsula and the central
part of the northern yellow sea.
(3) Net exchange of PON through the sediment-water interface: Sedimentation of PON
is bigger than resuspend in the Yellow Sea.

Figure 10 is the distribution of dominant external DIN input, as it shows: River input
DIN is concentrated in the estuary area, the controlled areas expand to the open sea insummer. The muddy are dominated by regeneration from benthic remineralization.
Atmospheric deposition dominates the rest areas of the region.

Fig.7 DIN from atmospheric deposition in the Yellow Sea

Fig. 8 DIN regeneration from benthic remineralization in the Yellow Sea

Fig. 9 Net sedimentation of PON through the sediment-water interface in the Yellow Sea4 / 5

Fig. 10 Distribution of dominant external DIN input
5. Publication/Conference presentation
Conference presentation (poster presentation)
Title: Annual Cycles and Budgets of Nutrients in the Yellow Sea: a model study
Lecturer: Jiang Hao
Time: 14~15 November 2019.
Location: Ehime University.
6. Perspectives in Future
To analyze the cycle and budgets of phosphorus nutrients and silicate nutrients，
including particulate organic phosphorus, dissolved inorganic phosphorus, biogenic
silicate and dissolved silicate.
To find out and discuss the difference between three types of nutrients.

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