4. Research report (Follow the guideline on the next page)

Development and application of intertidal carbon cycle model
Xinyu Lu

Ocean University of China

Xinyu Guo Ehime University
Jie Shi

Ocean University of China

Invited and funded by LAMER (Leading Academia in Marine and Environment
Pollution Research), Ehime University, Japan, I went to the Marine Environment
Research Center of Ehime University in Japan for a 28-day study exchange from July 21
to August 17, 2023. During this time, I have learned a lot, not only academic knowledge,
but also a lot of humanistic and social experience and understanding.
The tidal flat is considered to be an important place for coastal biological production(Yara et al., 2007). The ability of natural tidal flat to purify organic pollutants and its
ecological regulation function has attracted wide attention in recent years.The tidal flat
has a very high function of removing nitrogen, phosphorus and other biological elementsin the water, so the purification capacity of the tidal flat has been paid more and moreattention recently(Huanget al., 2021). However, there aren’t much researches on thequantitative assessment of tidal flat productivity around the world. The ecosystem ofinter-tidal wetland and seagrass bed has significant carbon absorption and sequestration
capacity, which has an important impact on the global carbon cycle(Shao et al., 2019).
I’m preparing for modeling the material cycle and carbon flux in is the basic platform forbiogeochemical research in coastal waters especially tidal flat.The tidal flat is considered
to be an important place for coastal biological production. The ability of natural tidal flatto purify organic pollutants and its ecological regulation function has attracted wide
attention in recent years. In recent years, more and more domestic studies have focusedon carbon fluxes in tidal flat, especially in inter-tidal wetlands and seagrass beds(Lima etal., 2022; Gräfnings et al., 2023). The ecosystem of inter-tidal wetland and seagrass bed
has significant carbon absorption and sequestration capacity, which has an important
impact on the global carbon cycle. Seaweed is an important primary productivity in
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marine ecosystems, and the study of its carbon sequestration and carbon storage
mechanism is conducive to improving the understanding of the potential of marine carbon
sequestration and carbon storage in waters. Furthermore, we can apply the new model toall coastal waters of China(Gao et al., 2022). The more interdisciplinary andcomprehensive research is a trend in the future, and the coupled modeling work is also
necessary.Furthermore, we can apply the new model to all coastal waters of China. The
more interdisciplinary and comprehensive research is a trend in the future, and thecoupled modeling work is also necessary.The objective of this study is to quantitatively
elucidate the material cycle and carbon flux changes in the intertidal zone, and to propose
accurate and effective measures for the assessment and protection of the intertidalecosystem. The main research content is to establish a hydrodynamic and ecologicalcoupling model applicable to the intertidal carbon cycle, simulate the intertidal algae(seaweed bed) through the calculation of carbon elements in the model, so as toquantitatively simulate and estimate the production and life of the water body in the study
area and self-purification capacity, and propose accurate and effective measures to protect
the intertidal ecosystem.
This study employs the Princeton Ocean Model (POM), an easy-to-use yet powerful
ocean modeling code that can simulate a wide range of issues from small-scale coastal
processes to global ocean climate change. POM08 is a model with dry and wet griddeveloped by Oey in 2008 based on POM and applicable to coastal waters (FIG. 1). The
feature of this model is that it can judge whether the grid is in a dry or wet state throughchanges in water depth (Oey, 2005).

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Figure 1 calculation of water depth in POM08
The establishment of benthic algae model refers to the benthic algae model of Yaraet al. (2007), and the specific model construction is shown in Figure 2. The upper layerof Box1 represents the material circulation process of phytoplankton in the water, and we
mainly consider the benthic algae model of Box2. At present, the main way of suspended
nutrient nitrogen cycle in tidal plain is: upper nutrients → phytoplankton → suspended
nutrients (bivalves)→ upper nutrients.

Figure 2 benthic algae model construction
Research schedule：(1) In the first quarter, Using the POM(Princeton Ocean Model) model to establish anecological model in the study area.
(2) Collecting the data to train and verify the accuracy of the model.
(3) In the second quarter, engaging to quantitatively predict the effects of regenerated
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nutrient and carbon storage fluxes on the productivity of adjacent coastal waters in thelost tidal flat and seagrass bed regenerated areas.
Month1-6: A preliminary inter-tidal three-dimensional dynamic-ecological coupling
model was developed, and the simulation results were corrected using observational facts.
Months 7-12: Model results are analyzed and studies are carried out in specific tidal
flat to simulate material cycling and carbon fluxes in that area.
Months 13-18: The simulation results were analyzed, and on this basis, thepurification capacity of the intertidal seaweed bed was analyzed.
Months 19-24: Summarize scientific problems and write articles.
In terms of study, the experience of going abroad is very meaningful to me. I had theopportunity to be exposed to different disciplines and courses and to learn from the ideas
and experiences of different professors and students.After the discussion and study, Ibelieve that using numerical simulation to simulate the carbon flux of the intertidal algae
bed and studying the self-purification ability of the intertidal algae bed through simulation
is a better way to understand the purification ability of the intertidal algae bed. In addition,
the coastal condition flux of the general shelf sea model is usually zero, which isinconsistent with the reality. In order to simulate the Marine ecological environment moreaccurately, it is necessary to consider the mass exchange flux between the intertidal zone
and the shelf sea. The establishment of the intertidal ecological model is also anindispensable part of the establishment of a more perfect and accurate offshore ocean
model. At the same time, the Marine biogeochemical model developed by Professor Guo
Xinyu on the basis of the Regional ocean model (POM) has been well applied in the studyof dynamic processes and nutrient budget in China's offshore areas.
References
Yara, Y., Yanagi, T., Montani, S., et al.(2007). Role of tidal flat in material cycling in thecoastal sea. la mer, 45: 117-134.
Shao, K., Gong, N., WanG, L., Qu, Y., Du, N. (2019). Simulation of carbon sequestration

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and storage potential of benthic algae in intertidal zone of Dalian temperate zone. Acta
Oceanologica Sinica, 41(12): 113-120.
Huang, X., Liang, S., Tao Y., et al. (2021). Distribution characteristics of organic carbon
storage in Spartina alterniflora wetland at the mouth of Fengjiang River in Beibu Gulf.
Guangxi Botany,, 41(6):9.
Gao, Y., Jiang, Z., Li, W., et al. (2022). Source analysis of organic carbon in surface
sediments and evaluation of carbon storage in grass beds in Songgou Bay, China [J].
Advances in Fishery Science, 43(5):10.
Lima, M. D. A. C., Ward, R. D., Joyce, C. B., Kauer, K., & Sepp, K. (2022). Carbon
stocks in southern England's intertidal seagrass meadows. Estuarine, Coastal and Shelf
Science, 275, 107947.
Gräfnings, M. L., Govers, L. L., Heusinkveld, J. H., Silliman, B. R., Smeele, Q., Valdez,S. R., & van der Heide, T. (2023). Macrozoobenthos as an indicator of habitat suitability
for intertidal seagrass. Ecological Indicators, 147, 109948.
Yara, Y., Yanagi, T., Montani, S., & Kuninao, T. (2007). Role of tidal flat in material
cycling in the coastal sea. うみ, 45(3), 117-134.
Oey L Y. A wetting and drying scheme for POM[J]. Ocean Modelling, 2005, 9(2): 133150.

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