Numerical modeling of blue carbon dynamics considering seagrass at Sashiki Port
(2026) In TVVR 5000 VVRM01 20252Division of Water Resources Engineering
- Abstract
- Blue carbon, defined as carbon fixed by marine plants, has gained attention as a climate change mitigation strategy. Coastal ecosystems play an important role in blue carbon storage due to their high carbon burial rates. Although the dynamics of the partial pressure of CO2 in seawater (pCO2) are closely related to blue carbon processes, studies investigating pCO2 variability in coastal areas remain limited. This study analyzes pCO2 dynamics in a seagrass bed together with relevant environmental factors and seeks to improve an existing numerical model by incorporating seagrass biological processes. The study site is located on the eastern coast of the Yatsushiro Sea in Kumamoto Prefecture, Japan, with field observations conducted at Sashiki... (More)
- Blue carbon, defined as carbon fixed by marine plants, has gained attention as a climate change mitigation strategy. Coastal ecosystems play an important role in blue carbon storage due to their high carbon burial rates. Although the dynamics of the partial pressure of CO2 in seawater (pCO2) are closely related to blue carbon processes, studies investigating pCO2 variability in coastal areas remain limited. This study analyzes pCO2 dynamics in a seagrass bed together with relevant environmental factors and seeks to improve an existing numerical model by incorporating seagrass biological processes. The study site is located on the eastern coast of the Yatsushiro Sea in Kumamoto Prefecture, Japan, with field observations conducted at Sashiki Port. A five-year dataset from six field surveys between 2021 and 2025 was used to evaluate the effects of varying environmental conditions on carbon dynamics. Model development was carried out using Delft3D, a hydrodynamic and water quality modeling framework. The results reveal the temporal variability of pCO2 and identify its major controlling factors. Weather conditions strongly influenced air–sea CO2 flux. Although incorporating seagrass processes improved model representation, simulated pCO2 showed only moderate agreement with observations, highlighting the need for further parameter refinement and continued field measurements. (Less)
- Popular Abstract
- Climate change is one of the most serious global issues today. In Japan, natural disasters have become more intense due to global warming, causing increasing damage to human life and property. One of the main drivers of climate change is the increase in greenhouse gases such as CO2.
“Blue carbon” has attracted attention as a natural solution for mitigating climate change. Blue carbon refers to carbon fixed by marine plants through photosynthesis. Among marine ecosystems, coastal areas with seagrasses are particularly important because their carbon burial rates are much higher than those of other ecosystems. Although coastal areas store large amounts of carbon, the reduction of atmospheric CO2 ultimately depends on air–sea gas exchange.... (More) - Climate change is one of the most serious global issues today. In Japan, natural disasters have become more intense due to global warming, causing increasing damage to human life and property. One of the main drivers of climate change is the increase in greenhouse gases such as CO2.
“Blue carbon” has attracted attention as a natural solution for mitigating climate change. Blue carbon refers to carbon fixed by marine plants through photosynthesis. Among marine ecosystems, coastal areas with seagrasses are particularly important because their carbon burial rates are much higher than those of other ecosystems. Although coastal areas store large amounts of carbon, the reduction of atmospheric CO2 ultimately depends on air–sea gas exchange. Atmospheric CO2 is absorbed into the ocean when the partial pressure of CO2 (pCO2) in seawater is lower than that in the atmosphere. Therefore, estimating seawater pCO2 and the air–sea CO2 flux is essential. However, pCO2 varies spatially due to the complexity of coastal ecosystems, and available pCO2 data are still limited. To address this issue, multi-year field observations were conducted in Sashiki Port, Ashikita Town, Kumamoto Prefecture, Japan, and the collected data were analyzed. In addition, an existing model that simulates pCO2 dynamics was improved by incorporating seagrass biological processes.
Field observations under different environmental conditions were carried out six times during both daytime and nighttime between 2021 and 2025 in Sashiki Port, where seagrasses are distributed. Water samples were collected and related parameters were measured to estimate pCO2 using established equations. The results showed that most pCO2 values were lower than atmospheric pCO2 in each year, indicating that the study site generally acts as a CO2 sink. Moreover, although the mean air–sea CO2 flux was negative for each year, the magnitude of the flux strongly depended on solar radiation.
Based on the results of the field observations, the existing model was improved using Delft3D, a comprehensive modeling framework capable of simulating various coastal and riverine processes. As a result, the model performance improved slightly (for example, the model error decreased from 17.3 to 14.3). The developed model numerically simulates the parameters used to calculate pCO2, meaning that the reproducibility of pCO2 depends on how accurately these parameters are reproduced. Therefore, further improvements are necessary to better simulate these processes and enhance the accuracy of pCO2 estimation.
Because pCO2 dynamics vary across both time and space, additional data are needed to determine whether coastal areas function as net CO2 sinks or sources. Continued observations and model development will improve the accuracy of these estimates. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/student-papers/record/9223643
- author
- Tsuchiya, Taichi LU
- supervisor
- organization
- course
- VVRM01 20252
- year
- 2026
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- blue carbon, climate change, carbon dioxide, seagrass, numerical modeling
- publication/series
- TVVR 5000
- report number
- TVVR25/5017
- ISSN
- 1101-9824
- language
- English
- additional info
- Examiner; Ronny Berndtsson
- id
- 9223643
- date added to LUP
- 2026-03-12 13:00:22
- date last changed
- 2026-03-12 13:00:22
@misc{9223643,
abstract = {{Blue carbon, defined as carbon fixed by marine plants, has gained attention as a climate change mitigation strategy. Coastal ecosystems play an important role in blue carbon storage due to their high carbon burial rates. Although the dynamics of the partial pressure of CO2 in seawater (pCO2) are closely related to blue carbon processes, studies investigating pCO2 variability in coastal areas remain limited. This study analyzes pCO2 dynamics in a seagrass bed together with relevant environmental factors and seeks to improve an existing numerical model by incorporating seagrass biological processes. The study site is located on the eastern coast of the Yatsushiro Sea in Kumamoto Prefecture, Japan, with field observations conducted at Sashiki Port. A five-year dataset from six field surveys between 2021 and 2025 was used to evaluate the effects of varying environmental conditions on carbon dynamics. Model development was carried out using Delft3D, a hydrodynamic and water quality modeling framework. The results reveal the temporal variability of pCO2 and identify its major controlling factors. Weather conditions strongly influenced air–sea CO2 flux. Although incorporating seagrass processes improved model representation, simulated pCO2 showed only moderate agreement with observations, highlighting the need for further parameter refinement and continued field measurements.}},
author = {{Tsuchiya, Taichi}},
issn = {{1101-9824}},
language = {{eng}},
note = {{Student Paper}},
series = {{TVVR 5000}},
title = {{Numerical modeling of blue carbon dynamics considering seagrass at Sashiki Port}},
year = {{2026}},
}