地球観測衛星しきさいから沿岸域の「ブルーカーボン」を広域的に把握する新たな可能性―相模湾・駿河湾で衛星観測による懸濁物質量と河川・海草藻場との関係を確認―

研究者情報

ポイント

• 日本の地球観測衛星GCOM-C「しきさい」の観測データから推定される全懸濁物質（Total Suspended Matter: TSM）を用いて、沿岸域のブルーカーボン分布を広域的に把握できる可能性を検証しました。
• 相模湾と駿河湾を対象に解析した結果、河口から離れるほどTSMが低くなる傾向が両湾で確認されました。
• 海草藻場が存在する場所では、周辺の沿岸海域に比べてTSMが有意に高いことが確認されました。
• These results indicate that TSM may partially reflect the distribution of particulate organic matter (POM) associated with blue carbon in coastal areas.

概要

Coastal ecosystems such as seagrass beds are attracting attention as ``blue carbon ecosystems'' that absorb, fix, and sequester carbon dioxide from the atmosphere through biological processes. There are several types of organic matter that are sequestered as blue carbon, and organic matter released and transported into the sea from seaweed beds is an important source. On the other hand, it is thought that some organic matter supplied from land is sequestered in seaweed beds and the deep sea. Remote sensing using satellites has been attracting attention in the study of blue carbon ecosystems, but much of the research to date has focused on understanding the distribution and area of ​​seagrass beds themselves, and insufficient consideration has been given to methods for understanding over a wide range of organic matter released and transported from seagrass beds into the ocean. In this study, we focused on Total Suspended Matter (TSM) estimated from data from the SGLI (Second-generation Global Imager) sensor on board the Japanese Earth observation satellite GCOM-C "Shikisai" and attempted to estimate the wide-area distribution of organic matter emitted from seaweed beds. TSM is an index that indicates the amount of fine particles such as organic matter and sediment floating in seawater, or in other words, the degree of turbidity of the water. In coastal areas, particulate organic matter (POM) derived from rivers and seaweed, which can be a source of blue carbon, is also a component of TSM, so the distribution of TSM may reflect the distribution of POM. Therefore, targeting Sagami Bay and Suruga Bay, we analyzed the relationship between the TSM obtained from observations by GCOM-C "Shikisai" in 2023, the distance from the river mouth, and the distribution of seagrass beds. As a result, TSM decreased significantly with increasing distance from the river mouth in both bays. At the same time, TSM values ​​were significantly higher in areas where seagrass beds were confirmed by surveys conducted by the Ministry of the Environment compared to surrounding coastal waters. These results indicate that the satellite-estimated TSM reflects the distribution of POM in the ocean. Furthermore, it is possible that the distribution of blue carbon-related substances in coastal areas, such as organic matter derived from seagrass beds and suspended solids trapped within seagrass beds, may also be partially reflected. This research is an outcome that will lead to a new approach for broadly assessing blue carbon in coastal areas using satellite observations. The results of this research were published on August 15th in the English journal "Environmental Advances" published by ELSEVIER. This research is a result of CREST's "[Ocean Carbon] Uncovering the potential of the ocean by elucidating the relationship between the ocean and CO2."

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