[A-CG56] 沿岸海洋生態系─２．サンゴ礁・藻場・マングローブ

[ACG56-P04] 温帯ガラモ場の代謝と炭素収支が大気中CO₂吸収に与える影響

*渡辺 謙太¹、吉田 吾郎²、堀 正和²、梅澤 有³、茂木 博匡¹、桑江 朝比呂¹ (1.港湾空港技術研究所、2.瀬戸内海区水産研究所、3.東京農工大学)

キーワード：大型海藻藻場、CO2吸収源、代謝、ブルーカーボン、炭素動態

Macroalgal beds are considered to be one of the vegetated coastal ecosystems (i.e., blue carbon ecosystems) that act as atmospheric CO₂ sinks. Macroalgal metabolisms and carbon budgets affect CO₂ sequestration by macroalgal beds, but its relationships are still poorly understood. In this study, we investigated air–water CO₂ exchange and budgets of dissolved inorganic carbon, total alkalinity, and dissolved organic carbon (DOC) in a temperate Sargassum bed during the productive winter. We estimated the metabolism of macroalgae and carbon budgets by using a field-bag method, a degradation experiment, and mass balance modelling over a diurnal cycle. Our results showed that macroalgal metabolism and carbon budgets affected atmospheric CO₂ uptake in and around the Sargassum bed. The macroalgal metabolism formed water with low CO₂ and high DOC that was then exported offshore. This export process potentially promotes CO₂ uptake in and around macroalgal beds.