[A-CG43] Coastal Ecosystems - 2. Coral reefs, seagrass and macroalgal beds, and mangroves

[ACG43-P06] The estimation of CO₂ flux in subtropical coastal ecosystems using a numerical model

*Hirotada Moki¹, Akio Sohma², Takashi Shibuki³, Takeshi Toyoda³, Anirban Akhand¹, Kenta Watanabe¹, Tatsuki Tokoro^1,4, Tomomi Inoue⁵, Hiroya Yamano⁵, Masayuki Bannno¹, Yasuyuki Nakagawa^1,6, Hiroyuki Matsuda⁷, Tomohiro Kuwae¹ (1.Port and Airport Research Institute, 2.Osaka City University, 3.Mizuho Information and Research Institute, Inc., 4.National Research Institute of Fisheries and Environment in Inland Sea, 5.National Institute for Environmental Studies, 6.Kyushu University, 7.Yokohama National University)

Keywords:Ecosystem model, Subtropical coastal ecosystem, Air-ecosystem CO2 flux, Carbon burial rate, Future prediction

Coastal ecosystems can play a role in climate change mitigation. One of the appropriate way to accurately quantify and predict the role is the utilization of numerical models. The mitigation effects can be facilitated by CO₂ uptake by net primary producers such as mangroves, zooxanthella in coral reef and seagrasses.

In this study, we developed a new ecosystem model that incorporates the biogeochemical processes of mangroves, tidal flats, seagrass meadows, lagoons, and coral reefs. We estimated CO₂ fluxes between air and the ecosystems and carbon burial rates in Yaeyama islands, Japan, which is the model site. In the future prediction, we selected two scenarios of representative concentration pathways, low emission (RCP2.6) and high emission (RCP8.5), adopted in IPCC 5^th Assessment Report and compared the model results in 2010 and 2100. The output of HadGEM2-ES from CMIP5 models were used as the boundary data.
Our model results showed that the mangrove absorbed CO₂ more than other ecosystems because of direct uptake of CO₂ from the air. The maximal carbon burial rate was found in the mangrove. Additionally, the inflowing of open waters affected the air-ecosystem CO₂ flux and carbon burial rate near the open boundary. We will also present the result of comparisons between the model results and observed data.