223
© Springer Nature Singapore Pte Ltd. 2019
T. Kuwae, M. Hori (eds.), Blue Carbon in Shallow Coastal Ecosystems,
https://doi.org/10.1007/978-981-13-1295-3_8
Chapter 8
CO 2 Flux in Tidal Flats and Salt Marshes
Sosuke Otani and Toru Endo
Abstract Tidal flats and salt marshes are sites where CO 2 is released to the environment by decomposing organic matter and CO 2 is absorbed by vegetation through
photosynthesis. It is thought that on balance, carbon is stored in tidal flats and salt
marshes. To explore this topic, we reviewed published estimates of air–water, air–
sediment, water–sediment, and air–marsh fluxes of CO 2 in tidal flats and salt
marshes. We also carried out multiyear measurements of CO 2 flux and related
parameters at two field sites in Osaka Bay, Japan, having flat intertidal and salt
marsh areas. The CO 2 fluxes were measured using the eddy correlation and chamber
methods. The air–sediment CO 2 flux data from tidal flats indicated net absorption of
atmospheric CO 2 into the sediment during daytime hours. The air–water CO 2 flux
data indicated that CO 2 was emitted from the water surface in small amounts, with
temporal fluctuations and seasonal changes that were strongly related to salinity, as
has been documented in the literature. We found that CO 2 was absorbed into salt
marsh and intertidal sediment and that CO 2 was emitted from subtidal sediment as
well as from the water surface of the tidal flat ecosystem during periods of submersion. The air–sediment CO 2 flux and its temporal fluctuation at the field sites appear
to be regulated by vegetation such as the reed Phragmites australis and
microphytobenthos.
S. Otani (*)
Civil Engineering and Environment Course, Department of Technological Systems, Osaka
Prefecture University College of Technology, Saiwaicho, Neyagawa, Osaka, Japan
e-mail: otani@osaka-pct.ac.jp
T. Endo
Graduate School of Engineering, Osaka City University,
Sugimoto, Sumiyoshi-ku, Osaka, Japan
© Springer Nature Singapore Pte Ltd. 2019
T. Kuwae, M. Hori (eds.), Blue Carbon in Shallow Coastal Ecosystems,
https://doi.org/10.1007/978-981-13-1295-3_8
Chapter 8
CO 2 Flux in Tidal Flats and Salt Marshes
Sosuke Otani and Toru Endo
Abstract Tidal flats and salt marshes are sites where CO 2 is released to the environment by decomposing organic matter and CO 2 is absorbed by vegetation through
photosynthesis. It is thought that on balance, carbon is stored in tidal flats and salt
marshes. To explore this topic, we reviewed published estimates of air–water, air–
sediment, water–sediment, and air–marsh fluxes of CO 2 in tidal flats and salt
marshes. We also carried out multiyear measurements of CO 2 flux and related
parameters at two field sites in Osaka Bay, Japan, having flat intertidal and salt
marsh areas. The CO 2 fluxes were measured using the eddy correlation and chamber
methods. The air–sediment CO 2 flux data from tidal flats indicated net absorption of
atmospheric CO 2 into the sediment during daytime hours. The air–water CO 2 flux
data indicated that CO 2 was emitted from the water surface in small amounts, with
temporal fluctuations and seasonal changes that were strongly related to salinity, as
has been documented in the literature. We found that CO 2 was absorbed into salt
marsh and intertidal sediment and that CO 2 was emitted from subtidal sediment as
well as from the water surface of the tidal flat ecosystem during periods of submersion. The air–sediment CO 2 flux and its temporal fluctuation at the field sites appear
to be regulated by vegetation such as the reed Phragmites australis and
microphytobenthos.
S. Otani (*)
Civil Engineering and Environment Course, Department of Technological Systems, Osaka
Prefecture University College of Technology, Saiwaicho, Neyagawa, Osaka, Japan
e-mail: otani@osaka-pct.ac.jp
T. Endo
Graduate School of Engineering, Osaka City University,
Sugimoto, Sumiyoshi-ku, Osaka, Japan