230
8.3.1.1 Yodo River-Mouth Site
The Yodo river-mouth site near Osaka Bay has both an intertidal flat area (without
large vegetation) and a salt marsh area (with reed vegetation). Salinity here ranges
from 0 to 23 (Otani et al. 2017). We measured the air–marsh CO 2 fluxes at Station 1
by the eddy correlation method and the air–sediment and air–water CO 2 fluxes at
Station 2 by the chamber method (Fig. 8.2a).
We conducted 10 observation campaigns, each lasting 2–6 days, in the supratidal
zone dominated by reeds during the months of May, August, and November of 2014
and February and April through September of 2015. Atmospheric CO 2 concentration was measured at 10 Hz (LI-COR Co. LI-7500), as was the three-dimensional
wind speed (Sonic Co. SAT-540), and other weather conditions such as air temperature were measured at the same stations (Fig. 8.2b). The air–salt marsh CO 2 flux,
latent heat flux, and sensible heat flux were calculated from the data every 30 min
using the eddy correlation method (see Chap. 6) (Tokoro et al. 2018).
Air–sediment CO 2 fluxes during emersion periods in the intertidal zone were
measured on a monthly basis from July 2013 to March 2015 using light and dark
chambers (inner diameter 12 cm, height 21 cm) with an NDIR Carbon Dioxide
Probe (Vaisala Co. GMP: 343) (Fig. 8.2c). During submersion periods from April
2014 to March 2015, air–water CO 2 fluxes were measured using a chamber floating
on the water surface using a light chamber (diameter 19.5 cm, height 12.5 cm) with
the same probe.
8.3.1.2 Bird Sanctuary Site
At the bird sanctuary site, on the shore of Osaka Bay, the artificial salt marsh
includes intertidal and subtidal flat areas. Salinity ranges from 13 to 30 (Yamochi
et al. 2017). About 17% of the north salt marsh is in the intertidal zone (tidal flat
area). This surface is covered with abundant microphytobenthos, thus photosynthesis contributes to the air–sediment CO 2 exchange. However, the CO 2 exchanges at
the air–water interface and the water–sediment interface affect the carbon cycle of
the north salt marsh because the rest of the north salt marsh is subtidal. We measured the air–sediment CO 2 flux in the intertidal area and the water–sediment and
air–water CO 2 fluxes in the subtidal area (Fig. 8.3a).
Figure 8.3b is a schematic diagram of the CO 2 flux measurements. The air–sediment and air–water CO 2 fluxes were measured every hour for 24-h periods in spring
(13–14 May 2014), summer (5–6 August 2014), fall (4–5 November 2014) and
winter (2–3 February 2015). In the intertidal area, a light chamber and a dark chamber (volume 1.27 × 10
−2
m
3
, bottom area 5.72 × 10
−2
m
2
) were placed on the sediment. The CO 2 concentrations inside them were measured by using a CO 2 data
logger (T&D Co.: Tr-76Ui), and the air–sediment CO 2 flux was calculated from the
changes in CO 2 concentration. For the air–sea CO 2 flux, a light chamber (volume
1.43 × 10
−2
m
3
, bottom area 5.74 × 10
−2
m
2
) was floated on the sea surface and the
S. Otani and T. Endo
8.3.1.1 Yodo River-Mouth Site
The Yodo river-mouth site near Osaka Bay has both an intertidal flat area (without
large vegetation) and a salt marsh area (with reed vegetation). Salinity here ranges
from 0 to 23 (Otani et al. 2017). We measured the air–marsh CO 2 fluxes at Station 1
by the eddy correlation method and the air–sediment and air–water CO 2 fluxes at
Station 2 by the chamber method (Fig. 8.2a).
We conducted 10 observation campaigns, each lasting 2–6 days, in the supratidal
zone dominated by reeds during the months of May, August, and November of 2014
and February and April through September of 2015. Atmospheric CO 2 concentration was measured at 10 Hz (LI-COR Co. LI-7500), as was the three-dimensional
wind speed (Sonic Co. SAT-540), and other weather conditions such as air temperature were measured at the same stations (Fig. 8.2b). The air–salt marsh CO 2 flux,
latent heat flux, and sensible heat flux were calculated from the data every 30 min
using the eddy correlation method (see Chap. 6) (Tokoro et al. 2018).
Air–sediment CO 2 fluxes during emersion periods in the intertidal zone were
measured on a monthly basis from July 2013 to March 2015 using light and dark
chambers (inner diameter 12 cm, height 21 cm) with an NDIR Carbon Dioxide
Probe (Vaisala Co. GMP: 343) (Fig. 8.2c). During submersion periods from April
2014 to March 2015, air–water CO 2 fluxes were measured using a chamber floating
on the water surface using a light chamber (diameter 19.5 cm, height 12.5 cm) with
the same probe.
8.3.1.2 Bird Sanctuary Site
At the bird sanctuary site, on the shore of Osaka Bay, the artificial salt marsh
includes intertidal and subtidal flat areas. Salinity ranges from 13 to 30 (Yamochi
et al. 2017). About 17% of the north salt marsh is in the intertidal zone (tidal flat
area). This surface is covered with abundant microphytobenthos, thus photosynthesis contributes to the air–sediment CO 2 exchange. However, the CO 2 exchanges at
the air–water interface and the water–sediment interface affect the carbon cycle of
the north salt marsh because the rest of the north salt marsh is subtidal. We measured the air–sediment CO 2 flux in the intertidal area and the water–sediment and
air–water CO 2 fluxes in the subtidal area (Fig. 8.3a).
Figure 8.3b is a schematic diagram of the CO 2 flux measurements. The air–sediment and air–water CO 2 fluxes were measured every hour for 24-h periods in spring
(13–14 May 2014), summer (5–6 August 2014), fall (4–5 November 2014) and
winter (2–3 February 2015). In the intertidal area, a light chamber and a dark chamber (volume 1.27 × 10
−2
m
3
, bottom area 5.72 × 10
−2
m
2
) were placed on the sediment. The CO 2 concentrations inside them were measured by using a CO 2 data
logger (T&D Co.: Tr-76Ui), and the air–sediment CO 2 flux was calculated from the
changes in CO 2 concentration. For the air–sea CO 2 flux, a light chamber (volume
1.43 × 10
−2
m
3
, bottom area 5.74 × 10
−2
m
2
) was floated on the sea surface and the
S. Otani and T. Endo