207
months of August and November, 2011 observed a much lesser mean CO 2 flux
(3.88 ± 0.38 g CO 2 m
−2
day
−1
) signifying the large scale seasonal variability of these
fluxes.
7.4.6 Short Term Variability of CO 2 Fluxes
Zablocki et al. (2011) gave stress on the fact that large uncertainties could be hidden
in the global estimates due to not considering the dramatic changes in wind speed
within one diel cycle. They inferred from their short term study, that extremely precise flux estimates computed on any given day can be tremendously influenced by
the wind condition of that particular day. As an example they noted that taking into
consideration the wind speed measured during their study of 1 day, the mean CO 2
flux amounted to 13.1 ± 4.8 mmol m
−2
day
−1
, however, if they tried to extrapolate
the data in a monthly scale taking into consideration the monthly average wind data,
the flux estimate would become 59.8 ± 17.3 mmol m
−2
day
−1
.The mangrove waters
lying in the periphery of the Australian landmass has received substantial attention
with respect to quantifying the air-water CO 2 fluxes. Call et al. (2015) carried out an
investigation in a mangrove creek near Moreton Bay of Australia in order to examine the spring-neap-spring air-water CO 2 flux variability. Earlier it was observed
that lower fluxes were observed during high tide phase and vice-versa, however, the
tidal amplitude varies to a great extent during the lunar cycle depending upon the
shift from spring to neap phase. Call et al. (2015) observed lower fluxes during the
spring phase and vice versa and depending upon the location of the sampling station
in the creek and gas transfer models used the effluxes within a small creek through
a complete spring-neap-spring cycle varied from 0.41 to 27.68 g CO 2 m
−2
day
−1
.
This observation again signifies the necessity of long term monitoring of these types
of fluxes in order to up-scale and compute large scale estimates.
7.4.7 Advancements in the Field of Gas Exchange
Parameterizations
The gas exchange parameterizations were carried out with a help of a tracer named
sulphur hexafluoride (SF 6 ) (Ho et al. 2014) and a dual tracer of SF 6 along with
3
He
(Ho et al. 2016). Both the studies revealed that the gas exchange taking place in the
air-water interface can be regulated by both wind speed and the bottom generated
shear/turbulence along with the residence time of the water. However, for large
estuaries, where wind flow is not obstructed by the mangrove canopy, wind speed
alone can serve as the deciding parameter to compute gas transfer velocity. Though
both of these short term studies were conducted with the main intention to compute
a universally acceptable formulation of gas transfer velocity, it gave us an idea about
the air-water CO 2 fluxes in this crucial mangrove waters.
7 CO 2 Fluxes in Mangrove Ecosystems
months of August and November, 2011 observed a much lesser mean CO 2 flux
(3.88 ± 0.38 g CO 2 m
−2
day
−1
) signifying the large scale seasonal variability of these
fluxes.
7.4.6 Short Term Variability of CO 2 Fluxes
Zablocki et al. (2011) gave stress on the fact that large uncertainties could be hidden
in the global estimates due to not considering the dramatic changes in wind speed
within one diel cycle. They inferred from their short term study, that extremely precise flux estimates computed on any given day can be tremendously influenced by
the wind condition of that particular day. As an example they noted that taking into
consideration the wind speed measured during their study of 1 day, the mean CO 2
flux amounted to 13.1 ± 4.8 mmol m
−2
day
−1
, however, if they tried to extrapolate
the data in a monthly scale taking into consideration the monthly average wind data,
the flux estimate would become 59.8 ± 17.3 mmol m
−2
day
−1
.The mangrove waters
lying in the periphery of the Australian landmass has received substantial attention
with respect to quantifying the air-water CO 2 fluxes. Call et al. (2015) carried out an
investigation in a mangrove creek near Moreton Bay of Australia in order to examine the spring-neap-spring air-water CO 2 flux variability. Earlier it was observed
that lower fluxes were observed during high tide phase and vice-versa, however, the
tidal amplitude varies to a great extent during the lunar cycle depending upon the
shift from spring to neap phase. Call et al. (2015) observed lower fluxes during the
spring phase and vice versa and depending upon the location of the sampling station
in the creek and gas transfer models used the effluxes within a small creek through
a complete spring-neap-spring cycle varied from 0.41 to 27.68 g CO 2 m
−2
day
−1
.
This observation again signifies the necessity of long term monitoring of these types
of fluxes in order to up-scale and compute large scale estimates.
7.4.7 Advancements in the Field of Gas Exchange
Parameterizations
The gas exchange parameterizations were carried out with a help of a tracer named
sulphur hexafluoride (SF 6 ) (Ho et al. 2014) and a dual tracer of SF 6 along with
3
He
(Ho et al. 2016). Both the studies revealed that the gas exchange taking place in the
air-water interface can be regulated by both wind speed and the bottom generated
shear/turbulence along with the residence time of the water. However, for large
estuaries, where wind flow is not obstructed by the mangrove canopy, wind speed
alone can serve as the deciding parameter to compute gas transfer velocity. Though
both of these short term studies were conducted with the main intention to compute
a universally acceptable formulation of gas transfer velocity, it gave us an idea about
the air-water CO 2 fluxes in this crucial mangrove waters.
7 CO 2 Fluxes in Mangrove Ecosystems