205
river bodies adjacent to mangroves situated in countries like Australia, USA,
Bermuda, Papua New Guinea, Tanzania, Vietnam and India. Notably three works
have been reported from the Indian part of Sundarbans which will be discussed
later.
7.4.2 Quantification of Air-Water CO 2 Fluxes – Role
of Tracers
Until the recent advancements regarding quantification of air-water CO 2 exchange
with the help of tracers were made (Ho et al. 2014; Wanninkhof 2014; Wanninkhof
and Triñanes 2017), the most challenging part in the quantification of air-water CO 2
exchange in any aquatic ecosystem was to accurately estimate the gas transfer
velocity. However, the bulk formula method has been applied in many eminent
works carried out in the last two decades.
Glancing through the magnitudes of air-water CO 2 fluxes observed throughout
the world (Table 7.3), it can be observed that the fluxes are much less than that
observed in case of atmosphere-biosphere CO 2 fluxes, however, quite similar to the
soil CO 2 effluxes. Borges et al. (2003) was among the first few comprehensive
works in this field that measured and analyzed the air-water CO 2 fluxes in the
mangrove waters of Papua New Guinea, India and Bahamas. They pointed out that
the mangrove waters usually remain oversaturated with CO 2 (having a varying
extent in terms of pCO 2 of 380–4800 μatm) and can prove to be potential source of
CO 2 to the atmosphere. Up-scaling their observed mean magnitude to the global
expanse of mangrove adjacent water mass, they assessed that the emission can be up
to 50 × 10
6
t C year
−1
.
They also stressed that the seasonal variability of these fluxes should be thoroughly studied to properly estimate the global budget. However, it is evident from
Table 7.3 that most of the studies that followed, were done in short term scale and
very few studies attempted the annual cycle or at least in seasonal scale.
7.4.3 Spatial Variability Within an Estuary
Bouillon et al. (2003) observed that in the oligohaline and the mesohaline sections
substantial production of DIC and total alkalinity (TAlk) was recorded, and the
pCO 2 in water varied over a range of 293–500 ppm only. Whereas, in the outward
fringes of the estuaries where extensive mangrove cover was crisscrossed by many
tidal creeks rapid mineralization of organic carbon was found to take place (reflected
from a wide range of pCO 2 in water from 1375 to 6437 ppm), eventually leading to
high magnitude of effluxes.
7 CO 2 Fluxes in Mangrove Ecosystems
river bodies adjacent to mangroves situated in countries like Australia, USA,
Bermuda, Papua New Guinea, Tanzania, Vietnam and India. Notably three works
have been reported from the Indian part of Sundarbans which will be discussed
later.
7.4.2 Quantification of Air-Water CO 2 Fluxes – Role
of Tracers
Until the recent advancements regarding quantification of air-water CO 2 exchange
with the help of tracers were made (Ho et al. 2014; Wanninkhof 2014; Wanninkhof
and Triñanes 2017), the most challenging part in the quantification of air-water CO 2
exchange in any aquatic ecosystem was to accurately estimate the gas transfer
velocity. However, the bulk formula method has been applied in many eminent
works carried out in the last two decades.
Glancing through the magnitudes of air-water CO 2 fluxes observed throughout
the world (Table 7.3), it can be observed that the fluxes are much less than that
observed in case of atmosphere-biosphere CO 2 fluxes, however, quite similar to the
soil CO 2 effluxes. Borges et al. (2003) was among the first few comprehensive
works in this field that measured and analyzed the air-water CO 2 fluxes in the
mangrove waters of Papua New Guinea, India and Bahamas. They pointed out that
the mangrove waters usually remain oversaturated with CO 2 (having a varying
extent in terms of pCO 2 of 380–4800 μatm) and can prove to be potential source of
CO 2 to the atmosphere. Up-scaling their observed mean magnitude to the global
expanse of mangrove adjacent water mass, they assessed that the emission can be up
to 50 × 10
6
t C year
−1
.
They also stressed that the seasonal variability of these fluxes should be thoroughly studied to properly estimate the global budget. However, it is evident from
Table 7.3 that most of the studies that followed, were done in short term scale and
very few studies attempted the annual cycle or at least in seasonal scale.
7.4.3 Spatial Variability Within an Estuary
Bouillon et al. (2003) observed that in the oligohaline and the mesohaline sections
substantial production of DIC and total alkalinity (TAlk) was recorded, and the
pCO 2 in water varied over a range of 293–500 ppm only. Whereas, in the outward
fringes of the estuaries where extensive mangrove cover was crisscrossed by many
tidal creeks rapid mineralization of organic carbon was found to take place (reflected
from a wide range of pCO 2 in water from 1375 to 6437 ppm), eventually leading to
high magnitude of effluxes.
7 CO 2 Fluxes in Mangrove Ecosystems