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edaphic factors govern and regulate the saptio-temporal variability of soil CO 2
fluxes (Joffre et al. 2003; Rustad et al. 2000).
7.1.3.2.3 Air-Water CO 2 Fluxes in Mangrove Surrounding Aquatic Bodies
It is almost unequivocally accepted that the entire mangrove ecosystem acts as a
sink for CO 2 (i.e. net autotrophic), however, the aquatic bodies adjacent to the mangroves are mostly heterotrophic in nature (Borges et al. 2003), though few exceptions are there. This heterotrophic character is mainly attributed to the factors like
low primary production due to highly turbid waters, a vast spectrum of changing
salinity, immense re-mineralization of leaf and wood litter from the canopy and
export of labile organic carbon from mangroves (Jennerjahn and Ittekkot 2002).
Due to these factors, measurement of the air-water CO 2 exchange in the mangrove
waters has become an utmost necessity for a holistic quantification of the carbon
budget of any mangrove ecosystem. The air-water CO 2 flux is either measured
directly by means of deploying closed chamber at the air-water interface or by the
bulk formula method (Chap. 2) (Tokoro et al. 2018); both these methods are applicable at present (Wanninkhof and Triñanes 2017). In the bulk formulation method,
the CO 2 fluxes are computed from the product of the air-water pCO 2 gradient, the
gas transfer velocity and the solubility of CO 2 in water (Takahashi et al. 2009). The
main challenge was to accurately quantify the gas exchange coefficient which is
based on the parameterization of wind velocity, however, several studies conducted
by purposeful tracers showed excellent correspondence with the global estimates
(Sweeney et al. 2007). The gas exchange parameterizations formulated by Ho et al.
(2011) and Wanninkhof (2014) are the newest estimations and these formulations
have shown least possible uncertainty (< 15%) in computing gas transfer velocities
and bulk CO 2 fluxes.
7.1.4 Objectives
The principal purpose of writing the present chapter is to provide a broad overview
about the present scenario and current knowledge on the quantitative aspects of the
different types of CO 2 fluxes that takes place in and around a mangrove ecosystem
giving special emphasis on the world’s largest mangrove of Sundarbans. An exhaustive literature survey was conducted to compile the data of three types of fluxes
introduced above (recorded in any mangroves of the world and Sundarbans), i.e.,
atmosphere-biosphere CO 2 fluxes above the canopy, soil CO 2 fluxes and air-water
fluxes in the mangrove surrounding waters. Apart from delineating a global picture
from the perspective of quantification of the CO 2 fluxes, this chapter also intended
to assimilate and discuss all the factors controlling and governing these fluxes (Fig.
7.3). Most of the research works considered in this chapter is being carried out
within the last two decades, except a few which dates back to the 1980s. Keywords
7 CO 2 Fluxes in Mangrove Ecosystems
edaphic factors govern and regulate the saptio-temporal variability of soil CO 2
fluxes (Joffre et al. 2003; Rustad et al. 2000).
7.1.3.2.3 Air-Water CO 2 Fluxes in Mangrove Surrounding Aquatic Bodies
It is almost unequivocally accepted that the entire mangrove ecosystem acts as a
sink for CO 2 (i.e. net autotrophic), however, the aquatic bodies adjacent to the mangroves are mostly heterotrophic in nature (Borges et al. 2003), though few exceptions are there. This heterotrophic character is mainly attributed to the factors like
low primary production due to highly turbid waters, a vast spectrum of changing
salinity, immense re-mineralization of leaf and wood litter from the canopy and
export of labile organic carbon from mangroves (Jennerjahn and Ittekkot 2002).
Due to these factors, measurement of the air-water CO 2 exchange in the mangrove
waters has become an utmost necessity for a holistic quantification of the carbon
budget of any mangrove ecosystem. The air-water CO 2 flux is either measured
directly by means of deploying closed chamber at the air-water interface or by the
bulk formula method (Chap. 2) (Tokoro et al. 2018); both these methods are applicable at present (Wanninkhof and Triñanes 2017). In the bulk formulation method,
the CO 2 fluxes are computed from the product of the air-water pCO 2 gradient, the
gas transfer velocity and the solubility of CO 2 in water (Takahashi et al. 2009). The
main challenge was to accurately quantify the gas exchange coefficient which is
based on the parameterization of wind velocity, however, several studies conducted
by purposeful tracers showed excellent correspondence with the global estimates
(Sweeney et al. 2007). The gas exchange parameterizations formulated by Ho et al.
(2011) and Wanninkhof (2014) are the newest estimations and these formulations
have shown least possible uncertainty (< 15%) in computing gas transfer velocities
and bulk CO 2 fluxes.
7.1.4 Objectives
The principal purpose of writing the present chapter is to provide a broad overview
about the present scenario and current knowledge on the quantitative aspects of the
different types of CO 2 fluxes that takes place in and around a mangrove ecosystem
giving special emphasis on the world’s largest mangrove of Sundarbans. An exhaustive literature survey was conducted to compile the data of three types of fluxes
introduced above (recorded in any mangroves of the world and Sundarbans), i.e.,
atmosphere-biosphere CO 2 fluxes above the canopy, soil CO 2 fluxes and air-water
fluxes in the mangrove surrounding waters. Apart from delineating a global picture
from the perspective of quantification of the CO 2 fluxes, this chapter also intended
to assimilate and discuss all the factors controlling and governing these fluxes (Fig.
7.3). Most of the research works considered in this chapter is being carried out
within the last two decades, except a few which dates back to the 1980s. Keywords
7 CO 2 Fluxes in Mangrove Ecosystems