Spatial variability of atmosphere-biosphere CO₂ and H₂O exchange in selected sites of Indian Sundarbans during summer

Spatial variability of atmosphere-biosphere CO₂ exchange was evaluated in Jharkhali, Bonnie Camp and Henry Island situated, respectively, in the inner, middle and outer estuarine part of Indian Sundarban mangrove ecosystem using micrometeorological methods, between 15th April and 15th May, 2011. Henry Island and Jharkhali acted as a sink for CO₂ with a rate of 18.94 g m^-2 d^-1 and 51.06 g m^-2 d^-1, respectively, whereas the sink strength of Bonnie camp was 1.51 g m^-2 d^-1. A positive correlation was obtained between solar radiation and 'atmosphere to biosphere' CO₂ flux. Varying magnitudes in leaf chlorophyll may be another decisive factor controlling CO₂ exchange. Greater chlorophyll content of the dominant species of a site leads to higher photosynthetic rate and hence increases the magnitude of 'atmosphere to biosphere' CO₂ influx. A mean daytime water vapor flux of 7.83 ± 4.95 m mol m^-2 s^-1 and a nighttime of 3.38 ± 3.32 m mol m^-2 s^-1 was observed at the three sites. The observed Bowen ratio values reflected a dominance of latent heat flux, compared to that of sensible heat flux in this ecosystem. The ecosystem on the whole acted as a sink for CO₂ (23.83 g m^-2 d^-1) but the magnitude of CO₂ influx was found to vary spatially.