Coupled micrometeorological and biological processes on atmospheric CO_2 concentrations at the land-ocean boundary, NE coast of India

摘要

This study reveals that land-sea breezes, atmospheric stability and influence of net ecosystem metabolism for the conversion of organic carbon to atmospheric CO_2 are the major driving forces behind the variation of atmospheric CO_2 at the land-ocean boundary, northeast coast of India. The seasonal variation of partial pressure of CO_2 (pCO_2) and its efflux from the coastal water were several fold higher in the pre-monsoon (1807.9 ± 757.03 μ atm; 579.03 ± 172.9 nM m~-2 h~-1) than in the monsoon (1070.5 ± 328.5 μ atm; 258.96 ± 185.65 nM m~-2 h~-1) and the post-monsoon (615.7 ± 121.6 μ atm; 53.27 ± 19.24 μM m~-2 h~-1). The mean photic zone productivity to column respiration ratio was 0.12 ± 0.08, revealing predominance of heterotrophic processes. Community respiration was at minimum during monsoon (38.82 ± 8.63 mM C m~-2 d~-1) but was at maximum (173.8 ± 111.8 mM C m~-2 d~-1) during pre-monsoon and intermittent (125.07 ± 11.97 mM C m~-2 d~-1) during post-monsoon. Diurnal variations of atmospheric CO_2 concentration were determined by local air circulations and atmospheric stability. Seasonal variations of atmospheric CO_2 bear a significant signature of biological processes occurring in the coastal water by means of air-sea exchange, markedly affected by the net ecosystem metabolism. Important predictors of coastal atmospheric CO_2 in decreasing order of explained variability are wind direction, stability, CO_2 efflux and wind velocity.