Coupled micrometeorological and biological processes on atmospheric CO2

concentrations at the landeocean boundary, NE coast of India

D. Ganguly a, M. Deya, C. Chowdhury a, A.A. Pattnaik b, B.K. Sahu b, T.K. Jana

a Department of Marine Science, University of Calcutta, 35, Ballygunge Circular Road, Kolkata 700019, India

b Department of Marine Science, Berhampur University, Bhanja Bihar, Orissa, India

a b s t r a c t

This study reveals that landesea breezes, atmospheric stability and influence of net ecosystem metabolism for the conversion of organic carbon to atmospheric CO2 are the major driving forces behind the variation of atmospheric CO2 at the landeocean boundary, northeast coast of India. The seasonal variation of partial pressure of CO2 (pCO2) and its efflux from the coastal water were several fold higher in the pre-monsoon (1807.9 _ 757.03 m atm; 579.03 _ 172.9 mM m_2 h_1) than in the monsoon (1070.5 _ 328.5 m atm; 258.96 _ 185.65 mM m_2 h_1) and the post-monsoon (615.7 _ 121.6 m atm; 53.27 _ 19.24 mM 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 CO2 concentration were determined by local air circulations and atmospheric stability. Seasonal variations of atmospheric CO2 bear a significant signature of biological processes occurring in the coastal water by means of airesea exchange, markedly affected by the net ecosystem metabolism. Important predictors of coastal atmospheric CO2 in decreasing order of explained variability are wind direction, stability, CO2 efflux and wind velocity.

_ 2010 Elsevier Ltd. All rights reserved.

D. Ganguly et al. / Atmospheric Environment 45 (2011) 3903e3910