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Carbon dioxide and methane dynamics in a human‐dominated lowland coastal river network (Shanghai, China)
Author(s) -
Yu Zhongjie,
Wang Dongqi,
Li Yangjie,
Deng Huanguang,
Hu Beibei,
Ye Mingwu,
Zhou Xuhui,
Da Liangjun,
Chen Zhenlou,
Xu Shiyuan
Publication year - 2017
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1002/2017jg003798
Subject(s) - environmental science , biogeochemical cycle , ecosystem , carbon cycle , streams , hydrology (agriculture) , terrestrial ecosystem , ecology , biology , computer network , geotechnical engineering , computer science , engineering
Evasion of carbon dioxide (CO 2 ) and methane (CH 4 ) in streams and rivers play a critical role in global carbon (C) cycle, offsetting the C uptake by terrestrial ecosystems. However, little is known about CO 2 and CH 4 dynamics in lowland coastal rivers profoundly modified by anthropogenic perturbations. Here we report results from a long‐term, large‐scale study of CO 2 and CH 4 partial pressures ( p CO 2 and p CH 4 ) and evasion rates in the Shanghai river network. The spatiotemporal variabilities of p CO 2 and p CH 4 were examined along a land use gradient, and the annual CO 2 and CH 4 evasion were estimated to assess its role in regional C budget. During the study period (August 2009 to October 2011), the overall mean p CO 2 and median p CH 4 from 87 surveyed rivers were 5846 ± 2773 μatm and 241 μatm, respectively. Internal metabolic CO 2 production and dissolved inorganic carbon input via upstream runoff were the major sources sustaining the widespread CO 2 supersaturation, coupling p CO 2 to biogeochemical and hydrological controls, respectively. While CH 4 was oversaturated throughout the river network, CH 4 hot spots were concentrated in the small urban rivers and highly discharge‐dependent. The Shanghai river network played a disproportionately important role in regional C budget, offsetting up to 40% of the regional terrestrial net ecosystem production and 10% of net C uptake in the river‐dominated East China Sea fueled by anthropogenic nutrient input. Given the rapid urbanization in global coastal areas, more research is needed to quantify the role of lowland coastal rivers as a major landscape C source in global C budget.