Sea surface pCO2 in an urbanized coastal system (Jiaozhou Bay, China) during summer

Various biogeochemical processes complicate carbon dioxide (CO2) behaviour in coastal oceans. Through eight summer surveys, detailed variations in CO2 mechanisms in the urbanized Jiaozhou Bay, China, were analysed. During the rainless period, respiration and dissolved inorganic carbon input from treated wastewater made the northeastern region a strong CO2 source, while the western region with cleaner seawater was a weak source because calcium carbonate (CaCO3) precipitation exceeded primary production. Rainfall events with different intensities and locations caused significantly different effects. When rainfall occurred over the sea, enhanced primary production caused a CO2 sink; when rainfall induced little terrestrial pollutant input, CaCO3 precipitation exceeded net primary production, leading to a CO2 source. When heavy rain caused bulk runoff, the northeastern region was a strong CO2 source because rivers flowing through downtown regions inputted considerable organic matter, while in the western region, runoff through suburbs and wetlands led to a strong sink.