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.