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Circulation, biogeochemistry and carbon cycling in ocean margins
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Understanding CaCO3 cycling in the Yellow Sea
Monday 7th @ 1050-1110, Concert Hall
Weidong Zhai* , Institute of Marine Science and Technology, Shandong University
Di Qi, Key Laboratory of Global Change and Marine-Atmospheric Chemistry of State Oceanic Administration (SOA), Third Institute of Oceanography, SOA
Cenglong Li, Institute of Marine Science and Technology, Shandong University
Tianqi Xiong, Institute of Marine Science and Technology, Shandong University
Presenter Email: wdzhai@sdu.edu.cn |
| Based on numerous field surveys of carbonate system parameters carried out from 2011 to 2016, we found that one third of the Yellow Sea suffered from severe bottom seawater acidification (with araganite saturation state values of <1.5) during summer and autumn, bringing much stress on local benthic fauna community. The seasonal subsurface acidification mostly resulted from the community respiration induced CO2 accumulation in the cold water mass of the Yellow Sea. To chemically quantify the stress of the seasonal acidified seawater on local calcified organisms and benthic communities, we tried to calculate summertime net calcification rate in the North Yellow Sea cold water mass in 2011. The net calcification rate declined to nearly zero when the seawater aragonite saturation state reached a critical level of 1.5-1.6. This is much different from a recently published coral reef case observed by Bradley et al. (2018, Science), which suggest that the seawater aragonite saturation state threshold of net calcification rate reaching zero should be 2.5-3.0 in coral reef systems. Much remains to be investigated in order to quantitatively evaluate the effect of ocean acidification on marine CaCO3 cycles. To further understand CaCO3 cycling in the Yellow Sea, we investigated the dissolved calcium dataset obtained in China Seas in 2011. The results suggested that terrestrial sources only accounted for a part of the Yellow Sea's high calcium salt ratio. Therefore this report implies that net dissolution of calcium carbonate may occur all over the Yellow Sea, changing the proportion of seawater major elements to some extent. These changes may affect many fundamental issues of oceanography, such as the definition and measurement of salinity. |
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