Inter-annual Variability of the Carbonate System in the Hypoxic Upper Pearl River Estuary in Winter

Frontiers in Marine Science

Lifang Wang¹  Xue Song¹  Ying Gao¹  Yaohua Luo¹  Xianghui Guo²  Yi Xu³  Tao Huang³ 

[1] College of Ocean and Earth Sciences, Xiamen University, Xiamen, China;Fujian Provincial Key Laboratory for Coastal Ecology and Environmental Studies, Xiamen University, Xiamen, China;State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China;

关键词: Pearl River estuary;    carbonate system;    inter-annual variability;    biogeochemical processes;    hypoxic;   

DOI  :  10.3389/fmars.2020.594725

来源: DOAJ

【 摘 要 】

Hypoxia has become a universal environmental and ecological problem in recent decades. The Pearl River estuary (PRE), the largest estuary in Southern China, is hypoxic year-round in the upper estuary. This study reports the inter-annual variation between 2005 and 2019 in the carbonate system of the hypoxic upper PRE in winter. In January 2005, both dissolved inorganic carbon (DIC) and total alkalinity (TA) concentrations were >3000 μmol kg–1 at the upstream-most station and decreased sharply downstream. However, DIC and TA were lower, with concentrations of 2300 and 1950 μmol kg–1, respectively, at the upstream-most in January 2019. At salinities >15, both DIC and TA were conservative and reached steady values at the downstream seawater end-member. The upstream-most station was taken as an example to quantify the influences of biogeochemical processes on DIC and TA, including CO2 degassing, organic carbon oxidation, pelagic nitrification, CaCO3 dissolution and benthic release. Among the biogeochemical process, a decrease in CaCO3 dissolution (from 734.4 μmol kg–1 in 2005 to 168.9 μmol kg–1 in 2019) was the major factor driving the decreases of DIC and TA in 2019. In the context of global change, inter-annual variability in biogeochemical process should receive more attention.

【 授权许可】

Unknown