Liu Qinyu, Chen Jianfang, Lan Fei, Wang Kui, Li Dewang, Wang Bin, Yin Kedong
Ocean College, Zhejiang University, Zhoushan 316021, China; School of Marine Sciences/Guangdong Key Laboratory of Marine Resources and Coastal Engineering, Sun Yat-Sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, China; Donghai Laboratory, Zhoushan, Zhejiang 316021, China.
Key Laboratory of Marine Ecosystem Dynamics & Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China.
Mar Pollut Bull. 2025 Jul;216:117969. doi: 10.1016/j.marpolbul.2025.117969. Epub 2025 Apr 16.
Ocean acidification poses a growing environmental threat to estuarine ecosystems. Most research has focused on bottom water acidification driven by eutrophication from riverine nutrient inputs. In contrast, the impacts of other riverine components in estuarine systems have received less attention. This study investigates the impacts of riverine carbonate and organic matter input on acidification in the Pearl River estuary (PRE), using field data from April 2015 to January 2016. The results show that DIC and TA in the PRE are primarily governed by river-ocean mixing, while their seasonal variations are largely influenced by changes in the freshwater end-member. Compared to the marine carbonate system, the riverine DIC:TA ratio is significantly higher. Riverine carbonate input weakens the estuarine buffering capacity during mixing, thereby amplifying acidification from atmospheric anthropogenic CO. The pH reduction in the estuary due to anthropogenic CO intrusion reached a maximum of 0.15 units at a salinity of around 15, exceeding the 0.12 reduction at the seawater end. With the urbanization of the Pearl River Basin, the increased input of anthropogenic organic matter enhanced aerobic respiration in the estuary, releasing CO that may further intensify acidification. Unlike eutrophication-induced bottom acidification, which is closely associated with water column stratification and mainly occurs in the outer estuary during summer, organic matter-driven acidification is most pronounced in the upper estuary and affects the entire water column year-round. Moreover, it caused a maximum pH decline of up to 1.01 units in the PRE, surpassing that induced by eutrophication.
海洋酸化对河口生态系统构成了日益严重的环境威胁。大多数研究都集中在由河流营养物质输入导致的富营养化所驱动的底层水酸化上。相比之下，河口系统中其他河流成分的影响受到的关注较少。本研究利用2015年4月至2016年1月的实地数据，调查了珠江口（PRE）河流碳酸盐和有机物质输入对酸化的影响。结果表明，珠江口的溶解无机碳（DIC）和总碱度（TA）主要受河海混合控制，而它们的季节变化在很大程度上受淡水端元变化的影响。与海洋碳酸盐系统相比，河流的DIC:TA比值明显更高。河流碳酸盐输入在混合过程中削弱了河口的缓冲能力，从而放大了大气人为二氧化碳导致的酸化。由于人为二氧化碳入侵，河口在盐度约为15时pH值下降最大达到0.15个单位，超过了海水端的0.12个单位的下降幅度。随着珠江流域的城市化，人为有机物质输入的增加增强了河口的有氧呼吸，释放出的二氧化碳可能会进一步加剧酸化。与富营养化导致的底层酸化不同，后者与水柱分层密切相关，主要发生在夏季的河口外海，而有机物质驱动的酸化在上游河口最为明显，并且全年影响整个水柱。此外，它在珠江口导致pH值最大下降高达1.01个单位，超过了富营养化引起的下降幅度。
