| 摘要: |
| 基于渤海两观测站点2020年12月至2022年8月的定点连续观测数据,本文研究了该区域底层溶解氧浓度的季节变化特征及影响机制。结果表明,两观测站点底层溶解氧浓度及其变化速率均呈现季节变化规律:溶解氧质量浓度冬季(10.26~15.36 mg/L)或春季(10.84~15.65 mg/L)最高,秋季(3.46~10.76 mg/L)次之,夏季(1.78~11.12 mg/L)最低;溶解氧质量浓度变化速率夏季最快,约为–0.06~–0.08 mg/(L·d)。进一步分析表明:春季到夏季,受底层海水温度升高和水体层结增强的共同影响,底层溶解氧浓度降低;夏末到秋季,由于底层海水温度降低和水体层结减弱,底层溶解氧浓度升高。近岸浅水区发生的大风过程会使底层溶解氧浓度快速升高至过饱和状态。生物地球化学过程也会对底层溶解氧浓度的变化产生一定影响:春季,浮游植物光合作用使底层溶解氧饱和度达到全年最高值,最高可达137%;夏季,底层水体的耗氧过程使底层溶解氧浓度降低至不饱和状态,最低可降至21%。2022年7月底,观测数据记录到唐山外海的低氧现象,溶解氧浓度最低值仅1.78 mg/L,这与水体层结和底层生物地球化学过程耗氧增强有关。本研究首次使用渤海底层溶解氧的长期定点连续观测数据,旨在为探讨渤海底层低氧的演化过程和控制机制提供有效参考。 |
| 关键词: 渤海 溶解氧 季节变化 海水温度 层结 |
| DOI：10.11759/hykx20230219001 |
| 分类号:P717 |
| 基金项目:海南省科技计划三亚崖州湾科技城联合项目(120LH001);国家自然科学基金项目(42176016);山东省自然科学基金项目(ZR2020MD059) |
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| Seasonal variations in the bottom dissolved oxygen concentration in the Bohai Sea |
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LI Wenbin1, LIU Zizhou1, ZHAI Fangguo1, WU Wenfan1, GU Yanzhen2, LIU Cong3
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1.College of Ocean and Atmospheric Sciences, Ocean University of China, Qingdao 266100, China;2.Ocean College, Zhejiang University, Zhoushan 316021, China;3.Hainan Institute of Zhejiang University, Sanya 572000, China
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| Abstract: |
| Based on long-term in-situ data collected from two observation stations in the Bohai Sea from December 2020 to August 2022, this study analyzed the seasonal variations in bottom dissolved oxygen (O2) concentrations and their underlying mechanisms. The results indicated significant seasonal fluctuations in both the O2 concentration and its rate of change. Winter (10.26–15.36 mg/L) and spring (10.84–15.65 mg/L) recorded the highest O2 concentrations, followed by autumn (3.46–10.76 mg/L), while summer showed the lowest concentrations (1.78–11.12 mg/L). The O2 concentration shifted most rapidly during summer, with rates declining at −0.06 to −0.08 mg/(L·d). Further analysis showed that from spring to summer, rising bottom seawater temperatures and enhanced stratification led to declining O2 concentrations. Conversely, as bottom water temperatures decreased and stratification weakened in late summer through autumn, O2 levels increased. Offshore shallow waters also experienced a rapid rise in bottom O2 concentration to supersaturation during strong wind events. Biogeochemical processes played a significant role in altering bottom O2 concentration: phytoplankton photosynthesis drove O2 saturation to its annual peak in spring, reaching up to 137%. However, oxygen consumption in bottom waters led to unsaturation during summer, with concentrations as low as 21%. In late July 2022, the observation system detected a hypoxic event near the Tangshan offshore area, where O2 concentration dropped to just 1.78 mg/L. This was attributed to intensified stratification and oxygen consumption caused by bottom-water biogeochemical activity. This study was the first to use long-term fixed-point continuous observation data on bottom O2 levels in the Bohai Sea. It provides critical insights and a valuable reference for exploring hypoxia evolution and its control mechanisms in the bottom of the Bohai Sea. |
| Key words: Bohai sea dissolved oxygen seasonal variation seawater temperature stratification |
