Hypoxia has been observed worldwide and causes great damage to marine ecosystems. In the northeastern mariculture areas of the Shandong Peninsula, summer oxygen depletion and even hypoxia have been observed in the bottom layer, but the underlying dynamics are still poorly understood. In the current study, the physical controls of variations in bottom layer oxygen concentrations in summer and their interannual variations in the northeastern mariculture areas of the Shandong Peninsula were first investigated using in situ observations collected during 2016–2020. Over the past 5 years, the dissolved oxygen (DO) concentrations of the bottom layer have ranged from 0.8 to 13.0 mg L⁻¹ and exhibited a robust annual cycle, with the lowest value occurring in August. Hypoxia events covering several days were observed intermittently in the summers of 2016 and 2017. Summer oxygen depletion was caused by the combined effects of ocean stratification and enhanced biogeochemical oxygen consumption. At the interannual time scale, stratification and bottom layer DO concentrations showed synchronous variations and both peaked in 2018. The underlying mechanism was related to bottom layer currents, which were created by southerly monsoon winds. Strong/weak southerly surface winds induced a strong/weak bottom shoreward advection of cold, oxygen‐rich water and resulted in strong/weak stratification and high/low DO concentrations. The results provide a good reference for coastal mariculture management in the Shandong Province and enrich our understanding of the global distribution of coastal hypoxia.

中文翻译：

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黄海山东半岛东北沿海低氧区夏季底层氧气浓度变化的物理控制。

缺氧已经在世界范围内观察到，对海洋生态系统造成了极大的破坏。在山东半岛东北部的海水养殖区，底层已观察到夏季缺氧甚至缺氧，但对潜在的动态仍然知之甚少。在当前的研究中，首先使用2016-2020年期间收集的现场观测资料，对夏季底层氧气浓度变化及其在山东半岛东北海水养殖区的年际变化的物理控制进行了研究。在过去的5年中，底层的溶解氧（DO）浓度范围为0.8至13.0 mg L ^-1并且表现出强劲的年度周期，最低值发生在八月。在2016年和2017年夏季间歇性地观察到了几天的缺氧事件。夏季氧气耗竭是由海洋分层和生物地球化学耗氧量增加的共同作用引起的。在年际时间尺度上，分层和底层DO浓度显示出同步变化，并且都在2018年达到峰值。其潜在机制与底层风流有关，底层风流是由南风季风产生的。南风强/弱，引起底部富冷的富氧水对岸的强/弱平流，并导致强/弱分层和高/低溶解氧浓度。