Large volumes of sand are needed in order to combat coastal land loss due to global sea-level rise for restoration of barrier island systems and beaches undergoing rapid erosion and submergence. The sediment required for such projects often originates from dredging of sand deposits on the adjacent shelf. Two dredge pits, with contrasting geology and located at varying distances from the Mississippi River Delta in the northern Gulf of Mexico shelf were sampled during spring and summer. Samples were also collected concurrently from surrounding continental shelf stations that are subject to seasonal hypoxia every summer. The bottom water dissolved O₂ inside the dredge pits were found to be consistently hypoxic or near hypoxic throughout both seasons, with high sediment O₂ consumption (SOC) rates of 23.7 to 51.8 mmol m⁻² d⁻¹ in spring and 34.3 to 51.3 mmol m⁻² d⁻¹ in summer. In contrast, control stations immediately outside the dredge pits showed lower SOC rates ranging between 6.3 and 35.9 mmol m⁻² d⁻¹. The SOC rates of the surrounding continental shelf subjected to annual seasonal hypoxia ranged between 25.7 and 59.6 mmol m⁻² d⁻¹ indicating that the dredge pits experienced similar high rates of SOC. Our results suggest that sluggish water circulation inside these topographic depressions coupled with higher SOC rates does result in persistent low bottom O₂ conditions inside these dredge pits well beyond the duration of the seasonal hypoxia period in this region. This is the first study to provide insight on the impacts of dredge pits to surrounding hypoxia in this region which is critical as future dredging operations are expected to increase worldwide with projected sea-level rise.

为了应对由于全球海平面上升而造成的沿海土地流失，需要大量的沙子，以恢复遭受快速侵蚀和淹没的隔离岛系统和海滩。此类项目所需的沉淀物通常来自疏通相邻架子上的沙子沉积物。在春季和夏季，对两个疏edge坑进行了采样，这些疏edge坑的地质条件不同，距墨西哥湾北部陆架的密西西比河三角洲的距离不同。每年夏天还从周围的大陆架站点同时采集样本，这些站点遭受季节性缺氧。发现在两个季节中，挖泥坑内部溶解的底部水O ₂始终为低氧或接近低氧，且沉积物O ₂高春季的消耗（SOC）速率为23.7至51.8 mmol m ^-2 d ^-1，夏季为34.3至51.3 mmol m ^-2 d ^-1。相反，紧邻挖泥坑的控制站显示出较低的SOC速率，范围在6.3和35.9 mmol m ^-2 d ^-1之间。遭受年度季节性缺氧的周围大陆架的SOC速率介于25.7和59.6 mmol m ^-2 d ^-1之间，这表明挖泥坑经历了相似的高SOC速率。我们的结果表明，这些地形凹陷内的水循环不畅，加上较高的SOC比率，确实会导致持续的低底O _2。这些挖泥坑内的状况远远超出了该地区季节性缺氧期的持续时间。这是第一项提供有关挖泥坑对该地区周围缺氧影响的见解的研究，这是至关重要的，因为随着全球海平面的上升，预计未来的挖泥作业将在全球范围内增加。