Abstract Coastal upwelling regions represent less than 2% of the marine biosphere's volume. Nonetheless, local biogeochemical processes have a considerable impact on the structure and functioning of the global oceans. In this study we characterize the evolution of biogeochemical properties during the upwelling seasons of 2009 and 2010 in the coastal ecosystem off central Oregon (west coast of USA). Both years displayed similar cumulative upwelling favorable winds and total input of preformed nutrients into the midshelf despite of their marked differences in the timing of the onset of the upwelling season, its duration and the number of upwelling relaxation events. However, these differences in upwelling forcing induced inter-annual variability in oxygen and nitrogen deficiencies, particulate matter accumulation and nutrient regeneration. Our results suggest that the summer evolution of nitrogen loss and oxygen depletion over the shelf does not follow a simple relationship with the cumulative upwelling index. We hypothesize that other factors, such as the intensity and persistence of the upwelling, which affect the residence time of water masses over the continental shelf, play a key role in the cumulative effect of biological processes leading to hypoxia in these coastal environments.

中文翻译：

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上升流间歇在俄勒冈大陆架缺氧和氮流失发展中的作用

摘要 沿海上升流区仅占海洋生物圈体积的不到 2%。尽管如此，局部生物地球化学过程对全球海洋的结构和功能有相当大的影响。在这项研究中，我们描述了俄勒冈州中部（美国西海岸）沿海生态系统在 2009 年和 2010 年上升流季节期间生物地球化学特性的演变。尽管上升流季节开始的时间、持续时间和上升流松弛事件的数量存在显着差异，但这两年都显示出相似的累积上升流有利风和预先形成的营养物质向中陆架的总输入。然而，这些上升流强迫的差异导致了氧和氮缺乏、颗粒物质积累和养分再生的年际变化。我们的结果表明，夏季大陆架上氮流失和氧耗竭的演变与累积上升流指数并不遵循简单的关系。我们假设其他因素，例如影响水团在大陆架上停留时间的上升流的强度和持续时间，在导致这些沿海环境缺氧的生物过程的累积效应中起着关键作用。