A shoaling hypoxic zone on the Oregon coast: genesis and mechanisms

2002年夏天，Bruce Menge博士和他的合作者在俄勒冈州海岸的Cape Perpetua地区，观察到缺氧情况的发生，深度低至8米，距离海岸近100米。深度浅，靠近海岸，持续（约2个月）的缺氧区在俄勒冈海岸是前所未有的。这些观察的新奇之处在于，在672平方公里的氧气覆盖区域内观察到的鱼类和无脊椎动物的高死亡率？枯竭的水舌及其与同时发生在离岸较深水域的类似情况的联系表明，它们可能见证了沿海海洋学条件广泛和重要转变的早期阶段，对沿海生态系统可能产生重大后果。该SGER项目将研究浅层(5？从2003年5月到9月，沿着俄勒冈中部海岸的内大陆架区域深度为75米。最直接的目标是确定2002年观测到的缺氧条件是否会在2003年再次出现，从而表征水柱氧动态的季节变化及其相关的生物地球化学和物理驱动因素。第二个目标是提供该地区海洋动态变化的详细地图集，并将它们与浮游植物、无脊椎动物和鱼类的反应联系起来。第三，将内部大陆架区域的调查所揭示的动态与计划于2003年夏季在俄勒冈海岸进行的同时进行的更大规模的海洋调查所揭示的动态相结合。第四个目标是收集和综合证据，以推断缺氧的成因，阐明这种变化的可能机制，并评估内大陆架系统对进一步缺氧复发的潜在敏感性。另外，如果缺氧不复发，2003年收集的数据可以与本小组和LTOP GLOBEC项目在2002年收集的数据进行直接对比，当时缺氧情况广泛且持续。因此，无论缺氧事件是否再次发生，我们都希望深入了解这种不寻常事件发生的潜在因素。

In summer 2002, Dr. Bruce Menge and collaborators observed the occurrence of hypoxic conditions in depths as shallow as 8 m, and as close as 100 meters to shore, along the Cape Perpetua region of the Oregon coast. The shallow depth, closeness to shore, and persistence (~ 2 mo) of such a hypoxic zone was unprecedented for the Oregon coast. The novelty of these observations, the high mortality of fishes and invertebrates observed in the 672 km2 area covered by this oxygen?depleted tongue of water, and its link to similar conditions occurring simultaneously further offshore in deeper water, suggest the possibility that they witnessed the early stages of an extensive and important shift in coastal oceanographic conditions, with potentially important consequences for coastal ecosystems. This SGER project will study the physical and biological processes in shallow (5?75 m) depths of the inner shelf region along the central Oregon coast from May through September 2003. The most immediate goal is to characterize the seasonal changes in the dynamics of water column oxygen and associated biogeochemical and physical drivers in the inner shelf should hypoxic conditions observed in 2002 recur in 2003. A second goal is to provide a detailed atlas of the changing oceanic dynamics of this region, and to relate them to responses by phytoplankton, invertebrates and fish. Third, is to couple the dynamics revealed by surveys in the inner shelf region to those revealed by simultaneous, larger scale oceanographic surveys scheduled for summer 2003 off the Oregon coast. A fourth goal is to gather and synthesize evidence in order to infer the genesis of hypoxia, elucidate the mechanisms likely for such changes and assess the potential sensitivity of the inner shelf system to further recurrences of hypoxia. Alternatively, if hypoxia does not recur, data collected during 2003 can provide a direct contrast to data collected by this group and by the LTOP GLOBEC program in 2002 when hypoxic conditions were extensive and persistent. Therefore, regardless of whether the hypoxic event recurs, we expect to obtain insight into factors underlying the genesis of such unusual occurrences.