青岛外海夏季水母路径溯源研究

ORIGIN OF THE GIANT JELLYFISH IN QINGDAO OFFSHORE IN SUMMER

2011年夏季,青岛外海发现大量大型水母,如沙海蜇、海月水母和白色霞水母等,而在冬、春季未在当地海区发现其幼体。本文采用拉格朗日方法,以粒子代表水母,不考虑水母自身运动,进行反向追踪,追溯其运动路径及可能源地。不同追踪实验结果显示,在不同时间不同深度处释放的粒子路径不同。在海面处释放的粒子分别可以追溯到海州湾、江苏沿岸及长江口附近的海域,其中8月1日和8月15日在海面释放的粒子最远可以追溯至长江口外海域;2m层上释放的粒子最远也可到达长江口附近,而10m层以深释放的粒子基本分布在35°N以北。由于反向追踪只考虑海流的影响,追踪过程可逆,因此,从运动路径来看,青岛外海的部分水母可能来源于海州湾、江苏沿岸及长江口附近海域。从水母种类分布特征来看,海州湾、江苏沿岸及长江口附近海域在有粒子分布时期的水母种类与7、8月份青岛外海部分水母种类一致,为寻找青岛外海夏季水母的潜在的来源地提供了依据。

In the summer of 2011, massive giant jellyfish was observed in Qingdao offshore. These jellyfish, including Nemopilema nomurai, Cyanea nozakii and Aurelia aurita, were remote origin because their larvae were not found in Qingdao offshore in the past winter and spring. We conducted a series of backward Lagrangian particle-tracking experi- ments driven by the Princeton Ocean Model （POM） hydrodynamical results to identify possible source regions of the ob- served giant jellyfish. Passive particles representing the jellyfish were released in surface layer and at some other depths at different times in summer. The trajectories of the particles depended on both the depth and the date of release. Backward tracking from the summer to spring, the released particles in surface layer were mainly found in Haizhou Bay, Jiangsu coast area, and the region adjacent to Changjiang Estuary, and those released at 10m depth and the bottom were all found to the north of 35°N. These places may be the source regions of the observed massive giant jellyfish. This conclusion was also supported by the consistence of the jellyfish species in these areas and Qingdao offshore.