SGER: Migration of a Hybrid Zone in Response to the 1997 El Nino Event

厄尔尼诺/南方涛动（ENSO）现象是调节太平洋气候年际变化的最重要过程。ENSO循环影响海洋环流和气候的模式。在厄尔尼诺年份，水向北流动增加；因此，许多海洋物种的分布向北移动。研究人员是南卡罗来纳大学（University of South Carolina）的托马斯·j·希尔比什（Thomas J. Hilbish）博士，他此前曾研究过本世纪初引入南加州的一种海洋贻贝的分布情况。自从引进以来，这个物种向北扩展了它的活动范围，并与一个本地贻贝物种形成了一个杂交区。这些贻贝是北美西海岸海洋群落的重要生态组成部分，引种物种被用于加利福尼亚和华盛顿的水产养殖作业。先前的研究表明，引进物种的迁移和杂交区已经在加利福尼亚州的门多西诺角停止。希尔比什博士将验证一种假设，即夏季门多西诺角附近形成的上升流阻止了贻贝进一步向北迁徙，这一上升流导致贻贝幼虫向近海移动，并在那里死亡。希尔比什博士预测，在厄尔尼诺年期间，向北迁移的人口将会恢复，因为在此期间，上升流会大大减少。1997年的厄尔尼诺事件是有记录以来的第二大厄尔尼诺事件，恰逢贻贝幼虫扩散的时期。因此，他预测今年引进的贻贝物种和杂交区将向北移动，并建议在门多西诺角附近和北部地区采集贻贝幼鱼的样本。这项工作将检验由ENSO循环控制的环流模式调节近岸海洋物种（包括海洋贻贝）的扩散和分布的假设。这项研究还将有助于确定引进的贻贝物种是否会继续扩大，以及哪些地区最有可能受到污染。H: \ POPBIO \文摘\ HILBISH.txt

Hilbish 9807055 The El Ni o/Southern Oscillation (ENSO) phenomenon is the most important process regulating year-to-year climate variation in the Pacific. The ENSO cycle affects patterns of ocean circulation as well as climate. During an El Ni o year there is an increased movement of water northward; consequently there is northward shift in the distribution of many marine species. The investigator, Dr. Thomas J. Hilbish of the University of South Carolina, has previously examined the distribution of a marine mussel that was introduced to Southern California earlier this century. Since its introduction this species has expanded its range northward and formed a hybrid zone with a native species of mussel. These mussels are important ecological constituents of marine communities on the west coast of North America and the introduced species is used in aquaculture operations in California and Washington. Previous studies indicate that the migration of the introduced species and the hybrid zone has stopped at Cape Mendocino, California. Dr. Hilbish will test the hypothesis that further migration northward has been prevented by upwelling that forms during the summer around Cape Mendocino, which causes the movement of mussel larvae offshore, where they die. Dr. Hilbish has predicted that migration northward would resume during an El Ni o year because upwelling is greatly reduced during this time. The 1997 El Ni o event is the second largest ever recorded and coincides with the period of time that mussel larvae are dispersed. Therefore he predicts that the northward movement of the introduced mussel species and the hybrid zone will occur this year and proposes to sample mussel juveniles as they recruit in the area around and north of Cape Mendocino. This work will test the hypothesis that circulation patterns controlled by the ENSO cycle regulate the dispersal and distribution of near-shore marine species, including marine mussels. This study will also help determine whether the expan sion of the introduced mussel species will continue and which regions are most likely to become contaminated. H:\POPBIO\ABSTRACT\HILBISH.txt