RAPID: Testing the rocky intertidal community consequences of the decimation of purple sea star populations along the Oregon coast by sea star wasting disease

这项研究将调查俄勒冈海岸沿岸因损耗性疾病导致海星数量大量减少的生态后果。消耗性疾病的特征是在海星上形成溃疡，导致手臂的丧失，最终导致动物死亡。早在2013年4月，不列颠哥伦比亚省、华盛顿州和加利福尼亚州就报道了包括紫海星（Pisaster ochraceus）在内的海星种群的消瘦病。在俄勒冈州，2014年4月首次观察到消瘦现象，到2014年6月，感染率高达80%，海星数量也有所下降。按照这个速度，到2014年夏末，许多种群可能会消失。先前的研究表明，在没有紫色海星的情况下，中岸贻贝的数量会增加，并最终过度生长在海岸低处的海草和无脊椎动物，从而降低生物多样性。然而，由于这种规模的疾病事件从未在整个海岸线上发生过，因此尚不清楚先前观察到的贻贝的小规模扩张是否是这次事件的一般结果。一种可能性是，不受消耗影响的捕食者，如海螺和螃蟹，将增加它们的捕食效果，并减弱贻贝对低海岸的预期入侵。该项目的研究将通过测试这些替代捕食者的作用来评估这种可能性。更广泛的影响包括对本科生和研究生的培训，沿海居民的参与以及微纪录片和视频的制作，以记录该生态系统不断变化的背景。该研究项目旨在验证三个假设。首先，在没有Pisaster ochraceus的情况下，通过增加海螺的数量和体积，海螺的捕食能力会增强，至少部分地弥补了Pisaster的缺失。其次，小型海星Leptasterias sp .也将扩大其作为捕食者的角色，通过增加体积和数量，并扩大其栖息地到贻贝床之外。虽然这种海星的个体也被观察到消瘦，但到目前为止频率似乎很低，似乎这个物种可能会继续存在。第三，蟹产品，通常主要是潮下物种，将扩大其范围到潮间带，有助于弥补Pisaster的损失。这些假设的检验将包括人工去除实验（去除海螺、去除细尾螺、同时去除和不去除）、笼外排除实验（去除海螺）、笼内包含-排除实验（去除细尾螺、去除细尾螺）。实验将在适当的控制下重复进行，并在俄勒冈中部海岸的多个地点进行，这些地点在种群数量、猎物数量和捕食者数量以及海洋条件方面自然不同。在这种前所未有的环境下获得的结果将加深和扩展我们对标志性生态系统动力学的经验理解，并将有助于参数化群落模型。

This study will investigate the ecological consequences of the decimation of sea star populations by wasting disease along the Oregon coast. Hallmarks of wasting disease are the formation of sores on the sea star that progress to cause loss of arms, and ultimately death of the animal. Wasting disease was reported in sea star populations including those of the purple sea star, Pisaster ochraceus, in British Columbia, Washington, and California as early as April 2013. In Oregon, wasting was first observed in April 2014, and by June 2014 rates of infection ranged up to 80%, and sea star abundance had declined. At that rate, many populations may disappear by the end of summer 2014. Prior research has shown that in the absence of the purple sea star, mid-shore mussel populations increase, and ultimately overgrow the sea weeds and invertebrates that occur low on the shore, reducing biodiversity. However, because disease events of this magnitude have never occurred along the entire coastline, it is unclear if the small-scale expansion of mussels observed previously will be a general result of this event. One possibility is that predators unaffected by wasting, such as whelks and crabs, will increase their predation effects and blunt the expected invasion of mussels to the low shore. The research in this project will evaluate this possibility by testing the role of these alternative predators. Broader Impacts include the training of undergraduate and graduate students, the involvement of coastal residents and the production of microdocumentaries and video to document the changing context of this ecosystem.The research project is designed to test three hypotheses. First, that in the absence of Pisaster ochraceus, predation by whelks will increase in strength through increases in whelk abundance and in whelk size, and at least partially compensate for the absence of Pisaster. Second, the small sea star Leptasterias spp. will also expand its role as a predator through increased size and abundance, and expansion of its habitat beyond mussel beds. Although individuals of this sea star have been observed to suffer from wasting as well, the frequency so far appears low, and it seems likely this species may persist. Third, the crab Cancer productus, normally mostly a subtidal species, will expand its range into the intertidal and help to compensate for the loss of Pisaster. Tests of these hypotheses will include manual removal experiments (whelk removal, Leptasterias removal, removal of both and of neither), cage exclusion experiments (whelk exclusions), cage inclusion-exclusion experiments (Leptasterias inclusion, Leptasterias exclusion). Experiments will be replicated with appropriate controls, and done at multiple sites on the central Oregon coast that vary naturally in population abundances, rates of prey and predator recruitment, and oceanographic conditions. Results obtained under this unprecedented set of circumstances will deepen and expand our empirical understanding of the dynamics of an iconic ecosystem, and will help parameterize community models.