Collaborative Research: Kelp forest interaction webs in the Aleutian Archipelago: patterns and mechanism of change following the collapse of an apex predator.

过去35年来对海獭和海带森林生态系统进行的研究提供了一个更广为人知的大型脊椎动物捕食者自上而下强迫的例子。这些研究表明，1)海獭通过限制食草性海胆间接维持海带森林，2)这种营养级联对其他一些物种和生态系统过程有很强的间接影响。这些洞察很大程度上是通过比较阿留申群岛上有和没有海獭的岛屿获得的，这是太平洋海洋皮毛贸易大量捕杀海獭后，海獭数量在空间上不同步地恢复所创造的机会。在超过35年的研究过程中，这些研究人员获得了大量关于海獭种群、海带森林群落以及来自许多阿留申群岛的相关海洋野生动物的数据，无论有没有海獭。自那以后，海獭的数量急剧减少，该物种现在整个地区都在生态上灭绝了。在这项研究中，Konar、Edwards和Estes博士将结合数十年的数据库和这次灭绝事件来记录海胆和肉质大型藻类(海藻和其他物种)分布和丰度的空间和时间变化的模式和机制。他们将通过重新考察他们拥有长期数据的20个岛屿来做到这一点，并重新审查历史上的海带森林监测点，以了解海胆的丰度和种群结构，以及海带和其他肉质大型藻类的丰度和物种组成。结合这些数据，这些数据将提供一个关于海胆-海带营养级联随着阿留申群岛上海獭的崩溃而发生变化的程度的说明。现有的信息表明，海带森林在海獭下降后非常迅速地崩溃，这种快速转变是由于海胆从深水向上迁徙而不是原地补充和生长。这组海洋科学家将通过测量各种温度和营养敏感的同位素模式来测试这一想法，这些模式沿着从浅水和深水收集的动物海胆脊椎的生长增量。与海胆的深度避难所类似，来自其他地区的研究表明，大型藻类可能有一个空间避难所，以躲避海胆在浅水或非常密集的藻类林中觅食。他们将利用重新调查海带森林监测点期间收集的数据，并将我们的调查扩展到较浅的水域和孤立的海藻床，以探索大型藻类空间避难所。这项研究是一个机会，可以严格探索和记录大型脊椎动物捕食者对其相关生态系统的相互作用网络动态的影响。该项目的学术价值突出了海洋岛屿和北极研究近岸生态系统结构和过程的特殊性。该项目的广泛影响包括社会效益、教学和培训。该项目将非常有新闻价值，因为它将描述一种快速下降的海洋哺乳动物的现状，并将记录由于该物种在过去20年中丰度的波动而发生的变化。将为来自三所不同大学的研究生提供培训和教育机会。该项目将涉及阿拉斯加大学费尔班克斯大学、加州大学圣克鲁斯分校和圣地亚哥州立大学。

Research on sea otters and kelp forest ecosystems conducted over the past 35 years provides one of the better known examples of top-down forcing by a large vertebrate predator. These studies have shown that 1) sea otters indirectly maintain kelp forests by limiting herbivorous sea urchins, and 2) this trophic cascade has strong indirect effects on a number of other species and ecosystem processes. These insights were obtained largely through the comparison of islands in the Aleutian archipelago with and without sea otters, an opportunity created by the spatially asynchronous population recovery of sea otters following their decimation by the Pacific maritime fur trade. In the course of more than 35 years of studies, these researchers have obtained an extensive amount of data on sea otter populations, kelp forest communities, and an array of associated marine wildlife from numerous Aleutian Islands with and without sea otters. Sea otter populations have since collapsed and the species is now ecologically extinct across the entire region. In this study, Drs. Konar, Edwards and Estes will combine the multi-decadal database with this extinction event to chronicle the patterns and mechanisms of spatial and temporal change in distributions and abundances of sea urchins and fleshy macroalgae (kelps and other species). They will do this by revisiting 20 islands for which they have long-term data and re-censusing the historical kelp forest monitoring sites for the abundance and population structure of sea urchins, and for the abundance and species composition of kelps and other fleshy macroalgae. In combination, these data will provide an account of the degree to which the otter-urchin kelp trophic cascade has changed with the collapse of sea otters across the Aleutian archipelago.The available information indicates that kelp forests collapsed very rapidly following the sea otter decline, and that this rapid shift was facilitated by the upward migration of sea urchins from deep water as opposed to in situ recruitment and growth. This group of marine scientists will test this idea by measuring various temperature- and nutrient sensitive isotopic patterns along the growth increment of sea urchin spines of animals collected from shallow and deep water. Similar to a depth refuge for urchins, studies from other areas have suggested that macroalgae may have a spatial refuge from urchin grazing in shallow waters or amongst very dense algal stands. They will explore macroalgal spatial refuges by using data collected during the re-censusing of the kelp forest monitoring sites and by extending our surveys to shallower waters and isolated kelp beds.This research is an opportunity to rigorously explore and document the influences of a large vertebrate predator on the interaction web dynamics of its associated ecosystem. The intellectual merit of this project emphasizes the special character of oceanic islands and the Arctic for the study of near-shore ecosystem structure and processes.Broader impacts of this project include benefits to society, teaching, and training. The project will be very newsworthy because it will describe the current status of a rapidly declining marine mammal and will document changes that have occurred due to fluctuations in the abundance of this species over the last 20+ years. Training and educational opportunities will be offered to graduate students from three different universities. The project will involve the University of Alaska Fairbanks, University of California Santa Cruz, and San Diego State University.