Mechanisms of stability of urchin-dominated barrens in southeastern Newfoundland

生态学的两个核心问题是：(1)不同物种的组合如何作为不同的群落状态并排发生；(2)哪些因素和过程触发从一种状态到另一种状态的转变（相移）并稳定每种状态。纽芬兰东南部的浅岩潮下带（SEN）显示出两种群落状态，这可能取决于一种关键食草动物——绿海胆的丰度：海胆稀少的海带床；在那里，海胆占主导地位，只有少数耐食草的海藻生长。与加拿大东部的许多地区相反，SEN的贫瘠地区占主导地位，并且在十年尺度上似乎是稳定的，很少有海带重新定居。对控制相移的生物和环境因素之间的相互作用以及SEN中荒地和海带状态的稳定性的有限理解限制了我们作为科学家和管理者的预测能力。相移（或缺乏相移）对商业鱼类、海胆和龙虾的影响尚不清楚，这些鱼类以海带床为栖息地、食物和育苗区，并可能像加拿大东部其他地区一样形成利润丰厚的渔业基础。***我提出的研究旨在了解生物和环境因素之间的相互作用，以及控制SEN中相移和显着稳定性的贫瘠状态的过程，同时开发有助于预测不同环境条件下物种丰度和相移变化的模型。我和我的学生将：(1)量化破坏性海胆放牧的动态和相移的阈值，(2)测量两种抗放牧海藻对群落状态恢复平衡能力的影响，以及(3)建立相移模型并探索海洋变暖和酸化对海胆-海胆相互作用强度的影响。我们将使用多种互补的方法，从动态过程的观察研究，到现场和实验室环境中的严格假设检验，再到数学建模。***我们的研究将对寒冷海洋底栖生态系统稳定性和生产力的原因和后果进行最详细和全面的调查。面对不断变化的海洋气候，它们将改变我们对寒温带珊瑚礁生态的理解。拟议的工作结合了发现驱动和应用研究，将有助于理解和预测加拿大大部分未被研究和日益受到干扰的地区的生态系统变化。它将为许多研究生和本科生创造一个富有成效的研究培训环境，并为政府和行业利益相关者以及科学家提供新颖的数据和预测工具，以支持政策决策

Two central questions in ecology are (1) how can assemblages of different species occur side by side, as distinct community states; and (2) what factors and processes trigger transitions from one state to another (phase shifts) and stabilize each state. The shallow rocky subtidal zone in southeastern Newfoundland (SEN) exhibits two community states presumably dependent on the abundance of a key herbivore, the green sea urchin: kelp beds where urchins are rare; and barrens where urchins dominate and only a few grazing-resistant seaweeds grow. Contrary to many regions in eastern Canada, barrens in SEN predominate and appear to be stable at decadal scales, with infrequent recolonization by kelp. Limited understanding of interactions between biological and environmental factors that govern phase shifts, and the stability of the barrens and kelp states in SEN, limits our predictive capacity as scientists and managers. Consequences of phase shifts (or lack thereof) for commercial species of finfish, urchins, and lobsters, which use kelp beds as habitat, food, and nursery areas, and could form the basis of lucrative fisheries as they do in other regions of eastern Canada, are unknown.***My proposed research is aimed at understanding interactions between biological and environmental factors and processes that govern phase shifts and the apparent stability of the barrens state in SEN, while developing models that aid in predicting changes in species abundance and phase shifts under varying environmental conditions. My students and I will: (1) quantify the dynamics of destructive urchin grazing and thresholds for phase shifts, (2) measure effects of two grazing-resistant seaweeds on the ability of community states to return to equilibrium, and (3) model phase shifts and explore effects of ocean warming and acidification on strength of kelp-urchin interactions. We will use a diverse blend of complementary methods from observational studies of dynamic processes, to rigorous hypothesis testing in field and laboratory settings, to mathematical modeling.***Our studies will yield one of the most detailed and comprehensive investigations of the causes and consequences of stability and productivity in cold marine benthic ecosystems. They will be transformative with respect to our understanding of the ecology of cold-temperate reefs in the face of a changing ocean climate. The proposed work combines discovery-driven and applied research that will contribute to understanding and anticipating ecosystem changes in a largely unstudied and increasingly perturbed region of Canada. It will create a productive research training environment for many graduate and undergraduate students, and provide government and industry stakeholders and scientists with novel data and predictive tools to support policy decisions.**