Species invasion and the ecology of rocky subtidal communities

作为海洋生态学家和研究人员，我们越来越意识到，由于人类的活动，沿海生态系统相对于其自然进化状态已经发生了深刻的变化。最紧迫的问题之一是将新物种引入海洋群落，然后迅速扩大以取代本地物种。这些人为介导的生物入侵会导致栖息地和生态系统结构和功能的显著变化，往往会带来可怕的生态和经济后果。栖息在加拿大大西洋岩石海床上的海藻、无脊椎动物和鱼类群落是生态系统受到严重影响的一个显著例子。从历史上看，这个群落在两种生态状态之间交替，这取决于一种关键的食草动物海胆的丰富程度：海胆稀少的海带床和海胆占主导地位的贫瘠海域，海胆占主导地位，没有海藻。这些状态之间的周期性交替是由一种杀死海胆的疾病的零星爆发所驱动的。在这种扰动和不稳定的背景下，最近引入的物种之间的协同作用已经将生态系统转向了一种由入侵的亚洲海藻主导的新型群落状态。我们研究的目的是了解调节生态系统状态之间转换或决定其持久性的生物和环境过程。特别是，我们将利用一系列实验和观察方法来研究入侵物种对生态系统结构和功能的影响，以检查物种相互作用，构建食物网，并开发预测数学模型，这些模型是智能管理这个日益受干扰的生态系统所需要的。

As ecologists and students of the ocean, we have become increasingly aware that coastal ecosystems have been profoundly altered, relative to their naturally evolved state, by the activity of humans. Among the most urgent concerns is the introduction of new species into marine communities, that then expand rapidly to replace native species. These human-mediated biological invasions can result in pronounced changes in habitat and ecosystem structure and function, often with dire ecologic and economic consequences. The community of seaweeds, invertebrates and fish that inhabit the rocky seabed of Atlantic Canada provides a striking example of a heavily impacted ecosystem. Historically, this community has alternated between two ecological states dependent on the abundance of a key herbivore, the sea urchin: kelp beds where urchins are rare and barrens where urchins dominate the seascape and seaweeds are absent. Cyclical alternations between these states are driven by sporadic outbreaks of a disease that kills urchins. Amid this backdrop of perturbation and instability, synergistic interactions between recently introduced species have shifted the ecosystem towards a novel community state dominated by an invasive Asian seaweed. The objective of our research is to understand the biological and environmental processes that regulate transitions between ecosystem states or determine their persistence. In particular, we will investigate the effects of invasive species on ecosystem structure and function using a range of experimental and observational approaches to examine species interactions, construct food webs, and develop predictive mathematical models that are needed for intelligent management of this increasingly perturbed ecosystem.