Species interactions, environmental variation and the balance of production and consumption in marine benthic communities

营养水平之间的相互作用的变化可以决定是否生产或消费过程主导社区结构（即“自下而上”与“自上而下”的控制），因此，我们必须了解哪些机制调节关键物种的相互作用，以及它们如何运作。在这里，我建议研究底栖藻类和无脊椎食草动物在两个海洋社区，其低多样性的性质，提供了一个相对简单的系统，以解决这些复杂的问题之间的相互作用。一般的方法是检查变化的生产和消费沿着环境梯度，以确定生产主导和消费主导的条件之间的过渡发生，然后进行额外的观察和实验，以确定如何在非生物因素的变化可以转移到一个或其他社区状态的平衡。这种方法将首先在潮间带系统中开发，其中丝状绿色藻类可以在不受草食性蜗牛控制的情况下形成广泛的藻垫，然后扩展到亚潮带社区，海胆的消费可以创建缺乏明显海带的贫瘠土地。在这两个系统中，我们将重点放在如何在对比的非生物因素（养分和水分运动）的变化可以允许早期脆弱的阶段，以逃避消费者的控制。结果不仅有助于一般的生态理论，但将是至关重要的理解沿海生态系统的功能，以及解决应用问题（如富营养化）。

Variation in interactions between trophic levels can determine whether productive or consumptive processes dominate community structure (ie, "bottom-up" vs. "top-down" control), and thus it is imperative that we understand which mechanisms modulate key species interactions and how they operate. Here I propose to examine the interaction between benthic algae and their invertebrate herbivores in two marine communities that, by the nature of their low diversity, provide a relative simple system in which to address these complex questions. The general approach is to examine variation in production and consumption along environment gradients to identify where transitions between production-dominated and consumption-dominated conditions occur, and then conduct additional observations and experiments to determine how variation in abiotic factors can shift the balance toward one community state or the other. This approach will first be developed in an intertidal system where filamentous green algae can form extensive algal mats when not controlled by herbivorous snails, and then extended to a subtidal community where consumption by urchins can create barren grounds that lack conspicuous kelp. In both systems we will focus on how variability in contrasting abiotic factors (nutrients and water motion) can permit early vulnerable stages to escape control by consumers. The results will not only contribute to general ecological theory, but will be critical for understanding the functioning of coastal ecosystems as well as addressing applied problems (eg, eutrophication).