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

营养水平之间相互作用的差异可以决定是生产性过程还是消耗性过程主导群落结构(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及其运作方式。在这里，我建议在两个海洋群落中研究底栖藻类和它们的无脊椎动物草食动物之间的相互作用，这两个海洋群落由于其低多样性的性质，提供了一个相对简单的系统来解决这些复杂的问题。通常的方法是检查生产和消费沿环境梯度的变化，以确定生产主导条件和消费主导条件之间的转换发生在哪里，然后进行额外的观察和实验，以确定非生物因素的变化如何将平衡转移到一个或另一个社区状态。这种方法将首先在潮间带系统中开发，在该系统中，丝状绿藻在不受草食蜗牛控制的情况下可以形成广泛的藻垫，然后扩展到潮下群落，在那里海胆的消费可以创造出缺乏明显海藻的贫瘠土地。在这两个系统中，我们将专注于对比非生物因素(营养物质和水分运动)的可变性如何使早期脆弱阶段逃脱消费者的控制。研究结果不仅有助于一般生态学理论，而且对于理解沿海生态系统的功能以及解决应用问题(如富营养化)也是至关重要的。

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).