Consumer versus resource control and the importance of habitat heterogeneity for estuarine bivalves

The relative influence of consumers (top down) and resources (bottom up) on the distribution and abundance of organisms remains a key question in ecology. We examined the relationships between consumer and resource variables along a productivity gradient for a dominant predator–prey interaction in a marine soft-sediment system. We 1) quantified density and size of the clam Macoma balthica (prey species) in six replicate sites at each of four habitat types (shallow mud, deep mud, muddy sand and detrital mud) in the Rhode River, Chesapeake Bay. We selected one habitat type of high food availability and clam density (shallow mud) and another of low food availability and clam density (muddy sand) for manipulative experiments. Then, we 2) measured M. balthica survival and growth through transplants, 3) measured food availability as sedimentary organic carbon content, 4) quantified predator density, and 5) calculated predator foraging efficiency in the two habitat types. Clam density in the f...消费者自上而下（top-down）调控与资源自下而上（bottom-up）调控对生物分布与种群丰度的相对影响，仍是生态学领域的核心研究问题。本研究聚焦切萨皮克湾罗德河（Rhode River）内海洋软沉积系统（marine soft-sediment system）中的优势捕食者-猎物相互作用（predator–prey interaction），沿生产力梯度（productivity gradient）探究了消费者与资源变量间的关联。我们1）在四种生境类型——浅泥滩、深泥滩、泥质砂滩与碎屑泥滩——中各设置6个重复样点，定量了猎物物种白樱蛤（Macoma balthica）的密度与个体大小；随后选取食物可获得性与白樱蛤密度均较高的生境（浅泥滩），以及二者均较低的生境（泥质砂滩）开展操控实验；2）通过移植实验测定白樱蛤的存活率与生长情况；3）以沉积有机碳含量衡量食物可获得性；4）定量捕食者种群密度；5）计算两种生境中的捕食者捕食效率。白樱蛤的密度在……