Relative influence of habitat complexity and proximity to patch edges on seagrass epifaunal communities
Relative influence of habitat complexity and proximity to patch edges on seagrass epifaunal communities
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栖息地复杂性和邻近斑块边缘对海草表层动物群落的相对影响
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发表时间：
2010
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通讯作者：
Kevin A. Hovel
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作者：
Elizabeth Moore;Kevin A. Hovel
生境结构在许多尺度上影响着动物群落。虽然不同尺度的生境结构往往是协变的，但研究很少考察多尺度结构对动物密度和多样性的相对影响。在浅水海草系统中，局部尺度上的脚底密度通常随着生境结构复杂性的增加而增加（如单位面积的枝密度）。反过来，在斑块尺度上，结构复杂性往往随生境结构的其他方面而变化，例如与斑块边缘的接近程度，这本身就改变了构成地表层群落的生态过程。本文通过对美国加州圣地亚哥湾大叶藻码头床的调查和操纵实验，研究了大叶藻结构复杂性、底面密度和多样性以及鱼类（捕食者）密度和多样性是否随斑块边缘的接近程度而变化，以及结构复杂性、接近斑块边缘和捕食者的存在对底面分布的相对影响。在所有样点和采样期内，海草结构复杂性总体上由斑块边缘向斑块内部增加。然而，在不同的样点和采样周期内，地表层密度、多样性和生物量的格局有所不同，从斑块边缘到内部，一些样点的密度和生物量增加，而另一些样点的密度和生物量则减少。在操纵实验中，我们将表层动物安置在稀疏或密集的人工海草栖息地的边缘和内部，并将一部分实验单元封闭在捕食者隔离笼中。总体而言，与结构复杂性或捕食者的影响相比，接近斑块边缘对脚底密度和群落结构的影响更大，但一些常见分类群对复杂性或捕食者排斥的反应更强烈。我们的研究结果强调了在多个尺度上解决和评估栖息地结构的重要性，以便更好地了解特定环境中生物的分布和相互作用。
Habitat structure at many scales influences faunal communities. Although habitat structure at different scales often covaries, studies rarely examine the relative effects of structure at multiple scales on faunal density and diversity. In shallow-water seagrass systems, epifaunal density at local scales generally increases with increased habitat structural complexity (e.g. shoot density per unit area). In turn, structural complexity often varies with other aspects of habitat structure at patch scales, such as proximity to patch edges, which itself modifies ecological processes that structure epifaunal communities. We conducted surveys and a manipulative experiment in the eelgrass Zostera marina beds of San Diego Bay, California, USA, to determine (1) whether eelgrass structural complexity, epifaunal density and diversity, and fish (predator) density and diversity vary with proximity to patch edges, and (2) the relative influences of structural complexity, proximity to patch edges and predator presence on epifaunal distribution. Seagrass structural complexity generally increased from patch edges to patch interiors at all sites and in all sampling periods. However, patterns of epifaunal density, diversity, and biomass varied among sites and sampling periods, with density and biomass increasing from patch edges to interiors at some sites and decreasing at others. In the manipulative experiment, we allowed epifauna to colonize sparse or dense artificial seagrass habitat at both the edge and interior of a seagrass patch, and enclosed a subset of experimental units in predator exclusion cages. Overall, proximity to patch edges had a larger influence on epifaunal density and community structure than did structural complexity or predation, with the exception of some common taxa which responded more strongly to either complexity or predator exclusion. Our results emphasize the importance of addressing and evaluating habitat structure at multiple scales to better understand the distribution and interactions of organisms in a particular environment.