Large- and small-scale effects of habitat structure on rates of predation: how percent coverage of seagrass affects rates of predation and siphon nipping on an infaunal bivalve
Large- and small-scale effects of habitat structure on rates of predation: how percent coverage of seagrass affects rates of predation and siphon nipping on an infaunal bivalve
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栖息地结构对捕食率的大和小规模影响：海草覆盖率如何影响动物双壳类的捕食率和虹吸咬食率
作者：
E. Irlandi
景观生态学主要是一门陆地学科，研究栖息地的大尺度（数十米到公里）空间格局对竞争、捕食和能量流动等生态过程的影响。在这项研究中，将景观生态学方法应用于海洋软沉积物环境，以检查植被栖息地及其周围的捕食率和二次生产转移。海草床自然地以各种空间配置出现，从1-10米宽、散布着无植被沉积物的斑块（即斑驳的覆盖）到几乎没有或没有裸露沉积物的更连续的覆盖。我设计了实验来研究 100 平方米海底区域的海草覆盖率以及等面积（100 平方米）植被的空间排列（斑块或破碎程度）如何影响动物双壳类硬蛤的捕食（致死）和虹吸咬合（亚致死）强度。还测量了不同海草覆盖率的海草密度和生物量。当将蛤蜊分别放置在海底有植被和无植被的部分时，99% 海草覆盖的活蛤数量几乎是海草覆盖 23% 时的两倍，而 70% 覆盖的存活率处于中等水平。来自植被和无植被沉积物的蛤虹吸管的生长也受到 100 平方米海底区域中海草覆盖量的影响：99% 海草覆盖处理的平均调整虹吸管重量比 70% 或 23% 覆盖处理重约 76%。连续海草处理中以非常斑驳、斑驳和连续的空间配置放置在相同面积的海草中的蛤的存活率比两种斑驳处理中的任何一个高 40%。这项研究表明，随着海草覆盖率的变化，以捕食和种植形式对动物生物进行二次生产的转移也会发生变化。虽然植被数量和空间格局的大规模变化可能会影响栖息地利用模式和觅食 HGLoop 行为，但随着海草覆盖率的增加，海草密度和生物量的增加限制了有关捕食者觅食行为和根据斑块形状和大小进食成功的结论。相反，海草特征的局部变化为观察到的结果提供了最令人信服的解释。
Landscape ecology, predominantly a terrestrial discipline, considers the effect of large-scale (tens of meters to kilometers) spatial patterns of habitats on ecological processes such as competition, predation, and flow of energy. In this study, a landscape-ecology approach was applied to a marine soft-sediment environment to examine rates of predation and transfer of secondary production in and around vegetated habitats. Seagrass beds naturally occur in a variety of spatial configurations from patches 1–10s of meters across with interspersed unvegetated sediments (i.e., patchy coverage) to more continuous coverage with little or no bare sediment. I designed experiments to address how percent coverage of seagrass in a 100-m2 area of seafloor, and the spatial arrangement (degree of patchiness or fragmentation) of an equal area (100 m2) of vegetation affected predation (lethal) and siphon nipping (sublethal) intensity on an infaunal bivalve, Mercenaria mercenaria (hard clam). Measures of seagrass density and biomass with different percent coverage of seagrass were also made. When clams were placed in both the vegetated and unvegetated portions of the seafloor nearly twice as many clams were recovered live with 99% seagrass cover than with 23% seagrass cover, while survivorship was intermediate with 70% cover. Cropping of clam siphons from both the vegetated and unvegetated sediments was also affected by the amount of seagrass cover in a 100-m2 area of seafloor: mean adjusted siphon weights were approximately 76% heavier from the 99% seagrass cover treatment than from the 70% or 23% cover treatments. Survivorship of clams placed within an equal area of seagrass in very patchy, patchy, and continuous spatial configurations was 40% higher in the continuous seagrass treatment than in either of the two patchy treatments. This study demonstrates that transfer of secondary production in the form of predation and cropping on an infaunal organism is altered as the percent cover of seagrass changes. While large-scale changes in the amount and spatial patterning of vegetation may affect habitat utilization patterns and foraging HGLoopbehavior, increased seagrass density and biomass with increased percent coverage of seagrass limit any conclusions concerning predator foraging behavior and feeding success in response to patch shapes and sizes. Instead, local changes in seagrass characteristics provide the most compelling explanation for the observed results.