Dynamics of Habitat Structure in Seagrass Landscapes; Ecosystem Implications

在为强调生态系统功能的海洋植被生境开发的模型中，一般不认为大型植被与更高的营养水平有主要的直接联系。相反，植物被视为碎屑池的重要营养贡献者。在本文的研究中，我们扩展了植物的作用，并考虑了由大型植物提供的栖息地结构，无论是作为物理或捕食者的避难所，还是作为资源积累的场所，对生态系统功能的重要性。本研究旨在1)探索已知的与营养相关的动物群（即小型驻地鱼和附生片脚类动物）与植物覆盖、高度和植物在空间尺度上的排列之间的关系；2)建立一个描述影响海草斑块发育和维持的沉积过程的模型。1994年春季和1995年秋季将在佛罗里达州坦帕湾取样24个大小和形状各异的海草床。海草斑块将在景观水平（来自航空照片）和子景观水平（即在景观中，斑块水平）上进行物理属性表征。回归分析技术将用于研究景观和亚景观尺度上海草床物理属性之间的关系。动物群组成和床层物理属性的关系也将使用回归分析技术进行研究。在相同的24个海草床中，将在四个罗经头分别测量沉积速率，并每月记录床缘的膨胀/收缩。这些综合数据将使我们能够确定沉积是否在定义海草斑块特征中起主要作用，斑块特征是否对动物群产生重要影响，从而对生态系统功能产生重要影响。我们的技术和结果应该对以大型植物为主要植被的生态系统研究项目有普遍的兴趣，包括淡水和盐沼。考虑到以大型植物为主的地区通常是那些被报道为更高营养水平的食物/避难所/筑巢地提供关键栖息地的地区，生境结构在这些生态系统中所起的作用可能与海草床相似。研究结果可为确定生境退化对生态系统水平的影响提供预测依据。

9318130 Bell In models developed for marine vegetated habitats which emphasize ecosystem function, macrophytic vegetation is not generally considered to have major direct links to higher trophic levels. Instead, plants are veiwed as important important trophic contributors to the detrital pool. In the study proposed here we expand the veiw of the role of plants and consider how habitat structure provided by macrophytes, either as physical or predator refuge, or as a site of resource accumulation, might be important to ecosystem function. %%% This study is proposed to 1) explore the relationship of fauna known to be trophically-linked (i.e. small resident fish and epiphytal amphipods) to plant cover, height, and arrangement of plants across spatial scales and 2) develop a model depicting sedimentation processes that influence seagrass patch development and maintenance. Twenty four seagrass beds of varying size and shape will be sampled during the Spring and Fall of 1994 and 1995 in Tampa Bay, Florida. Seagrass patches will be characterized for physical attributes on a landscape level (from aerial photographs), and on a sub-landscape level (i.e. within a landscape, patch level). Regression analyses techniques will be used to investigate relationships between the physical attributes of the seagrass beds at both landscape and sub-landscape scales. The relationship of faunal components and bed physical attributes will also be examined using regression analysis techniques. In the same 24 seagrass beds, sedimentation rates will be measured at each of the four compass headings and expansion/contraction of bed margin recorded monthly. These combined data should allow us to determine if sedimentation plays a major role in defining seagrass patch characteristics, whether patch characteristics have important influence on fauna, and hence, ecosystem function. %%% Our techniques and results should be of general interest to ecosystem research programs where macrophytes are the dominant vegetat ion, including freshwater and salt marshes. Given that macrophyte-dominated areas are often those reported to provide critical habitat for higher trophic levels as feeding/refuge/nesting sites, the role habitat structure plays in these ecosystems may be similar to that in seagrass beds. It is anticipated that results from our study can be used to build a predictive basis for determining the ecosystem level implications of habitat degradation.