Collaborative Research: Cascading effects of an invasive seaweed on estuarine food webs of the southeastern US

在过去的十年中，亚洲海草，即蠕纹紫菜，在乔治亚州和南卡罗莱纳河口的高盐度泥滩上大量繁殖。这种入侵是值得注意的，因为这些河口的泥滩在历史上缺乏以大型植物为基础的初级生产和结构。在这些泥滩环境中，紫菜几乎没有原生的类似物，因此为研究入侵在历史上未开发的生态位中的生态系统后果提供了机会。理论上，葛缕草会影响直接依赖入侵者获取结构和食物的物种种群，并改变群落和生态系统层面的过程，如碎屑生产和食物网结构。通过野外操作实验、实验室分析和稳定同位素分析相结合，研究人员将测试江蓠影响本地群落结构的三种机制。毛条草产生的新结构和初级生产可能是：1)提高次生生产速率；2)通过吸收溶解的营养物质提高泥滩微生物生产水平；3)增加微生物和微生物食物网的碎屑输入。该项目将提供对河口群落中入侵物种的多重级联影响的机制理解。改变生态系统功能的物种入侵通常是最深刻的。这些变化通常是由少数入侵者产生的，这些入侵者重新创造了物理结构，包括重要的生物栖息地。通过改变物理结构，这些非本地生态系统工程师改变了当地的非生物条件、物种之间的相互作用和物种组成。具有高度影响力的入侵者还可能改变食物网结构和能量和物质的营养流动。当一个有影响力的入侵者提供的营养物质或资源在质量、数量或两者上都不同时，就会发生这种实质性的食物网变化。当这些机制协同作用时，一个既提供新的物理结构又从根本上改变食物网结构的入侵物种可能对当地社区产生压倒性的影响。该项目还包括教育和外联部分，特别是指导。它将培养2名研究生和3名本科生，让他们独立开发与该项目相关的项目，为科学事业做好准备。他们的研究将把用于研究入侵物种的传统实验技术与稳定同位素分析、基于pcr的肠道内容物鉴定和微生物群落枚举等先进分析技术相结合。与他们过去的项目和NSF的目标一致，pi致力于指导不同教育水平（高中，本科，研究生）和种族的不同学生群体。他们将包括两名高中科学教师，通过“教师作为研究员”计划参与实地和实验室项目。每个人都将进行研究，并期望为他们的课堂制定新的单元计划。最后，pi将继续通过讲座、机构开放日活动以及广播、报纸和电视采访向公众传播他们的结果。最后，这项研究将对管理人员负责减轻入侵物种的影响有直接的好处。

During the last decade, the Asian seaweed, Gracilaria vermiculophylla, has proliferated along high-salinity mudflats in several Georgia and South Carolina estuaries. The invasion is noteworthy because the mudflats in these estuaries were historically devoid of macrophyte-based primary production and structure. Gracilaria has few native analogues in these mudflat environments, and thus represents an opportunity to examine the ecosystem consequences of an invasion within an historically-unexploited niche. In theory, Gracilaria affects populations of species that are directly dependent on the invader for structure and food, as well as altering community- and ecosystem-level processes such as detrital production and food web structure. Through a combination of manipulative field experiments, laboratory assays and stable isotope analysis, the investigators will test three mechanisms by which Gracilaria influences native community structure. The novel structure and primary production generated by Gracilaria vermiculophylla may be 1) increasing rates of secondary production 2) increasing levels of mudflat microbial production through leeching of dissolved nutrients, and 3) increasing detrital input to microbial and macrobial food webs. This project will provide a mechanistic understanding of the multiple cascading impacts of an invasive species within the estuarine community. Species invasions that alter ecosystem functions are usually the most profound. These alterations are often generated by a small number of invaders that create physical structure, including important biogenic habitat, de novo. By altering physical structure, these non-native ecosystem engineers alter local abiotic conditions, interactions between species, and species composition. Highly influential invaders may also change food web structure and trophic flow of energy and materials. Such substantive food web changes can occur when an influential invader provides nutrients or resources that are different in quality, quantity or both. An invasive species that both provisions new physical structure and fundamentally alters food web structure could exert an overwhelming influence on native communities when these mechanisms act in synergy.The project also includes education and outreach components, especially mentoring. It will prepare two graduate and three undergraduate students for scientific careers by having them independently develop projects related to the project. Their research will integrate the traditional experimental techniques used to study invasive species with advanced analytic techniques of stable isotope analyses, PCR-based identification of gut contents, and enumeration of microbial communities. Consistent with their past projects and the goals of NSF, the PIs are committed to mentoring a diverse group of students across multiple educational levels (high school, undergraduate, graduate) and ethnicities. They will involve two high school science teachers through a "teacher as researcher" program to participate in field and laboratory projects. Each will conduct research and be expected to develop new unit plans for their classrooms. Finally, the PIs will continue to disseminate their results to the public through lectures, open house events at their institutions, as well as radio, newspaper, and television interviews. Finally, this study will be of immediate benefit to managers charged with mitigating the impacts of invasive species.