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CAREER: Mechanisms of bioturbation and ecosystem engineering by benthic infauna

职业：底栖动物的生物扰动和生态系统工程机制

基本信息

批准号：
1844910
负责人：
Kelly Dorgan
金额：
$ 86.38万
依托单位：
Marine Environmental Sciences Consortium
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2019
资助国家：
美国
起止时间：
2019-06-01 至 2024-05-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1844910&HistoricalAwards=false
关键词：
CAREER Mechanisms bioturbation ecosystem engineering

项目摘要

Marine sediments are important habitats for abundant and diverse communities of organisms that are important as food sources for higher trophic levels, including commercially important species. Through burrowing, constructing tubes, and feeding on sediments, these animals modify their physical and chemical environments to such an extent that they are considered ecosystem engineers. Bioturbation, the mixing of sediments by animals, is important in regenerating nutrients and transporting pollutants and carbon bound to mineral grains. Despite its importance, our ability to predict bioturbation rates and patterns from the community structure is poor, largely due to a lack of understanding of the mechanisms by which animals mix sediments. This project builds on earlier work showing that animals extend burrows through muddy sediments by fracture to test the hypothesis that the mechanical properties of sediments that affect burrowing mechanics also affect sediment mixing. More broadly, this project examines the relative contributions of (i) the functional roles of the organisms in the community, (ii) the mechanical properties of sediments, and (iii) factors that might increase or decrease animal activity such as temperature and food availability to bioturbation rates. Burrowing animals modify the physical properties of sediments, and this project quantifies these changes and tests the hypothesis that these changes are ecologically important and affect community succession following a disturbance. In addition to this scientific broader impact, this project involves development of instrumentation to measure sediment properties and includes a substantial education plan to introduce graduate, undergraduate, and middle school students to the important role that technology plays in marine science. Through burrowing and feeding activities, benthic infauna mix sediments and modify their physical environments. Bioturbation gates the burial of organic matter, enhances nutrient regeneration, and smears the paleontological and stratigraphic record. However, current understanding of the mechanisms by which infaunal activities mix sediments is insufficient to predict the impacts of changes in infaunal community structure on important sediment ecosystem functions driven by bioturbation. This project tests specific hypotheses relating infaunal communities, bioturbation, and geotechnical properties with the ultimate goal of understanding the dynamic changes and potential feedbacks between infauna and their physical environments. This project integrates field and lab experiments to assess the relative importance of infaunal community structure and activities to bioturbation rates. Additionally, this project builds on recent work showing that muddy sediments are elastic gels through which worms extend burrows by fracture to propose that geotechnical properties of sediments mediate bioturbation by governing the release of particles from the sediment matrix during burrow extension. Finite element modeling determines how the release of particles by fracture during burrowing depends on the fracture toughness (cohesion) and stiffness (compaction) of sediments and complements laboratory experiments characterizing the impact of geotechnical properties on burrowing behaviors. The proposed research also aims to determine whether impacts of infauna on geotechnical properties are ecologically important. Changes in infaunal communities and geotechnical properties following an experimental physical disturbance address the hypothesis that ecosystem engineering of bulk sediment properties facilitates succession.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

海洋沉积物是丰富多样的生物群落的重要生境，这些生物群落是高营养级生物的重要食物来源，包括具有重要商业价值的物种。通过挖洞、建造管道和以沉积物为食，这些动物改变了它们的物理和化学环境，以至于它们被认为是生态系统工程师。生物扰动，即动物对沉积物的混合，在再生营养物质和运输污染物以及与矿物颗粒结合的碳方面很重要。尽管它的重要性，我们的能力来预测生物扰动率和模式的社区结构是穷人，主要是由于缺乏了解的机制，动物混合沉积物。该项目建立在早期的工作表明，动物通过断裂延伸洞穴穿过泥泞的沉积物，以测试影响洞穴力学的沉积物的机械特性也影响沉积物混合的假设。更广泛地说，该项目研究了（一）生物在群落中的功能作用，（二）沉积物的机械性能，和（三）可能增加或减少动物活动的因素，如温度和食物供应对生物扰动率的相对贡献。穴居动物改变了沉积物的物理性质，本项目量化了这些变化，并检验了这些变化在生态上具有重要意义并影响干扰后群落演替的假设。除了这一更广泛的科学影响外，该项目还涉及开发测量沉积物特性的仪器，并包括一个实质性的教育计划，向研究生、本科生和中学生介绍技术在海洋科学中发挥的重要作用。底栖动物通过挖洞和觅食活动，混合沉积物，改变其物理环境。生物扰动开启了有机质的埋藏，促进了营养物质的再生，并模糊了古生物和地层记录。然而，目前的了解底栖动物活动混合沉积物的机制是不够的，以预测底栖动物群落结构的变化对生物扰动驱动的重要沉积物生态系统功能的影响。该项目测试与底栖动物群落、生物扰动和岩土特性有关的具体假设，最终目标是了解底栖动物及其物理环境之间的动态变化和潜在反馈。该项目将实地和实验室实验相结合，以评估底栖动物群落结构和活动对生物扰动率的相对重要性。此外，该项目的基础上，最近的工作表明，泥质沉积物是弹性凝胶，蠕虫通过断裂延伸洞穴，提出沉积物的岩土性质介导的生物扰动，通过控制从沉积物基质中释放的颗粒在洞穴扩展。有限元建模确定如何释放的颗粒在挖掘过程中的断裂取决于断裂韧性（凝聚力）和刚度（压实）的沉积物和补充实验室实验表征的岩土性能对挖掘行为的影响。拟议的研究还旨在确定底栖动物对岩土性质的影响是否具有生态重要性。在实验性物理扰动后，底栖动物群落和岩土性质的变化表明，大量沉积物性质的生态系统工程促进了演替。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。