Mechanical consequences of flexibility for benthic marine organisms

科学背景和知识优势：机械灵活的海底动植物在几乎所有海洋系统中都是沿海社区中无处不在的成员。当水流过它们时，这类生物被动地移动以响应水流。然而，这一运动的全部影响，特别是它如何影响生物体对流动驱动的干扰的脆弱性，人们知之甚少。传统的观点认为，顺应的结构可以增强固着植物或动物在结构上应对时变水运动的能力。然而，最近的研究指出，流动中的被动运动也可能产生更微妙的后果。例如，被海浪来回席卷的附着的有机体获得动量，当生物体的质量达到其运动范围的极限时，这种动量可以施加随后的惯性力。这种复杂性强调了需要对潮间带和潮下生物的灵活性的生物力学和生存影响进行更全面和一致的检查。如果没有这些进一步的检查，试图建立对流动(长期以来被认为是干扰的主要因素，并作为影响这些社区人口动态的关键因素)死亡后果的量化和机械性预测的努力将仍然无效。满足这一需求是拟议研究的目标。研究工作将集中在测量施加到野外柔性生物上的实时力，并将这些力与基于流体动力形状因子(先前为相同样本个体确定的阻力系数)和同时记录的流动的准静态估计进行比较。实际和准静态的力时间序列之间的差异将被用来量化内在地伴随着生物体灵活性的被动运动改变所施加的力的方式。多组记录将在岸上三个不同的流体动力“领域”内进行(潮下、潮间潜水和生物在波间涌现的直接波浪冲击区域)。海藻，包括具有重要生态意义的巨囊藻属、海藻属、海带藻属和边缘海藻，将被作为重点物种。结果将被汇编并以潜在的无量纲参数的形式表达，这些参数共同控制着物种和三个海岸线领域的生物动态。将对无量纲参数之间的关系进行定量检查和全面综合，以开发一个通用的、连贯的框架，该框架定义了灵活性如何影响生活在各种流动环境中的各种生物体的外加力。随后的生物力学框架将被用来预测野外海带的实际流媒死亡率作为无量纲参数的函数，这些预测的死亡率将与不同大小的标记个体的观测死亡率进行比较，这些个体生长在海岸的不同水深和高度范围内。广泛影响：这里提出的活动对于预测至关重要的群落成员(巨囊藻为数百种沿海物种提供必要的栖息地，包括许多具有经济和娱乐价值的物种)对全球气候变化导致的波浪制度持续变化的反应具有重要影响。生物力学的洞察力还将为海藻影响近岸水流和泥沙运输的海岸工程问题以及仿生学领域提供信息。此外，还有很大的教育/伙伴关系影响，因为本科生和研究生助理，无论是带薪的还是志愿的，都将密切参与核心实验和分析。这样的机会将提供严谨的团队研究经验，促进学生在职业生涯早期的科学发展。该项目的成果将通过将成果纳入正式的大学课程、为一般科学领域编写的书籍以及通过与公共部门机构的现有联系，进一步传达给更广泛的受众。通过将来自三个机构的科学家和实验室聚集在一起的密切合作，将加强基本的知识交流和讨论。

Scientific context and intellectual merit: Mechanically flexible, benthic plants and animals are ubiquitous members of coastal communities in nearly all marine systems. Such organisms move passively in response to flow as water moves past them. However, the full effects of this motion, and in particular the way it influences an organism's vulnerability to flow-driven disturbance, is poorly understood. Traditionally, the view has been that a compliant construction enhances the ability of sessile plants or animals to cope structurally with time-varying water motion. However, more recent research has noted that passive movement in flow can also have subtler consequences. For instance, an attached organism that is swept back and forth by ocean waves acquires momentum, and this momentum can impose a subsequent inertial force when the mass of the organism is eventually decelerated upon reaching the limits of its range of motion. Such complexities emphasize the need for a more complete and consistent examination of the biomechanical and survivorship implications of flexibility for intertidal and subtidal organisms. Without these further examinations, attempts to develop quantitative and mechanistic predictions of the mortality consequences of flow (long recognized as a dominant agent of disturbance and as a critical factor influencing population dynamics in these communities) will remain ineffective. Meeting this need is the goal of the proposed study.Research efforts will focus on measuring real-time forces applied to flexible organisms in the field and comparing those forces to quasi-static estimates based on hydrodynamic shape factors (drag coefficients determined previously for the same sample individuals) and simultaneously recorded flows. Differences between actual and quasi-static time series of force will then be used to quantify the way in which the passive motion that intrinsically accompanies organism flexibility alters applied force. Multiple sets of recordings will be conducted within three distinct fluid-dynamical "realms" on the shore (subtidal, submerged intertidal, and regions subjected to direct wave impingement where organisms are emergent between waves). Laminarian kelps, including the ecologically important Macrocystis pyrifera, Nereocystis luetkeana, Egregia menziesii, and Alaria marginata will be employed as focal species.Results will be compiled and expressed in terms of underlying nondimensional parameters that together govern organismal dynamics across species and the three shoreline realms. Relationships among the nondimensional parameters will be examined quantitatively and synthesized overall to develop a general, coherent framework that defines how flexibility influences imposed force across a wide range of organisms living across a full spectrum of flow environments. This ensuing biomechanical framework will then be used to predict actual rates of flow-mediated mortality for kelps in the field as a function of the nondimensional parameters, and these predicted rates will be compared to the observed rates across tagged individuals of a spectrum of sizes, growing in a range of water depths and heights on the shore.Broader impacts: The activities proposed here have important implications for predicting the response of critically important community players (Macrocystis provides necessary habitat for hundreds of coastal species, including many with economic and recreational value) to ongoing shifts in wave regimes due to global climate change. Biomechanical insights will also inform issues of coastal engineering where kelps affect nearshore currents and sediment transport, and the field of biomimetics. In addition, there are strong educational/partnership implications, since undergraduate and graduate assistants, both paid and volunteer, will be involved intimately in core experiments and analyses. Such opportunities will provide for rigorous, team research experiences that foster the scientific development of students early in their careers. Results of the project will be further conveyed to wider audiences via the incorporation of results into formal university courses, books written for the general scientific arena, and through existing ties with public-sector agencies. Basic intellectual exchange and discourse will be enhanced through a close collaboration that brings together scientists and labs from three institutions.