Spatial and Temporal Characteristics of Entrainment and Transport of Horseshoe Crab (Limulus polyphemus) Eggs in the Swash Zone of Estuarine Beaches

鱼类和无脊椎动物卵的携带、扩散和沉积的位置和时间对许多生物的摄食行为和生命周期具有重要意义。一个重要的例子是，马蹄蟹卵对于从南美迁徙数千公里到北极的西半球滨鸟来说，是一种重要的营养来源。该项目将研究冲刷（波浪冲升和反冲）过程在马蹄蟹和迁徙滨鸟之间的关系中所起的作用，由于马蹄蟹的捕捞和河口海滩栖息地的改变，两者都处于压力之下。这些压力使得了解马蹄蟹和滨鸟之间保持联系的物理过程变得越来越重要。卵在激流中的运输机制尚不清楚，现有的沉积物运输模型是为暴露的海洋环境中的海滩设计的，而不是在河口。本研究将确定冲刷中解释沉积物和卵夹带和运输的关键过程，并使用新泽西州特拉华湾两个地点的实地数据测试冲刷运输模型的适用性。将收集以下方面的数据：1)水流速度、深度、宽度和冲刷的持续时间；2)在挖掘和运输由冲刷、破碎和冲刷单独造成的地点，使用在前海岸注入的示踪剂，对沉积物和卵进行夹带；3)使用总负荷沉积物捕集器，在冲刷中运输的沉积物和卵的数量。将确定冲刷参数与沉积物和卵的总负荷之间的统计显著关系，并将使用跨岸流速和沉积物负荷的数据来测试和校准一个运输模型。本研究的结果将填补我们对高微潮环境下河口海滩冲刷过程认识的空白。冲积带是在这些海滩上发生风暴的最高运输率的地方，研究结果将为侵蚀和增生的循环提供更好的过程解释。随着越来越多的河口沙质海岸被人工滋养，以保护人类住区，除了提供海岸保护和康乐空间的传统目的外，越来越需要制定海滩营养设计标准，以提高生物生产力和生态系统功能。通过增加对冲滩区鸟蛋运输的了解，可以提高候鸟种群的适应性和基于营养来源的潜在濒危模型。该项目还为两名本科生提供了密集的实地和实验室体验，他们将有机会与自然地理学和生物学的教师一起进行实地实验，从而获得独特的学习体验，将这两个领域的知识整合到关键资源问题的研究中。

The location and timing of entrainment, dispersal and deposition of eggs of fish and invertebrates have important implications for the feeding behavior and life cycles of many organisms. A key example is found in the significance of horseshoe crab eggs as a nutritional source for western hemisphere shorebirds that migrate thousands of kilometers from South America to the Arctic. This project will examine the role of swash (wave uprush and backwash) processes in mediating the relationship between horseshoe crabs and migratory shorebirds that are both under stress due to horseshoe crab harvesting and alteration of estuarine beach habitat. These stresses place increased importance on understanding the physical processes that maintain the link between horseshoe crabs and shorebirds. The mechanics of egg transport in the swash are not known, and existing models of sediment transport are designed for beaches in exposed ocean environments, not in estuaries. This study will identify key processes in the swash that explain sediment and egg entrainment and transport and test the applicability of swash transport models using field data from two sites in Delaware Bay, New Jersey. Data will be gathered on: 1) flow velocity, depth, width and duration of the swash, 2) entrainment of sediment and eggs using tracer injected in the foreshore in locations where exhumation and transport is due to both the swash and breakers and swash alone, and 3) amount of sediment and eggs transported in the swash using total load sediment traps. Statistically significant relationships between swash parameters and total load for sediment and eggs will be determined, and data on cross-shore flow velocities and sediment load will be used to test and calibrate a transport model.The results of this study will fill the gap in our understanding of swash processes on estuarine beaches in high micro-tidal environments. The swash zone is where the highest rates of transport occur in response to storms on these beaches and study results will provide better a better process explanation for cycles of erosion and accretion. As more sandy shores in estuaries are artificially nourished to provide protection to human settlements, there is an increasing need for beach nourishment design criteria that enhance biological productivity and ecosystem function in addition to the traditional purposes of providing shore protection and recreation space. Population fitness of migratory bird populations and models of potential endangerment based on nutritional sources will be enhanced from increased knowledge of egg transport in the swash zone. The project also provides an intensive field and laboratory experience for two undergraduate students who will have the opportunity to work on a field experiment with faculty from both physical geography and biology and thus have a unique learning experience that will integrate these two fields of knowledge to the study of a critical resource problem.