RAPID: Role of Ephemeral Bottom Roughness Patches in Unpredictable Recruitment of Surfclams on the Continental Shelf

由于新生的蛤蜊面临着巨大的捕食压力，所以它们必须大量定居和繁殖，以产生一年一班的成年蛤蜊。在沙质沉积物中，密集但短暂的贝壳杂碎斑块提供了底部的粗糙度，这可能会影响幼虫和食物到床上的通量，并为新兵提供躲避捕食者的庇护所。RAPID项目的目标是确定改变底部粗糙度的短暂贝壳斑块的存在和持续如何影响蛤的聚集、生长和生存。这项快速反应研究利用了去年在中大西洋湾长期生态系统观测站（LEO-15）发生的一次罕见的、高密度的水面蛤聚集和聚集事件。调查人员将在2009年春季调查Beach Haven Ridge的LEO-15区域，使用配备侧扫描声纳的自主水下航行器（REMUS）来识别贝壳堆积区域，绘制其位置和范围，并测量区域上方和外部的湍流。潜水员每周进行岩心取样，并测量蛤的大小，以确定和比较蛤在壳块内外的存活和生长情况。调查和抽样将在2009年秋季重复进行，以检查贝壳区域的持久性，并确定这些贝壳斑块如何影响2008年和2009年夏季新援的丰度和生长。这项研究将提高对贝壳聚集的短暂性及其对蛤体沉降、死亡率和早期生长的影响的认识。这些结果将有助于理解影响蛤种群动态的形态动力学和物理过程。这项工作的结果将为生境管理战略提供信息，并将有助于监测和管理生态和商业上重要的陆架物种。本科生将通过美国国家科学基金会资助的REU（海洋科学研究实习）项目参与这项工作。研究结果将在同行评议的科学期刊和国家科学会议上发表。

Surfclams must settle and recruit in large numbers to produce a year-class of adult clams because of heavy predation pressure on new recruits. In sandy sediments, dense but ephemeral shell-hash patches provide bottom roughness that may affect the fluxes of larvae and food to the bed and provide recruits with shelter from predators. The objective of this RAPID project is to determine how the presence and persistence of ephemeral shell patches that alter the bottom roughness affect the recruitment, growth, and survival of surfclams. This rapid-response study capitalizes on a rare, high-density settlement and recruitment event of surfclams which occurred last year at the Long-term Ecosystem Observatory (LEO-15) in the Mid-Atlantic Bight. The investigators will survey the Beach Haven Ridge area of LEO-15 in the spring of 2009, using an autonomous underwater vehicle (REMUS) equipped with Side Scan Sonar to identify areas of shell accumulation, to chart their location and extent, and to measure turbulence above and outside the areas. Weekly core-sampling by divers and surfclam size measurements will be used to determine and compare surfclam survival and growth inside and outside of shell patches. Surveys and sampling will be repeated in the fall of 2009 to examine the persistence of the shell areas and to determine how these shell patches affect abundance and growth of 2008 and 2009 summer recruits.This research will enhance knowledge of the ephemeral nature of shell aggregations, and their effects on surfclam settlement, mortality, and early growth. These results will contribute to understanding the morphodynamic and physical processes influencing surfclam population dynamics.Results of this work will inform habitat-based management strategies and will aid in monitoring and management of an ecologically and commercially important shelf species. Undergraduate students will be involved in this work through the NSF-funded REU (Research Internships in Ocean Sciences) program. Results will be presented in a peer-reviewed scientific journal and at a national scientific conference.