Fecal Pellets of Doliolids and Copepods: Two Different Microworlds?

广阔的亚热带大陆架上的高初级生产力与西部边界流产生的上升有关。对美国东南部大陆架的研究表明，经常出现的中上层被囊动物补丁，可以迅速殖民东南部大陆架和消耗的初级生产力的很大一部分。由于这些被囊类动物，桡足类相比，在利用摄入的浮游植物，而效率低下，大量的摄入的有机物质应该是提供给其他消费者，可能代表不同的微世界。在浅海后生动物中，哲水蚤桡足类被认为是较大浮游植物细胞的主要消费者，而在原生生物中，异养甲藻可以以这些细胞为食。浅海樽海鞘和珊瑚虫，因为它们偶尔出现，只被视为偶尔的主要消费者。现在已知Doliolids在一年中的大部分时间里都会在东南大陆架上发生，并且由于它们对浮游植物的利用效率低下，它们对大陆架食物网的影响可能相当大。本计画将探讨与珊瑚虫粪球早期分解相关的过程，并将这些过程与同期出现的哲水蚤桡足类的粪球分解进行比较。研究人员将测试与主要问题相关的几个假设：doliolids和桡足类粪便颗粒的早期分解率如何比较，以及它们与异养原核生物的丰度，大小和过程如何相关？由于摄食过程不同的哲水蚤桡足类和doliolids，主要的差异，在早期分解的预期。这应该会影响到生产性亚热带大陆架的浮游微生物循环，研究的重点是海洋浮游生物、海洋生物地球化学和大陆架海洋学等不同领域内的一个中心主题，即生物物质的加工，因此，其意义远远超出该项目的具体重点。由于海樽纲动物丰富是西部边界大陆架环境的一个共同特点，这项研究的结果将适用于远远超出南大西洋湾。此外，该项目将针对三个重要的教育和更广泛的影响主题：1）教师教育; 2）未来海洋科学家的人口多样化; 3）加强国际科学合作。为了帮助弥合研究和K-12学生和教师社区之间的差距，与格鲁吉亚水族馆和NOAA（河流到珊瑚礁教育工作坊）赞助的一个正在进行的科学教师计划合作，调查人员将与96 K-12在职科学教师互动，并为他们提供海洋学研究经验和对浮游生物生态学目前正在解决的具体问题的新见解。该项目通过与萨凡纳州立大学建立良好关系，支持本科生（主要是非洲裔美国人），将有助于增加未来海洋科学家和专业人员的多样性。最后，与德国和挪威同事的强有力合作将进一步推动该项目的科学目标，并加强美国和欧洲生物海洋学家之间的合作。

High primary productivity on wide subtropical continental shelves has been related to upwellings generated by western boundary currents. Studies on the U.S. southeastern (SE) shelf have revealed frequent occurrences of patches of pelagic tunicates which can rapidly colonize the SE shelf and consume a large percentage of the primary productivity. Since these tunicates are, as compared to copepods, rather inefficient in utilizing the ingested phytoplankton, large amounts of the ingested organic matter should be available to other consumers which might represent different microworlds. While among the neritic metazoa calanoid copepods have been considered the main consumers of larger phytoplankton cells, among protists heterotrophic dinoflagellates can feed on such cells. Neritic salps and doliolids, because of their occasional occurrence, were only seen as occasional major consumers. Doliolids are now known to occur predictably on the SE shelf through much of the year, and because of their inefficient use of phytoplankton, their effects on the shelf food web might be considerable. This project will investigate processes related to the early decomposition of doliolid fecal pellets and compare these processes to pellet decomposition of co-occurring calanoid copepods. The investigators will test several hypotheses related to the main question: How do the early decomposition rates of fecal pellets of doliolids and copepods compare, and how are they related to the abundance, size and processes of heterotrophic prokaryotes? As the feeding processes differ between calanoid copepods and doliolids, major differences in early decomposition are expected. This should influence the pelagic microbial loop of productive subtropical shelves.The research focuses on a central theme, processing of biogenic material, within the diverse field of marine plankton, marine biogeochemistry, and shelf oceanography, and therefore will be of interest well beyond the specific focus of the project. Because thaliacean abundance is a common feature of western boundary continental shelf environments, the findings of this study will be applicable well beyond the South Atlantic Bight. Moreover, the project will target three important education and broader impact themes: 1) Teacher education; 2) Demographic diversification of future ocean scientists;and 3) Strengthening international science collaboration. To help bridge the gap between research and K-12 students and teacher communities, a collaboration with an ongoing science teacher program sponsored by The Georgia Aquarium and NOAA (Rivers to Reef Educator Workshop) the investigators will interact with 96 K-12 in-service science teachers and provide them with oceanographic research experience and novel insights into the specific questions currently being addressed in plankton ecology. By supporting undergraduate students (largely African American) through a well established relationship with Savannah State University, the project will contribute to the effort to increase the diversity of future ocean scientists and professionals. Finally, a strong component of collaboration with colleagues in Germany and Norway will further the scientific objectives of the project and strengthen collaborations between US and European biological oceanographers.