Trophic ecology of small hydromedusae: a new perspective on their function in coastal ecosystems

研究的重点是小（钟形直径5毫米）水水母的营养作用。水母是重要的，通常是高度选择性的浮游捕食者，它们可以强烈地影响后生浮游动物以及鱼卵和幼虫的存量。捕食率、猎物选择模式和潜在的捕食机制导致了大型、显眼的水母的成功已经得到了很好的研究。然而，大多数水母都很小。这些小水母数量丰富，分类多样，通常分布在世界各地。然而，尽管它们是海洋中最大、最多样化的胶状浮游动物群体，但它们的摄食生态实际上是未知的。初步数据表明，许多小型水水母的摄食方式和营养作用都不同于它们的大型亲戚。这些初步研究表明，一些小型水母物种(1)以包括浮游植物在内的微型浮游生物为杂食动物，(2)数量足够多，摄食率足够高，可以清除沿海生态系统中季节性浮游植物的很大一部分。该项目将解决这样一个假设，即高丰度和高摄食率的结合使小型水水母在季节性生产高峰期间成为浮游植物的重要食草动物。因此，当代关于水母主要是浮游后生动物捕食者的范式可能需要进行重大修订，以涵盖小型水水母的营养作用。本研究的目的是通过研究小型水水母在罗德岛纳拉甘西特湾的营养作用，来研究它们的摄食过程和影响。我们将采用(1)量化小型水螅水母对罗德岛naragansett湾浮游生物群落的营养影响和(2)量化其取食和猎物选择的功能基础的综合方法。研究成果的智力价值：该研究将导致对群落摄食率、猎物选择模式和潜在的摄食机制的新理解，这些机制导致了最多样化的水母分类群体的成功和进化寿命。如果小型水母主要以杂食性浮游生物为食，并且能够显著影响浮游生物的存量，那么该研究将在后生动物和微生物食物网之间建立一个新的重要的营养联系。这一新发现将使原生生物生态学家对控制浮游生物存量和产量的因素有更深入的了解。该研究还将为进化生态学家提供更多的生物力学因素，这些因素影响了小型水水母的体型和功能以及原生动物的行为和体型的进化。从这个角度来看，本研究直接解决了理解海洋系统中影响生物多样性的因素及其生态后果的问题，这是美国国家科学基金会生物海洋学部门强调的一个特定主题。拟议活动的更广泛影响：该项目将通过记录远洋食物网中一个新的，但可能是常见的营养环节来鼓励科学发现。来自两所主要本科院校和一所主要研究生院校的科学家的参与增加了培训和指导的机会。每个机构将让学生参与研究的各个方面（提案每年有5名本科生，2名来自RWU， 2名来自PC； 1名来自URI海洋生物学项目的本科生将在每个项目年的春季学期与Gifford一起进行独立学习课程（15学分））。收到资金后，吉福德将申请预算补充，以支持一名中学科学教师在夏季参与该项目。和过去一样，我们将利用我们与公众教育媒体的联系（广播、电视纪录片、新闻文章和水族馆展览）来传播我们关于美杜莎生态的新发现。我们与这些媒体的持续对话使我们能够向广大公众传播我们的发现，并教育公众。

The focus of the research is the trophic role of small (bell diameter 5 mm) hydromedusae. Medusae are important, often highly selective, planktonic predators that can strongly affect standing stocks of metazoan zooplankton as well as fish eggs and larvae. The feeding rates, prey selection patterns and the underlying feeding mechanisms that have led to the success of large, conspicuous medusae have been well studied. However, most medusae are small. These small medusae are abundant, taxonomically diverse, and often have cosmopolitan distributions. Yet their feeding ecology is virtually unknown despite their status as the largest and most diverse group of gelatinous zooplankton in the sea. Preliminary data indicate that many small hydromedusae feed differently and have different trophic roles than their larger relatives. These preliminary studies have shown that some small medusan species (1) feed as omnivores on microplankton, including phytoplankton and (2) are sufficiently abundant and have sufficiently high feeding rates to remove a significant proportion of the phytoplankton standing stock in the coastal ecosystems where they occur seasonally. This project will address the hypothesis that this combination of high abundance and high feeding rates enables small hydromedusae to function as significant grazers of phytoplankton during periods of peak seasonal production. Consequently, the contemporary paradigm that medusae are primarily predators of planktonic metazoans may require significant revision in order to encompass the trophic role of small hydromedusae. The goal of the research is to examine the feeding processes and impact of small hydromedusae by examining their trophic role in Narragansett Bay, Rhode Island. We will use a combined approach of (1) quantifying the trophic impact of small hydromedusae on the plankton community of Narragansett Bay, Rhode Island and (2) quantifying the functional bases of their feeding and prey selection. Intellectual Merit of the Proposed Activity: The research will lead to new understanding of community feeding rates, prey selection patterns and the underlying feeding mechanisms that have led to the success and evolutionary longevity of the most diverse taxonomic group of medusae. If small medusae feed primarily as omnivores on microplankton and are able to significantly affect microplankton standing stocks, then the research will document a new and important trophic link between the metazoan and microbial food webs. The new knowledge will provide protistan ecologists with enhanced understanding of the factors controlling microplankton standing stocks and production rates. The study will also provide evolutionary ecologists with a greater understanding of the biomechanical factors that have influenced the evolution of small hydromedusan body form and function as well as protist behavior and body form. From this perspective, this study directly addresses the issue of understanding factors influencing biological diversity and its ecological consequences in marine systems, a specific theme emphasized by NSF's Biological Oceanography division. Broader impacts of the Proposed Activity: The project will encourage scientific discovery by documenting a new, but presumably common, trophic link in pelagic food webs. The participation of scientists from two primarily undergraduate institutions and one primarily graduate institution enhances opportunities for training and mentorship. Each institution will involve students in every aspect of the research (5 undergraduates during each year of the proposal, 2 from RWU and 2 from PC; 1 undergraduate from the Marine Biology program at URI will do an independent study course (15 credits) with Gifford during the spring academic term of each project year). Upon receipt of funding, Gifford will apply for a budget supplement to support participation in the project by a secondary school science teacher during the summer months. As in the past, we will use our contacts with media involved in education of the general public (radio, television documentaries, news articles and aquarium exhibits) to communicate our new findings about medusan ecology. Our continuing dialog with these outlets to the public allows us avenues to communicate our findings to a wide public audience and to educate the general public.