Collaborative Proposal: In Situ Quantification of Sponge N Cycling in Coastal Ecosystems

在早期由美国国家科学基金会资助的海绵氮循环研究中，北卡罗来纳大学教堂山分校的一个研究小组证明，海绵在珊瑚礁和其他浅水热带生态系统的氮收支中起着重要作用。他们对整个海绵呼吸、抽水速率和化学通量的原位测量表明，以往基于圈地或实验室实验的研究严重低估了净通量，无法提供建立溶解无机氮（DIN）和其他氮种实际净通量所需的数据。海洋海绵通过泵送和过滤大量的水，强烈影响沿海环境中的N循环，而它们的宿主微生物影响广泛的N转化，包括硝化作用、溶解有机氮和颗粒有机氮的吸收和降解，以及潜在的N2固定和反硝化作用，从而增加或减少沿海系统中的生物可利用N。佛罗里达群岛海螺礁上覆水域的海绵DIN通量比任何其他底栖生物N源都要大，这应该是所有海绵丰富的沿海系统的情况。在该奖项的额外资助下，UNC团队将与夏威夷大学的生物地球化学同事一起，通过(i)使用原位方法为海绵构建准确的N预算，以确定它们是营养来源或汇，以及（ii）调查海绵介导的N转化的环境控制，来量化海绵对沿海N循环的影响。海绵对沿海环境中生物地球化学氮循环的净影响在很大程度上是未知的。这项新工作将首次使用原位方法来量化海绵中的氮循环以及海绵中DIN和DON的最终通量。该项目将产生一系列更广泛的影响。本研究获得的信息虽然直接适用于海绵物种的一个子集，但将对海绵丰富的沿海生态系统的氮生物地球化学具有广泛的意义。一名研究生和几名本科生将在实验室和现场学习一系列最先进的技术和仪器，当结果最终合成发表时，他们将受益于与来自不同领域的知名研究人员的思想交流。夏威夷大学是指定的EPSCoR机构，也是联邦认可的少数民族服务机构，因此来自代表性不足群体的学生很可能被纳入拟议研究的参与者，并将受益于这项研究结果所产生的教育活动。最后，利用北卡罗来纳大学与地球生态国际（Phillipe Cousteau，主席）和海洋科学教育项目建立的联系，将产生重大的公共宣传工作，包括水瓶座与全国各地的高中和初中学生进行网络直播视频会议。

ABSTRACTOCE-0624406 / OCE-0624703In earlier NSF-funded investigations of nitrogen cycling in sponges, a research team at the University of North Carolina at Chapel Hill demonstrated that sponges play a major role in the N budget of coral reef and other shallow water tropical ecosystems. Their in situ measurements of whole sponge respiration, water pumping rates and chemical fluxes indicate that previous studies based upon enclosure or laboratory experiments seriously underestimate net fluxes and cannot provide data needed to establish actual net fluxes of dissolved inorganic nitrogen (DIN) and other N species. Marine sponges strongly affect N cycling in coastal environments through pumping and filtering tremendous volumes of water while their hosted microorganisms affect a wide range of N transformations, including nitrification and dissolved and particulate organic nitrogen uptake and degradation, and potentially N2 fixation and denitrification, thereby adding or subtracting bioavailable N from coastal systems. Sponge DIN flux to overlying waters at Conch Reef, Florida Keys, is larger than any other benthic N source as should be the case for all coastal systems where sponges are abundant. With additional funding under this award, the UNC team will be joined by biogeochemical colleagues at the University of Hawaii in an effort he to quantify sponge impacts on coastal N cycles by (i) using in situ methodologies to construct accurate N budgets for sponges that will identify them as nutrient sources or sinks, and (ii) investigating environmental controls over sponge mediated N transformations. The net impact of sponges on biogeochemical N cycling in coastal environments is largely unknown. This new work will be the first to use in situ methods to quantify the nitrogen cycling in sponges and the resultant fluxes of DIN and DON from sponges. The project will have a number of broader impacts. The information gained in this study, although directly applicable to a subset of sponge species, will have broad implications for nitrogen biogeochemistry in coastal ecosystems with abundant sponges. A graduate and several undergraduate students will learn in both laboratory and field settings a spectrum of state-of-the-art techniques and instrumentation firsthand and, when the results are ultimately synthesized for publication, will benefit from participation in the exchange of ideas with established researchers from diverse fields. The University of Hawaii is a designated EPSCoR institution and a federally recognized minority serving institution, thus students from underrepresented groups are likely to be included as participants in the proposed research and will benefit from education activities stemming from the results of this research. Finally, using the University of North Carolina's established connections with Earth Eco International (Phillipe Cousteau, President) and the Science Under the Sea, educational projects, significant public outreach efforts will result including live web-based videoconferences from AQUARIUS with high school and middle school students across the country.