N2 Fixation in Marine Sponges: A New Nitrogen Source for Coastal Ecosystems

氮（N）的微生物转化强烈地影响着海洋群落和生态系统的动态和多样性。 从N2固定的新N的输入是特别感兴趣的。 许多种类丰富的海绵被认为拥有大量多样的微生物群落来固定N2，尽管很少有数据支持这一假设。在最近的研究中，在FL键的多个海绵物种的稳定同位素的两个基本组的海绵被确定和区分其d15 N值。除了低d15 N值（其指示N2固定）之外，一组进行了15 N2掺入试验。在这项研究中，来自查佩尔山的北卡罗来纳州大学的研究人员将专注于量化低和高d15 N海绵中微生物N2固定以及光合作用和呼吸的速率。使用低和高d15 N海绵的进一步比较研究将使用分子生物学技术（例如，16 S、nifH、DGGE、FISH分析）以检查其微生物群落并识别测试海绵中活跃的N2固定微生物。 科学家团队还将研究整个海绵生命周期中N2固定共生体-海绵相互作用的动态，并估计海绵新N出口的水平。 在探索自然环境梯度的佛罗里达键的研究将扩大到贫营养的沃茨关闭圣萨尔瓦多岛，巴哈马群岛，以调查其他环境参数，如光照水平，影响d15 N值的海绵和N2固定率。 这项研究将不仅解决长期存在的问题，在海绵和海绵作为新的N的来源珊瑚藻礁和其他沿海生态系统的重要性，但也扩大了我们的海洋微生物无脊椎动物协会的生态地球化学意义的基本理解，以及环境因素如何控制这些系统内发生的生态地球化学过程的速率。

ABSTRACTOCE- 0351893 Microbial transformations of nitrogen (N) strongly influence the dynamics and diversity of marine communities and ecosystems. Inputs of new N from N2 fixation are of particular interest. Many species of abundant marine sponges are known to host large and diverse microbial communities thought to fix N2, although few data support this assumption. In recent studies of stable isotopes of multiple sponge species in the FL Keys two basic groups of sponges were identified and differentiated by their d15N values. In addition to low d15N values, which are indicative of N2 fixation, one group had a 15N2 incorporation assay. In this study, researchers from the University of North Carolina at Chapel Hill will focus on quantifying rates of microbial N2 fixation together with photosynthesis and respiration in low and high d15N sponges. Further comparative studies with low and high d15N sponges will use molecular biology techniques (e.g., 16S, nifH, DGGE, FISH analyses) to examine their microbial communities and to identify active N2-fixing microbes within test sponges. The team of scientists will also examine the dynamics of N2-fixing symbiont-sponge interactions throughout the sponge life cycle and estimate levels of new N export from sponges. After exploring a natural environmental gradient in the Florida Keys the study will be expanded to oligotrophic waters off San Salvador Island, Bahamas, in order to investigate how other environmental parameters, such as light levels, affect d15N values of sponges and rates of N2 fixation. This research will not only address the longstanding questions regarding N2 fixation in sponges and importance of sponges as a source of new N for coral-algal reefs and other coastal ecosystems but also broaden our basic understanding of the biogeochemical significance of marine microbial-invertebrate associations and how environmental factors control the rates of biogeochemical processes occurring within these systems.