Collaborative Research: The Role of Regenerated Nitrogen for Rocky Shore Productivity

在众多生态系统中，一个基本而持久的问题是新营养物质与再生营养物质对生态系统生产力的支持程度。在沿海海洋系统中，上升流产生的硝酸盐（=新氮）和沿海水域和沉积物中的铵再生（=再生氮）是促进沿海海洋生产力的主要氮源。由于无机氮的有效性明显调节着大量地区的产量，因此了解氮供应是必不可少的。在远离河口的开阔海岸地区，硝酸盐的输入是由大规模的物理过程决定的，这些物理过程促进了富含营养的深层水的上涌，包括风向和强度。相比之下，再生氮（主要是铵）通常是当地动物和微生物过程的结果。在海洋岩石海岸，上升流通常被用作生产力的代表，我们对再生营养物质的动态及其在更大范围内对生产力的潜在贡献知之甚少；只有上升流通常被用作生产力的代表。丰富的加利福尼亚贻贝（Mytilus californianus）与水体养分、藻类生产力、稳定同位素特征和微生物遗传学的关联表明，这些动物可能具有强大的氮再生能力，并表明与这些动物相关的硝化微生物具有重要的次要作用。在这个项目中，研究人员将通过对贻贝丰度梯度的普查和实验，量化岩石海岸上再生氮的相对贡献。他们将使用铵、亚硝酸盐和硝酸盐的稳定氮和氧同位素来解开不同生物过程对岩石海岸地区氮供应和吸收的贡献，而不是上涌。这包括天然丰度和示踪剂添加研究。更广泛的影响。与通过上升流产生的新氮相反，再生氮供应是一个依赖于完整动物群落的局部过程。然而，贻贝和其他近岸动物可能特别容易受到热环境变化、有毒藻华和海洋酸化的影响。鉴于近年来沿海氮循环的巨大变化，以及全球气候变化所预示的海流、上升流、海洋化学和El Niño频率的潜在变化，我们需要了解局部与更大规模海洋事件对氮循环的相对影响。拟议的工作将原地生物相互作用与其对沿海生产力的影响联系起来。除了预期在高质量期刊上发表文章外，教育活动将继续侧重于研究生和本科生的教育和指导。该提案每年将资助两名研究生和两名本科生。PI将与政府（奥林匹克海洋国家保护区）和部落（马卡部落）代表密切合作，交流这项研究。我们还将与麦加博物馆董事会和麦加高等教育委员会合作，确定麦加学生作为研究助理。这三位PI的教学范围遍及各自的校园，教授几乎所有类型的本科专业。

A fundamental and persistent question in a multitude of ecosystems is the extent to which new versus regenerated nutrients support ecosystem productivity. In coastal marine systems, nitrate derived from upwelling (= new nitrogen) and ammonium regeneration in coastal waters and sediments (= regenerated nitrogen) are major nitrogen sources that fuel coastal ocean productivity. Because inorganic nitrogen availability clearly regulates production in a large number of areas, understanding nitrogen supply is essential. In open coast regions away from river mouths, nitrate inputs are determined by large-scale physical processes promoting upwelling of deep, nutrient-rich water including wind direction and intensity. In contrast, regenerated nitrogen (mainly ammonium) is generally the result of local animal and microbial processes. Along marine rocky shores, where upwelling is typically used as a proxy for productivity, we know very little about the dynamics of regenerated nutrients and their potential contribution to productivity at larger scales; only upwelling is typically used as a proxy for productivity. Associations of the abundant California mussel, Mytilus californianus, with water nutrients, algal productivity, stable isotope signatures, and microbial genetics indicate potentially strong regeneration of nitrogen by these animals and suggest an important secondary role of nitrifying microbes affiliated with these animals. In this project, the investigators will quantify the relative contribution of regenerated nitrogen on rocky shores through censuses and experiments across a gradient of mussel abundance. They will use stable nitrogen and oxygen isotopes of ammonium, nitrite, and nitrate to disentangle the contribution of different biological processes versus upwelling to the nitrogen supply and uptake of rocky shore regions. This includes both natural abundance and tracer addition studies. Broader Impacts. Regenerated nitrogen supply, as opposed to new nitrogen via upwelling, is a local process dependent upon an intact animal community. However, mussels and other nearshore animals may be particularly vulnerable to a changing thermal environment, toxic algal blooms, and ocean acidification. Given the dramatic changes to the coastal nitrogen cycle in recent years, and potential changes to currents, upwelling, ocean chemistry, and El Niño frequencies portended by global changes to our climate, we to know the relative effect of local versus larger scale oceanic events on the nitrogen cycle. The proposed work links biological interactions in situ with its implications for coastal productivity. In addition to expected publications in high quality journals, educational activities will continue to focus on graduate and undergraduate education and mentoring. The proposal will fund two graduate students and two undergraduates per year. The PI's will work closely with government (Olympic Marine National Sanctuary) and tribal (Makah Tribe) representatives to communicate this research. We will also work with Makah Museum Board of Trustees and the Makah Higher Education Committee to identify Makah students as research assistants. All three PI's teach broadly across their respective campuses, instructing almost every type of undergraduate major.