RAPID: Hurricane Irma Impacts on Nitrogen Cycling in Florida Bay

营养元素氮的可用性通常限制了佛罗里达湾和大多数其他沿海生态系统中有机物的生产。在佛罗里达湾，大约90%的初级产量是由海草产生的，另外10%是由水柱中的单细胞藻类和细菌产生的。在飓风厄玛之前，北卡罗来纳大学教堂山分校的研究小组与佛罗里达鱼类和野生动物保护委员会（FWC）的科学家合作完成的研究表明，这些初级生产者所需的氮大约有一半是由一个巨大的海绵种群提供的，它过滤和分解新鲜产生的有机物质，然后通过有效地将无机氮回收到水柱来平衡氮预算。海绵群落能够在不到一周的时间内泵送和处理佛罗里达湾整个水域的有机物，从而有助于保持健康的海草群落和水的清澈。飓风“厄玛”的经过可能深刻地改变了佛罗里达湾中部的生态系统，造成海绵和海草生物量的巨大损失，并导致与氮循环相关的变化。该项目将通过定量评估代表性地点的海绵和海草生物量损失、水柱藻华特征以及测量佛罗里达湾氮收支变化来帮助评估Irma的短期和长期影响。拟议的新工作的总体目标是量化佛罗里达湾氮循环的潜在重大变化，以及与飓风Irma通过相关的氮预算，使用来自既定研究地点的风暴前后数据的组合。提出的新工作直接建立在团队最近完成的海绵在海湾整体氮收支中的作用以及藻华对其中心盆地氮循环的灾难性影响的调查基础上，该盆地的水柱停留时间为数天至数周。这项先前工作的结果对整个加勒比和热带太平洋地区以及许多其他沿海地区，包括海绵构成底栖动物主要组成部分的南极大陆架环境的海绵丰富的生态系统具有重要意义。飓风前的结果包括多年的氮调查和时间序列数据，重点地点的海绵和海草生物量调查，以及藻华元基因组学和细菌计数调查。这项研究将受益于北卡罗来纳大学教堂山分校和马拉松（FWC- m）的FWC实验室和圣彼得堡（FWC- sp）的科学家之间的新合作。马拉松（FWC- m）将进行厄玛后海绵调查，圣彼得堡（FWC- sp）将进行藻华元基因组研究。来自Pre-Irma研究的数据包括广泛的溶解氮（DIN和DON）水柱浓度和时间序列测量，海绵在有机C和氮循环速率以及氮预算中的作用的测定，由FWC-M科学家（2013-15）在我们的研究地点进行的多年（2013-16）相关海绵生物量调查，以及由FWC-SP领导的在其中一个地点进行的藻华荟萃基因组和细菌计数研究。两名研究生和两名本科生将参与这个项目。

Availability of the nutrient element nitrogen generally limits the production of organic matter in Florida Bay and most other coastal ecosystems. In Florida Bay, approximately 90% of this primary production has been generated by seagrasses with another 10% generated by single celled algae and bacteria in the water column. Research completed prior to Hurricane Irma by the UNC-Chapel Hill team in collaboration with scientists at the Florida Fish and Wildlife Conservation Commission (FWC), has revealed that approximately half of the nitrogen needed by these primary producers is supplied by a huge sponge population that filters and decomposes freshly produced organic matter, then balances the nitrogen budget by efficiently recycling inorganic nitrogen back to the water column. The sponge community is capable of pumping and processing organic matter throughout the entire water volume of Florida Bay in less than a week, thus helping to maintain healthy seagrass communities and water clarity. The passage of Hurricane Irma may have profoundly altered the central Florida Bay ecosystem by causing tremendous losses of sponge and seagrass biomass and resulting changes associated with nitrogen cycling. This project will help to assess short- and long-term impacts of Irma through a quantitative assessment of sponge and seagrass biomass losses at representative locations, characterization of water column algal blooms, and measurement of changes to the nitrogen budget of Florida Bay.The overall goal of the proposed new work is to quantify potentially major changes in Florida Bay nitrogen cycling and nitrogen budgets associated with the passage of Hurricane Irma, using a combination of pre- and post-storm data from established study sites. The proposed new work builds directly on the team's recently completed investigations of the role of sponges in the overall nitrogen budget of the Bay plus the catastrophic impacts of algal blooms on nitrogen cycling in its central basins that feature water column residence times of days to weeks. The results of this previous work have important implications for sponge-rich ecosystems throughout the Caribbean and tropical Pacific plus many other coastal regions including Antarctic shelf environments where sponges comprise a major component of the benthos. Pre-Irma results include multi-year nitrogen surveys and time-series data, sponge and seagrass biomass surveys at key sites and algal bloom meta-genomics and bacterial count surveys have been conducted. This research will benefit from new collaborations between scientists at UNC-Chapel Hill and FWC laboratories in Marathon (FWC-M), where post-Irma sponge surveys will be made and in St. Petersburg (FWC-SP), where algal bloom meta-genomic studies will be conducted. Data from the Pre-Irma studies includes extensive dissolved nitrogen (DIN and DON) water column concentration and time-series measurements, determination of the role of sponges in organic C and nitrogen recycling rates and the nitrogen budget, multi-year (2013-16) associated sponge biomass surveys at our study sites by FWC-M scientists (2013-15) and algal bloom meta-genomic plus bacterial count studies during a bloom at one of those sites led by FWC-SP. Two graduate and two undergraduate students will participate in this project.