RAPID: Hurricane Irma Impacts on Nitrogen Cycling in Florida Bay

在佛罗里达湾和大多数其他沿海生态系统中，营养元素氮的可用性通常限制了有机物的产生。在佛罗里达湾，大约90%的初级生产是由海草产生的，另外10%是由水柱中的单细胞藻类和细菌产生的。北卡罗来纳大学教堂山分校团队与佛罗里达鱼类和野生动物保护委员会（FWC）的科学家合作在飓风伊尔玛之前完成的研究表明，这些初级生产者所需的氮中约有一半是由巨大的海绵种群提供的，海绵种群过滤并分解新鲜产生的有机物，然后通过有效地将无机氮再循环回水柱来平衡氮预算。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量的有机物质，从而有助于保持健康的海草群落和水的清澈度。飓风“厄玛”的过境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。该项目将通过对代表性地点海绵和海草生物量损失的定量评估、水柱藻华的特征描述，和测量佛罗里达湾氮收支的变化。拟议的新工作的总体目标是量化与飓风通过相关的佛罗里达湾氮循环和氮收支的潜在主要变化Irma，使用来自已建立研究地点的风暴前和风暴后数据的组合。拟议的新工作直接建立在该团队最近完成的海绵在海湾整体氮预算中的作用的调查基础上，加上藻类大量繁殖对其中心盆地氮循环的灾难性影响，这些盆地的特征是水柱停留时间为几天到几周。这项先前工作的结果对整个加勒比和热带太平洋以及包括南极大陆架环境在内的许多其他沿海地区海绵丰富的生态系统具有重要影响，在南极大陆架环境中海绵是底栖生物的主要组成部分。Irma前的成果包括多年氮调查和时间序列数据，在关键地点进行海绵和海草生物量调查，并进行了藻类水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实验室的科学家之间的新合作，在那里将进行后Irma海绵调查，并在圣彼得堡（FWC-SP）进行藻类水华元基因组研究。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，确定海绵在有机碳和氮循环速率和氮预算中的作用，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和藻类水华Meta，在FWC-SP领导的其中一个地点进行水华期间的基因组加细菌计数研究。两名研究生和两名本科生将参加这个项目。

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.