The seasonal cycle of export production in an Antarctic coastal marine ecosystem

该研究项目将获得关于新群落生产、出口和净群落生产的季节周期的综合数据集，并使人们更好地了解南极沿海海洋生态系统中有机物（C和N）的生产和出口。在极地地区，对这三个过程的测量相对较少，在适当的尺度上进行的系统时间序列调查更少，以揭示其机制。因此，调节新生产、新冠病毒和出口生产的物理、生态和生物地球化学机制仍然缺乏特征。我们建议对从水柱238U:234不平衡中确定的出口产量进行详细的、长期的研究。新产量将通过15NO3的吸收来测量。净群落产量将通过测量海水中的O2:Ar比值来估计。从10月到4月，将在距帕尔默站5公里的一个定期占用和长期研究（自1993年以来）的地点每周进行一次采样，与帕尔默南极洲长期生态研究项目（PAL）正在进行的研究密切合作。每周将在两个深度部署沉积物捕集器，收集颗粒，以确定沉降颗粒的C:N:234比。这项研究将是首批获得新产品、出口产品和净社区产品的详细同步时间序列的研究之一。目前对南极洲沿海颗粒出口的估计仅限于几个近海地点，可能低估了真实出口的一个数量级。此外，季节和年际变率与初级产量、海冰覆盖和浮游动物种群的相应变化在数量上没有相关性。这些缺点可能是由于沉积物捕集器收集不足以及浮游生物群落采样与颗粒通量之间的时空脱节，从而模糊了两者之间的关系。如果这些假设是正确的，该项目将对南极海洋环境下的出口产量提供一个新的、可靠的估计，并对南极夏季生长季节出口产量如何以及为何变化提供一个新的解释。该项目将支持一名博士后，并利用MBL和PAL-LTER教育和推广项目发达的基础设施，向两个最具影响力的公共教育群体——K12教师和科学记者——介绍世界上最迷人、变化最迅速的生态系统之一的海洋碳循环和气候变化。

The research project will obtain a comprehensive data set on the seasonal cycles of new, export and net community production, and lead to a better understanding of the production and export of organic matter (C and N) in a coastal Antarctic marine ecosystem. There have been relatively few measurements of these three processes in polar regions, and even fewer systematic time-series investigations conducted at the proper scales to uncover mechanisms. In consequence, the physical, ecological and biogeochemical mechanisms regulating new production, NCP and export production remain poorly-characterized. We propose to conduct a detailed, season- long study of export production as determined from water column 238U:234Th disequilibrium. New production will be measured by 15NO3 uptake. Net community production will be estimated from measurements of the O2:Ar ratio in seawater. Sampling will be carried out weekly from October to April at a regularly-occupied and long-studied (since 1993) site 5 km from Palmer Station, in close conjunction with ongoing research by the Palmer, Antarctica Long Term Ecological Research project (PAL). Sediment traps will be deployed weekly at two depths to collect particles for determination of the ratios of C:N:234Th on sinking particles. This study will be among the first to obtain detailed concurrent time series of new, export and net community production. Current estimates of particle export in coastal Antarctica are limited to a few offshore sites and may underestimate the true export by an order of magnitude. In addition, seasonal and interannual variability are not quantitatively related to corresponding variations in primary production, sea ice cover nor zooplankton stocks. These shortcomings may result from sediment trap collection deficiencies and a spatiotemporal disconnect between sampling the plankton community and particle flux that blurs relationships. If these suppositions are correct, the project will provide a new, robust estimate of export production in the Antarctic marine environment, and a new explanation of how and why it varies during the Austral summer growing season. This project will support a postdoctoral fellow and take advantage of the well-developed infrastructure of the MBL and PAL-LTER Education and Outreach programs, to inform two of the most influential groups for public education, K12 teachers and science journalists, about the ocean carbon cycle and climate change in one of the world's most captivating and rapidly changing ecosystems.