Biocomplexity: Collaborative Research: Oceanic N2 Fixation and Global Climate

最近，海洋N2固定被确定为海洋氮（N）循环的重要组成部分，并且可能通过为上层水体提供新的N源而直接影响海洋中大气CO2的封存。将N2气体转化为活性N的原核微生物是共生生态系统的独特子组分，并表现出各种复杂的动力学，包括微生物聚生体和共生体的形成，有时，大规模的水华。越来越多的证据表明，铁（Fe）的可用性可能是一个关键的控制因素，这些浮游海洋固氮生物。因此，N2固定剂可能直接参与了全球气候系统的反馈，并且这些反馈在不同的时间也可能表现出复杂的动力学过程。鳞片假设的反馈机制将有以下组成部分：世界海洋中的N2固定率可以对大气中温室气体二氧化碳（CO2）的浓度产生影响。几十年的尺度（在表面地球化学的变化）到千年（在总NO3？来自N2固定和反硝化平衡的原料）。大气中的CO2浓度影响气候。反过来，气候系统可以通过控制灰尘中Fe的供应和影响上层海洋的分层来影响海洋中N2固定的速率。人类在目前这种反馈循环的表现中也有直接的作用，通过他们对灰尘产生的影响，通过沙漠边缘的农业，以及我们自己生产的二氧化碳进入大气。这些影响的循环性质可以导致反馈系统，特别是在较长的时间尺度上。本项目涉及研究这个系统的每个组成部分，然后模拟假设的反馈过程。由于这个系统的各个部分的相互作用，围绕着可以固定N2的原核微生物的独特行为和生物化学，这个反馈回路应该在不同的时间表现出复杂的行为。鳞片该研究将通过一系列有针对性的实验和实地观察进行，以了解和参数化这一全球过程的每一部分，包括通过灰尘沉积直接控制海洋N2固定。这种理解将提供一个建模过程，检查这个系统的复杂动态的时间？从几年到几千年建模过程将通过与时间上的数据进行比较来评估？从海洋时间的海洋地球化学的依赖行为？系列研究和沉积物岩心。

Oceanic N2 fixation has recently been identified as a significant part of the oceanic nitrogen (N) cycle and may directly influence the sequestration of atmospheric C02 in the oceans by providing a new source of N to the upper water column. The prokaryotic microorganisms that convert N2 gas to reactive N are an unique subcomponent of planktonic ecosystems and exhibit a variety of complex dynamics including the formation of microbial consortia and symbioses and, at times, massive blooms. Accumulating evidence indicates that iron (Fe) availability may be a key controlling factor for these planktonic marine diazotrophs. The primary pathway of Fe delivery to the upper oceans is through dust deposition.N2 fixers may therefore be directly involved in global feedbacks with the climate system and these feedbacks may also exhibit complex dynamics on many different time?scales. The hypothesized feedback mechanisms will have the following component parts: The rate Of N2 fixation in the world's oceans can have an impact on the concentration of the greenhouse gas, carbon dioxide (C02), in the atmosphere on time?scales of decades (variability in surface biogeochemistry) to millennia (changes in the total N03 ? stock from the balance of N2 fixation and denitrification). C02 concentrations in the atmosphere influence the climate. The climate system, in turn, can influence the rate Of N2 fixation in the oceans by controlling the supply of Fe on dust and by influencing the stratification of the upper ocean. Humans also have a direct role in the current manifestation of this feedback cycle by their influence on dust production, through agriculture at the margins of deserts, and by our own production Of C02 into the atmosphere. The circular nature of these influences can lead to a feedback system, particularly on longer timescales.This project involves studying each of the components of this system and then modeling the hypothesized feedback processes. Because of the interaction of the various parts of this system, keyed around the unique behavior and biogeochemistry of the prokaryotic microorganisms that can fix N2, this feedback loop should exhibit complex behaviors on a variety of time?scales. The research will be conducted through a targeted series of experiments and field observations to understand and parameterize each of the pieces of this global process including the direct control of marine N2 fixation by dust deposition. This understanding will then feed a modeling process that examines the complex dynamics of this system on time?scales of years to millennia. The modeling process will be evaluated by comparison with data on the time?dependent behavior of ocean biogeochemistry as available from ocean time?series studies and sediment cores.