The conundrum of marine N2 fixation

作者：Claire M. Mahaffey · 发表于：American Journal of Science · 年份：2005 · DOI：10.2475/ajs.305.6-8.546 · 被引用次数：262 · 研究领域：Marine and coastal ecosystems、Isotope Analysis in Ecology、Microbial Community Ecology and Physiology

Over the last 30 years, immense progress has been made in understanding the global significance of marine nitrogen (N2) fixation. Development of enzymological, isotopic and molecular techniques for identifying N2 fixers and quantifying N2 fixation rates, as well as more frequent and extensive field campaigns have fuelled such progress. Ship-based and laboratory experiments have revealed a large suite of previously unknown physiological characteristics of diazotrophs. More recently, geochemical estimates of N2 fixation, based upon N and phosphorus (P) stoichiometry, stable N isotope studies and carbon (C) anomalies in nutrient starved regions of the ocean, have provided basin and global- scale estimates of N2 fixation. While these achievements have revolutionized our understanding of the role N2 fixers play in global marine N and C cycles, there remain fundamental challenges in the study of N2 fixation. We here summarize the advances made and highlight the conundrums that remain regarding the basin and global scale quantification of N2 fixation, as well as the climatological, physical and biological factors that enable or constrain the distribution and growth of diazotrophs. Presently, direct estimates of N2 fixation, largely of the planktonic cyanobacterium, Trichodesmium, can account for only a quarter to one-half of the geochemically derived rates of N2 fixation in various ocean basins. This dichotomy may be partially a result of the spatial and temporal scales over which e...