期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2011
卷号：108
期号：3
页码：1011-1015
DOI：10.1073/pnas.1004904108
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Despite the importance of the nitrogen (N) cycle on marine productivity, little is known about variability in N sources and cycling in the ocean in relation to natural and anthropogenic climate change. Beyond the last few decades of scientific observation, knowledge depends largely on proxy records derived from nitrogen stable isotopes ({delta}15N) preserved in sediments and other bioarchives. Traditional bulk{delta} 15N measurements, however, represent the combined influence of N source and subsequent trophic transfers, often confounding environmental interpretation. Recently, compound-specific analysis of individual amino acids ({delta}15N-AA) has been shown as a means to deconvolve trophic level versus N source effects on the{delta} 15N variability of bulk organic matter. Here, we demonstrate the first use of{delta} 15N-AA in a paleoceanographic study, through analysis of annually secreted growth rings preserved in the organic endoskeletons of deep-sea gorgonian corals. In the Northwest Atlantic off Nova Scotia, coral{delta} 15N is correlated with increasing presence of subtropical versus subpolar slope waters over the twentieth century. By using the new{delta} 15N-AA approach to control for variable trophic processing, we are able to interpret coral bulk{delta} 15N values as a proxy for nitrate source and, hence, slope water source partitioning. We conclude that the persistence of the warm, nutrient-rich regime since the early 1970s is largely unique in the context of the last approximately 1,800 yr. This evidence suggests that nutrient variability in this region is coordinated with recent changes in global climate and underscores the broad potential of{delta} 15N-AA for paleoceanographic studies of the marine N cycle.
关键词：compound-specific isotope analysis ; deep-sea corals ; nitrogen cycle ; North Atlantic Oscillation ; stable N isotopes
