@ 1978, by the American Society of Limnology and Oceanography, Inc. Correlation of carbon and nitrogen stable isotope ratios in sedimentary organic matter1

Samples of organic matter separated from nearshore sediments of the Northeast Pacific are characterized by a linear correlation between ‘3C:‘2C versus 15N:14N. This correlation appears to represent the mixing of marine and terrestrial “end members ” of refractory organic matter. Exceptions to the linear plot include organic matter from riverbeds draining agricultural areas, eutrophic lakes or lagoons with large algal populations, and some other exotic envi-ronments. Nitrogen isotope ratios have been used to trace the plume of domestic and in-dustrial sewage in California coastal sed-iment (Sweeney et al. 197%) and to es-timate the percentage of terrigenous organic detritus in Santa Barbara Basin, California (Sweeney and Kaplan 1978). Systematic variations in carbon isotope ratios of organic matter have been mea-sured in sediment extending from rivers to the open ocean (Sackett and Thomp