Abstract
Radiocarbon (Δ14C) abundance and stable carbon isotope (δ13C) compositions were measured for total lipid, total hydrolyzable amino acids (THAA), total carbohydrates (TCHO), and acid-insoluble organic fractions separated from phytoplankton, zooplankton, and sediment cores collected from two abyssal sites, one in the northeast (NE) Pacific Ocean and one in the Southern Ocean. These results are compared with those obtained for a separate core from the NE Pacific and reported by Wang et al. [Geochim. Cosmochim. Acta 62 (1998) 1365.]. An uncharacterized acid-insoluble fraction dominated (43-57%) the sediment TOC pool at both sites. Sediment collected from the NE Pacific exhibited higher TOC, TN. and higher Δ14C values and contained both labile (THAA and TCHO) and refractory (lipid and acid-insoluble) fractions. In contrast, sediment from the Southern Ocean had much lower TOC and Δ14C values, which indicated that organic matter was extremely refractory. Sedimentation rates calculated from 14C ages of TOC for both sites indicate that the differences in the organic composition and Δ14C signatures of organic matter in the sediments likely resulted from the differences in production and deposition of organic matter to the sediment, and the diagenetic stages of sedimentary organic matter in the two oceans. Unlike Δ14C, stable carbon isotopic (δ13C) compositions of TOC in the sediments of the two oceans had similar values, which reflect not only the organic matter input from marine-derived sources but also the nature of degraded, predominately uncharacterized organic fraction in these sediments. The differences in δ13C values among the compound classes in sediments at both sites can be attributed to the carbon isotopic signatures in original sources during photosynthesis and associated environmental factors. Preferential degradation of organic matter and heterotrophic effects may also play important roles for the observed δ13C variations and these effects need to be further investigated. © 2001 Elsevier Science B.V.
Highlights
Deep-sea sediments, as one of the largest carbon reservoirs in the ocean, play an important role in the global carbon and biogeochemical cycles ŽEmerson and Hedges, 1988., and provide the most complete record of past and present-day oceans
Previous studies ŽWang et al, 1996, 1998. reported D14C values in organic compound classes: total lipid, total hydrolyzable amino acids ŽTHAA., total carbohydrates ŽTCHO., and acid-insoluble Žuncharacterized. organic fractions separated from particulate organic matter and sediments collected from an abyssal site Žstation M. in the northeast ŽNE
We report the results of our further investigations of D14C activities and stable carbon isotopic Žd13C. compositions of total lipid, THAA, TCHO and acid-insoluble organic fractions in sediments collected from two abyssal sites, one in the NE Pacific Ocean and one in the Southern Ocean
Summary
Deep-sea sediments, as one of the largest carbon reservoirs in the ocean, play an important role in the global carbon and biogeochemical cycles ŽEmerson and Hedges, 1988., and provide the most complete record of past and present-day oceans. Our knowledge of the circulation and chemistry of the past ocean is based in part on the isotopic and geochemical studies of sedimentary organic carbon. It is important to understand the sources and the processes, which control the contents and carbon isotopic signatures of organic matter in the deep-sea sediments. It provides an ideal tracer to study the transformation and cycling of carbon in the ocean ŽDruffel and Williams, 1992; Druffel et al, 1998. These results showed that organic matter preserved in the sediment is a mixture of organic carbon of different sources and with different diagenetic stages. Lipids exhibited much lower D14C signatures than THAA and TCHO fractions in the sediments. Onto sediment could be the major processes controlling the observed D14C signatures and abundances of the organic fractions ŽDruffel and Williams, 1990. onto sediment could be the major processes controlling the observed D14C signatures and abundances of the organic fractions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
