Carbon and nitrogen composition and stable isotope as potential indicators of source and fate of organic matter in the salt marsh of the Changjiang Estuary, China.
Elemental (TOC, TN, C/N) and stable carbon and nitrogen isotopic (delta(13)C, delta(15)N) compositions were measured for surface sediments, three sediment vibrocores, plants, and suspended particulate matter (SPM) collected from salt marsh of the Changjiang Estuary. The purpose of this study is to characterize the sources of organic matter in sediments and to further elucidate the factors influencing the isotope signature in the salt marsh. Our results indicate that organic matter preserved in the sediments is predominantly controlled by the particulate organic matter in the Changjiang Estuary. The in situ contribution of marsh plants carbon to sediment organic matter is clearest in the high marsh, where the low delta(13)C of the plants (-28.1 per thousand) is reflected by a sediment delta(13)C (-24.7 per thousand) lower than values found for the low marsh and bare flat sediments (-23.4 per thousand and -23.0 per thousand, respectively). The effect of grain size on the spatial difference of isotope composition in the marsh sediments is insignificant, based on the observation that similar isotope values are found in different size particles, both for delta(13)C and delta(15)N. Nutrient utilization by plant assimilation, however, shows great impact on the surface sediment delta(15)N composition, due to the isotope fractionation. With extensive plant coverage and the consequent low surface water nitrate concentration, delta(15)N values of the high marsh surface sediments show (15)N enrichment.
State Key Laboratory of Estuarine and Coastal Research, East China Normal University, 3663 Zhongshan Road North, Shanghai 200062, People's Republic of China. junlizh77@sina.com
Junli
J
Zhou
Ying
Y
Wu
Jing
J
Zhang
Qinshu
Q
Kang
Zhengtao
Z
Liu
D002244:Carbon / Q000032:analysis* / Q000378:metabolism; D002681:China; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000032:analysis* / Q000737:chemistry; D007202:Indicators and Reagents; D007554:Isotopes / Q000032:analysis*; D009584:Nitrogen / Q000032:analysis* / Q000378:metabolism; D009930:Organic Chemicals / Q000032:analysis* / Q000378:metabolism; D010316:Particle Size; D012492:Salts / Q000737:chemistry*; D012623:Seawater / Q000737:chemistry
D007202:Indicators and Reagents; D007554:Isotopes; D009930:Organic Chemicals; D012492:Salts; D002244:Carbon; D009584:Nitrogen