Sedimentary records of eutrophication in the Changjiang Estuary upwelling area over last 100 a |
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Authors: | FENG Xuwen JING Xianglong YU Xiaoguo LI Hongliang CHEN Jianfang QIAN Jiangchu |
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Affiliation: | 1. Geology Science Department,Zhejiang University,Hangzhou 310027,China;Second Institute of Oceanography,State Oceanic Administration,Hangzhou 310012,China 2. Second Institute of Oceanography,State Oceanic Administration,Hangzhou 310012,China;Laboratory of Submarine Geoscieuces of State Oceanic Administration,Second Institute Oceanography,State Oceanic Administration,Hangzhou 310012,China 3. Second Institute of Oceanography,State Oceanic Administration,Hangzhou 310012,China;Laboratory of Marine Ecosystem and Biogeochemistry of State Oceanic Administration,Second Institute Oceanography,State Oceanic Administration,Hangzhou 310012,China |
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Abstract: | The upwelling area in the Changjiang Estuary was selected to collect the core,where the red tide occurred frequently and hypoxic exis-ted.The total organic carbon (TOC),total nitrogen (TN),biogenic silica (BSi) and stable organic carbon isotopic ratios(813 Corg) were determined on the 210Pb-dated sediment core.The concentrations of TOC,TN,BSi as well as their sedimentation fluxes have in-creased to some extent since the 1970s.TOC and TN fluxes increased about 45%,36% respectively.The average δ13 Corg value in the core was -23.67 × 10-3 which remained nearly constant before the 20 century.The δ13 Corg values increased after the 1900s,two marked increases were observed from the 1950s and the 1970s.A simple δ13 Corg model was used to estimate the contribution of terrige-nous and marine organic matter inputs for the sediment,which indicated the increase in accmnulation since the 1970s has been almost exclusively marine.The increasing of marine organic matter accumulation (TOC,TN and BSi) was corresponding with the increasing of fertilizer consumption and the NO3-N budgets from the Changjiang River.The riverine runoff of fertilizers and nutrients stimulated the algae blooming.Enhanced primary production resulted in an enrichment of organic matter in the sediment.These data support the hy-pothesis that anthropogenie nutrient loading has been a significant factor on the eutrophication in the Changjiang Estuary. |
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Keywords: | Changjiang Estuary total organic carbon total nitrogen biogenie silica stable carbon isotopes eutrophication |
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