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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/50229

Title: Origins of Particulate Organic Matter Determined from Nitrogen Isotopic Composition and C/N Ratio in the Highly Eutrophic Danshuei Estuary, Northern Taiwan
Authors: Po-Chao Wu
Gwo-Ching Gong
Jun-Shiang Cheng
Kon-Kee Liu
Shuh-Ji Kao
Contributors: 國立臺灣海洋大學:海洋環境與生態研究所
Keywords: Particulate nitrogen
Urban river
Phytodetritus
Variable isotope fractionation
Date: 2016
Issue Date: 2018-09-25T08:34:22Z
Publisher: Aquatic Geochemistry
Abstract: Abstract: The Danshuei River flows through the heavily populated metropolitan area of Taipei and New Taipei cities, which causes remarkable additions of nutrient elements. In spite of the rather short residence time of water, the Danshuei estuary is distinctive for the very high ammonium concentration and extensive hypoxia in its lower reach. Because particulate organic matter (POM) is potentially the culprit of hypoxia, we investigate the isotopic characteristics of POM collected in February and July 2009 at a fixed station over four semidiurnal tidal cycles. By using nitrogen isotopic composition and C/N ratio of POM, we derive the relative contributions of POM from different sources. One potential source that combines dead and living phytoplankton, phytodetritus, has δ15N values that can be predicted by the δ15N of ammonium and the isotope effect during ammonium uptake; however, the isotope effect is concentration dependent. We employ a three-end-member mixing model based on δ15N and C/N ratio to calculate the fractional contributions from three major POM sources, i.e., phytodetritus, soil, and sediment. Sensitivity test was conducted for the derivations from both carbon and nitrogen basis. For February 2009 we found the three fractions (in terms of contribution to the particulate organic carbon) to be 45 ± 19, 10 ± 11 and 45 ± 13 %, respectively; for July 2009, 71 ± 18, 11 ± 10 and 18 ± 13 %, respectively. The results imply that phytodetritus is probably the major culprit for the hypoxic conditions in the estuary, especially, in summer.
Relation: 22(4) pp.291–311
URI: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/50229
Appears in Collections:[海洋環境與生態研究所] 期刊論文

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