Nitrogen Stable Isotopes in Primary Uptake Compartments Across Streams Differing in Nutrient Availability

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• 作者：Ada Pastor ; Marc Peipoch ; L铆dia Ca帽as ; Eglantine Chappuis ; Miquel Ribot ; Esperan莽a Gacia ; Joan Llu铆s Riera ; Eug猫nia Mart铆 ; Francesc Sabater
• 刊名：Environmental Science & Technology
• 出版年：2013
• 出版时间：September 17, 2013
• 年：2013
• 卷：47
• 期：18
• 页码：10155-10162
• 全文大小：318K
• 年卷期：v.47,no.18(September 17, 2013)
• ISSN：1520-5851

文摘

High variability in the natural abundance of nitrogen stable isotopes (未¹⁵N) has been reported for primary uptake compartments (PUCs; e.g., epilithon, filamentous algae, bryophytes, macrophytes) in human-impacted aquatic ecosystems, but the origin of this variability is not yet well understood. We examined how 未¹⁵N of different PUC types relate to 未¹⁵N of dissolved inorganic nitrogen (DIN) species (nitrate and ammonium) and to the stream nutrient concentrations in which they grow. We selected 25 reaches located across the fluvial network of La Tordera catchment (NE Spain, 868.5 km²), encompassing a gradient of human pressures from headwaters to the river valley. 未¹⁵N-PUC variability was mostly explained by location within the fluvial network and was strongly related to the 未¹⁵N of DIN species, especially of ammonium. Models were stronger for PUCs growing within the stream channel and thus using streamwater as their main source of nutrients. Regression models including nutrient concentrations improved the prediction power for 未¹⁵N-PUCs, suggesting that nutrient concentrations and stoichiometry cannot be ignored in explaining the natural abundance of nitrogen isotopes in PUCs. These results provide insights into what controls variability in 未¹⁵N of PUCs within a stream network, with implications for the application of stables isotopes as an ecological tool.