Effect Of Sample Treatments On Carbon And Nitrogen Stable Isotope Ratios Of Aquatic Organisms And Its Implication For Foodweb Studies

Stable isotope analysis has been widely used in freshwater ecology study, but there was a lack of standard protocols for sample preparation and preservation, which made data interpretation and cross-study comparisons difficult. Effects of sample treatments on carbon and nitrogen stable isotope determination of aquatic organisms were studied in this research. The treatments included:zooplankton gut clearance, different preservation methods on zooplankton, lipid extraction on subtropic animal, and sample acidification.The results showed that:gut content did not cause significantly change onδ13C andδ15N of Phyllodiaptomus tunguidus and Bosmina. But replicate analysis of zooplankton with gut contents intact revealed significant deviation on bothδ13C andδ15N, which showed that gut clearance was important.Preservation of zooplankton by ethanol showed 813C values significantly enrichment, while the frozen-preserved zooplankton showedδ13C significantly depletion. Four preservation procedures did not cause significantly change inδ15N of zooplankton.Zooplanktonδ13C andδ15N were both significantly enrichment after lipid extraction, except of Cyclopsδ13C.δ13C of Limnoperna fortunei was significantly enriched while itsδ15N was significantly depletied. Liuxihe Bellamyaδ13C was significantly enriched after lipid extraction, whileδ13C of Radix significantly depleted.δ15N of Radix was significantly depletied. There was not significant difference between lipid extraction of fresh fish muscle and dry fish muscle onδ13C. Lipid extraction did not cause significantly change onδ13C of Cyprinus carpio, Carassius auratus, Hemicculter Leuciclus and Tilapia nilotica, but it caused Aristichthys nobilisδ13C significantly enriched. There was no significant change on dry muscleδ15N of fish after lipid extracted, except of Tilapia nilotica, while all fresh muscleδ15N of fish were significantly enriched.After acidified with 1 mol/L HCL,δ13C of Huizhou fresh leaves, Vallisneria, Hydrilla verticillata were significantly depleted while 813C of wilted leaves and Liuxihe fresh leaves did not sifnificantly change.δ15N of Huizhou fresh leaves and Hydrilla verticillata were significantly depleted after acidification, whileδ15N of Liuxihe fresh leaves, Vallisneria and wilted leaves did not significantly change. After acidified with 12 mol/L HCL,δ13C of Hydrilla verticillata and Liuxihe wilted leaves were significantly enriched, while 813C of fresh leaves of Huizhou was significantly depleted. Andδ13C of Liuxihe fresh leaves and Vallisneria did not sifnificantly change.δ15N of Huizhou fresh leaves and Hydrilla verticillata were significantly depleted, while815N of Liuxihe fresh leaves, wilted leaves and Vallisneria did not significantly change.δ13C andδ15N of POM were depleted after acidification. Acidification did not cause significantly change onδ13C of soil, but acidified with 12 mol/L HCL caused significantly enrichment onδ15N of soil. After acidified with 1 mol/L HCL,δ13C of Ping lake and Beinan lake andδ15N of Beinan lake were all significantly depleted. And after acidified with 12 mol/L HCL,δ13C andδ15N of Ping lake were significantly depleted, while that of Beinan lake were not significantly changed.